High Pulley Ratios?

[silo_xtreme]

Hey All,

I'm trying to slow down a motor via belt and pulley (lighter, cheaper, etc..).  The problem I'm running into is that I'm trying to achieve a high ratio (i.e. 20:1, 30:1) and the best differences between 2 pulleys that I have been able to find are 5:1 - 7:1 between sdp-si.com and mcmaster.com.  I'm just wondering if anyone has come across a similar problem and decided to use multiple pulleys or have found the proper products some where? 

[SixRingz]

What kind of motor are you trying to slow down? It's a bit hard to give a solution without that knowledge. I'm guessing it's big if you are using pulleys and belts to slow it down?

[silo_xtreme]

Hi Six, my bad...

It's a brushless motor with 1500 (max load) to 3000 (max eff) RPM, that i'd like to slow down and get more torque. The shaft is 8mm (actually, it's 8mm with a 1.5mm cut on one side).

Yes, I would like to achieve a 20:1 - 30:1 ratio.

[bukowski]

Look at companies like motion industries or boston gear that deal exclusively with power transmission.
For a 20:1 you will probably have to use 4 pulleys.


Two 5:1 pulley systems = 25:1
bear in mind that as the input torque increases, so do the size of the belts and pulleys.

[silo_xtreme]

Bukowsi,

Perfect!  Just the confirmation that I was looking for. 

Thank You!