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Sprag instead of pawls or star ratchet hubs??

890 Views 8 Replies 6 Participants Last post by totally_fixxated, Dec 24, 2005

man w/ one hand

Discussion Starter · Dec 22, 2005

I was czechen out the latest issue of Decline & saw the DT Swiss advertisement with the star ratchet hub & my brother, a mechanic, asked me why don't they build hubs with a sprag instead of star ratchets & pawls. He explained they were bomb proof, instant engaugement & most importantly CHEAP! Anyone ever tried a sprag application that you know of ??

O'yeah......Merry Christmas !!!!!

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man w/ one hand

Discussion Starter · #2 · Dec 22, 2005

I did a search on sprags & found lil' to nuthin' of a definition of sprag. However, my bro says it's a oneway clutch that freewheels one way & engauges the other. He says automatic transmissions in cars & trucks have'em in them.

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shiggy

· #3 · Dec 22, 2005

This is the first hit from Google
http://www.renold.com/Renold/web/si...chFreewheels/Sprag_Clutch_Index.asp?menuID=21
Fairly complete.

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Mike B.

· #4 · Dec 22, 2005

man w/ one hand said:
I was czechen out the latest issue of Decline & saw the DT Swiss advertisement with the star ratchet hub & my brother, a mechanic, asked me why don't they build hubs with a sprag instead of star ratchets & pawls. He explained they were bomb proof, instant engaugement & most importantly CHEAP! Anyone ever tried a sprag application that you know of ??

O'yeah......Merry Christmas !!!!!

As far as I know there aren't any currently available that can be made small enough and still handle the loads required. Weight becomes an issue as you make them larger of course and then fitting them within the current geometric constraints creeps in to the equation. Not saying it couldn't be done though.

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shiggy

· #5 · Dec 22, 2005

Mike B. said:
As far as I know there aren't any currently available that can be made small enough and still handle the loads required. Weight becomes an issue as you make them larger of course and then fitting them within the current geometric constraints creeps in to the equation. Not saying it couldn't be done though.

I was wondering about size. Bicycles have space and weight issues that are less of a concern it other applications.

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Ligero

· #6 · Dec 23, 2005

I could be wrong but I thought True precision hubs use a sprag clutch in their hubs.

http://trueprecision.net/c_products_mountain.html

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shiggy

· #7 · Dec 23, 2005

Ligero said:
I could be wrong but I thought True precision hubs use a sprag clutch in their hubs.

http://trueprecision.net/c_products_mountain.html

No idea if they use the sprag clutch. I do know that red-haze killed one (SS version) in 4 months. A NovaTech SS hub with pawls/ratchet takes all he can give it.

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pecka

· #8 · Dec 23, 2005

man w/ one hand said:
I was czechen out the latest issue of Decline & saw the DT Swiss advertisement with the star ratchet hub & my brother, a mechanic, asked me why don't they build hubs with a sprag instead of star ratchets & pawls. He explained they were bomb proof, instant engaugement & most importantly CHEAP! Anyone ever tried a sprag application that you know of ??

O'yeah......Merry Christmas !!!!!

This is something different, but it's worth checking - just click "technique" and than "ROLLIN' ROLL" in the menu.
I don't know how well it works or anything but I think you may be interested.

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totally_fixxated

· #9 · Dec 24, 2005

sprag

sprag is a bearing with ramps that will only let a shaft roll in one direction.
if the shaft tries to roll in opposite direction the bearings roll up the ramps
and lock the shaft.

www.powercranks.com use this type bearing.

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