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Old 06-10-10, 08:13 PM   #1
FixedCommuter
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Cut in Seat Tube!?!

Ok, so, I have a Reynolds 520 butted frame and I had an aluminum seat post. I had the old seized up seat post issue. I tried everything and ended up having to attempt the frightening and cringe inducing cut-the-top-of-the-seatpost-off-and-try-to-hacksaw-down-the-center-to-free-up-a-chunk move. All was going well till I brought my bike to my parents house for the weekend to use some tools and (hopefully) go for a ride with my folks. Well, long story short, my dad went ahead (against my STRONG advice not to, btw) and used a metal cutting blade and reciprocal saw to speed up the process. In the process of this, he cut a 2 inch long gash through the seat tube about 8 inches below the top of the seat post (see Pics). My question is: Is this still rideable? I don't really feel comfortable with it for commuting (its previous use), and don't like the idea of water being able to get in through the gash and get to my frame/bb housing.

photo-1..jpgphoto-2..jpg

Thanks BF Mech's! Your the best!
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Old 06-11-10, 03:35 AM   #2
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You can ride it, but the strength of the tube is permanently compromised and water is going to get in there and wreck everything. The value of the frame pretty much drops to zero with something like that.
A framebuilder can replace the tube for you. That and a repaint aren't going to be cheap though.
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Old 06-11-10, 04:22 AM   #3
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Daddy owes you a rebuild/ repaint/ new frame. If you ride it and the seat tube splits with you on the bike, he could owe you a new colon.
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Old 06-11-10, 04:52 AM   #4
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Drill a small diameter hole at each end of the cut. 1/8" or less. That will eliminate the stress consentration at each end so it doesn't crack. Then have it welded. Call a number of people, bike stores too, until you find someone that knows what they are talking about and let them do it. Then paint the seat tube a contrasting color, as though it was ment to be. Done. Only problem is that the new seat post will have to be short. The weld buildup inside the seat tube will stop the post.

OR..........Just go buy a new frame and swap the parts. That would be much more fun, and to do the work I suggested you are going to have to take the parts off anyways. Nothing like a good excuse to get a new something or other. My suggestion is to have some fun replacing the frame but the fix would work too.

Good luck, Greg
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Old 06-11-10, 07:00 AM   #5
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When I was a teenager I had to tell my dad he wasn't allowed to give me mechanical help anymore... that was generally related to my R/C race cars and a ham-fisted adjustment he made to a battery connector with a screwdriver. He meant well and I felt bad doing it, but it worked out for the best in the end.

All that being said, I would drill a small hole at either end of the gash to stop cracks from forming, then the bike is almost definitely still ridable. If your dad offers to buy you a new frame I would accept if I were you..
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Old 06-11-10, 07:05 AM   #6
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Not a good thing, but certainly not difficult to salvage for a commuter bike.

If possible buy a seatpost long enough (Thomsons go to 410mm) to go more than an inch beyond the cut which will shore up the tube and carry any load below the damage. Grease it well so it doesn't seize later on. Then use silicone caulk to close up the damage so it's water tight.

If the cut is too low, find a junk seatpost of the right diameter & cut off a section about 5-6" long. Use a plunger handle or your seatpost as a pusher and depth gauge measure and mark a line so you can locate your support at the right depth (centered over the damage). Clean the inside of the seat tube as well as possible using a ball of steel wool, tied with strong cord and pushed (plunger handle) and pulled over the area. Apply a slow drying adhesive to your splice and push it into place. Finish with silicone caulk to weather seal.

If you do a decent job, no one will ever know it's been damaged, and it'll outlast your attention span.
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Old 06-11-10, 09:15 AM   #7
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thanks guys. Ive got a friend who is an auto welder coming out to look at it today, so I might go that route. That being said im still gonna use this as an excuse to save up and get a better frame anyway, so I guess all is not lost. Still, its sad to see something that has been there through so many storms and such go the way of the dodo. Thanks for all the advice!
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Old 06-11-10, 09:46 AM   #8
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I'd go with FBinNY's advice and use something like Loctite 660 to hold the piece in place. Welding means repainting and reaming out the seat tube, assuming it's successful. Not worth the risk or expense in my opinion.
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Old 06-11-10, 09:53 AM   #9
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Quote:
Originally Posted by joejack951 View Post
I'd go with FBinNY's advice and use something like Loctite 660 to hold the piece in place. Welding means repainting and reaming out the seat tube, assuming it's successful. Not worth the risk or expense in my opinion.
A cheap simple, yet effective repair lacks the illusion that something meaningful was done. With a simple splint made from an old seatpost he could ride this forever, but he won't have the feeling that all was OK. Fixing problems is often much easier than giving the owner the feeling that it's as good as new.

I've known folks to ride frames with problems far worse than this, and others to replace frames with far less serious problems. It isn't a problem between the seat lug and BB, but between the ears.
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Old 06-11-10, 11:13 AM   #10
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It may be quite rideable as it is but I know it would make me nervous as hell wondering if it were going to split open at some point. Especially if the seat post end was at or just above the slit.

If you got a longer post intended for MTB's so the end is buried well beyond the lower end of the slit THEN I think it would be fine with just some sealant to keep out the rain. I just know that I'd only feel OK with a slit like that in the frame if the end of an original length seat post was not trying to wedge the slit apart. And the only way to do that is to have a post long enough to fit down further by about 2 or 3 inches past the lower part of the damage.

For my own part I'd feel far better about it if it were welded or possibly filled with brass or silver brazing. The brazing would still require a repaint of that area but it would stabilize the tube and make it almost as strong as before. Certainly more than strong enough to ride for years to come. If welding it you won't need a hole at the end of the cut. The weld will totally reform the metal and a stress relief hole would be supurfluous. But if you go with a brazed repair then you would want a 3/32 or 1/8 hole.
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Old 06-12-10, 04:37 AM   #11
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Back in the 1980's, I had an intake manifold develop a leak where the antifreeze port flowed thru it. It leaked and I needed it welded to seal it, so I took it down to a welding place that does aluminum welding. It'll be ugly or no uglier than the welds they do on aluminum frames anyways, but it'll be structurally stronger than it was originally ? It really won't add any appreciable weight to the bike either, it'll be a cosmetic blemish on the back of the seat tube of the frame. Cost me $ 10 back in the day, drove that car a few more years and sold it to a girl who drove it at least another three years after I sold it to her.
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