How To – Servo and Servo Horn Replacement

Servo_and_Servo_Horn_Replacement

The steering system on a full-size off-road vehicle takes a lot of abuse. It is the same with RC. Whether you’re driving fast over bumps and jumps with an Yeti or crawling over rocks with an SCX10 II or doing a little of both with a Wraith, the steering is constantly taking hits. Whatever you hit, roll over or dig up onto, usually contacts the steering system first. In a similar fashion, and again just as it is in full-size off-road, one of the best ways to improve the capabilities of your RC vehicle is to make improvements its steering system. Instead of installing a hydraulic assist, in RC, we upgrade the servo. Instead of installing a custom pitman arm, in RC, we use an aluminum servo horn. These upgrades are simple tasks that can be performed by hobbyists of any experience level (if you aren’t an adult, get adult assistance and/or supervision).

Installing a New Servo Horn

Axial Servo Swap How To 2

STEP 1. Depending on your model, it may be necessary to remove some components to make servo access easier. On this SCX10, the bumper and cross-member have been removed.

Axial Servo Swap How To 3 Axial Servo Swap How To 4

STEP 2. Remove the servo horn. The horn is most likely retained by a Phillips head screw, or a 2 mm screw. Either way, the screw is easy to access and remove. There may be a lock washer under the screw, so be careful not to lose it. Set this hardware aside. A small dish or tray is handy to prevent losing parts. Pull the servo horn off the servo.

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STEP 4. Select your new servo horn. Axial offers heavy aluminum servo horns that are essentially indestructible. These horns are offered in 23, 24 and 25 spline counts to fit any brand of servo. Axial servos use 25 spline count output shafts. These servo horns are highly recommended and go a long way towards improving a vehicle’s reliability. They should, however, only be used with heavy-duty metal gear servos that can withstand the forces that will be pass through the steering to the servo.

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STEP 5. Attach the steering link to the servo horn. This is pretty simple. Note that even if you use a servo horn with threaded holes, you still need a locknut on the screw that attaches the link to the horn.

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STEP 6. The vehicle must be powered up to properly install a new servo horn. Install a battery and turn on your transmitter. Plug in the battery and turn your vehicle on. Next, set your transmitter’s steering trim (channel 1) to zero. If your transmitter has sub trim, you need to also set that to zero for steering. After the trims have been set to zero, you can turn off the vehicle and then the transmitter.

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STEP 7. Slide the servo horn onto the output shaft and secure it with the main center screw. Axial’s HD servo horns are a double clamping design, so if you’re using one, you will also need to tighten the two 1.5 mm screws on the sides of the horn. Tighten all three screws down tight. Thread lock is not recommended on any of these screws. If you find, over time, that the main screw repeatable loosens and using a new screw doesn’t help, you can use a small amount of medium strength thread lock. Never use high strength thread lock.


Removing an Old Servo

Refer to Steps 1 & 2 above to remove the servo horn from the installed servo.

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STEP 3. Open the radio box using a 2 mm wrench (it may vary by model). With the lid removed, you will be able to carefully unplug the servo lead from the receiver. Again, be careful so that you do not damage the receiver and its internal circuit board. The servo lead (wires connecting it to the receiver) may be attached to the chassis in some places with cable ties. It is essential that you be extremely careful when cutting any cable ties as you could easily damage the small wires.

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STEP 4. Before removing the servo, take note as to which side the output shaft sits. The servo itself is retained by four screws. These may be Phillips or hex. Some screws may have built-in wide shoulders and others may have washers. Either way, carefully put this hardware aside. The servo can now be removed and set aside.

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STEP 5. Place the new servo on its mounting plate. Servos can vary in size, but Axial vehicles have adjustable servo mounts. If you do need to adjust the servo mount (one is in a fixed position and one adjusts), the process is the same on SCX10 and Wraith, which all feature servos mounted directly on the front axle. On these vehicles, with the new servo set aside, remove the mounting plate from the axial. You can make this process easier by disconnecting the upper links and the upper shock mounts. This will allow the axle assembly to pivot forward and give you much better access to the screws attaching the servo mounting plate to the axle. After you remove the servo mounting plate, turn it over and locate the screw securing the adjustable mount. To identify this mount, look for the screw going into an oval shaped hole. The oval shape is what allows for the side-to-side adjustment for narrow or wide servos. Now, simply loosen the screw a small amount (usually a partial turn is all that’s needed) and test fit your new servo. Holding the servo in place, tighten the screw back down. Remove the servo and reinstall the servo mounting plate to the axle. You can now reconnect the upper links and shocks. If the male and female driveshaft pieces pulled apart, make sure it gets reconnected as well (before reconnecting the upper links).

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STEP 6. Slide the new servo into the mount, paying close attention to which side the output shaft sits. When working on an SCX10 or Wraith, and when viewed from the front, the output shaft is on the right-hand side. Secure the servo with the four screws that were holding the original servo in place. If the screw holes are stripped out and the screws cannot be fully tightened, you will need to replace the plastic servo mounts.

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STEP 7. The next step is routing the servo lead back to the radio box and receiver. Make sure the wires are not near any moving parts such as articulating suspension components or driveshafts. This is especially true if your Axial model has exposed gears. Small cable ties can be used to keep wires secure and out of harm’s way. Note that Axial includes provisions to secure wires on vehicles such as the SCX10 and SCX10 II. These should definitely be used to secure wiring.

Excessive wire should be neatly stored in the radio box. Do not make the wires too tight or they will get damaged as the suspension articulates. The wires should be slack enough to allow for complete suspension movement.

Once the wiring is complete, you reinstall the radio box lid. Some radio boxes are not fully sealed, but if you are using a sealed box, you should add grease to the area where the wires pass into the box.

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STEP 7. Finally reinstall the servo horn on the centered servo. Refer to STEP 7 above. Your servo swap is complete! You can now power up your radio and vehicle and go out for a drive.

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TIP: Radio Settings
You may need to slightly adjust your steering trim to get the vehicle to track straight with no input. If your transmitter has sub trim, this adjustment is used first.

If your transmitter has end-point adjustments, you should also use these to adjust how far the servo travels in either direction. A servo that turns farther than the steering system will allow can eventually burn out. The best tool to see if your servo is moving too far and straining is your ear. All servos, especially digital models, make an audible whine when pushing against a resistance. Bench test your steering. If you hear a whine at full lock in either direction, adjust the end points until you don’t hear a whine. If your transmitter doesn’t have end point adjustments, it may have dual rates, which also reduces steering throw, but does both sides simultaneously.

How To – Program Your ESC For NiMH Batteries

 

Program_NiMH_Batteries

Axial’s Ready-to-Run (RTR) vehicles are true hobby-grade products and, as such, they use sophisticated electronic components. One of the primary advantages to such high-tech gear is adjustability and an area of adjustability includes battery type. Axial’s electronic speed controls (ESCs) are designed to be used with a variety of battery chemistry types and can, and should, be adjusted for the type of battery you’re using.

IMPORTANT NOTE: As a safety measure, Axial uses the LiPo setting as the default setting on the ESC, but NiMH batteries, are often recommended for use with RTRs. NiMH batteries will provide best performance when the ESC is used in NiMH mode.

nimh_and_lipo

LiPo batteries must be run with the ESC set in LiPo for safe use. This isn’t optional. When properly set in LiPo mode, Axial ESCs are designed to eliminate the chance of over discharging the battery and permanently damaging it, which is a potential safety issue. As such, LiPo batteries should never be used in any other mode other than LiPo mode on the ESC.

