I need a small ratchet mechanism (not the wrench) with a very fine step
size while still being about to resist a large torque. It would be
about 1-2 cm (0.4-0.8 in) in diameter, with a step size of 1-5 degrees,
and able to withstand a torque in the neighborhood of 1 kilogram-meter
(7 foot-pounds).

Do ratchets with these requirements exist, and if so, who manufactures
them? I would gladly like to know anything about ratchets that are
close to these specifications.

Thanks very much for you help!

Jess Riedel

wrote:
I need a small ratchet mechanism (not the wrench) with a very fine step
size while still being about to resist a large torque. It would be
about 1-2 cm (0.4-0.8 in) in diameter, with a step size of 1-5 degrees,
and able to withstand a torque in the neighborhood of 1 kilogram-meter
(7 foot-pounds).

Do ratchets with these requirements exist, and if so, who manufactures
them? I would gladly like to know anything about ratchets that are
close to these specifications.


Is this something you're building? because you say, "not the wrench".
Maybe look at roller-clutches, aka. sprags.
They will give you close to 0 degrees.
A .375 ID. is about .675 OD. I don't have the info handy right now.
7 ft-lb., may be high for a .375 clutch, a .500 ID will do that
I think.

Look for "Torrington roller clutch".
They start at .250 & go up.
I use these quite often.

Hope this helps.
--
Gary A. Gorgen | "From ideas to PRODUCTS"
| Tunxis Design Inc.
| Cupertino, Ca. 95014

In article .com,
wrote:

I need a small ratchet mechanism (not the wrench) with a very fine step
size while still being about to resist a large torque. It would be
about 1-2 cm (0.4-0.8 in) in diameter, with a step size of 1-5 degrees,
and able to withstand a torque in the neighborhood of 1 kilogram-meter
(7 foot-pounds).

Do ratchets with these requirements exist, and if so, who manufactures
them? I would gladly like to know anything about ratchets that are
close to these specifications.

It sounds like a "needle roller clutch" would work. SDP/SI sells them,
on pages 5-56 through 5-59 of their catalog 790-1
(http://www.sdp-si.com). I'm sure there are many other sources.

www.mcmaster.com lists the needle roller clutch bearings, page 1024
Looks like you will have to go to the 1/2x3/4" version to get the torque
loading necessary.

Spec list below. ID/OD/ width/ torque/ rpm/ pn/ price

1/8" 9/32" 1/4" 0.238 50,000
2489K1 $8.30

1/4" 7/16" 1/2" 1.434 38,000
2489K2 6.36

3/8" 5/8" 1/2" 3.784 25,300
2489K3 6.52

1/2" 3/4" 1/2" 6.134 18,700
2489K4 6.62

5/8" 7/8" 5/8" 11.918 14,700
2489K5 7.08

3/4" 1" 5/8" 16.335 11,300
2489K6 8.14

1" 1 5/16" 5/8" 34.338 8,670
2489K7 10.62






wrote:

I need a small ratchet mechanism (not the wrench) with a very fine step
size while still being about to resist a large torque. It would be
about 1-2 cm (0.4-0.8 in) in diameter, with a step size of 1-5 degrees,
and able to withstand a torque in the neighborhood of 1 kilogram-meter
(7 foot-pounds).

Do ratchets with these requirements exist, and if so, who manufactures
them? I would gladly like to know anything about ratchets that are
close to these specifications.

Thanks very much for you help!

Jess Riedel

In article .net,
says...
www.mcmaster.com lists the needle roller clutch bearings, page 1024
Looks like you will have to go to the 1/2x3/4" version to get the torque
loading necessary.


And for higher torque capacity for a given size package, sprag clutches
are a possibility, for example...

http://www.gmn.de/e/

Ned Simmons