Hello
I'm thinking of building a singlespeed bike. I have a frame with vertical dropouts and was hoping to get a flip-flop hub with one side fixed and one a freewheel. I've heard that you can tension the chain enough simply by sensibly choosing the cog sizes and by removing links or half-links from the chain... is this really true? if this is not the case, I'd have to get a chain tensioner and that would spoil my whole fixed gear idea...
Am I gonna have problems with building this? (without an eccentric hub/BB or anything)

Any help much appreciated

it will just be annoying as chains rarely stretch in perfect chain-link increments. The biggest problem with vertical dropouts is that if your chain stretches and its in-between chain links, you are going to be running with some slack which can prove disastrous if you throw the chain and have no brakes.

If its what you have, then go for it. Just please run a brake and dont try skidding too much, for your and everyone else's sake.

ok thanks, good point. There is a slight angle to the dropouts (theyre vertical but they're not that vertical) so that might give me that bit of leeway I need....
I'd try skid stops as much as possible, but would run a brake anyway for when I had the freewheel on - planning to pop some forks on the front and use it off-road once or twice

While we're here, mind if I ask what your opinion on quick releases is? I'd prefer one so I could flip the wheel round quickly & just generally easier

i dont have much experience with em, but they make your bike easier to steal :X

hm I suppose they do.
Well thanks for your help mate.

you will probably have trouble building it. you have to find what's called the "magic gear" to make it work, which involves measuring the distance center-to-center from your bottom bracket to your cog. there are charts around, but i don't have one.

as for a quick releases and being new, let me introduce you to your new best friend, sheldon brown
https://www.sheldonbrown.com/skewers.html

You'll have to choose your cog/chainring combo carefully and maybe use a half link. I've had some luck with magic gear ratios in the past, the chain stretch issue isn't that huge if you don't mind replacing your chain a little more often.

Ok thanks for the help. Is there any reason why I can't just choose the chainring/cog combination that I want and then shorten my chain until it fits? can't be that hard surely... I mean how accurate does the chain tension need to be? Is it 1/8" sort of movement in the axle or even less?
cos by altering cog sizes I can get it within 1/8" and using half links I can do 1/4"...

Dont use a quick release on a fg, although it does make for a quick flip, youll just be asking for trouble on the fg side.

Give it a try youll learn as you go

You could run an eccentric hub...
https://www.sheldonbrown.com/harris/white-hubs.html

yeah those would be ideal but a little bit pricey for my liking!

Take a picture of your dropouts and post it up, if you have the right kind and are handy with a file you can file them out in an afternoon. Another option could be to have a shop put new dropouts on your frame, though at that point you could probably just spend a couple extra bucks on an IRO frame or something of the sort.

if you're using a freewheel, please use two brakes.

Naaaaaaahhhh, flinstones that sh1t.
Jokes, if its freewheel, 2 brakes. If it's fixed, one up front.

if you really want a diy project, you can always pop those track ends onto that frame yourself like this dude:

https://www.63xc.com/clausc/trackend.htm

Don't worry I'm planning to use 2 brakes (although while we're on the subject, am i likely to get away with a disc on the rear or not? I assumed not...)
Haven't really got the tools - or the inclination - to weld track ends on...
There is room in the frame for a small degree of filing away but that's a bit of the last resort

Cheers

dude, SS w/disc mounts FTW, but you will pay more fro frame & fork

I did this to a mountain bike with vertical drops and to get a tight chain I:
1) had to choose a gear ratio I was not crazy about (42/18=60in & 3 skid patches)
2) file the dropouts about 1/8" (0.125)
3) grind a "flat" in the axle to get some more adjustment room

I saw that sheldon brown was trying using a quick release axle, cut down to fit inside the dropouts, so only the skewer sticks through the dropouts, and you get some more adjustment room: (scroll down)
https://www.sheldonbrown.com/fixed-co....html#vertical

it seems like that wouldn't be strong enough, but since he tried it, I figured I would try it too, and it DOES work suprisingly well and does not slip.

just be sure to lock your rear wheel, or it might not be on the bike when you return. (I hate QR's for that reason)

Thanks - yeah I've seen the Sheldon Brown site and wondered about how strong that QR option would be - I think I'll leave it as a last resort nevertheless.
By the way can someone fill me in on what FTW means?

FTW = For the win!

What you're aiming at is called "magic ratio", a certain size of chainring + sprocket that will have your chain as tensioned as possible. Fact: magic ratios suck the big one. Even with a half-link. It's enough for the chain to elongate even a tiny little bit, and your chain will be too slack.

Magic ratios only work if you are ready to shell out for a new chain every 1000 Km.

The other bid effing disadvantage is that you are not free to chose your gearing - you are limited by the magic ratio options, which sometimes are equal to only one, and that one might be way too high or way too low.

That's generally speaking, ill-advise, unless you know very well what you are doing in terms of heat-treatment. If you DON'T know what the heck you are doing with the heat-treatment, you'll end up weakening your frame to the point that it will be unusable. Brazing is only a small part of the story.

Finding a frame with horiz. dropouts may in the end be actually cheaper than having the vertical ones replaced.

I'm a big fan of the Eno hub. They can be found for as low as $129.99 USD + shipping. It sure beats screwing around.

I've built a horizontal dropout bike with a "Magic Gear" but was never happy with the gear or the chain tension.

The Eno was a good investment for me and my time not spent with a Mickey Mouse set up. I bought two of them.

[QUOTE=wroomwroomoops;6146498]
Magic ratios only work if you are ready to shell out for a new chain every 1000 Km.
QUOTE]

To be honest I'm fine with changing my chain every 1000km - its gonna be a commuter/offroad bike so I won't be doing any long distance nonsense