NiMH batteries will work in LiPo mode, but there will be a noticeable reduction in performance that will suddenly become apparent as the pack starts to lose voltage (discharge). This is because LiPo mode has what is called LiPo cutoff or low voltage cutoff. As the voltage drops in the NiMH pack, it is still delivering usable power, but the LiPo cutoff engages and impairs performance. The LiPo cutoff is designed to reduce power to the motor in order to keep the battery at a safe minimum voltage. Let’s go over setting up NiMh mode on the various Axial ESC offerings so you can get maximum performance when using this type of battery.


 

axial ae-2 esc

AE-2. The AE-2 is a brushed motor speed control. While Castle Creation’s Castle Link system can be used to link the ESC up to a computer (availabe as an aftermarket item,) for ease of use, the AE-2 can be programmed manually by using the throttle trigger on your transmitter to indicate yes or or no to selections as you scroll through each option. To get the best performance when using a NiMH, the ESC should be programmed to operate in NiMH mode.

When programming, as a safety measure, remove the pinion from the motor. This will prevent the gears and/or vehicle from moving and causing damage to the vehicle or you. Turn the transmitter on and then connect a freshly charged battery to the ESC. Hold full throttle and turn on the ESC. You will hear four tones from the ESC and then another four tones. After the second series of four tones, release the throttle. The ESC will beep twice indicating you’re in programming mode.

There are three settings that can be adjusted on the AE-3. Each setting, in turn, has a varying number of options. You will use your transmitter’s throttle to select yes (full throttle) or no (full brake) for each option. When you select yes, the next setting will come up. Every time you select no, you will toggle to the next option within that setting. When you select yes or no, wait for a continuous tone and let the throttle go to neutral. If you selected yes, the ESC will go to the next setting.

To change to NiMH mode, you will need to go to the first setting. Remember, LiPo batteries must be used LiPo mode.

Setting 1 LiPo Cutoff
Option 1: None (NiMH mode)
Option 2: Auto-LiPo*

Setting 2 Drag Brake
Option 1: Disabled
Option 2: 15%
Option 3: 25%
Option 4: 40%
Option 5: 50%
Option 6: 100%*

3: Brake/Reverse Type
Option 1: Reverse enabled (2-second lockout)
Option 2: Reverse disabled
Option 3: Forward/Brake/Reverse*
* = Default factory setting

For additional reference, view the manual: HERE


 

axial ae-3 esc

Vanguard AE-3. The Vanguard AE-3 is a brushless motor speed control. It comes preprogrammed in the “Auto-LiPo” mode. Like the AE-2, you can use the Castle-Link to program the ESC with your PC, but you can also manually program the ESC with your transmitter.

When programming, as a safety measure, remove the pinion from the motor. This will prevent the gears and/or vehicle from moving and causing damage to the vehicle or you. Turn the transmitter on and then connect a freshly charged battery to the ESC. Hold full throttle and then turn on the ESC. You will hear four tones from the ESC and then another four tones. After the second series of four tones, release the throttle. The ESC will beep twice indicating you’re in programming mode.

There are nine settings that can be adjusted. Each setting, in turn, has a varying number of options. You will use your transmitter’s throttle to select yes (full throttle) or no (full brake) for each option. When you select yes, the next setting will come up. Every time you select no, you will toggle to the next option within that setting. When you select yes or no, wait for a continuous tone and let the throttle go to neutral. If you selected yes, the ESC will go to the next setting.

To change to NiMH mode, you will need to go through settings one through six to get to setting seven, which changes the battery mode. Remember, LiPo batteries must be used LiPo mode.

Setting 1 Brake/Reverse Type
Option 1: With Reverse*
Option 2: Without Reverse
Option 3: Crawler Reverse. No delay from throttle to brake to reverse.

Setting 2 Brake Amount
Option 1: 25% Power
Option 2: 50% Power*
Option 3: 75% Power
Option 4: 100% Power

Setting 3 Reverse Amount
Option 1: 25% Power
Option 2: 50% Power*
Option 3: 75% Power
Option 4: 100% Power

Setting 4 Punch/Traction Control
Option 1: High
Option 2: Medium
Option 3: Low
Option 4: Lowest
Option 5: Disabled*

Setting 5 Drag Brake
Option 1: Drag Brake off*
Option 2: Drag Brake 10%
Option 3: Drag Brake 20%
Option 4: Drag Brake 30%
Option 5: Drag Brake 40%

Setting 6 Dead Band
Option 1: Large – 0.1500 ms
Option 2: Normal – 0.1000 ms*
Option 3: Small – 0.0750 ms
Option 4: Very Small – 0.0500 ms
Option 5: Smallest – 0.0250 ms

Setting 7 Cutoff Voltage
Option 1: No low-voltage cutoff
Option 2: Auto-Lipo*
Option 3: 5v
Option 4: 6v
Option 5: 9v
Option 6: 12v

Setting 8 Motor Timing
Option 1: Lowest
Option 2: Normal*
Option 3: Highest

Setting 9 Motor Type
Option 1: Brushless*
Option 2: Brushed Reversing
Option 3: Brushed High Power
* = Default factory setting

For additional reference, view the manual: HERE


 

axial ae-5 esc

AE-5. The AE-5 is a brushed speed control and is by far the easiest ESC to program. To switch from the factory LiPo mode, remove the “jumper” and move it over one position. Not only is this ESC easy to program, it’s also waterproof.

For additional reference, view the manual: HERE

Axial AE-5


 

ae-1

AE-1. Axial’s AE-1 ESC does not have a LiPo cutoff. If you use LiPo batteries in a vehicle equipped with an AE-1 ESC you must use a separate LiPo low-voltage cut-off device. Axial does not sell a separate LiPo cut-off device, so the best choice would be to upgrade to an ESC such as the Axial AE-5 (see above), which is extremely easy to program and waterproof.

Rock Racing Tires

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yeti rock racing

If you didn’t already know, tires make the single biggest difference in the overall performance of a competition vehicle. A fast motor will increase top speed, but if you want lower lap times, if you want to be in front of the competition, if you want to win, it is absolutely essential you spend time to getting the right tire setup on your Axial Racing vehicle. This includes tread pattern, rubber compound, size, inserts and even, to some extent, wheels.

While all Axial Racing vehicles include high-performance scale tires, there is no single best tire. What works perfectly at one rock racing track simply may not work at all at another track. Also, track conditions change, so what worked at one point in a race day might not be the ideal choice later in the same day.

Rock racing is tricky because what works exceptionally well on rocks is unlikely to work on high-speed dirt sections and vice versa. It is essentially impossible to pick out a rock racing tire without making some sort of compromise. The specific track you are racing on will determine which way you want to compromise performance.

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Tread Pattern
The tread is the most obvious feature of a tire. All of the other features in a tire design matter to varying degrees, but it’s hard to argue that tread pattern makes a big difference.

Treads with taller, flexible lugs can sometimes be beneficial on rocks, but they are unlikely to do well on typical hard racing surfaces where the tread easily folds over. When the lug folds over, it provides inconsistent and unpredictable handling as they can slightly squirm around. If a track has a lot of silt, which is very common, tall lugs do help. Most racing-specific tires, however, have short lugs, so if the rock racing track you’re competing on has a lot of fast sections, select a tires with smaller, closer-spaced lugs.

Large voids (open spaces) between lugs help keep tires from clogging with soft, wet dirt. If the track is muddy due to weather conditions or heavy watering by the track crew, consider a tire with large spaces between the treads such as the Axial BFGoodrich Krawler T/A tire.

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Another part of the tread to look at is the sidewall. Tires such as the Axial Maxxis Trepador and Axial Ripsaw have significant tread wrapping down the side of the tire carcass. These side treads can be a huge advantage on the rocky section and typically won’t impact handling on the fast sections.

