What are some of the qualities we typically desire in an RC crawler? Okay, there are a lot, so I’ll spare you the guessing game and get right to the particular traits I have in mind–ground clearance, low gearing and strong drag brakes. If you have any experience crawling you know the benefits of the aforementioned characteristics, but you may not realize you can fairly easily get all three–rock clearing ground ground clearance, hill climbing low gearing and drag brakes for precision driving–with one modification. As I’m sure you’ve already guessed, the one mod that does it all is the swapping in of Losi Comp Crawler axles under an Axial SCX10 (oh, the title was such a spoiler).
ABOUT LOSI COMP CRAWLER AXLES
The Losi Comp Crawler axles do not use traditional ring and pinion gears. Instead they use what is called a worm drive. The absence of a tall ring gear allows for a very trim axle shape. This greatly increases ground clearance since there is no big center “pumpkin.” This ability to drive over what others would get hung up on is a huge performance advantage and probably the main benefit of switching to Losi Comp Crawler axles.
The Losi axles also provide really low gearing. If you need climbing power, these axles are a great choice. The worm-drive ratio is 25:1. This means the axles will rotate once for every 25 times the driveshaft spin. In comparison, the stock Axial axles use a 3:1 ratio. That’s a huge difference. The downside is your once somewhat-fast scaler will make a turtle look like a Lamborghini. So, if you need/want speed, these axles may not be for you. For example, if you use Axial SCX10 as your hiking partner and need it to cruise along at your walking pace for extended periods of time, even with a gearing change and a high-zoot brushless setup, these axles may not suit your needs. If, however, you compete on technical coureses that have a lot of difficult obstacles, these axles will give you advantage over the competition.
Unlike most other gear arrangements, worm drives do not free spin. They must be powered to move. This means the Losi Comp Crawler axles provide instant drag brakes. Not only are the drag brakes instant on, they are as strong as you’ll ever need. If you want precise control on hills–going up or down–the Losi axles are a good choice. If you do comps with your scaler, these axles will, again, give you an advantage.
Losi offered its worm drive axles in the previously mentioned Comp Crawler and its more sport-tuned Night Crawler. The Comp Crawler was sold as a pre-built “Race Roller” while the Night Crawler is available only as a RTR. While there are a good number of differences between these two crawlers, Losi Senior Project Manager Richard Trujillo confirms the axles are identical. Richard points out that the Night Crawler uses a molded plastic steering setup, but whether you use the Losi steering links–plastic or aluminum–is entirely up to you. Richard also added that Losi offered a Heavy-duty Worm Gear Set that had a 21:1 ratio. This set has been discontinued, but you can sometimes get lucky and find them out there.
GETTING THE GEAR
If you’re still reading, you’re probably sold on the idea of installing Losi Comp Crawler axles under your Axial SCX10. Great! Oh, but wait, now there is the problem of getting a set of these axles. Unfortunately, the Losi Comp Crawler has been discontinued. The Night Crawler is an option, but a new truck will set you back $300 and you only need the axles. Time to cruise the buy and sell forums? The problem with picking up a used Comp Crawler or Night Crawler is that you will still be paying for more than you need and you run the very big risk of paying good money for trashed parts. The solution I used is a company called RC-Recycler that specializes in used RC parts–all sorts of RC parts. Not only do they have a huge selection, but you know you are getting exactly what you’re looking for. Speaking of looking for something specific, make sure you source the latest version Losi offered as running changes were made to improve the gears.
While the Losi axles aren’t a direct swap, per se, they are pretty close. My swap was both easy and complicated at the same time. The rear axle was easy because I had already converted my SCX10 to a 4-link setup. Removing the stock axle and installing the new axle took a few minutes. I mounted the shocks to the outside of the mounting tabs instead of between the two tabs for a double-sheer mount. The lower links are still mounted double sheer, so I do not believe any real durability is being sacrificed. If you decide to install these axles, you may or may not have to experiment with different length links–not really a big deal.
In front, I have a chassis mounted servo setup (Hand Brothers Off Road) that has a 3-link with a panhard bar configuration. The front required a little bit of tinkering to get right. And, then some more tinkering when I realized I didn’t get it right the first time. Also, as I did on the rear axle, I mounted the lower shock to the outside of the axle tabs. While the front took longer, I believe I have the new setup working better than the old.
First impression? Holy smokes there is a big difference in gearing. Other than some brief runs, the first real test of my new setup was at a weekly scale competition at RC Madness in Enfield, CT. The axles worked great, but the lack of wheel speed killed me. It was just too slow to pop over some obstacles, and I had already switched from 2S to 3S for the extra voltage. I have a Novak Crawler 18.5 brushless motor installed. This motor has served me well, but a 13.5 or faster brushless system may be in order.
While I had underestimated how much I’d miss the wheel speed, the benefit of the added ground clearance was immediately noticeable. A truck that gets hung up less is simply a more capable rig–less equals more in this case. My SCX10 was a pretty dialed in scaler before the axle swap, but I could see how the extra ground clearance paved the way so to speak for even more performance potential. On many courses, other trucks scratched and clawed their way in an attempt to make progress, racking up penalties along the way, while my truck often made its way like it was cruising on asphalt.
For the next comp, I installed the biggest pinion I could squeeze in without a spur gear change. This small alteration made a big difference. I may make further changes, but I am holding off until a motor swap is made. I may even switch to a 4S setup. I did notice the axles got very hot after a 10-gate course. I plan to clean out whatever grease in there now and use a liberal amount of high-quality marine grease. Worm drives are inherently inefficient and heat is a byproduct of that inefficiency. Even though the gears in my mind were spinning thinking about doing this or that for the next time, the worm gears played a big part in me taking first place overall in Class 2. This comp was a trophy event, and while I didn’t take first on any of the individual courses, I was consistent enough to get the overall win.
Overall, I have been very happy with this modification, and I’d certainly recommend it. Just know what you’re getting into. Read this article a few times and make sure this mod is right for you and how you use your RC truck. RC-Recycler delivered a high-quality product that was in the exact condition described (mine barely had a scratch on them) and they did all of this promptly and for a fair price. I’m not sure if the final cost was higher than I could have found from a private seller, but knowing I wasn’t getting scammed was well worth any potential price increase. If you’ve bought used RC gear or have done trades, you know all too well that descriptions aren’t always accurate. Using RC-Recycler removes that variable from the equation.
Some photos supplied by Losi and RC-Recycler