Rockin’ Crawlin’ Revo?
One of the most impressive features of the Traxxas Revo is its suspension travel. Believe it or not, most Revo owners aren’t even coming close to experiencing the full potential of this incredible suspension system.
Generally, my articles point out ways to improve lap times on a racetrack, and show how to set up your truck for increased durability and ease of use. This time I’m going to show everyone, what I believe is, one of the absolute coolest things to do to your Revo - turning it into a rock crawling monster.
Rock crawling is a great way to experience the Revo’s endless suspension travel maneuvering and literally wrapping itself around the terrain. It’s really like no other nitro R/C vehicle. What’s really cool about this project, is the most important factor in this conversion (the long-travel rocker set) is included right in the box with every new Revo. I’ll show you what I did to my Revo-crawler for when I want to take a break from the track and just relax out on the rocks.
Preparing your Revo to crawl
Rock crawling is an art form that requires your suspension system and drivetrain to perform under extreme conditions. Below, I’ll explain what to do and why.
The long-travel rocker set is a must for getting the most out of the suspension system. Rock crawling is all about obtaining the maximum amount of traction in the most extreme situations. The long-travel rocker set delivers 120mm of travel to keep the tires in contact with the surface at all times.
The long-travel rocker set is included in the instruction pack that comes with every Revo, and is very simple to install. Each rocker arm is clearly marked for its designated corner. They also use the same pushrods as the P1 rocker set, which is what is installed on the Revo from the factory. Simply replace each P1 rocker arm with its long-travel counterpart, and you’re done.
I chose the stock (long-travel) spring set included with the Revo for my project crawler. This spring set performed great for most situations that it encountered. I installed the silver springs up front and the blue springs in the back. Hard impacts are usually not experienced when Rock crawling, so softer springs can also be used to further increase the plushness of the suspension.
I chose to use the #1 pistons all around for faster damping, and refilled the shocks with the stock 30wt shock fluid. Damping performance for crawling needs to be little on the light side to help get the tires back to the rocks’ surface as quickly as possible, and to respond to on coming rocks in the same manner.
Speeds during rock crawling are rather slow, so there are really no adverse effects from light damping. This also means that the shock fluid will not heat up as much as it would under general running conditions.
7075 aluminum push rods part #5318X
These new aluminum pushrods and toe-links from Traxxas aren’t totally necessary for rock crawling, but man, they sure look sweet when watching the suspension arms stretching out over the rocks.
7075 aluminum toe-links part #5338R
|To get the most up-travel available from the suspension, I chose to remove the blue bump-stops from each shock shaft.|
|I set my Revo-crawler up with the pushrods located in the inner position on the lower suspension arm for maximum down travel. Even though it is recommended to use only the middle position with the long-travel rockers, it is ok to use the inner position without any negative side effects. That recommendation was based on extreme angles being adjusted into the camber and toe settings, in which I will not be using.|
Crawling requires all four wheels to be driving all of the time to ensure that whichever wheel has the most traction has the power to move the vehicle. The use of a differential is this case will transfer the power to the wheel with the least amount of traction. This will leave you spinning you wheels virtually immobilized.
It’s best to replace your differential with a solid spool. I installed Traxxas part #5381X (spool) in place of both the front and rear differentials. Caution must be taken when driving your Revo with spools.
Important: Spools cause extra stress to most of your driveline components, so only use spools in low traction conditions to avoid drivetrain damage. Larger tires will also add to the stress levels felt by the driveline, so if you intend on using the same truck for crawling and for bashing on a variety of surfaces, you may want to try using a very heavy weight diff fluid in the differential instead of a spool. This will slow the differential action way down to help with traction on uneven terrain while still maintaining the action of a diff to relieve your driveline of the extra stress induced by high traction surfaces.
Check with your local hobby shop for their selection of heavy differential fluids.
|Revo Spool #5381X||Option: Fill the diff|
with heavy diff fluid.
I recommend the heaviest available - 100Kwt
There’s only one word to describe what kind of gearing is needed for rock crawling, Low. For climbing and tugging on large inclined rocks, a low gear ratio is a necessity for pulling the truck up and over. It’s especially important for any nitro-powered crawler, which greatly depends on engine rpm to provide torque.
I went with the smallest clutch bell gear that Traxxas offers, the 14t bell (part #5214), as well as the 40t spur (part #3955), which is the largest spur gear for the Revo. There may be aftermarket gears available for the Revo to gear even lower by the time you read this, so check with your local hobby shop for what’s available.
Engine & Slipper settings
While on the subject of gearing, I would like to comment on the slipper adjustment. I initially felt that a fairly loose slipper setting would be better suited for crawling. This will be a good way to allow the rpm to rise, thus increasing the torque of the engine. That it did, but as you may have guessed, the power was there but the slipper would allow too much of the power to be wasted in the slippage.
