Beat Your Truck - Project RC Rock Crawler

We hope you enjoy "Project Rock Ripper". We started this project as rock crawling newbies and still have a lot to learn. Throughout the project pages, you will see what we did with our truck and we will also try to list some alternatives to get the job done. Our hope is that by providing some alternate methods to acheive the same end goal, more people will tackle a project like this and get into crawling!

FIELD TESTING / PERFORMANCE

TIME TO SEE WHAT THIS THING CAN DO!

The bad thing about living in Wisconsin is the weather. The evening we finished up the crawler project, it decided to snow outside! All of our premium rock piles were covered by 5 inches of the white stuff.

HEADING BACK TO THE WOOD SHED

So we were forced to begin our testing in the BYT shop. We started with a pile of tires and that seemed to be a decent challenge however with rubber tires grabbing rubber tires, we felt this was giving our truck an unfair advantage. It was easily able to conquer pretty much every tire pile we came up with.

Ok, day two of testing and some good news, the weather man says "it will warm up"! Great! Then more bad news, rain. It got into the 50's outside but the pouring rain kept us inside again. Urgh! After sulking for a few minutes, it hit us...the wood pile! The BYT shop burns wood for heat and we had a nice pile of stacked wood waiting to get conquered. The stacked setup would not be much of a challenge so we tore part of it down and built a mini-mountain of wood. The tossed together (not nicely stacked, various diameters) wood pile of about 15-20 pieces was able to give the crawler a significant challenge at times and actually seemed to be an OK test of the trucks ability.

Crawler video on a wood pile (20MB) .zip file

The tires (without foams) did an excellent job of conforming to the uneven pile and traction was decent. Articulation of the axles seemed ample and the shocks also performed well against the uneven, jagged pile of oversized sticks.

ON THE ROCKS - CLIMBING ABILITY

Finally, a small break in the weather. We could hit some rocks (we used a backpack blower to blast off the snow as much as we could) and see how the truck would perform. The LST tires really did a great job of grabbing whatever they could, even with the extra slippery snow factor figured in. The weight balance appeared to be a big plus as it was pretty tough to flip the truck over. We tried different amounts of weight in the tires and found that a little extra weight in the front tires seemed to work pretty well. One of our last setups had 10 oz. of weight in the front tires and 8 oz. in the rears. This of course could be altered (bonus of using bead locker rims) to achieve different results depending on what exactly you were crawling.

The overall crawling ability of the truck is good to very good in our estimate. Granted, we were running by ourselves and were not comparing it to World Champion crawlers however the performance level it delivered was very impressive.

We found a couple of rocks under a huge pine tree and the snow was not too deep. There are some good clips showing the articulation ability of the truck in this video clip.

Crawler video on some smaller rocks (5.7MB) .zip file

We have started building our own crawling test field and here are some shots during our initial runs with the crawler. AS we build this pile of rocks, we will add mroe video!

Crawler video on the BYT Test Pile (9.3MB) .zip file

ARTICULATION

The original design went all the way to 90 degrees and that was simply too much! The tires would end up on their side walls and movement of the truck would stop. The final design of our chassis allows for approximately 80 degrees of articulation on the front and rear axles. We reduced the amount of articulation by widening the chassis slightly (we installed longer 3/16" aluminum chassis plate spacers/supports). The wider chassis prevented the axle links from twisting as far, hence limiting the articulation.

STEERING

The HiTec HS-645MG High-Torque MG Servo's did a good job and overall we feel they are a great place to start when building a crawler. Be sure to use the Kimbrough Servo Saver #124 units as the servos will overpower a lighter saver easily, especially with weight in the tires. As we continue with our crawling career, we will most likely add some more powerful servos however we would rate our current setup as good/above average.

POWER

The Integy 55 turn lathe motors have a TON of torque. Our setup included 9 tooth pinions and the motors were LiPo powered. We never found ourselves looking for more power. Even with the 9 tooth pinions, the truck actually seems to move a little too fast for our liking. We will be running 8 tooth pinions soon to try and slow down the wheel speed a little bit more.

CENTER OF GRAVITY

Overall we are very pleased with the center of gravity. It can climb a vertical wall to almost 90 degrees before it flips over. Rarely does it seem top heavy and since it has been tearing up rocks and wood, we have only flipped it a few times.

Adding some NiMH's on the axles could further enhance the trucks climbing ability and it is on our list of future enhancements for the truck.

PROJECT "ROCK RIPPER" DIMENSIONS/SPECIFICATIONS
Wheelbase: 17.5"
Overall Truck Length (fully assembled): 24"
Ground to axle clearance: 2.25"
Center Ground Clearance: 5" (max); 4.3" (normal resting height)

Click here to check out the final review of Project Rock Ripper.