After showing off my four-legged MountainBeest here, it was finally time to attempt to motorize it. I don’t think it will ever walk (at least not well) without a few more legs, but having it move by itself is much more impressive than me turning it. Luckily (?) I had parts left over from a bike’s cassette, and several windshield wiper motors. Here are my initial results:
Power transmission using PVC pipe, a windshield wiper motor, and bike chain seems to be fraught with challenges.
The chain (as you certainly noticed) kept coming off. There were several reasons that I could see for this. The first was that the legs were moving quite fast despite the gear reduction applied causing the chain to jump around. This combined with poor alignment of the two sprockets caused some obvious problems. My wood/PVC setup isn’t exactly great for precision alignment.
To compensate for this, I tried using a sturdier and wider single speed chain (This one from Amazon). Although it looks awesome, and at is wider than a normal chain, it wasn’t able to compensate enough for the somewhat shoddy way that I’d attached the small sprocket to the windshield wiper motor. It’s not a total loss though, as it might end up looking great on my single speed bike.
In order to make this work consistently, I think I would have had to slow down the motor, and anchor the small sprocket’s axis securely to the other side of the wooden frame. Although I tried several ways to make this work (see the photos after the “read more” link), I didn’t really feel like pursuing it further. Getting it to fit up accurately with wood seems like a losing proposition, especially for the work that would be involved.
Either way, maybe these photos will give someone some inspiration if they want to try to somehow combine bike parts with PVC pipe for power transmission. Note that I had to turn the 1″ pipe down a little on a lathe to allow the sprocket to fit on it. Also, a turned wooden plug was used to attach the pipes that drive each set of legs. Finally, note how I fastened the small sprocket with a screw through the bottom of it. There were some good ideas on this attempt, but I think it’s time to step back and punt on this project.
Since there are many, many other things that could go wrong with my ‘Beest, I decided that instead of fooling with the chain, I would just buy a more appropriate motor. I decided to go with, a 3 RPM motor from Servocity. The MountainBeest doesn’t have to move quickly, and along with this slow speed comes a torque rating of 1102 oz-in. Or in terms that area a little easier for me to think in, 5.7 ft-lb. Hopefully that will keep the legs moving consistently.
Taking a little complexity out of the drive train will hopefully allow it to work when I need it to!
Be sure to check back to see if I actually ever do get the ‘Beest working. If you don’t want to obsessively check this blog (which is fine too), you can follow me on Twitter here, or if you want to get emails every time there’s a new post, input your address in the upper right hand corner of this, or any JCoPro.net page!
Thanks for reading!