Mid Motor Rustler - V2

[SnowTheProto]

I was curious if you'd be considering releasing the files and maybe a simple guide to allow people to build on of their own, (i would like to build one).

[rc10nick]

Files have been released for a few weeks now - https://www.printables.com/model/890186-nickcnc-mid-motor-conversion-for-traxxas-bandit-ru

Warning, though, the transmission cases have a bit of a design flaw that causes melted internals and stripped gears. I fixed the issue but haven't yet updated the files on printables.

Unfortunately I just don't have time to make any kind of a guide outside of what's written on printables or what I've said in my youtube videos about the car. Maybe I'll get there when things slow down over the winter.

[rc10nick]

It's been a while since my last update so I suppose I'm a bit overdue for one. Since my last update I've had lots of fun racing this car, finding and fixing design issues, and dialing in a setup.

Since the last update where I blacked the car out and switched to the LD2 body, I've spent some time working on 3D printed inserts. Their popularity in the crawler world combined with another user on the rctech forums having success with his inserts inspired and motivated me to give them a try. Sparing the boring technical details about design, filament, and printing them, I've arrived at this design:



I've found they work quite well and it's for the same reason the crawler guys like them so much - they're really soft when you compress them, like an open cell insert, but the internal webbing gives you the most sidewall support you've ever had in your life. The result is a tire that grips really well yet is super stable and precise.

My bandit with these inserts in them allowed me to win not one but two races in a row.

Here's a video of my first win (skip to 1:54 for the start of the race):


I got a bit of help in that win with 2nd place having electronics issues, but even once his car got sorted out I was able to reel him in and nearly put him a lap down by the end of the race.

My second win was against a bigger and more competitive field, but unfortunately I didn't get that on camera at all.

It hasn't been all sunshine and roses, though. My transmission case had a bit of a design flaw that resulted in the idler gear slightly rubbing against the transmission case. I learned of this design flaw when I was at the track and stripped out the main gear on my ball diff. When I took the transmission case apart to see what had happened I noticed the recess for the idler gear shaft had melted and deformed which allowed the idler gear to move out of position and wreck my stuff up. A quick redesign later and now everything is good.

In terms of setup, I've noticed my car feels really planted and stable up until the moment it doesn't - it abruptly lets go and is difficult to control once that happens. Up until recently I was trying to tune the car to keep it locked in and prevent any kind of sliding. I think that was a mistake - when you think about it you're going to slide around on dirt no matter what, so you're better off tuning to optimize for a car that's easy to control when it does slide. I think it's also why my car felt like it didn't have any corner speed - it was too "locked in" and couldn't rotate through the turn without losing control.

With that in mind I figured from a physics standpoint the centralized mass of a laydown car would make it easier to control while sliding around so I swapped it back over to the LD config. Another motivating factor to switch back to LD is the fastest guys at the track are running laydown even though they could easily switch to standup. Seeing how fast they are made me start second guessing the idea that you need a rearward weight over the tires to be fast even in low grip conditions.

I also bought a set of Schumacher Honeycombs because I wanted a hard, long wearing tire to run on my basement track. The harder compound means tires last much longer than the clay slicks I was using on my basement floor, and with less grip it gives me a way to test my car's stability as it slides around.

I've spent the last few days testing setup changes like a mad man, but it was worth it. The laydown car is now easier to drive and faster than I could ever get the standup car to be. It's really easy to control as it slides which lets me hammer the throttle like an idiot and the car doesn't spin out (exaggerating a bit, but it kind of feels that way compared to how it was before). I also really like these Schumacher Honeycombs - they still drive surprisingly well and they have no visible wear even after days of hard driving on my basement floor. A similar bar tire in a clay compound would be 100% slicked out by now.

The next race is this Saturday and now I'm super excited to test out the car with this new setup!