Designing The Drivetrain

January 6th, 2019

Sunday, Week 0

An unofficial meeting. A couple of students got together to think through things like wheel types, spacing, frame dimensions, and bumper mounting. Because we knew we would base our drivetrain off of one we designed in the preseason, making modifications to the CAD was very simple.

We started off by narrowing down our wheel options and making pros and cons of each. The image above shows our thought process. We realized that one major constraint would be this year’s bumper zone (between 0″ to 7.5″ off the floor). Therefore, having pneumatic wheels that extend past our front and back would not help us get over any bumps, or the platform, as the bumper would be the first thing to hit them anyway. Another reason we decided to go with 6″ traction wheels is that the pneumatic wheels were very wide (taking up more width in our perimeter). They were also very costly.

The second step in our design process was to determine our wheel spacing and overall frame dimensions. For this, we used concept sketches!

We determined with 4-1/2″ tall bumpers (as short as they can be) raised as high up as they can (top reaches 7-1/2″ off the ground), we would be able to drive up to the second platform without dragging our back bumper on the ground.

Also decided on 10-1/2″ wheel spacing and overall 30″ x 28″ frame perimeter. We had also already planned on doing a 1/8th-inch drop center to ease driving and turning.

It was brought up that our previous method for bumper mounting could be an inconvenience later on when we try to mount mechanisms using the side holes. We then designed a 1/8th-inch aluminum plate that backs the bumper and connects to our frame via spacers and L-brackets. Below you can see how our bumper mounting evolved.

Old Bumper Mounting
New Plate to Mount Bumpers

By the end of the day, we had a full drivetrain CAD with new smaller (but stronger) corner gussets, a better bumper situation, polycarb, battery box and gearbox supports, as well as chain!

Ready for our design review tomorrow morning!!

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