Singlespeed & Fixed Gear - Singleator Shot ... Derailed?

So, the spring in the Surly singleator that I'd been using on my SS is completely shot. I'm not really sure how it happened, but it seems that the spring, which is essentially a corkscrew with two very short 90 bends at the tips (these create pins that fit into holes in two parallel plates to hold the tension on the chain), is stripped out of the holes that hold it in place, meaning that the tension is gone off the chain. I've talked to a few friends about the possibility of using a regular derailer and just messing with the limit screws to get my chainline straight again. This seems like a reasonable idea to me.

The quesiton is -- should it be an MTB derailer or a RB derailer? The chain is an SS (BMX) chain and I have a BMX cog back there. Is an MTB derailer better suited to the heavier chain? Is an RB derailer too narrow to accomodate the chain? Which is going to hold up better? I'm really disappointed in the singleator; I've had it lest than six months and it's already shot (no crashes, abuse, etc.). Whatever. I'd love to get rid of the problem with a set of horizontal dropouts, but that's not to be (and free bike frames converted to singlespeed are gift horses, and not to be looked in the mouth).

Thanks!

you'll never do it. derailleurs "default" to either the most inner or most outer setting, so unless your chainline is really screwy you won't be able to adjust the play to somewhere in the middle.

i'd try a half-link set up or fooling with the chainring/cog combos, rather than a halfway-house measure like a singleator.

failing that a dh-type chainguide system seems to be more robust

pm me, I have a singleator not in use, and may be up for trading.

it was used for like 3 months, at most.

you'll never do it. derailleurs "default" to either the most inner or most outer setting, so unless your chainline is really screwy you won't be able to adjust the play to somewhere in the middle.

i'd try a half-link set up or fooling with the chainring/cog combos, rather than a halfway-house measure like a singleator.

failing that a dh-type chainguide system seems to be more robust

you could set up the derailleur with a short section of dummy cable. tension it so that the jockey wheels line up properly, and lock it out with the limit screws.

pm mrRed and play with chain links, half links, moving the wheel...stuff like that.

you'll never do it. derailleurs "default" to either the most inner or most outer setting, so unless your chainline is really screwy you won't be able to adjust the play to somewhere in the middle.

i'd try a half-link set up or fooling with the chainring/cog combos, rather than a halfway-house measure like a singleator.

failing that a dh-type chainguide system seems to be more robust


there's plenty of deraileurs that will let you set them where ever you want...
just not indexed shifters...

you'll never do it. derailleurs "default" to either the most inner or most outer setting, so unless your chainline is really screwy you won't be able to adjust the play to somewhere in the middle.

i'd try a half-link set up or fooling with the chainring/cog combos, rather than a halfway-house measure like a singleator.

failing that a dh-type chainguide system seems to be more robust

With most shimano derailleurs it will work just fine. Remove the phillips head limit screws, take them to your local hardware store, and ask for allen head bolts in the same size but longer. Re-install your extra long limit screws and adjust the upper and lower limits until you lock the derailleur in the ideal position. Road or mountain will work just fine, although you will probably have to find longer bolts for the pulleys and some spacers to increase the cage width if you want to run fat 1/8" chain. I don't know if shimano pulley bolts are an easily obtainable size, but if you can't find any longer bolts, just use the closest thing you can find that is long enough and put a nut outside of the cage. You can probably get a free used derailleur at your LBS, there is no point in buying a new one when a beat up derailleur works just fine for your purposes.

If you want to get fancy (and slightly reduce the effectiveness of your derailleur as a tensioner) you can cut off the lower section of the derailleur cage and replace the upper pulley (the one with more lateral play) with the pulley from the removed lower section of the derailleur cage. provided you have the limits set perfectly, and good chainline, it will be a little quieter. I have used both cut and un-cut derailleurs as tensioners, un-cut derailleurs work slightly better but look much worse.

/Edit: One of the advantages of cutting off the cage and lower pulley is that you are less likely to bend your rear derailleur/tensioner thing.

Thanks for all the help. I'm ticked that the singleator was such a piece-o. I'd much rather be able to adjust chain tension with the wheel, as some suggested, but I have vertical drops. I thought about messing with the chain length, but I would need a half length to do that; I've already tested the chain-length by taking out a couple of links. If I can get the deraileur to run without a problem, even if it is noisy, I think that's the priority.

... or get a new spring for the tensioner, or, if you feel ghetto, zip tie it to the chainstay (if it can tension upwards).

Thanks for all the help. I'm ticked that the singleator was such a piece-o. I'd much rather be able to adjust chain tension with the wheel, as some suggested, but I have vertical drops. I thought about messing with the chain length, but I would need a half length to do that; I've already tested the chain-length by taking out a couple of links. If I can get the deraileur to run without a problem, even if it is noisy, I think that's the priority.

then get a half-link.

You could always get a Melvin (http://www.webcyclery.com/product.php?productid=16382) instead.

Guess who's a moron . . . that's right . . . it's me! Wow. So apparently, when I got this frame off my friend, I had a singleator lying around and so I threw it on. An essential ingredient in all my work in bike grease. Oh, and I almost forgot -- beer. Evidently in my happy state, I neglected to take note of the horizontal drops (which I was bemoaning the absence of above). When I began taking off the singleator this afternoon, *****ing and griping about what a cheap piece-o it was, I noticed the dropouts. A few links gone later, I have my bike back up and running. I guess the moral of the story is that it's cheaper to be stupid than productive, since I would have replaced a completely superfluous part if I had felt like going to the LBS yesterday!

Thanks again to all for the suggestions! BTW -- that Melvin looks cool. Is there a spring in it?

wow

that Melvin looks cool. Is there a spring in it?

Looks like it- they advertise it as being able to aid in tensioning with a two-chainring-one-cog setup.

Thanks for all the help. I'm ticked that the singleator was such a piece-o.

I had one a while ago on a single speed mountain bike and the exact same thing happened. I think the alu of the arm isn't strong enough to take that much pressure on the small hole (about 1mm) that the spring goes into. It is a pos though and damn expensive too.