Don’t be afraid to mix and match tires to achieve the desired handling. Often rock racers have a hard time with squirrelly handling on the fast sections and at the start. Going with a less aggressive front tire can help reduce oversteer. If the car slides (not spins out) in the corners, it will benefit a more aggressive front tire and might need more traction overall.

compound

Rubber Compound
There are numerous rubber compounds to choose from. Softer compounds such as Axial’s R35 compound (white dot) are softer and stickier. Soft compounds provide more traction, but wear faster. A soft compound such as R35 is almost always better for rock racing.

In the same way treads can be mixed and matched, different compounds can be used the front compared to the rear. It might make sense to start with R35 compound with the rear tires only.

size

Size
Often, when selecting tires for rock crawling, the focus is on tire height, but width is just as important when choosing a rock racing tire. In general, and with all things being equal, a wider tire has an increased contact patch and will provide more traction. Narrow tires up front teamed up with wider rear tires can be an ideal setup. This is especially worth trying if your truck is struggling to track well in the corners.

While width is important when looking for the right front to rear balance, height is still important. The main benefit of taller tires is increased ground clearance. Taller tires also have taller sidewalls since we only use a few wheel sizes in R/C. Taller sidewalls have no benefit on the fast sections, but tall sidewalls do allow for a more flexible tire that can wrap around rocks and aid in climbing.

inserts

Inserts
In full-size tires, compressed air supports the tire. There are a few exceptions, of course. In R/C, foam inserts replaces the air, and just like the air inside a full-size tire, the foam supports the tire. Firmer foam is like higher PSI and softer foam is like less PSI.

Foam can be divided into four groups: open-cell, closed cell, memory, and multi-stage.

Open-cell foam is the most common type of foam found in R/C. Not all open-cell foam is the same; there are countless varieties. This is the same for all of the foam types. Axial Racing includes a medium density (firmness) foam insert.

Closed-cell foam is molded foam and in the last five years has become the most common type of foam used with racing vehicles. A solid closed-cell insert is, however, almost always too firm to work well for rock racing.

Memory foam is often used in rock crawling, but it can have some ill effects when rock racing. Memory foam is heavier than both open- and closed-cell foam. This helps with rock crawling, but can actually cause accelerated parts wear. Unlike traditional foam, memory foam is slow to return to its original shape after encountering an obstacle. This characteristic of memory foam helps when rock crawling where going slow is the norm. The memory foam conforms to and wraps around obstacles. When rock racing, if memory foam is compressed it will cause an out-of-balance tires and erratic handling.

Multi-stage foams use more than one type of foam and allow you to have a “best of both worlds” setup. Just about any combination is possible, but the best setup for rock racing would be a closed-cell inner ring surrounded by an open-cell outer ring.

Dual_Stage_Foam_500px

 

How the foam fits inside the tire also impacts how firm it feels. For rock racing, it is best to use a foam insert properly sized to the tire. An oversized foam insert will make the foam firmer than possibly desired and an undersized foam will provide erratic handling as it moves around inside the tire. In high-speed racing, a slight air gap (space between outside top of the foam and inside of the tread are) will increase traction without hampering handling as long air gap isn’t too large. Creating a consistent air gap when using open-cell foam can be difficult, but with careful attention to detail it is possible.

An important item to consider is that foam inserts wear out. Sometimes tires might not show a lot of visible wear, but the inserts inside have broken down. Open-cell foam wears out the fastest. Often simply squeezing a tire doesn’t demonstrate how the foam is holding up. Instead, squeeze all of the tires and make sure the foam rebounds at the same in rate in all of the tires. Carefully feel the tires to see if the is an increased gap between the tire and the foam insert. If you’re using bead lock wheels, disassembling the tires and wheels may be in order.

wheels

Wheels
Where rock crawlers often favor heavier aluminum wheels, lightweight wheels are best rock racing. Increasing rotational mass, such as with heavy wheels, is never desirable on a high-speed vehicle. In fact, lightweight and more flexible wheels will most likely improve handling over bumps and jumps.

While bead lock wheels have the advantages of being easily reused and unlikely to fail (have a tire come apart) if properly installed, they are heavier. Glue-up style one-piece wheels are often appropriately flexible and lightweight, which, as stated, are good qualities for racing.

Rock Racing Setup – Key Elements

newtorc_rockracingsetup

Rock racing combines rock crawling with off-road racing, and yet, it’s so incredibly different than either. It’s more brash and intense than technical rock crawling and it’s more about sudden bursts of speed than wide-open off-road racing. As such, setting up a vehicle for competitive rock racing can be a little tricky. Whether you’re brand new or already experienced, used this guide to make sure your Axial Racing rig is properly prepared for the ultra-demanding world of rock racing.

tires

Tires
Rock racing calls for true dual purpose tires. The tires must deliver high speed performance on dirt and also provide rock grabbing traction—two very different tasks. And, the amount of each type of terrain—dirt versus rocks—isn’t likely to be equal. Depending on where you are rock racing, it may make more sense to concentrate on the high speed portions and go with tires that work best on dirt, or vise versa. No matter what, you will most likely be making some sort of compromise. Typically the compromise comes in the form of the foam inserts. Soft foam inserts will help tires conform to rocks, while firmer foam inserts will improve high speed performance. The track you’re racing on will determine which way to go. When selecting tires for competition, go with a soft compound such as Axial Racing’s R35 (white dot). These will provide the best traction on dirt and rocks.

It’s also worth noting that if your vehicle is hard to control on the fast section and wants to spin out, you can try a harder compound tire up front and/or a less aggressive tread pattern on the front tires. Another secret to know is a larger pinion gear can also cure spinning out as it eases acceleration and the ability for the tires to break traction.

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Center of Gravity
In rock crawling there is no such thing as too low of a center of gravity. This still hold true for rock racing. A low center of gravity will improve your vehicles ability to climb without tipping over backwards and a low center of gravity will keep your vehicle stable in high-speed corners. Depending on the class you’re running how you can lower the center of gravity easily varies. If you’re running a full Lexan body, lower it as much as possible and open up the wheel wells to allow room for the tires to move as the suspension cycles. Bodies weigh more than most people realize and you can see a huge performance improvement by simply lowering. Unless rules require it, lose unneeded accessories such as spare tires. While light buckets only weigh a few grams, for the best possible performance, you may consider removing or moving light buckets.

jumping

Weight Distribution
Since rock racing involves jumps, weight distribution (also known as weight bias) is very important and a little more complicated compared to a pure rock crawling setup. More weight up front is best for rock crawling, it isn’t that simple for rock racing. A neutral or slightly weight forward weight distribution is preferred as it will not overly compromise rock crawling performance, but too much weight forward of center can cause (or exasperate) nose diving off jumps. You simply have to test on the track your racing or on jumps of similar size at the speeds you’ll be hitting the jumps. While not a weight distribution issue, the first thing to check when experiencing chronic nose diving is your ESC’s drag brake setting. While drag brake is essential for rock crawling, it can cause nose diving by automatically applying brakes when you let the throttle go to neutral in the air. Less drag brake is more when it comes to rock racing. Just be sure to maintain control on the downhill sections many tracks have.

durability

Durability
Most people think racing is all about speed—all about being the fastest. In rock racing, durability is far more important than speed. In real racing and in RC, no racing competition is as hard on a vehicle as rock racing. Rock racing is an incredible challenge—one that’s very hard on the vehicle. In full-size rock racing, at events such as the King of the Hammers, most entries don’t finish. RC racing is often the same if vehicles are properly prepared for the rigors of racing. Aluminum parts are they way to go for rock racing. They increase durability without adding too much weight. Titanium, if your budget allows, is an even better choice. Be warned, titanium doesn’t bend and rebound like aluminum. It’s stronger, but it snaps instead of bends when stressed to its limits. Start with an aluminum servo horn. This is an absolute must. Axial’s Universal Axle Set is also an item to have at the top of your list. Other aluminum upgrade parts can be added as parts fail or show excessive wear.

