pic: 1382 Brazil - Gear box

[tribotec_ca88]

Originally Posted by dez250

great job with the gearboxes and especially with the polycarbonate covers. I think its a great idea when a team has covers on their gearboxes, it keeps foreign debris out and it keeps damaged parts and grease contained within the robot.

Correct, the covers were a terrific addition...we used LEXAN , a sort of polycarbonate material that is one of the most widely known "plastics". (actually, I don't work with mechanics, so I just barely learned what Lexan was a few days ago...long story... It's amazing the variety of things FIRST teaches us!!!)...anyway, they're very lightweight...I'll try to post how much they weigh exactly, but unfortunately the only scale available in our room isn't working . also....affirmative: it's a dual-speed gear box.

Feel free to ask any other questions you may have....or visit our Forum at www.tribotecteam.com ...there are students there far more knowledgeable than me when it comes to mechanics...I'm just the "person-that-posts-pictures-of-our-creations-on-chiefdelphi" ...

[Stephen Kowski]

Originally Posted by tribotec_ca88

we used LEXAN , a sort of polycarbonate material that is one of the most widely known "plastics".

lexan is polycarbonate.....just more expensive since it is a trademarked name from GE....

[Andy A.]

I suspect that they've run some numbers and are sure that the gears will be up to the loads they are expecting. What concerns me is that as the gears wear, their strength will go down. Depending on what type of plastic it is, even exposure to sunlight could weaken it. What works now may not work a few weeks from now after some hard driving. I guess it hinges on the material. If they manage to get away with it, they'll have a nice little advantage in not having heavy steel gears.

As an aside, I noticed the other day that aluminum gears were available, and cheap! Is there any marked difference between an aluminum gear and say a nylon equivalent? Any practical experience with them?

-Andy A.

[sanddrag]

Originally Posted by Andy A.

As an aside, I noticed the other day that aluminum gears were available, and cheap!
-Andy A.

Care to give the source?

[Tristan Lall]

Originally Posted by Andy A.

As an aside, I noticed the other day that aluminum gears were available, and cheap! Is there any marked difference between an aluminum gear and say a nylon equivalent? Any practical experience with them?

For what it's worth, 188 managed to break a couple aluminum ones last year.... Actually, I ended up misjudging the loads on the gears a little, and ended up with too much torque on one particular pair of gears. (This was, mind you, in a very powerful transmission.) The aluminum gears above it (i.e. spinning faster, with less torque) in the transmission have worked perfectly, without so much as an unsightly mark on the teeth, after two regionals, the championship and an off-season event. For reference, the failed gears (26 & 84 T, 20° PA, 3/16" FW, 0.7 M, 2024-T4) were spinning at 3500 & 1000 (free) rpm, respectively, with around 1.2 HP driving them. The gears of the same size and composition (and the 32 P, 20° PA ones, which are very similar) at 5500 (free) rpm and above were undamaged and still function as intended. We actually bought nylon ones as spares for the upper stages, when we replaced the broken gears--thinking that the aluminum might have been unsuitable for those too--but as it turned out, they were never needed. Without knowing too much about the exact plastic properties under load, I would simply note that the tensile yield point is much lower for the nylon than the aluminum--a definite warning sign.

Originally Posted by sanddrag

Care to give the source?

Both of the following stock aluminum gears, and can (theoretically) cut custom sizes of stock pitches, including the ever-popular 0.7 module at PIC; also, be wary of the stamped 5052 aluminum gears at SDP/SI--I don't think they're too precise:
SDP/SI
PIC Design

[Squall]

We'll be using pneumatics to make the Gear's change.

The problem is that we'll have to be stopped to make this happen.

I'm more into eletronics and programming so I can't help you guys with the Gear Rations and stuff, but I'll se if I can get someone tomorrow to answer you guys!