Converting my 7 speed beach cruiser to single speed.
 

I bought a cheap walmart beach cruiser a while ago on craigslist, and I've been having trouble ever since. Shortly after getting the derailer in tune, The grip shifter fell apart. I decided I was going to try to convert it to a single speed, and I tried just taking off my derailer, and shortening up my chain so that it went around the 6th gear in the back. I thought it would work, but the chain kept getting pulled onto a different gear, even thought the chain was tight. In retrospect I should have just kept the derailer on it, as it was working perfectly as a single speed then...

I don't really know what I'm doing. What would be the easiest (and cheapest) way to convert this bike to a single speed? Is there any way I could use any of the existing parts (freewheel, the cogs from the freewheel, the hub) to convert it?

Just how you did it, but you need the gear you want the chain to stay on to be directly in line with your chainring. That's the cheapest way. You need to redish/respace your wheel and/or add a spacer between the hub and freewheel.

See here for redishing/respacing instructions.
http://www.sheldonbrown.com/deakins/...onversion.html

Something a little less cheap is this
http://www.treefortbikes.com/95_3332...Tensioner.html
The pulley can be moved back and forth to help keep the chain on the plane you need

keep the derailure on and just adjust the rear derailure screws to the gear you want,you should be able to get the first 4 biggest gears.

I really should have just left the derailer on there, but unfortunately I removed the chain from the derailer in a manner that the derailer didn't survive. I assumed I didn't need a cheap walmart derailer. I'm trying to do this without spending a lot of money on parts or labor. So as I understand it, my choices are to take apart the rear free wheel and use spacers to line the cog up with the crank, or to just put a freewheel cog on the hub, and redish the rear wheel to line it up with the crank. Is that right?

I broke two chains that way on my beach cruiser. The third time I reset the rear wheel it has been holding steady. I don't know what will happen if I have to change a tire.

It seems I have to get the wheel perfectly straight. Otherwise, when I really step on the pedals, the rear stays flex enough for the chain to try to grab the next (SIS) cog, but it doesn't quite make it and the chain is stuck between cogs, slightly bent.

Gale