3 speed freewheel on a fixed hub?
Gavin Gilbert
Posts: 4,019
Possible? Wise?
Playing with my mictometer this evening tells me the average ratio of thread to 5 speed freewheel width is 38% - i.e. 38% of the freewheel is supported on the hub.
With the fixed FB hub I want to use on the '47 Claud/Osgear, a 3 speed freewheel gives a 33% ratio.
I'm not good on the engineering side of things - is the 5% difference going to be significant and would mounting the 3 speed unit be safe?
Playing with my mictometer this evening tells me the average ratio of thread to 5 speed freewheel width is 38% - i.e. 38% of the freewheel is supported on the hub.
With the fixed FB hub I want to use on the '47 Claud/Osgear, a 3 speed freewheel gives a 33% ratio.
I'm not good on the engineering side of things - is the 5% difference going to be significant and would mounting the 3 speed unit be safe?
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Comments
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if your proposing haveing a mech on there and running a geared fixed then, as was pointed out to me when i was considering doing the same with a 5 speed, when you put resistance to the pedals, you'll have to take up the slack in the mech first, it laying out allong the chainstay and when you pedal it moving itself back to its normal positon before it affects the rear wheel.
your actual question is are you able to mount a 3 speed freewheel (and due to how long i've been awake and driving for i missed what you were asking) i'd guess it'd be ok, how many mill is it out?My signature was stolen by a moose
that will be all
trying to get GT James banned since tuesday0 -
Not running fixed - running one of these:
www.classiclightweights.co.uk/designs/osgear-hs.html :shock:0 -
Gavin, it is possible but I wouldn't myself.
Though having said that I bought a Carlton Gran Sport years ago and the freewheel thread was shot. The chap had just fitted it on the fixed side and ran it like that for 5 or 6 years. The hub was a steel barrell l/f campag.
I threw it out because it was rusty! DOH!
The minimum thread engagement needed for safety is 3 full turns, this is a general workshop rule of thumb so not gospel. Are the freewheel threads a good fit or piss fit on the hub?
Can you measure the amount of thread on the hub and freewheel and let me know.
I said P I S S fit not wee wee fit!0 -
what you really need to do is build up a wheel with a Sturmy-Archer ASC hub - 3 speed fixed.
mine rides ever so smoothlyRecipe: shave legs sparingly, rub in embrocation and drizzle with freshly squeezed baby oil.0 -
pete.whelan wrote:what you really need to do is build up a wheel with a Sturmy-Archer ASC hub - 3 speed fixed.
mine rides ever so smoothly
ASC? It's a bloody Osgear project :roll: I chose a fairly bland luggless Claud Butler to show off the gear!
Dickie: the hub thread measures 6mm but I will need lose 0.5mm of this to fit the alloy spoke protector disk. The freehub is 18mm.
It's not looking likely is it
Hope I can pick up a rear Blumfield at Ripley in October.... 0 -
Am I missing something here? (Quite possible.)
Why not just use a hub designed for a freewheel."Swearing, it turns out, is big and clever" - Jarvis Cocker0 -
NorwegianBlue wrote:Am I missing something here? (Quite possible.)
Why not just use a hub designed for a freewheel.
because a period correct matched pair of 'racing' freewheel hubs are as rare as hens teeth - but it looks like I'll need to keep on looking 0
