wheel re-building question

BigSpecs

I am building up a new fixed wheel bike. I have an old pair of multispeed wheels. They are 8 speed shimano cassette from a 2004 Specialized Allez. What I want to know are the options for converting these wheels to fixed.
So far I know I could:
a. buy a Surly fixer for about 60 quid (cheaper to get a new back wheel)
b. weld the cassette together (as described by Sheldon Brown), I can't weld.
So...
...could I get a fixed hub and re-build the rear wheel using the same rim and spokes? The rim is an Alex, I think it is 32 hole in a fairly traditional pattern (I am at work and don't have the wheel to hand) Will the rim be suitable and can you re-use spokes. I realise that spokes come in many lengths but have no idea why? :oops:

tatanab

Yes you can use the same rim, provided of course it is in reasonable condition.
Yes you can reuse spokes but probably not in this case because you would have to find a hub with exactly the same flange dimensions as your existing hub, and even then there is a chance that the spokes will not be right length.

Spokes are different lengths for many reasons-
1. The obvious- wheel size.
2. A deeply dished aero rim will possibly use a different spoke length to a flat surface rim. Or it may use long nipples.
3. The number of times you cross the spokes changes the length since a radial spoke is logically shorter than a tangential spoke.
4. On a geared hub (and some other places) the spokes on the drive side are shorter than those on the non drive because the rim has to be centarl in the frame (over the hub axle) not central between the flanges of the hub. Some fixed hubs, double sided or modern flip-flop hubs, will use the same length spoke left and right because the hub and axle are symetrical. Some do not.

So, in your case, reuse the rim by all means but you may need new spokes because of length issues. Given all of that, I'd keep the wheel the way it is and buy or build a complete new wheel becasue the difference in cost is only the price of a rim.