88ss

Got this frame that had a broken seat-tube right where it goes into the BB. Took it apart, took out the seat-tube fragment that was brazed into the BB, then cleaned up and shaped the bottom of the seat-tube, shortened the head tube to match what was lost off the seat tube, then welded and brazed it all back together. Next will cut the fork's steer tube down to match and chase it's threads down the distance of what that will lose, and then can try building it back up and taking it for a ride.....

Abara....


cadabara.....

Andrew R Stewart 

I have never seen this approach to fixing a broken seat tube before. Andy

88ss

It just worked for me because it was an extra-tall 26" frame, so taking about 5/8" out of it actually made it close to the 25" frames I usually ride anyway. The seat-stays just needed to be very slightly bent forward to line back up with the seat tube lug, and I did not even trim them shorter as they did not stick up enough to cause any problems.

88ss

Shortened the fork today to match, it worked well. Cut it in the middle above the serial number to preserve that feature.

PhilFo 

Pardon my language but that fork mod seems like doing dental work by going through the anus. Why not just cut more threads into the steer tube and cut off the extra?

88ss

It is the method that fit the tools and skills I possess so it took very little time and I did not have to spend time looking around for steer-tube cutting tools to borrow, and I did not have to spend any money buying a tool I may never use again. That clear things up for you ???

88ss

After doing the frame and fork I threw a bunch of parts on the bike from the junk-box, and this morning took it for a ride of about 25miles, including up and down some steeper grades. As it is the bike is a single-speed stuck in 52/18 gearing, but that is okay because I am very used to riding a single-speed bike with similar gearing. So that was the acid-test for the brazing etc. stomping it up hills with 200+ pounds on the pedals in a high gear. So two days of spare time it went from trash to treasure. Stopped at a local Starbucks on the way home and snapped this shot of it's 50th birthday ride;

bulgie 

"Just" cutting more threads with a die sometimes ruins the fork. Before you say something like "not if you do it right", let me add that I have heard this from some of the most experiemced and careful technicians out there. If you've never seen a fork ruined by a threading die, it makes me think you haven't done very many. Sometimes the die, even with proper technique and plenty of oil, just decides to rip all the threads out as you remove the die.

There are some tricks to improve your chances, and I won't say I'll never do it (I've done two so far this year), but you have to weigh the risk into your cost/benefit analysis.

OP's shortening method relies on the skill and care you put into welding it, but it's been done many times by lots of welders and I've never actually heard of one breaking later. Maybe it's me who needs to "get out more"? Anyone here ever heard of a spliced steerer failing in use?

From my limited data, it seems like splicing is safer than rethreading.

Mark B

Andrew R Stewart 

I might suggest dulling down the seat stay caps. Two little knives pointing toward one's jewels...

I've only done something like this once. One of my early frames suffered a crack right below the seat lug on the sides of the seat tube. (Too many heating cycles at too high a temp will do that) before the frame was painted. As it had a rather short top tube for the tall size it was I cut off the top tube and removed the seat stays. A new top tube located a few cms below the first one and the stays were shortened at the bottom ends. Painted and sold it off after sitting around the shop for a couple of years. I forget how I dealt with the fork, likely replaced the steerer with a shorter one. Andy

88ss

Today in a bucket of parts in my garage I did find a clamp-on Shimano cable guide and got my rear derailleur going, also a friend of mine gave me a Paramount head-badge he had in his stash. The badge is off a lot newer bike I am sure, but it is good enough. I drilled new holes for the badge with a tiny drill and then hit them with a 4-40 tap because it matched the screws I found in a parts bin in the basement.

