Quote:
Originally Posted by Munchskull
Nice drivetrain. Might want to shorten that shaft. Also congratulations for getting on the cad train  |
Thanks, I chalk the excess shaft up to offseason laziness.
Quote:
Originally Posted by KohKohPuffs
Nice drivetrain 
Couple questions: - What was the reasoning behind using different-sized wheels for such a drivetrain?
- I believe you asked me this same question on my first custom butterfly drive, but to this day I am still confused on how to solve that problem
 . Here's the question: With a chain-in-tube drive like that, does it take into account rivets and other pieces of hardware that share the drive rails?
|
1. (Exactly as z_beeblebrox said above) Making the outer wheels smaller in diameter than the inner wheels erases the need for dropping the center wheels as you would on a usual 8WD or 6WD (to reduce turning scrub). They do have different linear speeds, but we found this difference to be negligible since the outer wheels are only contacting the ground a fraction of the time.
2. As you can see in the picture, we don't use any gussets in the corners. This is for the reason you stated above. The wheels are too close to the corners and we can't have any bolts or rivets where the chains and sprockets run. In place of a gusset, we machined 8 aluminum blocks that would slot into each end of each rail. We then bolted them in place at the top and bottom and ran two 1/4-20 countersunk bolts through each corner pair. We found this to provide a rigid replacement for gussets and rivets. All the hardware passes through the tube perpendicular to the chain, allowing the chain to run above and below it. In this way we avoid interfering with the chain.