Originally Posted by
Retro Grouch
What do you have to lose?
1. I'm not positive about the sizes of PVC pipe that are available, but I'm betting you could find one that would work. If not, you can actually BUY commercially manufactured spacers to convert a cassette hub to single speed. For that matter, just leave the rest of the cogs in place.
2. That's what the high and low limit screws on your derailleur are for.
Actually, I think that the biggest peril of this plan is that you might like it. If that's the case, at some point you'll probably have to buy yourself a spiffier, new single speed bike.
That's a real danger, because I'm sure exactly that would happen if I did like it, and the road bike would revert back to form. I wouldn't give up the SS when I want my road bike back.
Even if I buy spacers and a chain tensioner, I don't see it costing more than $20-$30. Plus the chain ring, almost forgot about that.
PVC pipe, that's a different approach ... reckon cutting an aluminum pipe would work, assuming it was the right size? I'm not sure I'd trust pvc not to wear out or crack.