I’ve said it before and I’ll say it again: I was very pleased with Cannon’s second-place performance at Motorama. Still, its three fights against the eventual champion, Low Blow, highlighted some severe design flaws:
- Exposed wheels. This is probably the single biggest flaw a robot can have.
- The ball bearings pushing against the sides on big hits expand the beater holes.
- There was no firewall; parts could be ejected from inside the robot into the blade.
- Slow drive motors. 22.2:1s would have been a much better choice.
The scale was hardly Cannon’s friend, so figuring out how to add more material to the robot without adding any weight will be a challenge in and of itself. However, the first (and easiest) place to look is the wheel hubs. Cannon used aluminum “Dave’s Hubs” to hold its wheels on. Much lighter alternatives exist, such as the FingerTech Robotics Lite Hubs. Switching to the Lite Hubs will save over half an ounce off the next version of Cannon. That is more than enough to get started.
The next place I will look for weight will be the back of the robot. The old back weighed about 0.6oz and was made of 3/32″-thick garolite. Although stiff, garolite is about twice as dense as UHMW and is very brittle. The next Cannon will use a piece of (likely 1/16″-thick) UHMW that wraps around the back and protects the wheels. Kitbot creator Pete Smith gave me some UHMW bending tips at Motorama that should mean the clearance between the wheels and the UHMW is better on Cannon than it is on Coercion. Actually, I’m not sure Coercion actually has any clearance!
I put together a quick sketch of my thoughts for the next version of Cannon:
I am not a very talented artist.
The new firewall will be bolted to the side rails, which will help to make the entire robot stiffer. I will make a groove in the sides so that the pieces fit together relatively snugly.
I also sketched the side rails (remarkably well). I think I might apply to art school if the whole top-ten school in the world thing doesn’t work out.
Note that the pockets are bigger and I have added holes for the firewall. Also note that the hole that will hold in the weapon bearing has been enlarged. This will allow me to put in a custom bushing, which will increase the surface area inside the hole and keep it from enlarging.
The next step will be to design the firewall and do more weight calculations. I’ll then need to order parts. Unfortunately (well…fortunately), I will be in Washington, D.C. from March 9th to the 16th, which isn’t conducive to robot design work, and over the next week, I’ll be busy getting ahead on schoolwork to get ready for my week off: not much will get done. Still, it feels good to finally put some of the ideas I have come up with on my blog.
Keep checking back–Bot Blast registration is up on the Builders’ Database. I’ll be taking Cannon, lolcat, maybe Coercion, and maybe Amatol if one of my friends wants to drive it.