Battery Rules Question

[Mike Betts]

Laura,

One way to determine how good your battery restraint needs to be is to do a little math.

A robot being driven with CIM motors via an AndyMark Toughbox transmission (12.75 gear ratio) can achieve speeds of 11 ft/sec.

This is the speed at which a robot could hit a wall or another robot (traveling at the same speed, bumper to bumper contact).

The equation for the velocity, v, of a falling object after it has fallen a certain distance, x, under a uniform acceleration (gravity), g, is:

v = sqrt (2gx)

Solving for x we get

x = (v**2) / 2g

So, for v = 11 ft/sec we get x = 1.9 ft

Now, an engineer will normally design for and test with “design margins”. That is, some value above and beyond the design point. It is convenient that most tables are 2.5 ft tall. This is 32% more than our design point.

DO NOT ACTUALLY DO THIS NEXT STEP WITHOUT CHECKING WITH YOUR MENTOR!

Now imagine putting your robot onto a table at school and pushing it off such that the bumper hits the floor first.

This is the shock that your robot can (and will have to) withstand in a typical match. Usually many times in each match… Note that even if your robot does not move that fast, the other guy probably will be.


Under this shock load, your battery must not come loose. Your bumpers must not fail. In fact, your entire robot must be able to withstand this shock load.

Now look at your robot’s design. Is it up to the challenge?

Regards,

Mike