[Ben Piecuch]

I'm posting to this a bit late, but we've used a similar 8020 setup to this for many years, so I thought I'd add some notes.

You may find that there's a lot of corner to corner twist in the frame alone. When you add any upper structure, it greatly stiffens it up. But, the 1010 extrusion, and especially connectors, leave a bit of stiffness behind compared to a welded 1" x 1" tube frame. (This is a similar problem with the kitbot chassis)

The bearing blocks, while convenient to use as tensioners, are always a nightmare to keep aligned. When you need to switch wheels, you'll need to un-tension the chain, remove the shaft, and reassemble after. It's not so simple. In our experience, even when you think you have an aligned wheel and axle, it's still not perfect. We've thrown more 35 pitch chains with a similar setup than I care to admit.

I've always found approach angles to be difficult (re: shallow) when you have a minimum of 1" of frame in front of the wheels. There aren't too many ways around this issue when using a frame like this.

Carefully plan out where you'll be adding extra mounting points, and pre-assemble some T-nuts into the rail. The drop-in's are a pain, especially when you need to line them up with the mating component. 8020 makes some T-nuts with a set screw, to hold them in position. I highly recommend those on any vertically oriented channel.

One last note, when cutting 8020, always square off the edges. Chop saws work well, as do milling machines. A band saw, however, does not.

Finally, for all those weight conscious folks... The 8020 brand, 1010 extrusion is within 2% of the weight of a 1"x1"x.125" aluminum tube. The bending stiffness is also withing 2%. Torsionally it's not quite as good, but a frame doesn't see the twist like an arm/appendage would. The connections are the key, and using the double-anchors on all corners are your best options (and lightest weight...) While the connectors do add weight, you're talking around 1-2lbs when done correctly. Using the proper material for your upper structure is the key to weight savings when using 8020.

Simplicity in design and manufacturing is always good, especially if you can make it as reliable as a highly machined and labor intensive chassis. I highly recommend building a practice bot and (literally) shaking out all the issues. Oh, since we only build one 8020 frame with the new bumper requirements... Figure out a way to mount the bumpers prior to week 6. Best of luck!

Bengineer