Belt pulley options

[WarehouseCrew]

Can someone recommend a source for pulleys that work with the belts in the kit of parts? We would like to gear up a CIM motor to spin a wheel faster.

We would also like to use a hex bored pulley (am-2452) for the drive train (AndyMark is out of stock).

[Mk.32]

My team's bot this year runs pretty much only GT2 3mm and 5mm timing belts for just about everything.

The belts/pulleys that come in the KOP are known as Gates HTD 5mm, Gates GT2 3mm/5mm sizing are a different line from the same company that is newer. The are some what interchangeable (gate's site has info on this) but not recommended.

The "fastest" option if you have an CNC mill is with the 5mm HTD/GT2 pulleys you can just machine them out with an 3/32 endmill finish cut: http://www.chiefdelphi.com/media/photos/38380 this allows you to also machine in a hex bore because 99.999% (minus AM) of the stuff you buy will not be in hex.

But commercial suppliers we like are: https://sdp-si.com/eStore/ and http://www.bbman.com/
SDP ships from NY and BBman shipped from IN, and lead teams are generally 1-2 days before shipping IF ALL items in a order ARE IN STOCK. For belts that are out of stock, lead times are in the weeks. None of the pulleys you get them these guys will come with a hex bore, you have to do it your stuff with a broach or mill (we got a local team to help us out there).

You can also use gears to gear up a CIM, the new AM Spinbox does this and AM has the gears with the right bores. Or chain even.

Good luck!

[WarehouseCrew]

Thanks for the information. This is our first year using belts.

[Lil' Lavery]

Remember that changing the diameter of your pulleys also impacts the length of belt required (assuming you keep your wheels at the same spacing).

[Mk.32]

Originally Posted by Lil' Lavery

Remember that changing the diameter of your pulleys also impacts the length of belt required (assuming you keep your wheels at the same spacing).

Also: https://sdp-si.com/eStore/cd.asp
Useful tool for calculating C-c distance.

[WarehouseCrew]

What do you use to tension your belts?

[Alan Anderson]

Originally Posted by WarehouseCrew

What do you use to tension your belts?

Proper center-to-center distance.

[WarehouseCrew]

Do belts stretch like chains do?

I think some cars have idler pulleys to keep the belts under the correct tension. It would be nice (and lighter) if idler/tension pulleys were not needed.

[Mk.32]

These belts have a fiberglass cord backing so in FRC usage they don't have a big problem stretching. We add .005 - .003 inches to the C-C distance given by the calculator and have no had any issues.

[sanddrag]

Originally Posted by Alan Anderson

Proper center-to-center distance.

How do you determine this? I used the online calculator from SDP-SI for some XL belts and pulleys from McMaster, and when they showed up it was way off. So, I'm just going with holding the actual setup tight and measuring it out. Does this sound like a plan?

[Mk.32]

Originally Posted by sanddrag

How do you determine this? I used the online calculator from SDP-SI for some XL belts and pulleys from McMaster, and when they showed up it was way off. So, I'm just going with holding the actual setup tight and measuring it out. Does this sound like a plan?

We used the SDP-SI calculator for over 8 belt runs and they have all been dead on, we are using GT2 3mm and 5mm pitches. I believe you can also calculate this using pitch lengths and diameters giving by the part's specs.

Could you have had an inches metric conversion error? Or an mis ordered part?

[mikegrundvig]

I've used the SDP calculator for multiple projects as well, FRC and others, and it's never led me wrong. I'd suspect something else happened there.

-Mike

[JCharlton]

If you're planning to spin a shooter wheel at high speed I'd suggest urethane belting instead of a toothed belt.

• It's a piece of cake to make a pulley on a lathe
• The center distance isn't critical
• Belting is cheap and easy to make in any length
• If the wheel jams the belt can be set to slip a little preventing a full stall.