pic: Shaker 2011 Arm Gearbox (Maybe?)

[Chris is me]

loading photo ...

[MrForbes]

what if you were to use 1/8" stock for the sides? Have you done any loading or deflection calculations that show that the thicker stuff is actually needed?

[Sh1ine]

I like that. What type of sprockets do you plan on uses when attaching that to the arm?

I know H was thinking about using a Giant sprocket which adds bulk to the system. This is slightly more complex but it will still be easy and it will be way cleaner. If we use Al box for our vertical post , we could mount it directly to the beam, like the drive train.

Nice render too!

[Chris is me]

Originally Posted by squirrel

what if you were to use 1/8" stock for the sides? Have you done any loading or deflection calculations that show that the thicker stuff is actually needed?

Nope, none at all. The 1/4" is heavily pocketed on the inside and is mainly used as a shim to prevent that bearing right next to the Planetary from sticking out. I figured that worse comes to worst, a little overkill on such a vital part of the robot wouldn't hurt.

This is designed to interface with a 16 tooth hex sprocket to a 54 tooth sprocket, both available in 25 chain size on AM's website. I think if I did a bit more work we could squeeze a stage of reduction out of the gearbox by using a larger sprocket reduction - I can't figure out how to right now but that could save a lot of weight. Either way, this puts less load on the chain by doing more "work" in the gearbox.

I don't see why this couldn't be integrated into the side of the arm - the only thing is that the 50 / 56 tooth gears are more than 2 inches wide so they'd stick out.

Pocketing the middle 50 tooth gears brings this box down to about 4.2 pounds.

[JamesCH95]

I like it. Can the gears handle the amount of torque the FP may be capable of providing?

[IndySam]

Nice work Chris.

What about back driving?

[Tytus Gerrish]

4 stages! it's going to make your robot sound cool
Looks good, cant wait to see more

[Chris is me]

Originally Posted by JamesCH95

I like it. Can the gears handle the amount of torque the FP may be capable of providing?

No idea if the lightened gears can, but I would be very surprised if the .4 inch steel gears from AndyMark could not handle the load the FP puts on them, considering people lifted robot-size loads with those gears last year.

To be safe I'd personally forego lightening the final gear even though it's the biggest one.

Originally Posted by IndySam

Nice work Chris.

What about back driving?

Hopefully the arm can be balanced with surgical tubing in all states but it's "reverse dunk slamma jamma mode". For the rest of it, the arm is a surprisingly light load on the motor and running it at ~5% power or so to hold it up should be very easy, especially with balancing reducing the already light load further.

[Chris is me]

So a nice and easy way to reduce weight is to replace most of the gears with 50 tooth AL cluster gears. I assume for the first two reductions this won't compromise gearbox strength - but how can I check on the third? I swore I learned how to do this in Strength of Materials but it's escaping me right now.

[JamesCH95]

Something like this will give you a good idea.

[Chris is me]

Thanks.

Looks like going aluminium on that third reduction is pushing it - so two AL gears and one steel 50t gear would be the best configuration for the gearbox.

[JamesCH95]

That sounds sane. You could also pocket out the gears quite a bit.

[AdamHeard]

For high reduction arms, depending on how they are loaded, it's possible the motor never even comes near stall torque, so aluminum may work fine.

Also, if you space your plates 1.125 apart, you can make this same gearbox with ZERO custom shafts, and the use of no spacers, by utilizing the toughbox and cimple box gears. It's a trick we've been using for three seasons now.

[Chris is me]

I did try and use all Toughbox custom shafts, but with the compound gear reduction a wider gearbox was needed to prevent gears from meshing with multiple stages.



However I think I'll try and use gears with different center-center distances to try and get away with TB shafts.