I am trying to build a single speed on the cheap. I have a mountain bike frame with vertical drop outs. I plan on using a half link chain.
In my mind I don't see how even with a half link chain, the chain tension will be perfect.
How many have made a vertical drop frame into a SS, without using a derailluer or some other chain tensioning device?

Chain tension isn't all that critical on an SS, so you should be OK w/o having to add a spring loaded chain tensioner. The chain won't come off when you are pedalling, only possibly when coasting if you hit a bump, but you have brakes on both wheels so it's not a safety issue. I'd give it a go, it'll probably work OK.

I got lucky with an old C'dale road frame and magic ratio. Ran it fixed no problem, but then I moved to a place where a fixie doesn't fit the riding so I put some gears and a derailleur back on it.

Don't worry about it, just get it as close as you can with/without the half link.

Also, a half-link chain will have double the wear... what may fit nice for a while will get sloppy much faster as the chain wears...



btw, I hate half link chains.

I'm sorry I just think this post is hilarious.

"Here's what I plan to do. In my mind, every possible outcome is complete disaster. Has anyone had results that weren't complete disaster?"

Anyway, there are tons of posts about this. You pretty much have to get lucky with a magic gear.
If you want to be super cool, you could try adding a ghost chainring into your drivetrain. But that's technically a "chain tensioning device."

At least I made someone laugh today..........
Actually thats pretty close to what I was thinking.
Eh, I will give it a shot.
I am starting with a 42/14, I can go down in the front to find the magic gear.

that sounds like a very strange gear ratio to start out in. usually people start our with 48/16 i thought

check your math

I converted an old Cannondale frame once without a tensioner - just had a set of single cogs for the rear cassette on hand and my chain breaker handy. I got pretty close with (one of) the original chainring(s) - buying a 42 ring for up front did the trick. Rode perfect.

Did the same thing! A '91 Cannondale SR400. I used a 42/16 setup with a half-link and it was perfect for SS. It was ridable fixed but a few months of wear would haave made it all bad! There are tricks to get just a little extra adjustment with vertical dropouts. Some people file the back of the dropouts a little if they don't mind doing that to the frame, others file the actual axle a bit to give it a flat spot. Again, these are just ways to get it closer to perfect if you're tension is just a little off. Remember, parts wear and you'll be loosey chain in no time. Eccentric hub if you have the $ and LOVE the frame