Axial RR10 Bomber Project

Page 2: Upgrades!

This image shows a whole pile of upgrades. These are all genuine Axial parts intended for this model. They are a mix of things being added to solve problems and also just things I thought were cool. More upgrades were made later in a second wave. I don't know what it is about their "titanium" anodize color, but I really like it.

The first problem I wanted to solve was rollovers. The model proved quite unstable at speed while trying to make any kind of turn due to high CG and lack of differentials. I added a wheel weight ring to each of the 4 wheels which adds 4oz (114g) per corner. The rings clamp around the outside of the wheel center and end up completely hidden inside the tire. I wanted even more weight on the front wheels to improve climbing traction, so I filled the slots on the weight rings with 6 weights bringing the total at each front wheel to 8.5oz (240g). This made a huge difference. Of course, it also means a lot more rotating mass for both the motor and steering servo to deal with. It also means no more wheelies.

As long as I was tearing things apart, I decided to add the Axial aluminum motor mount. You can see the cam system that is used for mesh adjustment here. Instead of loosening screws and translating the motor to adjust mesh, you rotate the cam ring. This is convenient in one way, but rotation of the motor can really mess up the wires if they are direct soldered as I did.

I stripped a couple of teeth off the plastic spur gear when I hit a curb under power (you can see the mangled teeth if you zoom in on the left hand image). Since it was fairly difficult to access and replace, I didn't want it to happen again. I installed a steel spur. This requires new slipper clutch pads because the adhesive can't really be removed from the old spur. The sound of the vehicle is now totally different with metal contact on all the gears.

I also wanted to change the external appearance. A YouTube video from RCSparks alerted me to the existence of these aluminum body panels out of Korea and I had to have them. They are a direct replacement and really make it look nice, in my opinion. The blue anodize matches the servo and the springs nicely. The above pictures show the stock and updated panels. In the second image you can also see the white paint I added to the raised letters on the tires using a paint pen.

There have been a lot of broken parts on this model, many of which can probably be attributed to the increased weight in the wheels. The first major issue was the fracture of the diff locker as shown. I replaced it with a Hot Racing steel version. As a structural engineer, I recognize this as a very bad design. The rotating flattened axle acts as a wedge which attempts to open the slot, and all the stress concentrates at the sharp corner. This wouldn't be so bad except that the sharp corner coincides with the thinnest part of the wall. The whole problem could be fixed by rotating the slot 45 degrees within the locker.

The next major problem was the loss of the steering link. It fell off in a rock pile and I couldn't find it. It was not retained well by the ball joints. I replaced the missing part with some titanium links as shown on the left. Even the new parts had problems later as the rod end kept pulling out of the threads, again probably due to the increased wheel weight. I tried some Boom Racing one piece arms as shown on the right, but these had terrible wobble and backlash and were unusable so I reverted to the titanium links with an epoxy repair.

The next problem I encountered was elongation or fracture of the rod ends on the front 4-link bars as shown. This happened over and over even as I kept replacing them. The geometry of the 4-link is such that extreme loads are applied due to vertical loads such as landing a jump. Once the rod ends are elongated, the suspension becomes very sloppy affecting the steering and overall stability.

Again I turned to some Boom Racing solid links. Since these are solid one piece parts with no separate rod ends I figured they would be indestructible. Wrong. The ball ends are pressed into the aluminum with serrated retainers and migrated out almost immediately rendering them even sloppier than the stock parts. I think the final solution will be to go back to the old parts and remove the wheels weights that are causing so many problems.

Update: I ended up removing the wheel weights and reverting to the stock aluminum links with some steel rod ends from RC4WD. This actually makes the model run much better. It is back to rolling over pretty easily, but that can be resolved with some throttle control.

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