10-30-2015 10:41 AM

Ari423

Re: pic: Poly-carbonate 2 Speed Gearbox

I'm not going to comment on the mechanics of the gearbox because there are a lot of people on here more qualified to debate that than I am.

I just have two questions:
1) How much does it weigh?
2) Do you have any plans to cover the very exposed gears to protect dust and fingers from getting stuck in there and jamming it up?

10-30-2015 11:48 AM

notmattlythgoe

Re: pic: Poly-carbonate 2 Speed Gearbox

Many of the current FRC gearboxes are open like this.
http://www.andymark.com/product-p/am-0957.htm
http://www.vexrobotics.com/vexpro/mo...es/wcp-ds.html
http://www.team221.com/viewproduct.php?id=100

10-30-2015 12:01 PM

Chris Endres

Re: pic: Poly-carbonate 2 Speed Gearbox

Very nice.

However, you're going to want to watch out for possible deformation of the plates under load, especially the plate that CIMs are mounted to.

10-30-2015 12:16 PM

Chris is me

Re: pic: Poly-carbonate 2 Speed Gearbox

If you want to be extra safe against deformation, you'll want to upgrade to 3/8ths polycarbonate. 1/4" probably deflects too much, even un-lightened.

It doesn't end up saving you weight over an optimized aluminum gearbox, but it's hard to do gearboxes with polycarbonate.

10-30-2015 12:16 PM

jkelleyrtp

Re: pic: Poly-carbonate 2 Speed Gearbox

Very nice, I've been researching good plastics for gearboxes and found that acetal and thick polycarb will work fine, but polycarb does have more flex in it. I'd recommend some sort of bracing/stand for the cims to hold them in place during load (as said above).

Also, 254 has made a plastic-based gearbox and made their mounting frames out of acetal.

10-30-2015 03:54 PM

asid61

Re: pic: Poly-carbonate 2 Speed Gearbox

If you could do a stress test on the holes compared to the WCP gearbox plates, that would be interesting to see.

10-30-2015 04:09 PM

Cory

Re: pic: Poly-carbonate 2 Speed Gearbox

It wasn't worth it though and I'm pretty sure the solid delrin plate was just about as heavy as a pocketed aluminum plate...and substantially less rigid.

10-30-2015 07:15 PM

cbale2000

Re: pic: Poly-carbonate 2 Speed Gearbox

Having built several polycarbonate gearboxes I would have to agree with this. If it were designed like an actual box, where you have polycarbonate connected on all 6 sides supporting itself you might be able to get away with 1/4" (as my team has in the past), but if you plan to support it like that, you'll definitely want to go to 3/8" for rigidity.

You might also consider mounting another plate of polycarbonate between the gearbox and the output sprocket. Having less distance between plates should improve the rigidity.

This is what we built a few years back. Note that the aluminum plate was eventually replaced with polycarbonate. Also worth noting that the gearbox is still around 8 years later. The gears failed a while back, but the box is still in great shape.

10-30-2015 08:34 PM

kiettyyyy

Re: pic: Poly-carbonate 2 Speed Gearbox

On top of that, I recall having issues with being unable to draw heat out of the CIM motors since we used delrin plate.

We did a test with the same gearbox under the same load using pocketed aluminum plate. It resulted in having a cooler motor over the same testing duration.