So now that I have my Trusty Triumph, about 2 miles into my 2.1 mile trip to my first bike maintenance class the pedals stop moving.

Looks like the chainring has moved over and is now on top of the the chain stay... there must have been play in the crankset that I didn't notice when I bought it.

Going back to the shop to work on it myself tonight, and they have volunteer mechanics to help out, but I have no idea what I'm doing. The mechanic I talked to at class last night seemed to think it had been put back together improperly and once we reset it, it won't do this. Have done a cursory search online but I'm not sure what to call it and this may not be a common problem.

Sorry no pictures, I left the bike at the shop since I couldn't actually ride it.

Any advice?

Hard to say. Probably he's right and the crank wasn't attached to the spindle properly. Possibly the spindle's broken. Possibly the chainring's bent.

Cottered crank?

The flats on the spindle are wider than the cotter bolt, allowing some adjustment in and out to the arm on the spindle. You'll need to remove the bolts, re-adjust and re-seat.

Or are the bb cups or the chainring loose?

It's kinda hard to diagnose the problem based only on your description, but I suspect the adjustable cup unscrewed, perhaps far enough to let the balls out of their races, perhaps jamming the whole crank. You will have to remove the left side cotter and perhaps the right side cotter as well; repack the whole BB, and (once you have the adjustment right) tighten down the lockring a bit better.

Took it into the bike kitchen last night. The drive side cup had continued to thread to the point where the chainring was pressed against the stay. Took it all apart, new bearings, etc, but it looks like the spindle is the wrong size. Leaving it for now to see if it happens again, at which point we'll find a new spindle and a new cup (with a lip so it can't thread itself too far into the bracket). Good times.

That said, it was my first time taking apart any part of my bicycle (other than taking a wheel off) so I would say I know at least 1,000,000 times more. A good learning experience and I'll take off those cottered cranks in no time next time.

Thanks for the help!

Wait... The drive side cup continued to thread in? Does that sound improbable to anyone else? It should be all the way in already. I guess if the spindle is too long, it could have been installed partially unthreaded? If so, it will certainly happen again.

Is it possible that an adjustable non-drive-side cup has been installed instead of the proper fixed cup? That's the only thing I can think of to make sense of the "cup continuing to thread in" line. The shoulder of the fixed cup should be tightened against the bottom bracket. Curious.

I've never seen that on an English 3-speed. Anybody else?

I've only taken one fixed cup out, and boy, was that hard.

A photo would be worth 10,000 guesses.

Yeah, it wasn't until we had it all put back together that we noticed that the spindle was the wrong length, so we're fully expecting it to happen again. I think it's a problem that there's nothing stopping the drive-side cup from going into the bracket if it starts to move along with the crank -- we're going to look for one with a lip/rim to prevent that next time. I'll get my greasy fingers on a camera for photos and show you what it looks like next time I'm in the shop.

At least now I know what it's supposed to look like and will be able to tell if it starts moving around again. You know, BEFORE the pedals are full-stop. And if/when it happens again, we've got a couple of strategies (and a different guy at the shop who is the go-to guy for English bikes) to fix it.

I've also got a fun gear-slippage problem, but that's a project for next week too.

I'd sure like to see a photo of this. I'm not sure I'm following 100%; something sounds out of whack.

I'm standing by my earlier prediction.

Asymmetrical spindle installed backwards?

The problem with this theory is that the drive side cup ("fixed cup") has a left hand thread. So this is possible only if they screwed up at the factory and put a right handed thread through both sides of the BB shell. What are the odds of that? Huh, anyone's guess.

Hmm... Hadn't thought of that. But what can the OP'er mean when he talks of trying to find a cup with a rim that will prevent it from screwing too far in? Curiouser and curiouser.

Yeah!

I'm not discounting your theory, that the bike came from the factory with two adjustable cups. As wrong as that would be, I think I've heard of it happening before. Even from the Raleigh factory.

I used two adjustable cups on a french bike once. I didn't have any fixed ones. Seems to me maybe it's a good idea cause the lock ring would keep it from coming undone like french bikes do sometimes. That bike is out on the front porch. I should go look at it and see how it's doing. It's one that the neighbor kids flog around the yard. I don't usually fix them until someone complains.