Source for Belts and pulleys

[lemiant]

The KoP this year is using belts. Has FIRST told us where they are getting them, or if they will be available to be bought separately? Additionally where have teams bought belts and pulleys in the past (and what post-machining was necessary to get them on an FRC robot)?

[AdamHeard]

We love sdp-si for plastic pulleys, and some general ones.

BB manufacturing is also decent for pulleys and belts.

[R.C.]

Originally Posted by AdamHeard

We love sdp-si for plastic pulleys, and some general ones.

BB manufacturing is also decent for pulleys and belts.

Ditto,

We have made our own pulleys from SDP-SI models as well. It seems to work well and so far no issues. Its a super low cost option to buying them but it requires a CNC mill/laser/water etc...

-RC

[CalTran]

Originally Posted by R.C.

Ditto,

We have made our own pulleys from SDP-SI models as well. It seems to work well and so far no issues. Its a super low cost option to buying them but it requires a CNC mill/laser/water etc...

-RC

I'm curious as to how you "make" a pulley. Does this involve not having a flange on the edge, or somewhat complicated machining?

[R.C.]

Originally Posted by CalTran

I'm curious as to how you "make" a pulley. Does this involve not having a flange on the edge, or somewhat complicated machining?

Its not bad at all really.

We plan for the 2013 season to just buy .375" plate. Router out the shape and do the bore at the same time (not out the corners of the hex). Create a bolt flange pattern similar to the bolt pattern AM/IFI uses. And just rivet on 1/32 flanges out of polycarb or 1/16" polycarb.

Our biggest gripe is normally just getting the pulleys along with changing ratios down the road with belts. So having the ability to make whatever size pulley we want is awesome. I've contacted the FIRST gates rep about models before and they've been happy to send pdf's or coordinates of the belt/pulley profile. I'd love to just find a generator, but no luck so far.

-RC

[CalTran]

Huh. That makes more sense than I thought it would.

[lemiant]

Originally Posted by R.C.

(not out the corners of the hex)

What do you mean by this?

[R.C.]

Originally Posted by lemiant

What do you mean by this?

So instead of broaching later, you can just mill out the corner of the hex. Allowing you to fit the part over hex shaft without broaching. Used this technique on our shooter wheels last year and our arm sprocket.



-RC

[CalTran]

Never though about doing hex like that. Makes a lot of sense. And it saves our team kinda a lot in terms of us, if ever switching to hex (hopefully!) the we wouldn't have to buy a broach machine.

[Nuttyman54]

Originally Posted by CalTran

Never though about doing hex like that. Makes a lot of sense. And it saves our team kinda a lot in terms of us, if ever switching to hex (hopefully!) the we wouldn't have to buy a broach machine.

I've used this method before on other non-FIRST projects that required high precision hex alignment, and it works quite well. The only downside is that you can't go very deep with it on small hex sizes. Typically you don't want to broach very deep anyways, so it's not usually a problem.

That being said, in most cases it's easier to broach. You can hex broach most wheels/hubs for FIRST with just a regular arbor press and some cutting fluid if you're careful, so it tends to require less time than trying to mill it. If you have access to a mill, you most likely have access or room for a press that can broach.

[Cal578]

I'm surprised there hasn't been any action on this thread since the game was announced and we got the details on the drive parts in the KoP. Maybe it's in another thread that I've missed, but I've searched and haven't seen it.

The KoP contains two 39-tooth aluminum pulleys, 5mm pitch, 30mm wide. The belts are 15mm wide, so the idea (I presume) is to run two belts side by side on each pulley, going to 15mm width pulleys on separate wheels. Not sure I would have designed it that way, because I don't like the belts rubbing where they cross, but I guess it will work.

The part number given in the Drive Base checklist is P39-5M-30 AL. Searching for "pulley" on AndyMark yields the am-2265, which gives more details such as Gates part number 39-5M25SP01. I can't find either part number, or anything like them, on Gates (or McMaster, or anything else). I've found pulleys (or "sprockets") for 5mm HTD belts, but only in 15mm widths.

We're considering using a different size pulley on the gearbox driveshaft, to change the torque/speed characteristics. For now, we'll try to stay close to the original design of two belts coming off the drive pulley, but we may need to change that. AndyMark doesn't sell any other size, and I can't find it anywhere else.

We don't have the ability to make these parts from scratch. We could combine two smaller pulleys, machining off the flanges where needed (but maybe best to leave at least one flange). How to mount these would be a design consideration, but I think we can figure that out.

Any help on finding sources for these parts would be greatly appreciated. Links are especially helpful.

[pfreivald]

Originally Posted by Cal578

Any help on finding sources for these parts would be greatly appreciated. Links are especially helpful.

http://www.mcmaster.com/ (My favorite site for everything, not always the best for pulleys, though, because they carry mostly steel or plastic)
http://www.bbman.com/products/belts.html (Official Gates distributor)
https://sdp-si.com/eStore/ (Lots of variety especially in timing belt pulleys and belts)

[iyermihir]

Originally Posted by R.C.

So having the ability to make whatever size pulley we want is awesome. I've contacted the FIRST gates rep about models before and they've been happy to send pdf's or coordinates of the belt/pulley profile. I'd love to just find a generator, but no luck so far.

-RC

Is it possible to design a pulley of any size with just the belt profile?
We made some pulleys of weird sizes out of acrylic for the 2012 season that were light and cheap, but it took some tweaking to get it right.

-Mihir

[R.C.]

Originally Posted by iyermihir

Is it possible to design a pulley of any size with just the belt profile?
We made some pulleys of weird sizes out of acrylic for the 2012 season that were light and cheap, but it took some tweaking to get it right.

-Mihir

We don't use the belt profile but instead the actual pulley profile.

We use only GT2 5mm x 9mm wide. But you can use other sizes: 2mm/3mm work, 973 used those sizes successfully this year.

-RC

[Joe G.]

https://sdp-si.com/ is a good source. In addition to a wide array of standard belts and pulleys, they sell timing belt pulley stock, which allows you to custom turn pulleys out of an extruded profile. Big money saver if you have the machining resources. They also have one of the best center-center distance calculators I've ever used.