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-   -   cracked seatpost clamp on 531 frame - what to do? (http://www.bikeforums.net/classic-vintage/877150-cracked-seatpost-clamp-531-frame-what-do.html)

bro 03-10-13 05:38 PM

cracked seatpost clamp on 531 frame - what to do?
 
http://i1298.photobucket.com/albums/...ps40350ea2.jpgdiscovered this crack on my ron kitching frame today. from previous owner. worried about it. i was going to install one of these on it http://i.ebayimg.com/t/Seat-Post-Cla...isw~~60_12.JPGwhen i realized it didnt fit, because the holes on the clamp are kind of ovalized. and i noticed the crack. could i just use a washer and it wont get bigger? why wont a regular bolt fit through? do i need to get a mallet out? eeeek. this bike was supposed to be a cheap quick build and rode to work for the next few years. this crack bugs me. and i HATE when my saddle moves around. it says "72" on the seat lug, assuming it requires a 27.2 seatpost, not sure if thats whats in there now, it came with the bike. along with a quick release that was too long and missing a part.

Michael Angelo 03-10-13 06:11 PM

72 degrees. The lug can be fixed. A good frame shop can do it. I had one fixed that was almost as bad, my frame builder back filled
The lug with silver braze. I just had to redrill the bolt hole and repaint it.

rhm 03-10-13 06:15 PM

The 72 on the lug probably refers to the angle between the top tube and the seat tube, says nothing about the post size. I'm afraid your frame needs the attentions of someone who knows how to braze, and is going to need a partial repaint when he's done. At the moment i don't think it's a very serious job. Whether you can put this off for a while and ride it safely, I don't know. I don't think there's a major safety issue. My chief concern would be making it so much worse that it becomes a serious repair. I don't know.

repechage 03-10-13 06:42 PM

Quote:

Originally Posted by rhm (Post 15369504)
The 72 on the lug probably refers to the angle between the top tube and the seat tube, says nothing about the post size. I'm afraid your frame needs the attentions of someone who knows how to braze, and is going to need a partial repaint when he's done. At the moment i don't think it's a very serious job. Whether you can put this off for a while and ride it safely, I don't know. I don't think there's a major safety issue. My chief concern would be making it so much worse that it becomes a serious repair. I don't know.

Silver in general does not fill voids well. There is a product from cycledesign that will fill big voids and that with a tube set in the lug ears (the way the Italians did it before investment cast lugs, but they used brass during the initial build).
As mentioned, this will require removal of paint in the adjacent region and probably push you to a refinish. The reason to consider silver is it melts at a lower temperature, and that will make it easier to do the repair and not effect the original construction.

Or, you could buy a seatpost with a self expanding feature, think quill stem, there are a few of them around, Bicycleville in Philly had a 27.2 American classic with this feature for sale for example, and push off the repair.
Set the post, add a true bolt with washers for appearance and be off.

If you have not ridden this bike to assess how much you really like it, I would go that way for sure.

gerv 03-10-13 07:26 PM

I'd head down to your local bicycle co-op and see if you can find a seatpost collar that would fit.

Unfortunately the curvature of the top of the seat tube is going to present an issue finding one big enough... but you might get lucky.

Creme Brulee 03-10-13 07:29 PM

If it is indeed a common size, try to find a quill seatpost

Six jours 03-10-13 07:34 PM

I might try repairing with brazing, but that's not a really great place for it, IMO. Any kind of silver wants an absolutely clean surface to stick to, and getting that kind of ragged surface really clean can be tough. Even an acid wash with a lot of brushing might not get into all the nooks and crannies. Beyond that, brazing doesn't really make for great butt joints (yeah yeah yeah, you in the peanut gallery) even under ideal circumstances. So I wonder if a simple brazing repair would last.

Welding probably has more potential. Done quickly it probably will not seriously affect the nearby brazing. It will almost certainly be strong enough. It's not likely to look very good, though.

A "proper" repair, IMO, involves grinding off the existing clamp entirely and silver brazing in a new one. Something like this would probably be the ticket.

calstar 03-10-13 08:04 PM

Thats an easy fix for a framebulider, grind off the ears and braze on a new barrel, the higher cost would be new paint/powder. If the seat willl stay put when you tighten it I would ride it with no concern, its not a part that will have a catatrosphic failure and throw you on your head.

repechage 03-10-13 08:07 PM

Quote:

Originally Posted by Six jours (Post 15369783)
I might try repairing with brazing, but that's not a really great place for it, IMO. Any kind of silver wants an absolutely clean surface to stick to, and getting that kind of ragged surface really clean can be tough. Even an acid wash with a lot of brushing might not get into all the nooks and crannies. Beyond that, brazing doesn't really make for great butt joints (yeah yeah yeah, you in the peanut gallery) even under ideal circumstances. So I wonder if a simple brazing repair would last.

