Aluminium Gears

[Chris is me]

Hey CD, I'm looking for any and all COTS aluminum gears on the market. In particular, larger 32DP gears with decent face widths would be really cool. I realize aluminum gears are pricey and hard to find, but I wanna know if CD has any sources I don't know about and couldn't find on a Google search. Thanks!

[AdamHeard]

Originally Posted by Chris is me

Hey CD, I'm looking for any and all COTS aluminum gears on the market. In particular, larger 32DP gears with decent face widths would be really cool. I realize aluminum gears are pricey and hard to find, but I wanna know if CD has any sources I don't know about and couldn't find on a Google search. Thanks!

I recently noticed that the tetrix gears are .25" face width 32DP. Using an 8T brass pinion to the 120T that's 15:1!

Sdp-si is the only place I've found aluminum gears at a reasonable price (aside from the limited 20DP selection at AM). Although I've only seem them up to 3/16".

What is this for?

[Chris is me]

I'm interested in prototyping various gearbox arrangements to see if I can save space or weight in small reductions. I also want to test a drivetrain with these gears. I haven't run the numbers on tooth loads, though.

[Chris Hibner]

Back when I was on 308 we did aluminum gears in the drivetrain for two seasons (2001 and 2002). I think we used 24 DP in 2002 and they lasted the entire year until the first match of the world championship finals - then they shredded. Pretty bad timing. I think you can find pictures of the gearbox carnage somewhere on this site. In fairness to those gears, we're pretty sure the shaft shifted leaving only about 60% engagement along the face width.

In 2002, those gears were 1/4 inch face width, but we sandwiched multiple gears together to increase the effective face width. I really wish I could remember the source where we bought the gears. Although, as long ago as that was they may not be in business any more.

One important note: when we were doing tooth stress calculations, I remember that 24 DP was pretty marginal in later stages of the gearbox, so I would expect 32 to not be able to withstand the loads without getting crazy with the face width. Just be sure to do all of the calculations and double check them.

In 2001, we machined custom aluminum gears because we were worried about tooth loads with small gear teeth. I want to say we made them in the neighborhood of 12 to 16 DP. They looked a little weird, but worked great.

[Redo91]

Check out JVN's post about aluminum plate gears here.

[Chris is me]

Originally Posted by Redo91

Check out JVN's post about aluminum plate gears here.

That's the idea, but unfortunately we don't have any sponsors with a laser. The hope is to buy a bunch off the shelf and play with them.

I'm not sure if the Tetrix gearset is worth trying or not, I imagine they are probably pricy.

[AdamHeard]

Originally Posted by Chris is me

That's the idea, but unfortunately we don't have any sponsors with a laser. The hope is to buy a bunch off the shelf and play with them.

I'm not sure if the Tetrix gearset is worth trying or not, I imagine they are probably pricy.

Get some sponsors then, google, phonebook, etc... It doesn't have to be laser either, could be waterjet.

The tetrix gears aren't really bad at all in price when compared to other 32DP aluminum gears. a 120 tooth for $30. Now that I know about it, we're certainly interested in doing a 32DP based gearbox for 500 sized motors as 32DP pinions are cheaply and easily available in varied sizes at EVERY hobby shop.

I think effective design and pocketing of existing steel gears would yield more bang for your buck than investigating aluminum gears.

You should also learn how to calculate gearstrengh using Lewis Bending Numbers, once you do it's trivial to determine if a gear will survive; no need to experiment to solve a problem that's been solved for a hundred years.

[Chris is me]

Originally Posted by AdamHeard

Get some sponsors then, google, phonebook, etc... It doesn't have to be laser either, could be waterjet.

We're certainly working on it. Our economic region isn't particularly bright (Troy has 14% unemployment and I bet Latham isn't much better), but if we do we'll see. I'm just generally a fan of modifying COTS parts in house, since that's more reliable than counting on the donated services of a sponsor, plus it puts less stress on them.

I think effective design and pocketing of existing steel gears would yield more bang for your buck than investigating aluminum gears.

That's probably true, I'm just interested in seeing if we can throw a few bucks at the problem to avoid having to pocket steel.

You should also learn how to calculate gearstrengh using Lewis Bending Numbers, once you do it's trivial to determine if a gear will survive; no need to experiment to solve a problem that's been solved for a hundred years.

I've heard that Lewis numbers tend to be conservative, but I've still been meaning to learn. Thanks for the reminder. Lewis numbers do say my drivetrain application should hold up.

[Cory]

Originally Posted by Redo91

Check out JVN's post about aluminum plate gears here.

I would be extremely concerned about runout in a high speed application such as the initial reduction(s) in a gearbox, if using this method.

The tetrix gears are probably 5000 or 6000 series aluminum which is less than ideal for any high torque situation.

[Aren Siekmeier]

If you've found a bunch of reasonably priced 32dp aluminum gears that just aren't wide enough for your purposes, you can always just stack them. I'm no expert, but that seems to accomplish the same thing, in terms of pressure. Maybe not so much in terms of the statics of the material stress or whatever is going on there, since the gears aren't actually connected, but you're at least distributing the same load over a larger area.

[Hawiian Cadder]

There was a team at CMP that used anodized aluminum gears that were similar to the gearset that andymark sells, i believe they were going to try to start selling them, does anyone else have any more information?

[R.C.]

Originally Posted by Hawiian Cadder

There was a team at CMP that used anodized aluminum gears that were similar to the gearset that andymark sells, i believe they were going to try to start selling them, does anyone else have any more information?

That was Team 1323/973. I'll put up a pic soon.

-RC

[sanddrag]

Originally Posted by Cory

I would be extremely concerned about runout in a high speed application such as the initial reduction(s) in a gearbox, if using this method.

And the draft angle.

[sgreco]

Originally Posted by AdamHeard

Get some sponsors then, google, phonebook, etc... It doesn't have to be laser either, could be waterjet.

Waterjet is probably better for this application. Laser would require plate gears since all lasers are limited in the thickness of aluminum they cut (some more so than others) due to aluminum's reflective properties. Waterjet could cut the proper thickness material in one cut.

Chris, I wish I could help you out, but our metal shop has been unresponsive recently on account of new business and tied up equipment.

[JesseK]

I know it's an anecdote, but the Space Cookies (1868) had a gorgeous gearbox for their arm that didn't seem to have the same DP for more than 2 stages. It started at 32 DP on the motor pinion gear and was much much lower by the last stage (16DP maybe?).

PINK had something similar for their crazy arm rotary joint. If you didn't get a chance to see that thing in action, sometimes it would snap from one side to the other -- so lower DP on the final stages was almost necessary. Their mentor in DC told me they would gear it down some more before Championships, but I didn't get to see the effect in St. Louis.

IMO, 32 DP is a bit risky to put on all stages of a drive train for the sheer fact that 32 DP gears need more alignment precision for proper mesh than their lower DP counterparts.