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Ground Clearance
Optimal ground clearance will vary depending on the track, but you will want to get your rock racer as low as you can without making it impossible to navigate the rock portions. Scraping and dragging is okay. A lower will vehicle is more stable and less likely to roll in corners, on rocks and when taking jumps. Few crashes means less waiting for corner marshals and much faster laps.

motor

Speed
The fastest car isn’t guaranteed to win in rock racing. While you don’t want purposely make your vehicle slow, don’t worry too much about having the fastest vehicle on the track. Stability and durability are far more valuable in rock racing than speed. Axial’s brushless setup are more than fast enough for rock racing. Some classes allow 3S LiPo batteries, which will provide a significant speed increase. If the track has a good amount of high-speed sections, running a faster 3S setup may be ideal.

shocks

Suspension
Axial vehicles all have highly adjustable suspensions. While you can change internal shock components such as pistons and oil viscosity, a lot can be done to dial in handling by simply changing shock springs. Axial offers a wide variety of springs in both firm and soft rates. The goal is to have a plush suspension. Most rock racers are setup with overly stiff suspensions that don’t absorb impacts well. You can see these vehicles reacting to everything they hit as both ends bounce up and down without the suspension really working. Setup up your vehicle so that it lands from a one-foot-tall test drop with no bounce. It should land as if there were a pillow under it. This may require experimenting with oil and pistons to get just right. Thicker oil will absorb more energy and keep the springs from acting like pogos and smaller holes in the piston will slow down how quickly the oil can travel through the piston and slow down how quickly the suspension compresses. This will help keep the chassis from slapping the ground. A little chassis slap isn’t a bad thing. You just don’t want hard hits. Use sway bars to compensate for this soft suspension. The sway bars will keep the vehicle from rolling over in the corners.

You
The biggest factor in how successful you will be at rock racing is you. Of course, you provide the driving skill, but what is really at stake is how well you take care of the vehicle on the track. There’s an old saying in racing that goes: to finish first, you must first finish. These words couldn’t be more true than they are for rock racing. Don’t let the other vehicles determine how fast you go. Know what your vehicle can handle without breaking or crashing and stick to that pace. If a vehicle passes you, do not chase it down. Pretend you’re the only vehicle out there and concentrate on nothing other than consistent, crash-free laps.

Budget-friendly Axial-based Monster Truck Build

adventures_budgetmonster

There’s a growing number of Axial-based monster trucks being built. And, specifically, many builders are using Axial Racing AR60 axles and drivetrain components. This actually seems to be the most popular choice for newer builds. Many of these rigs being built are simply amazing, so if you’ve seen any of these custom creations, it’s likely that you’ve been inspired to build your own. But, if you’re on a budget, you might think these trucks are out of your reach. RC Truck Stop showed that building your own solid axle monster truck can be done on a budget without sacrificing any performance. The build below uses an Axial AX10 as the base for the project. This saves time and money. Interestingly, this same type of configuration has since been used to national-level solid monster truck racing competitions.

ax10zilla2

With the body off, you can see this build isn’t that big of a departure from the standard AX10 setup.

You can read the full article here.

 

Crawler Setup – Key Elements

newtorc_crawlersetup

Whether your idea of competition is attending a national championship or one-upping your friend at the local park, getting your rock crawler dialed in for top performance is an obvious plus. Out of the box, your Axial vehicle is setup for high performance, but so is everyone else’s. You need an edge. The following tips cover the key elements that you should address when you want to have the best setup crawler possible. Every aspect of tuning is not covered. These are the key elements. Also, as you learn about setting up a rock crawler you’ll quickly see that almost everything is a compromise; what works for one type of competition and/or terrain doesn’t necessarily work for another.

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Tires
Tires profoundly influence performance—maybe more than anything else. While there is no single best tire, you want to make sure you have the best tire for the conditions you’re running on. Also, not all rocks are the same, so there isn’t one best tire for all rocks. For competition, the softer the compound is better. The compromise here is wear and the need to get the tire’s foam insert right for the weight of the vehicle. Axial’s softer and stickier compound is called R35 (white dot).

While outfitting your rig with new tires will cost you, it is money well spent. You can learn more about picking the right tire here.

cog

Center of Gravity
Specifically where your center of gravity (CG) is located isn’t important—meaning you don’t need to calculate its exact position. What is of key importance is that the CG is low—as low as you can possibly get it. A lower CG is always better. On a rock crawler, an optimized CG will help on climbs, descents and side hills.

There are a number of ways to lower your CG. First, identify your heavy components and try to identify ways to mount them lower. Sometimes lowering a component isn’t possible, but lighter options are available. An excellent example is your battery. If you’re using a NiMH battery, a LiPo will make a profound difference. If you’re already using a LiPo, consider a smaller pack. It’s understandable that if you’re trail riding you want maximum runtime. Just know that the compromise of a big battery with a lot of capacity is a higher CG. Instead of one large battery, consider two packs wired in parallel with one mounted on each side of the chassis. Another way to lower the center of gravity is to add weight to your vehicle down low such is in the wheels or on the axles. The problem with making your vehicle heavier is that it can rob power and decrease durability.

A great way to lower the CG is to the body as much as possible. You will need to open up the wheel wells with body scissors, but doing this will make a big difference in handling.

1

Maneuverability
If you’re running a course with gates and judges tracking the use of reverse and each  touch of a gate marker or out-of-bounds line, maneuverability is of huge importance. If available, high clearance knuckles combined with universal axles provide maximized steering throw. If you’re running a G6 or similar event, this can move down your list of importance.

scale comp 14

Weight Distribution
Weight distribution, or weight bias, is a close cousin of CG. Your crawler will perform better on climbs if more weight is located over the front axle than the rear. This is why it is better to have the battery mounted up front. While this makes for a tighter squeeze and is a little harder to access with the body on, the end result is improved weight bias.

The difference between a front weight bias and a low CG is that with a front weight bias, you can have too much of a good thing. A 60/40 split is probably ideal. Like CG, however, it is best to start by moving components as opposed to adding weight.

durability

Durability
There are drivers who can compete in competition after competition and never break a single part and then there are drivers who need every single heavy duty aluminum hop-up offered. Axial has numerous upgrade parts that improve durability, but you don’t need to buy them all at once. For crawlers it’s best to start at the front (aluminum servo horn, aluminum steering knuckles, aluminum steering links) and work your way back (heavy-duty gears, aluminum rear axle lockouts). The only exception to the front to back rule of thumb is driveshafts.

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Ground Clearance
Increased ground clearance allows a vehicle to travel over obstacles without struggling or possibly getting stuck. The axles are the lowest components on the vehicle and the most likely to come in contact with obstacles. Without major modifications, the only way to raise axle clearance is to use taller tires.

Center skid plate clearance is increased when taller tires are installed and when the suspension height is increased. The latter, however, adversely impacts the CG so proceed with caution.

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Speed
Rock crawling has changed. It wasn’t that long ago that rock crawling was literally crawling. Now, competitions are entirely different and you may need some speed, but it depends on the type of competition. The key here is to know what you’re getting into. A G6 competition is going to require you and your vehicle to cover some significant ground in the shortest amount of time possible. A 55-turn motor might be good for climbing, but too slow for the long spaces between checkpoints. If you’re running a G6, consider setting up vehicle so that it’s faster than a brisk walk. In other words, it should be closer to 10 mph than 5 mph. Over 10 mph and you might be giving up more crawling performance than you should, but it really all depends on the terrain. If you’re running brushless, a high voltage, low Kv setup provides the best of both worlds.

