Fixed gear question

[paczki]

I went to the local fixie shop to buy a single-speed freewheel to put on one side of one of my fixed/fixed wheel sets -- a set with Phil hubs. I'd understood that this was no big deal after reading 11.4s comment about a wheelset identical to mine here:

http://forums.thepaceline.net/showpost.php?p=673330&postcount=2

The local fixster at the shop told me it would work but it was a bit dangerous, the threads on the cog might get stripped and it would be "hanging off". Does this sound right?

Thanks.

[cp43]

My understanding is that the pitch of the threads is the same, so you can fit the freewheel on there. However, the track cog has fewer threads, so your freewheel won't be held on by as many threads as designed. So, what you were told is based in fact, but may not be an issue. I haven't tried it, but somewhere (that I can't find right now) Sheldon Brown says that it's ok, and won't cause problems. YMMV.

Chris

[mister]

if the amount of threads on the fixed side are enough to not strip with a cog on it why would a freewheel on there instead be any worse...

[Mike748]

Its going to thread down tight against the hub. Should be fine.

[Ti Designs]

Given the depth of the threading and the thread pitch (24 TPI) you can calculate the surface area with which you are working. Knowing the offset from the end of the freewheel to the center line of the cog and the diameter(s) you can calculate the sheer. Knowing the gear ratio you are running and the crank arm length, I think it's safe to say there's never going to be more than 1000 pounds of force on the pedal, so you can calculate maximum force. Given all this info, you can stop listening to what fixsters have to say...

Track cogs thread onto threaded sections which are half the length of what the old freewheels threaded onto. A good track cog with clean, sharp threads isn't going anywhere once locked down. A really cheap track cog can strip the hub, but that's a function of surface area - it didn't have good contact to start with. Freewheels had more threaded area because the cogs were offset well past the end of the threading - think of where the smallest cog sat and think about where it was all connected to the hub.

[RudAwkning]

You'll be fine. The only thing that may be a bit off is your chainline (assuming you were centered with your fixed cog to begin with).

[goonster]

Sheldon said it's OK.

[Ti Designs]

Sheldon said it's OK.


Our understanding of the bicycle comes down to this - how sad.

[paczki]

Our understanding of the bicycle comes down to this - how sad.

It's good enough for me!
Thanks everyone for the advice. I'm going to run my Igleheart 48/22 fixed and free.

[goonster]

Our understanding of the bicycle comes down to this - how sad.
Not sure how to interpret this . . .

Citing Sheldon's endorsement does not purport to be understanding of a particular mechanical system, rather it is a reference to his many years of experience with such systems. If there were an inordinately high rate of failure, he might well have been aware of it.