Quote:
Originally Posted by s_forbes
Maybe someone from 125 can shed some light on the subject, they had an amazing drivetrain last year utilizing belts.
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Guys, thanks for pointing us out as an outstanding belt drive. I personally, along with a lot of the other team members spent a considerable amount of time hashing out the details of our belt system.
We used 3/8" pitch belts from sdp-si.com, along with the pulleys they sell. We chose to use the kevlar reinforced timing belt because it gave us a considerable amount more breaking force than the fiberglass reinforced ones. The picture above shows the main part of our drive "pods". We used a single speed gearbox with 3 motors, 2 CIM 1 Fish. The center wheel shaft extended itself into the gearbox where it was integrated via spur gears into the system.
We used hex on the wheel shafts because it makes the system very robust and easy to assemble (no keyways to lose). The belts come in very specific lengths, so we designed our center to center wheel distance to be a round number (16" exactly). The belt sizes are whole numbers plus the pitch diameter (to give you the "circumference" of the pulley system, otherwise known as the belt. We ordered the belt as the *exact* size that it would be. After assembling the entire drive system, I measured the slack in the belt and went and machined down a chunk of delrin to the size needed to pick up the slack (which wasn't that much). The delrin slid right over our standoffs used to attach the two drive plates together. Throw in an e-clip on both sides and voila, you have a tensioner.
The reasoning behind this system, as opposed to an adjustable system you may see in a chain drive is that kevlar, for the most part, does not stretch....at least not anywhere near where you might see a chain stretch to. The tension put on the belts when the drivetrain was first assembled is the same as it is now.
As for changing the belts....our bumpers came off with 4 pins you could remove by hand. A few bolts after that you had the sideplate off, and could replace anything you needed in the side...wheel, tread, pulley or belt....although we never needed to do that.
I really like belts, and aside from the weight savings, it was just a cool little addition to a drivetrain. If anyone has any questions, or wants to see so me CAD let me know, I am the guy to ask.
-Brando