If you’re running on a super technical course with extremely challenging obstacles, a slow and torque-based setup might be ideal. Even then, however, having some wheel speed at your disposal can come in handy on many obstacles.

4

Articulation
If you are expecting tips and tricks on getting more articulation out of your Axial Racing vehicle, you’re mistaken. The only thing massive suspension twisting articulation is good for is flexed out photos. In the real world, it will hurt far more than it ever helps you. In stock form, your Axial Racing vehicle has all the articulation it needs. More will just allow it to get twisted up like a pretzel.

This article explains why articulation is often misunderstood and overrated.

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Suspension Stiffness
Rock crawlers generally work best with slightly stiffer rear springs than front springs and you want to avoid an overly soft suspension that easily collapses when side hilling. Most people don’t consider how increasing the weight of the vehicle with hop-ups and accessories might increase the overall weight and thus require stiffer springs. Stiffer suspension also resist torque twist far better than soft, mushy suspensions.

Axial-based Solid Axle Monster Truck Project

guide_monstertruckproject

Solid axle monster trucks patterned after real monster trucks have a long history in R/C. And while these big rigs have been around a long time, it has always been the case that you need to make it yourself to get what you really want. Creative modelers have fashioned a plethora of scale versions of the legendary Bigfoot and Grave Digger trucks and numerous other popular trucks. At the heart of this segment is a creativity that we can all appreciate. Lately, builders have turned to Axial to build high performance competition worthy monster trucks. The most common part they’re reaching for are a set of Axial AR60 axles. One of the early movers in the Axial-based monster truck movement was RC Truck Stop. Their build used a variety of Axial parts. In fact, the drivetrain is just about all Axial. Check out the article and photos below:

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Could you imagine showing up to the track with a 25-year-old RC car? Me either. Like all other club racers, I’m a sucker for having the latest and greatest, and when I wanted to build a new monster truck for side-by-side racing, I couldn’t bear to start a new build with outdated equipment. But, that’s exactly what the vast majority of solid-axle monster truck racers do when they lineup for side-by-side action. I am, of course, making reference to the Tamiya Clod Buster and its legions of loyal owners. I am a huge fan of the Clod, and you probably are too. Tamiya’s classic car crusher is truly iconic and one of the most significant releases in RC history, but while we celebrate its 25th year, it seems odd to race it in anything other than the vintage class. I knew with some tinkering and some creativity, I could build a modern monster for racing.

chassis1

chassisbottom1

CHANGE OF CHASSIS
In my opinion, side-by-side monster truck racing is a lot like rock crawling. Huh?! Lower that eyebrow and let me explain. I see the appeal of monster truck racing being in both the performance and scale appearance of the trucks. As such, many of the race chassis just don’t do it for me because while they perform well, they don’t look anything like a real monster truck’s tube frame. Going the other way, while not all are super heavy, steel or even brass tube frames are generally not very light or built with a low center of gravity. They look great, but aren’t the first pick for racing for a reason. I wanted the lightness of fiberglass, graphite or plastic and the realism of a tube chassis. As such, I went with HPI Wheely King plastic side plates. They are feather weights and look like the real deal. All I used from the stock Wheely King are the side plates. To get a more custom look and inspired by the way the full-size Grave Digger’s chassis is painted green, I painted the frame rails with a plastic-specific spray paint. The cross members I made are solid Delrin rod that I cut to length and drilled for 3mm hardware.

The only possible downside to the Wheely King plates is that they allow a noticeable amount of flex. Even with five Delrin rod cross members spanning the chassis, the finished frame can be twisted by hand. It’s unlikely this will negatively impact handling, but it’s worth noting.

skid1

SKID PLATE
While the frame rails are what most people initially notice, the real heart of the truck is the use of Axial Wraith drivetrain components (axles and transmission). I’ll outline the benefits of the Axial components a little later, but the transmission required a custom skid plate to be fabricated. While I would eventually like to get a higher quality skid plate professionally machined, I was able to fabricate my own out of plastic. I started with some blank plastic stock that I received from my friend and fellow RC’er Tom St-Onge and from Pin Shop Hobbies in Oakville, CT.

When designing the new skid plate, I used my preferred method–CAD or Cardboard Aided Design. In addition aiding in marking the transmission mounting holes, I used the stock Wraith skid plate as a guide for how to position the lower link mounts. Axial’s engineers know heaps more about suspension geometry than I do, so I saw no need to mess with their design. One I had all the measurements I needed, I made cardboard template. And, after transferring the template to the plastic, I cut the template (hacked at times, to be honest) with my bandsaw and Dremel rotary tool fitted with a reenforced cut-off wheel(See safety note below).

WHY THIS WIDE?
The determining factor in how wide I built the skid plate was actually the axles. I wanted to use the AR60’s stock shock mounting positions to maintain as much of Axial’s geometry as possible. So, I built the skid plate to position the side plates about 4″ apart. The link geometry of this truck is the same Wraith with the exception of link length and the upper inner link mounts.

shock

SUSPENSION
As I have said, I took as much as possible from the suspension design of the Axial Wraith. I did vary from the formula when building the link length. I made the links longer to achieve the 13-inch wheelbase I desired. I also made the rear links slightly longer than the front to increase front of center weight bias.

The shocks I used are HPI Wheely King aluminum upgrade pieces. I removed the purple anodizing to make them better fit the look of the rest of truck and filled the shocks with 30-weight shock fluid after rebuilding them using Team Associated Green Slime on the O-rings. I also installed limiters under the pistons to decrease the extended length of the shocks and lower the truck a fairly low race-ready stance. I used Axial shock bushings for the top mounts and trimmed (narrowed) the shocks lower plastic balls to allow them to fit in the AR60 lower shock and link mounts. I used Axial’s aluminum lower link and shock mounts because they offer more adjustability with three holes for the shocks and three holes for the links.

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Most monster trucks benefit from sway bars, but they are absolutely essential on a shaft driven monster truck. I bent and cut music wire in a variety of thicknesses. The music wire is attached to the lower links with cable ties. This is how many people add sway bars to trucks like the Wheely King and is similar to the factory sway bars on Tamiya’s TXT-1.

axlelinks

DRIVETRAIN
The only things Clod Buster about most racing Clods are the axles. While the motor-on-axle (MOA) design of the Clod Buster axles have the huge advantage of no torque twist, the axles were never intended for competitive use. The Axial AR60 axles have many of their own advantages. There is no denying that shaft driven trucks are plagued by torque twist, but it can be tamed and in the case of the AR60 axles, I strongly believe the pros outweigh the solitary con.

AR60 Advantages:
> Streamlined design
> Option of sealed, tunable differentials
> Replacement parts readily available
> Significantly durable
> Wider than most other modern axles
> Easily adjustable caster
> Numerous hop-up parts available
> Easy to service
> Excellent steering geometry
> Easily made straight or steerable
> Gearing options

I installed Axial EXO differential parts (Thank you, Axial) to replace the stock locked differentials. I did this because I preferred actual differentials for this application, but also because No Limit RC–one of the sanctioning bodies I will be racing in–requires front and rear differentials. I have started with simple black grease in the diffs, but thicker grease or silicone fluid is a possibility.

I installed Axial’s heavy duty bevel gear sets, front and rear, and I took advantage of the fact that I could run different gear ratios in each axle. Using an under drive (43T/13T) gear set in the rear axle and the stock ratio (38 to 13) is a common trick used in rock crawling to control torque twist.

