rock_ten

Hi. Yesterday, after completely stripping and rebuilding my Dawes Galaxy, I took it out to ride up the road a bit. While changing gears down, i.e. to a larger sprocket, at the back, things suddenly felt strange and when I looked down, my rear derailleur was moving along the chain. The rear dropout had snapped off. I have no photos of the actual frame but here is where it failed (along the green line):



As you can see there's a bolt right through it, and so it is a rather weak area.
These are the options I can think of right now:

> Get a new frame, just a frame, and transfer everything over from my Dawes.
> Have the broken piece welded back on.
> Cut off the whole broken dropout, and the dropout on the other side, and weld on two knew dropouts cut from some other frame.

The first idea is probably the best. For the welding ideas I'd have to find someone to do it for me, and perhaps it would always be weaker there anyway? I will speak to someone about it later.

Any comments and ideas will be appreciated

Thanks

--Joe

Steev

A new frame is the usual approach. A competent frame builder could put in new drop-outs but the cost is likely more than you would put into such a frame. Only consider this if you're particularly fond of the frame.

dabac

Well, that's certainly doable, but not required.

If you go that route, better then to contact a frame builder. He'd be able to completely remove the old dropout and would probably have another dropout around to replace it with.

It's steel, and chunky steel at that. I'd have no qualms at all about welding it back together. Here's how I'd do it:
1) grind the paint off from the crack and 1/2 inch out, put an temporary bead on the inside face of the dropout.
2) grind a v-shaped groove along the crack on the outside face. The bottom of the groove should just about penetrate into the hole for the wheel alignment screw.
3) run a weld down the groove, the weld should fill the groove completely.
4) flip the like over, remove the temporary bead and grind another groove along the crack,
5) run a weld down the groove, the weld should fill the groove completely.
6) grind the welds flush with the surrounding material, maybe attempt to chase the threads of the wheel alignment screw hole.
7) check for hanger alingment, repaint dropout, install RD and ride.

For someone who has the equipment already setup the actual welding and grinding is probably something like a 10-minute job.

rock_ten

Thanks for the replies. Here's another picture with a diagram to show the surfaces involved:

rock_ten

I just realised that there appears to be a way of attaching rear derailleurs to bikes without the special tab/hole for them (as is in my pictures above). I have a spare frame, just a fraction smaller than my old one, that I thought would be unsuitable because it just has plain dropouts with no tab and hole. If I can't get it welded then I'll use that frame instead, if I can acquire a suitable attachment for the derailleur. I'd rather weld it if possible, because I don't want to have to strip EVERYTHING off the old frame and move it over to a new one.

Thanks

--Joe

dabac

The wheel alignment screw isn't actually required. It's helpful for someone trying to do really quick wheel changes, but it works just as well (albeit a little slower) to simply stick the wheel in there, eyeball the alignment, and then do up the QR.

There's nothing stopping you from widening the weld groove a little so that the welding actually fills up the that screw hole as well, which would make the drop out a little stronger.

dabac

Yep. Low-end Rders sometimes comes with that bracket already assembled. Otherwise the part you're looking for is often called an adapter (adaptor) claw, which'll let you stick a RD on just about any bike.

It really shouldn't be a problem with welding it. The challenge will probably be finding someone willing to tackle such a small job.

unterhausen

I'd contemplate having it brazed back together without the adjuster. It's a bit tricky to take the dropouts out of the frame. Probably the best way is to have it tig welded.

HillRider

First, a new dropout won't be welded in, it will be brazed and any frame builder could do it. They may want to replace both dropouts to have identical (and stronger) shapes on both sides. The cost will be significant and the bike will require a repaint, or at least a major touchup, when the work is done.

I don't think a braze or weld repair of the old broken dropout will be strong enough or accurate enough to be worth the trouble.

dabac

Haven't done much brazing, so I really can't say. But I would gladly both do the repair for someone else, or ride a weld repaired dropout myself. Last spring I actually did a barnyard track-end conversion by cutting a dropout off just a tad higher than the indicated crack, flipping it around and then welding it in again. Not a hint of trouble so far.

As for "worth the trouble", the actual grind & weld really is a 10-minute job (at most). Finding the guy might take some doing, but the actual repair isn't much to talk about.

eddy m

Replacing or repairing the dropout is an easier job than repairing the paint. If it's good lightweight frame, be sure the welder knows how thin bicycle tubing is.
Dropsouts fail for the same reason as axles. If the axle is too flexible, the dropout flexes as well, and one or the other will eventually fatigue. It wasn't much of a problem with 120 mm OLD 5 speeds, but the longer axle for 6 and 7 speeds were too unreliable. That's why all the 130 wide hubs are cassettes, which have much less flexible axles.

em

Crank57

In my former job I was a project manager for a fab shop; and had been a steel foundry engineer for 26 years before that. Welding that dropout is absolutely no problem. If done correctly, the final product will be better than the original.

