Polycarbonate side plates for lighter gearboxes

[Joseph Smith]

Originally Posted by Kevin Sevcik

It's interesting that you did that to lighten up some AM Toughboxes, since the TB back plate is polycarb (Lexan) and the front plate is 1/8" aluminum. And AM will sell you aluminum spacers as well.

At any rate, 1/4" Lexan will be about 10% lighter than 1/8" aluminum, for starters. If you're not direct driving out of the gearbox, 1/4" Lexan will be plenty strong enough. The main downside to Lexan is that it's prone to cracking. Not as much as acrylic, but much more so than aluminum. So you'll want to be careful about tightening things and subjecting it to heavy shock loads. There's a reason AM chose aluminum for the front plate of the TB, that's the plate that takes the most load from radial forces on an overhung shaft.

Since 1/4" Lexan only saves 10% over 1/8" aluminum, perhaps you should look elsewhere in the TB for weight savings? AM will sell you aluminum versions of the large gears that will save you 0.56 lbs together. In the past, I've tossed the large gears on a CNC and webbed them to save a similar amount of weight. And there's the aluminum hex output shaft that would save you another 0.1 lbs or so.

So what I'm basically saying is that if all you did to lighten up a TB is custom side plates and spacers, then you have some other low hanging fruit available.

Thanks for the advice, what we did was machine out pockets of aluminum from the plates just for extra weight loss, and we were forced to make them custom because we added an extra banebot 775 to each gearbox.

[Joseph Smith]

So, reading through these replies, it looks like most teams either stick with aluminum or have the plate closest to the motors polycarbonate (or delrin) and the other plate aluminum. The general consensus seems to be that you can easily remove weight by changing your gears (switching to aluminum or milling out the steel ones.) This is probably what we will try next year. Has anyone had problems with the aluminum gears, or milled out steel? I would like to avoid any stupid rookie mistakes

[Cory]

Originally Posted by Joseph Smith

So, reading through these replies, it looks like most teams either stick with aluminum or have the plate closest to the motors polycarbonate (or delrin) and the other plate aluminum. The general consensus seems to be that you can easily remove weight by changing your gears (switching to aluminum or milling out the steel ones.) This is probably what we will try next year. Has anyone had problems with the aluminum gears, or milled out steel? I would like to avoid any stupid rookie mistakes

We have been pocketing steel gears since 2004. Never had a failure.

968/254 used custom aluminum gears in 2007 (some pocketed, some plain) with no problems.

Same thing with WCP aluminum gears this year.

[MichaelBick]

Originally Posted by Gray Adams

We have a gearbox this year that is one side 1/4" delrin, other side 1/4" aluminum. We pocketed the aluminum plate out and it weighed almost the same as the delrin. It really doesn't seem to be any better not to use aluminum, and the aluminum looks a whole lot nicer after bead blasting and anodizing. In fact, the delrin was a little bit warpet because it was such a large piece (9"x 6" I believe). We only used delrin because we mounted Banebot 775s to it and that way we didn't have to worry about the cases shorting to the frame.

Please do not do this. It WILL NOT SOLVE YOUR PROBLEMS. The case will still short, just through the metal gears instead. You most likely got lucky with your 775s

[Hawiian Cadder]

Originally Posted by MICHAELABICK

Please do not do this. It WILL NOT SOLVE YOUR PROBLEMS. The case will still short, just through the metal gears instead. You most likely got lucky with your 775s

You could use Plastic gears out of a FP Gearbox to help with that.

[MichaelBick]

Originally Posted by Hawiian Cadder

You could use Plastic gears out of a FP Gearbox to help with that.

Could definitely work. Also, you could try sourcing gears from sdp-si.

[MrForbes]

we made our own mechanism gearboxes using older FP plastic gears and polycarbonate side plates. Very easy to make with minimal shop equipment....

We haven't found any reason to try to reduce weight on the drivetrain gearboxes, we'd rather take the weight out of the higherer-up mounted parts.

Don't use thread locker with any polycarbonate parts

[Joseph Smith]

Originally Posted by Cory

We have been pocketing steel gears since 2004. Never had a failure.

968/254 used custom aluminum gears in 2007 (some pocketed, some plain) with no problems.

Same thing with WCP aluminum gears this year.

When you pocket steel gears, do you mill them out in a spoke shape (comparable to the aluminum performance wheels you can buy at AndyMark) or do you just drill holes out of them?

[Cory]

Originally Posted by Joseph Smith

When you pocket steel gears, do you mill them out in a spoke shape (comparable to the aluminum performance wheels you can buy at AndyMark) or do you just drill holes out of them?

We drill holes and then pocket a step on each side with a .125 radius at the edges,leaving a web thickness of .075" if i remember correctly.

[Joseph Smith]

Originally Posted by Cory

We drill holes and then pocket a step on each side with a .125 radius at the edges,leaving a web thickness of .075" if i remember correctly.

Thanks. We might have to look into that as a way to save weight next year.

[Gray Adams]

Originally Posted by MICHAELABICK

Please do not do this. It WILL NOT SOLVE YOUR PROBLEMS. The case will still short, just through the metal gears instead. You most likely got lucky with your 775s

We also had plastic inserts so that it wouldn't short through the gears, which is an important detail if you try this, but I was really just thinking about the delrin vs aluminum.

[PAR_WIG1350]

Originally Posted by Hawiian Cadder

You could use Plastic gears out of a FP Gearbox to help with that.

Yup

[DampRobot]

I for one would reccomend against this. In 2008, we tried polycarb side plates for our drive gearboxes. The plastic insulated the motors, and caused significant overheating problems. In 2010, we tried using the plastic toughbox plates. Same thing.

In my experience, plastic plates are a bad idea. Anyway, as mentioned above, there are other ways to save more weight more easily.

[thefro526]

Originally Posted by squirrel

we made our own mechanism gearboxes using older FP plastic gears and polycarbonate side plates. Very easy to make with minimal shop equipment....

Mr. Forbes' post made me want to note something, when using smaller motors like 500-series, 700-series, etc, you can get away with using Polycarb, Delrin or other strong plastic Side-plates depending on the application. On my former team, all of the aux boxes for their 2012 robot have Delrin side plates and are holding up just fine.