pic: Sheet Metal Drive Module Idea

[cadandcookies]

Beautiful CAD. I love seeing sheet-metal designs, if only because our team doesn't have the resources to ever do one on the level that we'd like to (and I don't think we have the patience to CAD everything ).

I do have a question regarding the custom housing for the gear-box, namely, why? Don't get me wrong, I'm not criticizing the design-- I don't have nearly enough experience with custom gearboxes to offer anything constructive or unique there-- but I assume it's for weight? If so, then what are the actual weight savings over the original housing?

[roystur44]

Hi Madison,

Your tensioner brackets look a little flimsy. Try a triangular shape instead of the long rectangular flanges. The triangle will distribute the force to the base of the flange instead of bending or twisting. The forces on a collision and the stress of changing directions is directly on the chain tensioner. It needs to be strong and also think of putting two slots on the top flange instead of thur holes and insert the tensioner from the top. Use 3 screws to locate and tighen down. That way you could shim the tensioner and that will adjust the tension on the chain by moving the tensioner a little higher. I think the tensioner should go in the middle between the wheels. When the chain starts to stretch it will sag on the top and might possible rub together where you have it.

One important thing is you need to take a 1:1 cutaway of the main piece and make sure the goose neck brake die will fit inside the part and clears the first flange when the last bend takes place. If the brake die isn't the right shape you can't make the last bend without hitting the other flanges. This results in what they call a back bend. You could plot the flat pattern on paper and fold the plot up and experiment with where you want the flanges. Paper and tape is a sheet metal designers tools.

I wouldn't worry too much about the cutout on the bottom for the gear box. Once you have it riveted to the belly pan it will lock down and stiffen.

There are some places were you can tab and notch the sheet metal for locating and increasing the strength. Ask your sheet metal sponsor how you can do it. Basically it is like a creating a jig saw piece where the two pieces fit and lock together.

On the gear box plates you might consider to bend the side plates flanges the opposite direction to clear the chain and sprocket.

Your front and back panels would be stronger if you added some triangular gussets when you assemble the frame. Also could add another return flange to the top flange.

Need chain brake access. Your design looks pretty tight inside where the wheels are. Why?

Think about how you want to mount your battery and build a cool bracket that rivets on and holds your reset switch.

There are pictures of our 2010 soccer playing robot. Your frame shape is very similar to that one. It was a 8 wheeler with idler sprockets to allow for fast traverse on the big bump with the lowest COG

[MichaelBick]

Originally Posted by sentientfungus

Beautiful CAD. I love seeing sheet-metal designs, if only because our team doesn't have the resources to ever do one on the level that we'd like to (and I don't think we have the patience to CAD everything ).

I do have a question regarding the custom housing for the gear-box, namely, why? Don't get me wrong, I'm not criticizing the design-- I don't have nearly enough experience with custom gearboxes to offer anything constructive or unique there-- but I assume it's for weight? If so, then what are the actual weight savings over the original housing?

There are two reasons for repackaging a gearbox. The first reason is for form factor. Repackaging a gearbox means that you can make your frame adapt to it in any way you want. The second reason is weight. The repackaged gearbox has walls that are thin(comparably to the original housing). The Supershifter walls are .25" thick, the repackaged ones are at most .125" thick. Assuming that the sidewall sizes are the same, you basically just removed the weight of one AM shifter sidewall.

Andymark Shifter Sidewall = 5" * 5" * .25" * .0975 lbs/in^3(density of 6061 al) = .61 lbs

So you saved .61 of a pound if not more.

[cadandcookies]

Thank you very much for that response, Michael-- very helpful.

Team 2220 might have to consider doing custom gearboxes this next year (though we'll probably still be a 120lb robot anyway).

[Madison]

Originally Posted by MICHAELABICK

There are two reasons for repackaging a gearbox. The first reason is for form factor. Repackaging a gearbox means that you can make your frame adapt to it in any way you want. The second reason is weight. The repackaged gearbox has walls that are thin(comparably to the original housing). The Supershifter walls are .25" thick, the repackaged ones are at most .125" thick. Assuming that the sidewall sizes are the same, you basically just removed the weight of one AM shifter sidewall.

Andymark Shifter Sidewall = 5" * 5" * .25" * .0975 lbs/in^3(density of 6061 al) = .61 lbs

So you saved .61 of a pound if not more.

All of this is true, though the sheet metal shown is .060" rather than .120"

The real reason I did this, though, was because on a stock SuperShifter, the output shaft is 1.5" from the closest edge and, with 4" wheels, that leaves very little clearance between the Super Shifter (and its servo) and the ground. By repackaging it, I was able to increase the ground clearance -- though it seems to require pneumatic shifting rather than servo shifting.