Custom Two-Speed Transmission

[tennispro9911]

Our team is going about designing a two-speed transmission. We are planning on designing it similar to an AndyMark supershifter, with some AndyMark gears and some gears that are purchased from other suppliers.

At this point we are trying to decide on gear ratios for our high and low speed, and what teams have decided is their "optimum" high and low speed. We used AndyMark 8" mecanum wheels on our robot for 2008, and they worked beautifully for us. We plan on using them again next year. Because we are using mecanum wheels, we will have four independantly driven wheels and four transmissions. We intend to direct drive our wheels off of the output shaft of the transmission.

Right now we have a 4:1 ratio between our high and low speeds. We are using the specs of the CIM motors at "Normal" load to give us a fairly realistic maximum speed that our robot should be able to reach in a competition setting.

We are assuming a .90 efficency for our gearbox because all the stages have bearings and it uses external spur gears. We are adding .002" center to center distance for our gears to reduce friction. Is this a good distance?

This will be our third season as a team, and our first foray into both custom transmissions, and shifting transmissions. We considered AM transmissions, but we did not want to purchase four of them, we hope that we will be able to make them lighter, we want the knowledge from building it, and we wanted to be able to customize the gear ratios for our robot and our wheels.