25# Sprockets

[Cory]

Originally Posted by sanddrag

More like $12 each. Hubbed sprockets. It's only probably $2 of bar stock so there's some savings. Not much trouble at all in a VMC. On a router I wouldn't bother.

Are you unable to use the Vexpro sprockets?

[Akash Rastogi]

Originally Posted by AdamHeard

This is all true, but is way overkill.

Sprockets for FRC use can be cut by just about any 2d method (CNC router, mill, waterjet, laster) into 6061 Aluminum plate and be just fine. The cut time isn't crazy high to do so either.

I've been meaning to run plate sprockets and gears on a sponsor's laser, do you have experience with any pros/cons of having them waterjetted vs laser cut?

Thanks,
Akash

[AdamHeard]

Originally Posted by Akash Rastogi

I've been meaning to run plate sprockets and gears on a sponsor's laser, do you have experience with any pros/cons of having them waterjetted vs laser cut?

Thanks,
Akash

It really depends on the specific machine, and the knowledge of the person operating it.

First I'd say get some samples cut, and see for yourself. That trumps all advice I'm about to give.

We've had gearing water and laser cut on multiple different machines and different sponsors.

Most waterjets take a real quality hit on curved teeth as the cut is slowed down and excessive blowout seems to happen. The lower the toothcount, the more the teeth are curved. Even with this, pretty much every gear we've cut at 16DP or larger (including a 9T pinion) has run fine after some wear in. Our swerve also ran a 50T 20DP gear that ran fine.

When you get into huge gears, like the 300ish toothcount 24DP turret gear for Encore, the teeth are essentially straight and the smaller toothsize isn't really an issue.

Every waterjet gear we've cut has required some run/wear in, but has performed fine and lasted the season.

For Lasered gears, if they know how to run their machine right, you should get far better results that allow much more freedom in terms of small teeth and small toothcount. I did have one laser run that was just too gummed around the edges and was a total failure; this however was from a company that primarily worked in steel, and never worked on parts with fine detail.

As for sprockets, pretty much everything should work. For some waterjets you may want to artificially shrink the sprocket a few thou. Wear in will also be necessary (but can be done on the final vehicle of course) unless they are nicely tumbled or something. Laser should make beautiful sprockets.

In summary, we love it as a process. It's not the greatest method for small gears, and small teeth; but these are the easiest gears to cheaply get premade, so it isn't really an issue.

[ajlapp]

We routinely make our own #25 sprockets from 0.09" plate aluminum on the waterjet. 6061 works fine.

We also used custom sprockets in our drivetrain this season using the same process....no maintenance and no failures.

[Akash Rastogi]

Originally Posted by AdamHeard

For Lasered gears, if they know how to run their machine right, you should get far better results that allow much more freedom in terms of small teeth and small toothcount. I did have one laser run that was just too gummed around the edges and was a total failure; this however was from a company that primarily worked in steel, and never worked on parts with fine detail.

As for sprockets, pretty much everything should work. For some waterjets you may want to artificially shrink the sprocket a few thou. Wear in will also be necessary (but can be done on the final vehicle of course) unless they are nicely tumbled or something. Laser should make beautiful sprockets.

In summary, we love it as a process. It's not the greatest method for small gears, and small teeth; but these are the easiest gears to cheaply get premade, so it isn't really an issue.

Thanks for all the input and feedback!

One more item: Would the heat from the laser make the teeth brittle or anything?

[nathan_hui]

If anything, should anneal the metal, unless you quench the part after fabrication.

[AdamHeard]

Originally Posted by Akash Rastogi

Thanks for all the input and feedback!

One more item: Would the heat from the laser make the teeth brittle or anything?

Don't take this as fact. I would wager it anneals the material, but I've heard that if the settings are correct it can locally harden.

I'd ask the shop to be sure.

[Akash Rastogi]

Originally Posted by AdamHeard

Don't take this as fact. I would wager it anneals the material, but I've heard that if the settings are correct it can locally harden.

I'd ask the shop to be sure.

Will do!

Thanks,
Akash

[sanddrag]

Originally Posted by Cory

Are you unable to use the Vexpro sprockets?

Need 7/16" hex. If they made them in 7/16" hex, we'd be all over it.

[Redo91]

We had our sponsor laser cut some steel sprockets for us when I was a student. The only trouble we had was the chain would skip off. That was solved by beveling the teeth on a belt sander. We never had an issue with them after that.

[R.C.]

Originally Posted by sanddrag

Need 7/16" hex. If they made them in 7/16" hex, we'd be all over it.

Do you use 1/2" hex on the other side for the wheel?

We do the 7/16" step down as well (thanks adam!) and we love it. But the sprocket side is 1/2" hex.

I can see why its 7/16" on both sides as you can just buy precision 7075" (1/2" round) and just hex the portions you'd like vs machining everything down from a larger size. Is that the reasoning?

-RC

[AdamHeard]

Originally Posted by R.C.

Do you use 1/2" hex on the other side for the wheel?

We do the 7/16" step down as well (thanks adam!) and we love it. But the sprocket side is 1/2" hex.

I can see why its 7/16" on both sides as you can just buy precision 7075" (1/2" round) and just hex the portions you'd like vs machining everything down from a larger size. Is that the reasoning?

-RC

That's why 254 does it.

254 is still forced to use 1/2" hex on the gearbox though.

[sanddrag]

Originally Posted by R.C.

Do you use 1/2" hex on the other side for the wheel?

We do the 7/16" step down as well (thanks adam!) and we love it. But the sprocket side is 1/2" hex.

I can see why its 7/16" on both sides as you can just buy precision 7075" (1/2" round) and just hex the portions you'd like vs machining everything down from a larger size. Is that the reasoning?

-RC

Exactly. .500 PG 7075 round. Mill the hexes, done deal.