Drive train in vain

[spyfoxy]

So, we were having problems with our thumbshifter, and decided to try swapping it out for one of those twist-grip shifters thinking it might help. (The thumb shifter was very difficult to shift with.) At the same time, we re-aligned the rear wheel, it had gotten knocked a little off-kilter after a spill (high speed turns are fun!), but we just loosened and re-tightened the axle bolts, no big deal. AND we installed the front brakes, which made for a bit of a cable mess (the stiffness of the tangle of brake and gear cables was affecting the Ackerman steering, the wheels had a tendance to turn to the left instead of track forward.)

Any, all, or none of that may be related to the fact that we had a pretty bad drivetrain failure today. Not sure in what order things happened but:
-One of the links of the chain became unriveted and was bent and nearly disconnected
-The front derailleur was completely bent and pulled into the chainring
-A large amount of the front gear shift inner cable seems to have been pulled out of the housing, way more than there should be

Any theories? Should I just chalk it up to a bad chain and not worry about it? Just trying to figure out what happened. :) For the record, it was a slight uphill

[spyfoxy]

attached a couple photos

[spyfoxy]

And more photos attached.

[SirJoey]

Man, what a drag! I feel for ya!

I may be stating the obvious, but are you sure you got the pin centered perfectly, when you put your chain together?

[TheKid]

Was the derailler set in the right position on the tube? Was it centered on the large chainring when it was in the highest gear? Was it trimmed correctly when you were riding?

[Odd Man Out]

Another Q:
You said you were going slightly uphill -- were you pushing hard or spinning? If you were pushing hard it might be an indication of too tight (too few links in) a chain.

Also was the derailer positioned above the largest chainring correctly before the catastrophe -- right around 1 mm above?

[spyfoxy]

SirJoey: Yea, I'm sure the pin was centered, but it was old chain, so, you know, it's possible. But I did check the chain on several occasions for anamolies.

TheKid: I followed Sheldon Brown's guide for the front derailleur, and as far as I know it was set correctly. It was actually on the smallest front sprocket at the time, and as far as I know trimmed correctly. The drivetrain is a noisy, but I didn't notice any MORE noise than normal when it happened, heh.

Odd Man Out: Heh, I'm positive the chain isn't too short. If anything, it may still be too long. When it's on the smallest 2 sprockets, it likes to hang a little low. I think I'm going to remove the broken link but not add any, just reconnec the chain minus 1 link.

Also, I took a photo of the idler pulley. Anyone else notice this? I bought the size of pulley mentioned in the plans (it even looks exactly like the one in the plans!) but there's an awful lot of wear on the pulley. Gonna try a wider one I think. Also, some new chain may help with overall problems. :)

[Pagan Wizard]

Is it possible that when you bolted the pulley into place you may have over tightened the bolt causing the pulley to not spin freely? If the pulley was restrained, that could easliy explain that wear. Also, if the pulley was not parallel to the chain, it would have caused excessive drag on the chain.

[TheKid]

I'd also check the rod the pulley is spinning on. If it bent, or just pulled away a little bit, it may no longer be perpendicular to the frame. I'd also opt for a plastic pulley. The metal pulley makes a lot of noise, and may cause you to not notice that the chain isn't trimmed properly when shifting. Another possibility is that the chain got caught between the pulley and the keeper.

[spyfoxy]

It's possible the pulley wasn't spinning freely due to rubbing against the seat, but not from overtightening the bolt. I used an acorn nut which isn't even capable of turning far enough to tighten on the pulley. The pulley not being parallel is definitely a problem, gonna cut off and weld on a new rod to see if that helps. We're also going to try replacing the pulley with a cog from a BMX bike, just to see how it does. Got a larger pulley on the way as well, so we have options.

I don't think we are using two different types of chain, we measured all the chains used on the trike. In any case, we've got brand new chain on the way, all of the correct size, so maybe the problem will just be fixed by new chain.

[SirJoey]

Hmmmm.... "Train in vain"... might be a good name for a song. ;)

[mattc]

is it an optical allusion or is your bottom bracket a little off square with the main tube? if it is that might account for some of the derailleur problems

[spyfoxy]

Well you can use it as a song title... as long as it's not a country and western song. ;)

And yea, I'm sure that the bottom bracket is square with the main tube, heh.

[mattc]

the "Train in vain" sounds like my normal atempts at exersize

[SirJoey]

Good one, Matt! (Me too) :D