Aluminium Gears

[AdamHeard]

Originally Posted by sgreco

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.

You wouldn't want to cut direct to thickness on the waterjet anyway with the draft angle created (unless you've got a sponsor with a tilting head).

You'd want to stack thinner gears with both processes, and laser arguably is the faster process for thinner material.

[Chris is me]

Originally Posted by 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?).

This is pretty smart design. The FP gearbox is actually quite similar. Emulating this kind of gearbox in other applications is something I'm aiming to do.

[AdamHeard]

Originally Posted by Chris is me

This is pretty smart design. The FP gearbox is actually quite similar. Emulating this kind of gearbox in other applications is something I'm aiming to do.

It is smart design in terms of pure tooth loading, but for FRC it can be more difficult to do. It requires ordering gears of multiple varieties. This could be a nonissue for some teams, but it can take longer and be more expensive for others.

We nearly "standardize" on 20dp, and try our best to stick to AM. His gears are cheap, in stock, and ship fast. We also have a large stockpile on hand, and have sometimes grabbed stock gears off old robots to modify then replace when the real order comes in.

Also, utlizing his 50T 6061 Al gears and heavily pocketing them, you can probably get gearboxes comparable in weight. Even with using pure 20DP, our gearboxes are some of the lightest I've seen made (for drive and mechanisms).

[Cory]

Originally Posted by Chris is me

This is pretty smart design. The FP gearbox is actually quite similar. Emulating this kind of gearbox in other applications is something I'm aiming to do.

The only problem is it relies on (Out of) Stock Drive Products to get the 32 DP gears. They also come in plain bore, which is no problem for our two teams since we lighten all our gears anyways and have hex broaching capabilities, but it can add up to a lot more work for the average team.

[Tristan Lall]

PIC Design is another supplier of aluminum (and other) gears that may work for you. Although their lead time was not exactly spectacular the last few times I used them, their aluminum gears are available in conveniently small sizes. (32 pitch, 0.7 module and 0.8 module, for example.)

SDP/SI's catalogue is well-provisioned with aluminum gears. However, they seem to have been slashing stock the last few times I tried to order from them. There were numerous items unavailable, which necessitated some creative choices of gears and pitches. This included the substitution of a 0.8 module gear for a 32 pitch one (0.8 module = 31.75 pitch, so they work very well together), and the use of an acetal pinion (with brass hub) on a BaneBots motor.

Incidentally, for almost every gearbox I've done, I've tried to choose the pitches based on the expected load at every interface (mesh and shaft). (That turned out badly one year, in 2004, when an underestimate of the dynamic loads resulted in gear teeth everywhere—somewhat ironically, it was partly because I was trying to standardize the pitches between the first two stages. On the other hand, once corrected with an appropriate gear set, the transmission was fantastic—this was a 6-motor, 2-speed drivetrain using three different motor types, and needed a fair bit of complexity to interface with two pinions and a shaft, all driven at different speeds.) It definitely saves weight and space, and definitely adds complexity and lengthens the design process. My opinion is: do the bulk of the design ahead of the season, so that you can concentrate on little details like optimizing the gears. Then improve it as much as the rules demand (to ensure legality), and then pull the trigger on the supply chain as soon as possible after kickoff.

[Chris Hibner]

Originally Posted by leesa

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. 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.

Reported.