I went to school for "tool and die" forty-some years ago before the digital age, we were taught to do things like they must have been taught at the dawn of the tool&die industry. Among many other things we were taught to turn a tap or die only the number of degrees it took to curl up a good chip of metal, often far less than ninety degrees, then turn it back and break the chip before turning it that far again past the last point. And of course there are specialty lubes for tapping and threading, the brand "Sulphlo" comes to mind. I talked to two old cycle shops in my area, one had sold their tools for threading steer tubes, the other had them but said they did not have good luck with them, and Park wants about $250 for the tool. If I had the tool I am sure I could have competently used it, but then too you have to cut the keyway that the tab-washer uses, which could be done by hand with what I believe is called a Cape Chisel, or with a perhaps a pillar file. Soon all of the old bike shops with tools for the old steel bicycles and the persons who know how to use them will be gone along with all of us who rode the bikes when they were current. I am not a bicycle mechanic, just an old jack-of-all-trades. To me all mechanical work is the same no matter if it is done on a wrist-watch or a backhoe.

bulgie 

My machinist training was also 40+ years ago and what you describe is the procedure I've always used for hand tapping. The sulphur-bearing cutting oils have gone out of fashion in the decades since, but I'm not enough of a cutting-oil expert to know why. Top brands like Tapmatic, Tap Magic and Anchor Lube are clear or light-colored, not the almost-black of the old sulphur stuff. Anyone here know why?

Nowadays I'd do it on the milling machine but I have done a lot of them with a warding file, which seems fairly ideal for the job. Makes a nice groove. However you may want to consider just skipping the groove and not using a tongue-washer. The tongue doesn't to much good, and can be bad if it slips sideways and gnarfs up the thread. Without a tongue-washer, you need two wrenches to tighten the headset against itself, but two wrenches is strongly advised even if you do have a tongue washer.

I have never had a headset loosen up when tightened with two wrenches and no groove, no tongue-washer. YMMV but I prefer forks without the groove, personally.

Mark B

88ss

I don't groove steer tubes at all, shortening or lengthening the existing tube by welding would be too easy for me to have to mess with it. Also this is the only bicycle frame I have ever taken apart and put back together in my life, it was on a whim and something fun to do. I had the torches out to work on the exhaust system of my car, so went down and got the frame out of the corner of the basement where it has been the last six-months. I have an idea for a custom frame I might like to build someday, but it is so much fun to just ride the bikes I have, and it is so easy to find frames/bikes in good shape cheaply on the market, that I will not bet on ever having to do it.

So I am not a "framebuilder" and not interested in being one, I just thought this was the appropriate section of the forum to post this in.

duanedr 

I am with Andrew, I think I would now go back and try to nip a bit off the seatstay ends so they are a bit more flush with the joint. If careful, you may be able to taper them in place and braze on a thin plate to close them off - or cut them much lower and braze in some plug-style stay caps. Bravo for taking this on in a way that preserves as much of the original as possible.

88ss

Thanks for the input. Someday if I feel like it maybe I will alter the seat-stays to fit the average world-view, but there is no functional reason for me to, and it is my bike I am going to ride and it is fine the way it is for me. Today I put a front derailleur on the bike and some less-used brake-pads. I have put forty miles on it today and yesterday and it is a great fun ride. My plan is to keep riding the heck out of it this fall and over the winter throw some of the Campy stuff on it, a set of Record hubs I got at a house-sale for ten bucks, and a friend has donated some Campy shifters and a cable guide. I will check the local auto-paint shop for a can of touch-up paint in a bomb similar to what it has on it and cover up the repairs. After I am dead the next owner can worry about it having more snob-appeal.

88ss

Now I have about 500 miles on this bike. Over past weeks have added Campy Record Hubs, shifters and cable-guide, Vittoria tires and a new BB bearing because of a disintegrated cage. Bike handles and rides like a champ at any speed in any maneuver. Also sent it's number in to be added to a registry of Paramount bicycles.

guy153

It looks solid. Did you put a sleeve inside and TIG weld it? In theory a sleeve shouldn't be necessary but it's good for peace of mind.

88ss

Everything I do gives me peace of mind, same with anyone else. I used gas-shielded MIG on whatever needed welding, bronze rod on the joints that needed brazed, rod I got to do repairs on a motorcycle frame that was Reynolds tubing also.