Fitting belts within your frame

[dellagd]

I'm currently designing a prototype frame for possible adaptation in the coming FRC season. To save space, I'm looking to run one of the 15mm belts on each side of the drive train inside of the frame element itself. I know this is commonly done with 9mm belts, but to stay on the safer side I figured we should design for 15mm. The problem I'm having is I'd like to stay with 2 inch x 1.5 inch frame without having to move up to 3 x 1.5, and this mean the only HTD pulley I can fit (accounting for a center wheel drop of 1/8 inch) in the frame is a 18T one. The 24T is just a bit too big from my calculations.

Also if it matters I'd like to do this all exact C-C. I've heard it works well and we do have access to machining that is accurate down to the thousandth, so I think its the best solution.

My question is whether or not 18T pulleys are big enough to handle the loads that an average drive train subjects them to. Has anyone used 18T pulleys on their drive train? Is 9 teeth of engagement enough?


As a side note, I'm also wondering if 6063 aluminum is good to use for frame elements over 6061. Online its about half the price, so I'm hoping we could use that since we would probably be able to buy more stock.