Securing a fixed sprocket

BigSpecs

Didn't know whether to put this in Special Interests or here but figured there was more traffic here and that most of the "big brains" hang out here!
I am building up a cheap fixie project. As part of it I am using an old rear wheel that originally had a five speed freewheel attached. I know that the fixed sprocket fits straight on (I have done this before) and that I can use various things like Locktite and old BB lock rings to try and keep it in place. However, I am also aware that with enough "reverse thrust" the sprocket can unscrew. I have seen various re-designed hubs on the Fixed Gear Gallery, including welded cassette hubs and renovated internal hubs. Nothing for this scenarion though other than the usual described above.
So...I am looking for any ingenious ideas as to how you could stop the sprocket coming off. Needs a little thinking "out of the box" I think (terrible phrase, sorry) I cannot resort to things like welding (no equipment or skill) and only have the usual tools (drills, saws etc) to use. Anyone got any bright ideas???
Cheers, Col.

Smokin Joe

It is many years since i rode fixed, but I must admit to often not bothering with a lockring and I never had the sprocket unscrew. I used to find the opposite in fact, the blooming things were a nightmare to remove when you wanted to change them.

Though that is what could be considered bad advice. :shock:

Monty Dog

A standard BB lockring should work fine - whilst a left-handed threaded lockring is seen as the best, two threads locked against each other is nearly as effective because of the inherent 'slopiness' or backlash in the thread which enables them to be tightened against each other. For the true belt and braces approach, you could use Loctite too. That said, I've ridden fixed wheels with no lockrings too without problem, but if you live in a hilly area and haven't developed a good souplesse, then it's worth considering.

BigSpecs

If I was to go down the locktite, BB lockring route. What's the best way to get the spocket on as tight as it will go? I don't have a vice but do have a chain whip. Ta.

Eddy S

Just use the chainwhip on the sprocket and the correct tool to tighten the lockring and this should suffice.

Once you've ridden the bike a few times, the sprocket will tighten with the forward pedalling force so just tweak the lockring tighter after a few rides.

Don't over-do it with "gorilla engineering" - you might want to take the sprocket off at some point.

I always run a lockring, whether it's my road fixie or my track bike - sprockets fitted with lockrings are not known to come off... 8)

andyp

I'd echo what others have said - when I was building up my first fixed a couple of months ago a friend of mine, who's a bike mechanic by trade, said to not worry about a lockring. So far I've had no problem.

provenrad

The torque you can generate using the rotofix method is enough to stop the cog unscrewing under back-pressure.

http://204.73.203.34/fisso/eng/schpignone.htm
Good luck!

BigSpecs

Thanks guys. Provenrad, I have actually seen this link before but had totally forgotten it. Thanks for reminding me. Do you think it would shag the paintwork on the frame around the BB shell? My frame is home painted, so not the most durable finish. Perhaps I could get away with wedging a bit of cardboard or something between the frame and chain. Ta. Col.

andrew_s

I'd suggest using a piece of old tyre to protect the BB paintwork.