While the AR60 axles are wider than most 1/10-scale axles currently being made, I needed a wider stance for racing. I used RC4WD’s 12mm to 12mm aluminum wideners (Z-S0449). These wideners increase the width on each side 1.25-inches for a total increase of 2.5-inches.

AXIAL PARTS LIST*

  • AR60 OCP Front Axle Set >> AX30831 >> (2X)
  • AR60 OCP Machined Link Mount >> AX30830 
  • Aluminum Servo Horn 24T (Hard Anodized) >> AX30835 
  • Heavy Duty Bevel Gear Set – 43T/13T >> AX30402 
  • Heavy Duty Bevel Gear Set – 38T/13T >> AX30395
  • WB8 Driveshaft Set (2pcs) >> AX30794 
  • Differential Bevel Gears >> AX30390 >> (2X)
  • Differential Shaft >> AX30170 
  • Differential O-rings >> AXA1162 
  • AX10 Locked Transmission Set >> AX30487 
  • Steel Outdrive Shaft Set >> AX30435 
  • AX10 Slipper Clutch Set >> AX30414 

 *List does not include all possible parts and hardware needed as builds can vary

axles

STRC PARTS PACKAGE
There are a number of manufacturers that offer aftermarket parts for the Axial AR60 axles (Axial included). One of my favorites is STRC. The reason I like STRC is they make a wide variety of direct fit aluminum parts with a quality finish, and best of all, the parts are durable. Since the axles take a real beating on a truck like this and because I wanted rear steer, I upgraded the axle C’s and knuckles with STRC’s aluminum pieces. I also replaced the plastic diff cup retainers and diff covers. My upgrades didn’t end there. I added STRC’s upper link mounts and aluminum steering links.

STRC PARTS LIST

  • CNC Machined Precision Aluminum Steering Knuckles for Axial Wraith (1 pair) Black >> STA80061BK >> $31.99 (2X)
  • CNC Machined Precision Alum. C-Hubs for Axial Wraith (1 pair) Black >> STA80062BK >> $30.99 (2X)
  • CNC Machined Alum. HD Diff Cover for Axial Wraith (Silver) >> STA80070DS >> $15.99 (2X)
  • CNC Machined Alum. Internal Diff Holders (1 pair) for Axial Wraith Silver >> STA80070S >> $$15.99 (2X)
  • CNC Machined HD Alum. Front Servo Mount Block/Upper link mount, Axial Wraith (Black) >> STA80072FBK >> $23.99
  • CNC Machined HD Alum. Rear Upper Link Mount, Axial Wraith (Black) >> STA80072RBK >> $23.99
  • CNC Machined Aluminum Servo Mounts (1 pair) for Axial Wraith (Silver) >> STA80072SS >> $14.99 (2X)
  • STRC Heavy Duty Aluminum Steering linkage set for Axial Wraith (Silver) >> STA80073S >> $12.99 (2X)

rumbletires

GETTING GRIP
In RC racing, I often preach that tires are the single most important part of setup, so why would a monster truck built for racing be any different? To get improved traction over the stock rubber, I selected RC4WD Rumble tires (Z-T0015). These are direct a fit on the odd ball sized Clod Buster rims. The Rumble tires look like shaved full-size monster truck tires in that the backside of each lug have been removed. The compound is significantly softer than stock, and the tires include foam inserts. Even though the Clod rims have vent holes, I added three small additional holes to the tires. The goal is to allow the tires to compress and distort when landing or cornering without causing bounce or not returning to their proper shape immediately.

bodyon3

BODY
Traditional thought is that looks don’t matter in racing, but you better believe appearances matter in monster trucks. Looks may never win a race, but the body on a monster truck is its personality–the basis of its persona. I envisioned a truck that looked bad to the bone, but wasn’t a dime a dozen like RC Grave Diggers. And, I wanted to avoid a typical pick-up truck body, so I selected the ’55 Bomber body (182) from McAllister Racing. This gives my truck the styling of the popular Advance Auto Parts Monster Jam Avenger truck, but the simple black paint job sets it apart. The McAllister ’55 Bomber body is a little wide, but is otherwise perfect for this application.

motormount

MORE MOTOR
As much as I personally love solid axle monster trucks, the reality is that this segment isn’t short course racing. What I mean is there isn’t a race class at every hobby shop. So, I have to go where the racing is and play by their rules. And, that’s where it gets complicated. To maximize my potential racing opportunities, I designed this truck to be able to compete in No Limit RC competition and at RC Monster Truck Race Series (RCMTRS) races. Both series require 2.6-inch Clod rims, but the similarities between the rules pretty much end there. Ironically befitting the name, No Limit RC has no wheelbase or track width limitations. In contrast, RCMTRS limits wheelbase to 14″. For now, I’m sticking with a 13″ wheelbase but may change to 14″. More on that later.

The biggest dilemma I faced was that No Limit RC requires dual motors and RCMTRS does not. I’m not a big fan of running two motors when one can get the job done, but I needed to be able to comply when needed. I installed Level3-RC dual motor mount for the Axial transmission. Level3-RC makes two versions, and I selected the one that positions the motors one on top of the other because it makes for the most compact arrangement.

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servo

ELECTRONICS
After an initial round of testing, it was clear I needed to go with a sensored brushless system for my single motor setup. The local RCMTRS affiliated club, RC Monster Truck Challenge of NY, limits motors to 5700Kv and limits the battery to 2S as opposed to no motor limit and a 3S limit outlined by RCMTRS. At first I tested with a sensorless 5700Kv 4-pole motor just to push the suspension and general setup. The low speed hesitation (often referred to as cogging) was unbearable, so I installed a Duratrax DE10 speed control (DTXM1300) and a sensored Duratrax 8.5-turn motor (DTXC3425) which is rated for 4450Kv. To tap into the full potential of this speed control, I also used Duratrax’s handheld digital programmer (DTXM13500).

With 4WS, I needed exceptionally strong servos, so I bolted in Hitec HS-7950TH servos (37950S). These servos feature coreless motors, titanium gears and deliver 403 oz./in. of torque at 6V and can put out 486 oz./in. of torque on 7.4V.

To control the truck, I went with a Spektrum DX3R Pro. This 3-channel radio is easy to program and allowed me to quickly setup my on-demand rear steer. I programmed Switch B which is normally used for steering trim (moved to switch C) to control my rear steer. Switch B is easy to reach while driving and I have to set up in such a manner that when turning right I flip it to the right for more steering and vice versa for turning to the left.

Because the battery sits high, I am using a MaxAmps.com 3250mAh 2-cell (part no. varies). This pack is incredibly thin and lightweight, but will easily keep up with the power needs of the truck and offer plenty of runtime–more than enough considering I’ll be doing side-by-side runs.

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PERFORMANCE
Since this project is more of a custom creation than, say, a modification of an existing platform, I was exceptionally eager to test it. While the concept seemed sound in my head, there were no guarantees that it would even work. My first tests quickly proved that my fear of torque twist was very real. Adding sway bars, as planned, immediately helped, but were not enough. I even doubled up the rear sway bars at one point. I also experimented with extremely stiff spring setup on the right rear and left front shocks. While stiff springs can be used to tame the torque twist, jump handling is diminished too much for this to be a viable solution. Ultimately, I installed the under drive gears in the rear axle and switching to the milder Kv motor. With the rear axle geared lower than the front and the slightly lower Kv motor (also less torquey 2-pole), the truck was pretty close to dialed. Thicker sway bars are needed and in the works. I simply underestimated how thick the wire needs to be to control torque twist at launch.

