pic: Frog Force 503 Drivetrain & Chassis Size Comparison



Here is our chassis and drivetrain on top of our off season test robot. The competition robot is 27X27, the practice robot is 37X27. They’re both 8wd, with 4 inch wheels and 25 chain on 1/16th inch 5052 bent aluminum.

Have you used 1/16th" before? We have thought about it but have always been afraid of it getting bent from a hard hit. If it works well for you we may have to try it in the future.

From my experience, with the mandatory bumper rules implored nowadays, 1/16" is more than strong enough. It was only back in the day with frame-on-frame contact did you NEED 1/8" aluminum.

Even back then we used 0.063 sheet for drivetrains and it held up fine. With bumpers we’ve gone down to 0.050. Folded sheet metal structures get their strength from how they are jointed much more so then from their thickness.

You make a great point. So much of engineering is finding better geometries for parts so that you can use less to get more.

My favorite examples of this principle are actually from the late 1800s, at the Paris and Chicago World’s Fairs, the where the Eiffel Tower and original Ferris Wheel were respectively unveiled. Both were somewhat controversial when proposed, as many refused to believe that structures made of such thin members could support themselves. Initially, many people refused to ride the Ferris Wheel, because they thought it would collapse at any moment. The Eiffel Tower, if made into a solid block the size of its base, would only stand 6 cm tall.

Another good example is a soda can. You can support the weight of most average people on top of a sheet of aluminum about as thin as paper.

How are your wheels mounted, it looks like dead axels with custom (plastic?, 3D printed?) pieces that are able to slide in the slots. Am I on the right track?

It looks to me that they are using the same method that 67 uses. If that’s the case then that is a tapped 1/4" aluminum plate which supports a dead axle in shear and can be slid to tension its respective wheel.

Bryan is a very good observer. 503 actually met with us over the summer to review our chassis / drivetrain strategy.

It looks like they took some pretty good notes. This chassis looks very similar to the sheet metal chassis we have produced in the past. Though, we typically have sometype of mid panel designed in for additional support.

I believe they water-jet aluminum axle blocks for the wheels. We typically use 0.25" rectangular blocks with capture nuts to secure the blocks to the frame. 1/2" axles are typically bolted to the blocks with a flat head 1/4-20 bolt.