Many shops will have a minimum charge. Even a 10 minute job might get charged for a 1/2 hour of labor @ $75 to $95 per hour. Only you can decide if that frame is worth ~$50 to fix. Often if someone came to our shop with a little "walk up" job like this and had the paint sanded off and bolts and cables removed so the welder didn't have to do anything but grind and weld we might not even charge but 1/4 hour or $25.

Of course it depends on how busy someone is also. With the economy like it is right now, you should not have any problem at all.

miamijim

+1.

rock_ten

Thanks for all the replies. I took the frame and fragment to a local garage and asked if they'd be able to weld it for me. He thought it was possible, though said the metal looked unusual. I was under the impression that it would be steel, but he wasn't sure. I don't know how good a job he did (there was no cleaning, sanding or grinding involved) but it appears to be pretty solid now. The wheels never went right to back of the dropouts, because of the position of the adjuster pin, and so we were able to fill the weld into the slot of the dropout for a good few mm or more.

It cost me £5 and took about 15 minutes, including some filing and bending after the welding was finished.

I just rode my bike a bit and it felt ok, and very, very smooth from my BB/chain/etc work yesterday.

Thanks for your help,

--Joe

EDIT: I forgot to mention that I also discovered a wonky link in my chain, perhaps it was that which caught on the derailleur last night and tore the dropout off? I was getting started on a steep hill, so I was putting a lot of force through the pedals and chain at the time. I removed the link and it seems to run ok now.

TallRider

excellent to hear. the main issue I'm worried about with welding was whether the derailer hanger (and bottom of the dropout) is aligned as it's supposed to be, but assuming that's okay, then you should be golden. Sticking a piece of metal at the back of the dropout should improve the strength because there's more contact area for the weld.

The dropout is most definitely some kind of steel, based on your picture.

Panthers007

If you removed a link, I hope you replaced it with a new one. Otherwise your chain may be to short to get all the gears and/or could cause the RD to hit the cassette/freewheel.

One standard way to check chain length is to shift it into it's highest gear - shift a 10 spd. to 10, a 12 spd. to 12, etc. The two pulleys should now be at 6:00 o'clock and 12:00 o'clock - Straight up & down like the number 8.

dabac

Well, that's not ideal, but it isn't necessarily catastrophic either. What you want in a weld is a good melt through all the material in the seam. Since you had that hole for the alignment screw running through it should be be possible to get that w/o prepping the seam. Not grinding the paint off can add impurities to the seam, byt if he's using TIG most of the paint will burn away before he adds the filler material anyhow.

Close enough to my expectations!

Don't really know about that. unless already weakened I believe that the RD would destruct explosively before exerting enough force to snap off a dropout.

San Rensho 

Just have the piece that broke off ARC WELDED, not torch welded back on. A torch will heat everything up to much and cause the whole dropout to come out of the chain and seat stays.

Have them fill the hole for the axle adjusting screw, its not necessary, nice to have, but not required.

SSSTANG

TIG welding would generate less heat.

DannoXYZ 

Well... it's not so simple. The slag and impurities from arc-welding will result in about as poor a weld as an oxy-acetylene torch anyway. If you're going to weld it, TIG is the way to go and can result in as strong a part as the original. Depends upon the expertise of the welder in identifying the original alloy, selecting the correct filler-rod, and how skillful they are at the actual welding.

However, in this case, it's not really that big a deal HOW the lower part of the dropout is re-attached as it doesn't face much stress anyway. The rider's weight is carried by the upper part of the dropout and the only thing the lower-half faces is the weight of the wheel when he catches air.

When the derailleur shifted into the spokes, the rider's momentum generated A LOT of torque that ripped the bottom half off originally; a very rare occurrence anyway. As long as the limit screws are set properly, that dropout can be re-attached with arc, gas or TIG-welding and it should be fine.

San Rensho 

Agree that TIG is the way to go.

My main point was that an oxy-acetalyne torch would require heating up the entire drop out which would likely melt all the solder holding the droupouts in the frame tubes, requiring extensive frame repair.

rock_ten

Interesting. Today the derailleur snapped off. Well it's luckily not snapped, just bent and pulled to pieces, so I might be able to repair it (I have spares but this is the original one). It happened when changing down (to a bigger sprocket) while moving [too] slowly up a hill.

So, either the factor that cause the dropout to snap off struck again and this time broke the derailleur, or, as Panthers007 mentioned, maybe the derailler caught in the sprockets themselves?

Tomorrow I will replace the derailleur, inspect the chain, and add a new link into it, then ride very, very cautiously for a while.


--Joe

Panthers007

I'd suggest a new chain while you're at it.

cuevélo

Yellow Jersey can do it for you.

rmfnla

FWIW, those old Campy dropouts are mild steel castings.