Further testing included a short run on carpet at Pin Shop Hobbies in Oakville, CT. My impression of the truck on carpet is that it handled extremely well, but covers a lot of ground quickly. Quickly enough to make me nervous. I didn’t hit anything too hard, but I now know what the full-size drivers feel like when racing in the small arenas. While not every carpet track is the same, I was surprised how well the truck rotated on the fuzzy stuff.

My first real test that featured some competition took place at a Touch-A-Truck event that the Eastcoast RC Trucks club was participating in. In addition to demonstrating the truck, I raced it on the club’s timed course. Even while running at a fairly conservative pace, I was happy with how competitively the truck performed. My times were among the fastest recorded and I wasn’t running all out. After the timed runs (I ran two official runs to settle a tie-breaker), I started to get braver with my freestyle antics. The truck jumps great and responds extremely well to throttle inputs. It also recovers well from less than perfect landings. If you’ve ever driven or seen a truck like this run, you know how much fun watching one handle like the real trucks.

Only once during my day of time trials and freestyle, did I encounter any sort of breakdown. A particularly nasty end-over-end landing popped the front steering link off. I snapped the rod end back in place, made a mental note to add a washer as a retainer and was back on my way. But, speaking of breaking stuff, previous to the Touch-A-Truck, I did have some minor parts carnage. The early victims were the body mounts. Even though the body mounts are fairly short, the thinner 1/10-scale touring car style ones I first tried pretty much instantly broke. So far, the slightly beefier replacements have held up, but I’ll be watching them and thinking of an even stronger solution. I also broke the original Clod Buster rims–all four. I have no idea how old these rims were, but they didn’t last too long. Pin Shop Hobbies came to the rescue with a set of new Clod Buster rims from Tamiya. The “un-aged” ABS have worked out great and withstood all sorts of abuse.

The best way to describe the overall experience of driving this truck is that it’s fun. I know that’s vague, so to be more specific, it drives, reacts and generally behaves like a real monster truck. All of that makes it–a lot of fun. It’s a handful off the line when too aggressive with the throttle, but I’m working on that. As described above, jumping is a blast. Hit a jump square and it flies perfect, is easy to control and lands on all four without even the slightest bounce. Fly through the air crooked and it’s even more fun as you land one wheel first, bounce the front up and power out like the real deal.

Unlike most race Clods, this truck has rear steer. The rear steer adds to the fun, but I have to admit I largely ignore it even though I have the rear steer throw turned down to less 25% of the front steering. I’d have to get tons of wheel time and develop some real synergy with the truck to use it in racing, but it rocks in freestyle type use.

While the testing will continue and I will certainly learn even more when I race it side by side with other trucks, I can say I am highly satisfied with the truck thus far. At this early stage, it isn’t perfect, but this truck clearly has potential to be a legit racer.

FUTURE PLANS
While I’m sure there will be changes that I can’t predict as getting more real racing experience with the truck will show what needs to be done–or not done. I do hope to have a skid plate professionally machined. I would also love to have new side plates cut out of G10 fiberglass. My design for the fiberglass side plates would mimic a tube frame and the look of Wheely King plates, but will have more tuning options for the upper shock mounts and upper link mounts. Even better, it will be more durable.

I also plan to cut down the lugs of the RC4WD tires and balance the tire and rim setup. While these tires are proven to be exceptional thus far, I would like to also try Imex’s Baja tires for the Clod Buster rims.

The one item I am on the fence on is the rear axle and whether to keep the rear steer or go with a straight axle. On testing and experimentation will reveal which is best. I have lightheartedly dubbed this project the Clod Killer or CK-1 as it’s the first version. Maybe CK-2 will be based on the Axial XR10 if I can talk someone into making a differential for the axle.

Grassroots Competitions

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No events near you? No worries. You don’t need a hobby shop or RC club in your town to get in on the fun of RC competition. Don’t join in on the action, start the action. Check out these alternative ways to get competitive with your Axial vehicle. One bit of advice before you tear off: keep the rules simple and the focus on fun.

Backyard Racing

Rock racing is growing quickly, but not every hobby shop has a course. Most hobby shops don’t have traditional race tracks. If you want to race your Yeti across more than the lawn, the best solution might be to to make your own rock racing course. If fact, it’s far easier to make a rock racing course than race track. You’re really only limited by your imagination. The whole course doesn’t need to be rocks. Collect a few wheelbarrows full of rocks of varying sizes to create the rock section. Use dirt to build ramps up onto the rocks. Use a little more dirt to fill in the bigger holes and gaps in the rock piles and you’ll be good to go. Like desert races such as the Baja 1000, a race like the full-size King of the Hammers doesn’t have clearly defined lanes, so don’t worry about creating and grooming a whole track layout. Make your rock section and mix it up with the go-fast sections. A few cones placed around your yard can search as gates that have to be raced through in a certain order. Your homegrown King of the Hammers doesn’t have to be in your backyard. Scout out local parks. Many have rocky sections of naturally exposed rock or areas filled in with rocks. To keep it safe, make sure you’re away from other people.

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Truck Pulls

While they are extremely cool, you don’t need an official pulling sled with a moving weight box. A dead weight box is easily made out of wood and good old fashioned tug-o-wars are a lot of fun. Dead weight pulls are best on smooth, level dirt. Make sure you’re prepared to groom the track as needed to keep it fair. Dead weight pulls can work two ways. You can load a box with a modest amount of weight such as one or two bricks and time each truck to see how fast they can pull the weight 10’ to 12’. The key is to use a weight most if not all of the vehicles will be able to get a full pull with. The other way is to start with more weight, measure the distance of pull and add weight for the vehicles that do get full pulls. Generally, the first method works best with a dead weight sled. When doing simple tug-o-war contest, pavement actually works best. On loose dirt, both vehicles often end up in a wheel spinning stalemate. Make sure you practice commonsense safety measures when having a tug-o-war.

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DIY Scale Rock Crawling Comps

If there isn’t a scale club near you or if the local outfits aren’t offering what you want, you can host your own competitions. You might find out you’re not alone. One example of DIY scale competitions done right comes from the east coast. Eric Bresnahan of Connecticut and a couple friends started building a course on a dirt mound out in the woods. As their course grew, so did the crowds. Now, 40 people sign up for 1.9-tire based class. They have to cap the classes to keep the day manageable. And, they keep the rules simple and focus on having fun. As a result, hours after announcing a new comp has been added to the calendar, the classes fill to capacity. Many hobby shops and clubs wished they had that problem. The courses are carved into the dirt with a shovel, rocks and some manmade obstacles are added as needed and the whole thing is again only limited by their imagination. The group has also made good use of social media to grow. Almost all of the club’s communication is done via Facebook. As long as you’re extremely careful and exercise common sense safety measures, social media is a good way to find other people interested in RC competition.

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Alternative Racing

There are a lot of times when things are done a certain way simply because that’s the way it’s always been done. RC racing is often a perfect example of this. Many people stop racing just because they’re bored. Sometimes the focus is far too much on the competition and not on the fun. Nothing changes because people are so used to doing it a certain way. Nothing changes and racers disappear. Some inventive racers in southern California have come up with an interesting twist on the racing format. Two changes make for a very different racing experience. First, after each race, the running order is reversed. Finish first and you’re going to the back of the pack. In a big field, it pays to not break away if you don’t want to have to contend with trying work your way through the entire field on the next race. The second twist in the program is each race goes in a different direction. Talk about really mixing things up. They also allow you to jump in at the start of any race. It doesn’t matter if you missed the first three races. Again, the focus is on fun, not determining who’s the world champion.