Welding probably has more potential. Done quickly it probably will not seriously affect the nearby brazing. It will almost certainly be strong enough. It's not likely to look very good, though.

A "proper" repair, IMO, involves grinding off the existing clamp entirely and silver brazing in a new one. Something like this would probably be the ticket.

I think that it way too drastic. I have seen the braze in a tube method years ago in a "prediction" facility, what happens is a tube with an 8 mm inside diameter is inserted into the lug ears, this will require some removal of the existing material but in plan view will get very close to the actual seat tube. After the file work, I would sandblast the area adjacent to remove paint, then brighten the primary contact areas of the tube. Braze the tube in place and cut the lug ears free after the heat is done. Recut the slot and the repair will be essentially the same strength as what the Italians like Masi, Colnago, Galmozzi, Fiorelli, DeRosa etal. did. In the bike shop way back we always appreciated their effort as we never worried about the seat lug ears distorting under load.

Welding a small repair still required things to be clean, I do not like the paint stress also showing at the root of the damage.

If you really wanted to go cheap, I would file out the lug ears to have an 8 mm bolt fit, set the post and drill and set a screw at the base of the frame slot, tap for an allen key bolt add some compression to the lug ears as they are with the new bolt and washers, and be off. Most 8 mm ID washers will be too big for typical use, in this application a bit bigger would help.

busdriver1959 03-11-13 01:00 AM

Either the seatpost is the wrong size or the person who tightened that bolt should be forbidden from ever touching a wrench again. You first need to determine if you have the correct size there. Another option for the fix is to braze a correctly sized washer on each side. 45% silver would allow the person doing the repair to fill where needed and file down to a good looking shape.

ftwelder 03-11-13 02:49 AM

Once you have it straightened out, a decent TIG welder should be able to do that in 30 seconds and require a dime-size paint touch-up.

Sixty Fiver 03-11-13 03:08 AM

Quote:

Originally Posted by calstar (Post 15369913)
Thats an easy fix for a framebulider, grind off the ears and braze on a new barrel, the higher cost would be new paint/powder. If the seat willl stay put when you tighten it I would ride it with no concern, its not a part that will have a catatrosphic failure and throw you on your head.

This.

I'd replace those lighter stamped ears that are added to the lug with a modern threaded barrel and then you'd only need a single threaded bolt to keep everything tight. It is a small job that, if done properly, would not effect the surrounding joints.

You can see the new seatpost clamp on this frame that used to have a collar... we use brass on these fittings because they do need more strength and even with the higher heat, it does not travel far before the job is done.

http://www.ravingbikefiend.com/bikep...estpowder4.JPG

Sixty Fiver 03-11-13 03:09 AM

Quote:

Originally Posted by ftwelder (Post 15370761)
Once you have it straightened out, a decent TIG welder should be able to do that in 30 seconds and require a dime-size paint touch-up.

Or what Frank said.

I don't TIG weld so am stuck with this old fashioned torch.

:)

Michael Angelo 03-11-13 04:47 AM

A while back I bought a Paramount that had the seat lugs mashed, very similar to the OP's pictures but mine was not cracked. I had our local Frame Builder Mike Terraferma, straighten the lugs and back fill each lug ear completely. I had to redrill for the new bolt, and cleanup the area, before paint.

This picture shows what he basically did. ( Picture from the Net)

http://i1128.photobucket.com/albums/...nforcement.jpg

After painting
http://i1128.photobucket.com/albums/...untCables7.jpg

JohnDThompson 03-11-13 08:25 AM

Quote:

Originally Posted by Michael Angelo (Post 15370863)
A while back I bought a Paramount that had the seat lugs mashed, very similar to the OP's pictures but mine was not cracked. I had our local Frame Builder Mike Terraferma, straighten the lugs and back fill each lug ear completely. I had to redrill for the new bolt, and cleanup the area, before paint.

This picture shows what he basically did. ( Picture from the Net)

http://i1128.photobucket.com/albums/...nforcement.jpg

That's what I'd do, if it were my frame.

When building frames with that style seat lug, I put a short piece of seat stay scrap inside the ears and braze it solid as Terraferma did in the picture above. It's easier before the frame is built, because you can drop the tube section in the opening the seat tube will cover, but as above it can be done after the fact as well, with some judicious filing of the lug ears to open them enough to insert the tube section.


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