pic: 6WD Sheetmetal Chassis

[Andrew_Schreiber]

Where do the encoders go? Here is where keeping a live axle wheel might be useful as it would be a simple way to toss an encoder onto a shaft. Other options (if you wanted to go dead axle) would be to use follower wheels, I believe 148 has a great picture of one from 2009 on CDM here.

[Brandon_Holley]

@apalrd

A few questions:
-Why the 0.090" 5052? We looked at 5052 this year, but decided to go with 0.063" 6061 (and later decided we should have gone with 0.050" 6061). A thinner material would be lighter, and 6061 0.063" is strong enough for a FIRST robot with bumpers.

Sorry I’m a bit late to the party on this, but one huge advantage to 5052 Al over 6061 Al is formability. 5052 is much more conducive to sheet forming than 6061 is (bending, rolling, etc). It is also easier to weld if you plan on implementing welds in your design. I’d stick with 5052 for a sheet metal design like this, but thats just me. I’m sure 6061 can be made to work as well with special considerations like large radii etc.

-Brando

[Jeff_Waegelin]

@Brandon Holley

Sorry I’m a bit late to the party on this, but one huge advantage to 5052 Al over 6061 Al is formability. 5052 is much more conducive to sheet forming than 6061 is (bending, rolling, etc). It is also easier to weld if you plan on implementing welds in your design. I’d stick with 5052 for a sheet metal design like this, but thats just me. I’m sure 6061 can be made to work as well.

-Brando

We do our bent parts all out of 5052, and our flat sheet parts (gears, sprockets) out of 6061, for this exact reason.

[apalrd]

For gearboxes, we actually used AM shifters with a final drive chain to a live axle. The gearboxes used 0.090" aluminum plates, and there were four slots in the frame where the gearboxes would bolt, and we could slide the entire gearbox up/down up to 3/4" or so to tension the final drive chain. The encoder was integrated into the AM shifter output. We really liked this design, and would do something similar again. The ability to change the final drive ratio was very nice, we changed it three times during the season.

On sheet metal alloy, we’ve had no trouble bending 6061 0.050" and 0.063" in our shop on a manual finger brake, but 5052 is easier to bend, especially thicker sheets. Using 6061 allows us to use thinner sheets.

[BrendanB]

@apalrd

For gearboxes, we actually used AM shifters with a final drive chain to a live axle. The gearboxes used 0.090" aluminum plates, and there were four slots in the frame where the gearboxes would bolt, and we could slide the entire gearbox up/down up to 3/4" or so to tension the final drive chain. The encoder was integrated into the AM shifter output. We really liked this design, and would do something similar again. The ability to change the final drive ratio was very nice, we changed it three times during the season.

On sheet metal alloy, we’ve had no trouble bending 6061 0.050" and 0.063" in our shop on a manual finger brake, but 5052 is easier to bend, especially thicker sheets. Using 6061 allows us to use thinner sheets.

Sounds like a very nice setup! Do you have any pictures to share?

[apalrd]

I don’t have any pictures of the gearboxes. I’ll see if I can take some soon.

[apalrd]

I took some pictures. Here are two.

The case bolts go all the way through both gearbox plates, the spacers, and the frame. There is a nut on the outer gearbox plate, then some washers, the frame panel, more washers and another nut. The frame panels have slots to move the gearbox up/down to adjust the chain tension of the final drive chain. The final drive ratio is 12:22, the final drive sprocket is an AM 22T with AM 500 hex hub. The CAD model will be released in the next week or so.