Rock Racing Class Selection

guide_rockracingclass

R/C is a hobby, and a fantastic and fun one at that, but there is also a competitive side—most often in the form of racing. R/C racing has been around just about as long as there have been R/C cars. Racing first took off in parking lots on temporary tracks. As a whole, the hobby has come a long way from the days of parking lot racing. Today there are all sorts of type of competitions. The rock racing segment is a prime example of the awesome variety available. You can learn more about rock racing here. Getting started in racing or even just a segment new to you can be a bit daunting. One of the biggest questions is what class does my rig belong in and what are the rules. Using U4RC as the guideline, here is a breakdown of what class you can expect to compete in at a rock racing event with your Axial Racing vehicle.

scx10

SCX10
If you have an Axial SCX10 with stock or stock-sized 1.9 tires, you can run and be competitive in the 1.9 Trail Limited or 1.9 Trail Pro classes. The 1.9 Trail Limited class is suggested because it is limited to solid axles only and the competition will not be heavily modified.

27t

The 1.9 Trail Limited class only allows for 2S LiPo and motors are limited to 21-turn brushed motors or 18.5 2700 Kv brushless motors. The SCX10 RTR models include Axial’s 27T motor is within the legal limit for 1.9 Trail Limited. While the 27-turn motor will be slower than other motors allowed, your RTR SCX10 won’t require a motor change to compete.

Motor selection can be a little tricky if you don’t know how the motor nomenclature works. When a motor limit is set at 21-turn, such as in the U4RC 1.9 Trail Limited class, the rule is indicating that 21-turn and higher motors can be used. The fewer turns a motor has the faster it will be compared to a similar motor with motor more turns. If the motor limit rule indicates a brushless Kv rating such as 2700 Kv, the  legal motors are 2700 Kv or lower. This is because the higher the Kv rating, the faster the motor.

The 1.9 Trail Pro class removes the battery and motor limits, but is still limited to solid axles. This class will feature more heavily modified vehicles.

2900 kv

The Vanguard 2900KV brushless motor is legal for the 1.9 Trail Pro class and is an excellent motor for this class.

yeti

Yeti
If you have a stock Yeti, the Yeti Limited class is the perfect class. The rules do allow you to upgrade the servo and servo horn, but the rest should be stock.

The next step up is the Yeti/EXO Pro class. There are no motor and battery limits. EXO Terra Buggies will need to be fitted with 2.2 tires to be competitive.

Heavily modified Yetis and EXO Terra Buggies are ideal for the Trophy 2.2  class. Metal cages are required, so this class is for more advanced racers.

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Wraith and Ridgecrest
The 2.2 Competitor Limited class is limited to solid axles only, so this class is ideal for the Wraith and Ridgecrest. The U4RC rules even state, “This Class is designed for RTR and kits with Axial only parts.”

3150 kv

The 2.2 Competitor Limited class does restrict motors to 3150 Kv or less, but 550-sized motors are allowed. This means the Axial Racing Vanguard 3150KV is an ideal choice. This motor is loaded with torque and delivers more than enough speed.

The 2.2 Competitor Pro is also an option, but this class will be faster, so it is recommended that a Wraith and Ridgecrest receive some attention before entering this class. This class is ideal for a modified Wraith.

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Yeti XL
Even though the Yeti XL RTR can handle 6S, the Yeti XL class is limited to 4S to keep speeds reasonable.

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Don’t Stress
U4RC is understanding that many people may be building rigs without a real understanding of their specific rules, so they will allow anyone to compete the first time they show. They will review the rules and your vehicle and explain what needs to be done to comply with the rules. Violations will not be an issue for the first race day, but will be expected to be resolved for the second race.

Axle and Suspension Designs Explained

solid axle articulation

Axial Racing vehicles are patterned after full-size off-road vehicles, and at Axial, scale realism is more than skin deep. That means that Axial’s RC models are more than just realistic bodies on top of universal or generic platforms. The SCX10, for example, features solid axles and a linked suspension. The EXO Terra Buggy, on the other hand, has what is called independent suspension, front and rear. The Yeti has independent front suspension and a solid rear axle. In addition to axle types, there are different suspension types found on the same axle designs. Here are the basics of axle and suspension designs and what they are generally best for. sc10 solid axle

Solid Axle

The solid axle gets its name from the solid axle housing that goes from one side to the other, not the axle shafts inside. The internal axle shafts aren’t actually a single solid piece going all the way across. Inside the housing, there is an axle shaft on each side. This is true in the full-size world and with Axial axles. Axial’s design is extremely similar to a real solid axle. The AX10, SCX10 and Wraith all feature solid axles front and rear. The SCX10 features a narrower axle design; the Wraith platform and the current AX10 feature Axial’s wider AR60 axle that is the RC equivalent of a full floating 1-ton design. wraith solid axle

Often the terms live axle and solid axle are used interchangeably. Most solid axles are live axles, but they aren’t the same thing. A live axle is any axle that is powered and not free rolling. When rock crawling, the solid axle is often the preferred design. In addition to the durability solid axles are known for, they also don’t lose ground clearance as a tire is pushed up during suspension articulation. The easiest way to visualize this to grab a pen or pencil and imagine it is a solid axle. Tilt one end up and over an obstacle and you can see how by driving tires up and over obstacles makes maintaining ground clearance easy. This exercise also makes it easy to see why it’s often best to place tires on rocks in the trail instead of trying to straddle them. independent

Independent Suspension

Independent suspension means the two opposing sides work independently from each other. If the right front tire hits a bump, the left front tire is not impacted. When speed is involved, the independent suspension is a better choice as it provides a much smoother ride. Keep in mind that when a tire on an independent setup encounters an obstacle, the tire and suspension components travel up, but the vehicle typically doesn’t. This allows the vehicle to go over rough terrain at a fast rate and remain stable. Picture all of the wheels moving up and down independently as a truck races across a desert terrain. The downside is when traversing rocks, the center section of the chassis will stay low to the ground as the tires move up and over rocks. Many full-size trucks have independent front suspensions (IFS) paired with a solid rear axle. This used to be common on only 2WD trucks, but is essentially the standard for the majority of factory trucks. There are many SUVs that have front and rear independent suspensions.

 

scx10 aluminum 3 link

3-link

A solid axle can be attached to the frame or chassis of the vehicle in a number of ways. Probably the oldest and simplest way is via a leaf spring setup. Vehicles that are engineered for better ride quality and articulation (suspension movement) now use coil springs. Using coil springs, however, requires the axle to be held in proper position (and still articulate or move). This is done via links. There are a variety of link setups. A 3-link setup, as the name implies, uses three links to connect the axle to the chassis. Take the SCX10, for example, the front suspension setup has two bottom links and a single upper Y-shaped link. Since the upper Y-shaped link attaches to the axle at one spot, this is called a traditional three link setup. To add a degree of confusion, the name a suspension design gets isn’t always based on the total number of links. This is because some suspension designs, even in R/C, will have a pan hard bar (or track bar) that helps locate the axle under the vehicle and keeps the axle housing from moving from side to side. So, someone may say they have a 3-link setup with a pan hard bar. This is a total of four links. It’s worth noting that a link design that is properly triangulated will not need a pan hard bar.

 

wraith 4 link

4-link

The Wraith uses a traditional triangulated 4-link suspension design. A close look reveals that at the axle the lower links are mounted far apart and then closer together at the chassis. The opposite is the case for the upper links, which have an even more pronounced triangulation. This design properly positions the axle, allows for plenty of articulation and is very strong. The previously mentioned Wraith has a 4-link setup front and rear. Depending of the particular version, you are most likely to find a 4-link rear suspension on the SCX10. The Yeti uses a 4-link rear suspension. And, the current AX10 platform, Ridgecrest and Deadbolt, use 4-links front and rear. The XR10 competition crawler also uses a 4-link design front and rear.

 

Example of an IFS and 4-Link vehicle: Yeti XL