Starter sprag clutch specifications

[karlburroughs]

Hi,
Looking at running a sealed bearing sprag clutch, rather than the standard (wet, oiled) sprag bearing. Does anyone know the max torque specification for the standard sprag, or what I should aim for please?
Thank you.

 

[karlburroughs]

Hi, found the spec in a 2010 discussion. Steiber DC4127(3C) - 224Nm

 

[worntorn]

I've been using a Bok Choy DC4127. Works great!

Glen

 

[karlburroughs]

Thanks Glen. It's not for a Mk3, it's for a belt drive 750!

 

[worntorn]

Cool!
Have you found a supplier for a sealed version of the sprag?

Glen

 

[baz]

Hi,
Looking at running a sealed bearing sprag clutch, rather than the standard (wet, oiled) sprag bearing. Does anyone know the max torque specification for the standard sprag, or what I should aim for please?
Thank you.

I have an Alton starter running in a dry belt drive primary
Alton told me there is no need for lubricant on the sprag

 

[karlburroughs]

Cool!
Have you found a supplier for a sealed version of the sprag?

Glen

Not really. Most bearing stockists list sealed sprag clutch/freewheel bearings.
But to achieve the same torque capacity they are much larger than the Norton bearing. For instance there is a 40*80*22 sprag bearing with a rating of 325Nm. Or a 35*62*20 rated at 175Nm (224Nm standard bearing).
I am trying to drive a belt drive clutch drum with a second belt, but struggling for space to fit such a freewheel bearing, etc. Work in progress!

 

[Tripler]

I have an Alton starter running in a dry belt drive primary
Alton told me there is no need for lubricant on the sprag

that seems counter intuitive. most bearings last longer if lubricated, is there not a possibility of it sticking in the engaged position due to no lubrication. just thinking out loud Baz

 

[baz]

that seems counter intuitive. most bearings last longer if lubricated, is there not a possibility of it sticking in the engaged position due to no lubrication. just thinking out loud Baz

I agree
Even though I was told by Alton no lubricant was needed I give it a squirt of oil every couple of months or so

 

[kommando]

It's an all metal clutch, when freewheeling there is no load, when engaged you have loads but only movement during the short engagement time. Air Conditioning clutches are metal to metal and run dry, the problem with dry running is rust as they are out in the open.