A few members of the team have completed the design for a quite ambitious project.
The problem: We know the torque output of our motor, and we are not running a transmission. We can trade low end torque at the wheels for higher top speed by adjusting our final drive ratio. By analyzing the track we will run on, we determined that our final drive ratio should be about 6:1. This means that the sprocket in the rear would have to be 6 times larger in circumference than the sprocket in the front. Such a large rear sprocket means that the entire set up has to be longer and will take up a lot of space.
Solution: There will first be a planetary gear reduction system that reduces the speed of the motor 3:1. A planetary gear set would be very complicated to design and extremely difficult and expensive to manufacture. So a planetary gear set from an old GM transmission was used to start with due to availability and price (see picture below). Although starting with a complete planetary gear set makes things easier, modifying the parts has proven to be a challenge. To get the gears to the right thickness and splined on the center gear, we had to use a combination of hard-turning, diamond blade chop saw, wire EDM cut, and surface grinding. Plus we designed an entirely knew carrier for the gear set. This has to be made out of 4140, roughed, normalized, finished, splined, and heat treated. Shout out to Louis Quindlen at Laney College, none of this would get done without him and the Laney Machine shop!
Here is the planetary gear set we are starting with. The center gear will have the visible portion removed and will be driven by a spline on the inside.
Well, that was a lot of info, and lots of details were left out. Have a question? Feel free to ask in the comments below.