I found that it was actually best to set the slipper to where it was a little on the firm side to prevent excessive slippage, so that most of the power would be distributed to the wheels where it needs to be. Instead, the focus should be gearing and traction for best results.
It’s also very important to have the engine tuned for crawling conditions. This means tuned for the best bottom-end performance possible. Before approaching a rock or a desired crawl path, clear the engine first by either driving the truck around at a decent speed before approaching the rock, or just pick the truck up and throttle the engine to clear it out.
To get maximum traction on the rocks, full-size rock crawlers are known to run as little as 10lbs. of air pressure in their tires. That’s really low. This allows the tires to flex and bend easily increasing traction.
This same kind of performance advantage can be tuned into your R/C crawling tires as well, by trimming the foam inserts down to allow the tires to flex. The more material trimmed off, the more traction acquired, but at the expense of hindering high-speed handling. This is something to keep in mind for those of you who intend on using the same tires for general bashing. The insert shown below has been trimmed to increase traction, but with enough material left for ample support during high-speed operation. For all-out traction, try removing the inserts completely.
There are many different wheels available that will serve the purpose of rock crawling without any trouble, but why not go for something that looks like a rock crawling wheel? I found a set of Maximizer BeadLock wheels which are the perfect fit for my project Revo-crawler. They’re available in different colors, but the blacked-out look is the way to go. I chose the 5-hole BeadLock wheels designed for the T-Maxx?, but they also work on the Revo without any problems.
The Maximizer BeadLock rims are a true BeadLock design that actually pinches the tire’s bead between the separate wheel components to ensure that the tires do not slip during the rigors of off-road abuse. This also eliminates the use of tire glue, which permanently attaches the tire to the rim. The BeadLock rims, tire and insert changes can be made without having to go through the tedious process of using solvents to remove tires, or the worst-case scenario of having to buy all new stuff just to try something different... plus, they just look too sweet!
It’s important to have ample clearance between the body and the tires when negotiating large rocks and crevices. This prevents the tires from rubbing on the body at extreme angles.
Lifting the body for my project required longer body mounts than what came installed on the Revo. Although there are optional extended body mounts available from various aftermarket companies, I chose to make my own with parts I already had in my workshop. The T-Maxx body mounts worked perfect for the front and rear, and was very easy to install.
Front body mount
I used the rear body mount posts for the T-Maxx (part #4914) to lift the body on my project Revo-crawler. Just remove the stock Revo body posts, and flip the T-Maxx rear body posts upside down to insert the top of the posts into the Revo body mount (shown at top left). Next, secure the posts to the mount with a 3mm screw and locknut (shown at top right). Finally, use the T-Maxx front body retainer, as you would on the T-Maxx, to keep the body in place on the posts. Bingo.
Rear body mount
|I stacked three EZ-Start® receptacle retainers on top of the stock Revo body mount to raise the receptacle up to the surface of the lifted body.|
This is basically the same modification that I have explained before in previous articles. There are two molded bump-stops designed into the Revo cross brace (part #5343) that straddles the steering bell crank. These stops limit the travel of the steering arm, which was designed to keep newer drivers from over-steering the truck.
With the stops ground down (shown above), and the the bell crank arm beveled shown below, the steering angle of the wheels is significantly increased for better steering. This is very important for crawlers with locked diffs, or spools.
|Tip: Install the Traxxas heavy-duty servo saver spring (part #5344X). This is generally reserved for high-end servos, but the low speeds of rock crawling should pose no problems for the twin stock Traxxas 2055 servos.|
Rock crawling can be hard on the silver finish of the stock bumpers, so I decided to strip them of the silver paint using acetone and a little elbow grease. This left a nice flat-black finish that complimented the black Maximizer BeadLock wheels.
I actually use a rear Revo bumper and bumper mount up front to position the bumper further out, which will help keep the truck from flipping over forward during steep downward crawling. It also offered more clearance from the body than the stock front bumper. I reshaped the rear bumper for the front (to look more like a front bumper) with my Dremel? tool (shown above).
I hope you enjoyed learning about my project Revo-crawler as much as I enjoyed putting it together. This has been one of my favorite projects. There’s just something about rock crawling vehicles that are so cool to me. The gnarly looking tires with beefy BeadLock wheels coupled with the amazing suspension system and versatility of the Revo, makes this project so special.
As for bodies, I’m a big Jeep? fan, which explains the Rubicon body on my own personal project crawler. However, there are many different off-road and rock crawling bodies available at your local hobby shop. Check with your local dealer to find out what they can get for you.
Well, that’s going to wrap it up for this story. I’ll leave you with another sweet pic, and some awesome video of this particular Revo in action. See ya!!!