Bought a bike by, uhhhh, accident

Don't know much about bikes, but can you just replace the head tube that is cracked like replacing a tire or derailer.

Now that could lead to all sorts of trouble.



That's in line with what I'm thinking. FWIW, welding the head tube doesn't concern me much; I do fabrication work for my race car and others as a sideline. I'm the experts' worst nightmare..a semi-educated amateur.
http://www.secondhandsix.com/images/upp_ctrl_arms_001.jpg

Part it out. Get another frame, by accident or otherwise. This one could kill you. Of course, even there, the components are 7 yrs old. Seen ALOT of miles. Not a bad thing, but hopefully they were well maintained.

500 is ALOT for a 7 yr old cracked frame bike. If you're lucky, there's other undisclosed frame cracks and you can try to undo the the deal.

Definitely have the bike totally inspected by a good shop when you get it.

My advice to you would be break it down and sell everything on ebay except the frame. You should at least make up for the money spent on the auction. I wouldnt ride anything TIG-ed after a crack even if it came from the manufacturer. Whats the warranty on the frame? They may offer you a discount on a new frame also? Cannondale offered a friend of mine a discount on a new MTB frame when he cracked his hucking of a cliff. You never know...

sorry to be the bearer of bad news, but i think you need to take her out back and put her out of her misery...
i wrecked my bianchi in a collision, and it sucked. had kind of the same damage. no frame is worth my neck. parted her out and put her down. sigh

as far as parting it out, go ahead. but the wheels are 650c and you're a big guy. i don't think they will be much use to you.

ok, you can send me the wheels. Maybe that will help you feel better about all of this 

Thank you everyone for the comments..now I'm going to ignore you all and fix it when it gets here.

Seriously though, this ain't yer cousin Vern with the propane torch in the back yard tryin' ta fix the lawnmower. We do .063" 6061 aluminum all the time for intercooler piping. Guess I need a pic:


That's my friend Tracy Grimm's work; he's the best TIG welder I've ever seen, and I have taken courses from experts who teach the commercial and aerospace certifications.

That's the nicest thing about aluminum in general; it's eminently repairable. I spend some time helping out in a race machine shop and you'd be shocked at some of the blocks and heads that are resurrected. I'm talking welding up holes you could put your fist through.

Anyway..back sort of on topic. I am a 200 pounder, but I'm only 5'9" and after reading slowtwitch.com, I figured the 650c wheels might work well for me.

Edited by KendallF 2005-03-21 9:14 PM

The real problem with this bike is, as I see it, is not that the headtube is cracked, it is that it has been chashed into something hard enough to crack the headtube! The headtube is the damage you can easily see. I would have to suspect that if the frame has taken that hard of a lick that there might be other damage you can't see. I wonder if this seller has looked at the sterrer tube for example.
Since you are experienced with working with alumnium, I am sure you know how it has a finite fatigue limit, and that stress risers are a big risk .
 I don't doubt the welding prowess of you and your colleagues, that is not the issue here, You are getting ready to trust your life to a  bike that has known problems with  its frame.  I regularly descend mountains  at  45-50+ MPH, and frequently cruise at 30+ on gentle downslopes.  Stack it in at those speeds and you can easily die, or be FUBAR for the rest of your life. I have to trust my equipment. It's not worht it to me to "get a deal" on something and have it fail on me and get me hurt.
At the end of the day, it's your ass not mine. You're fully capable of making your own decisions and dealing with the consequences. But since you solicited opinions.......
Dont ride that frame. There are too many perfectly safe options for a safe (under warranty even) frames out there. This is a silly way to risk your life.

I'll step off the soap box now.

Think there is some overreaction to the cracks in the aluminium. If you TIG weld it you will have time to see how well it is holding, you should be able to see the cracks start to grow again. Then if they do it is time to throw it away. Also check all the welds on the bike for cracks. If they are cracking then this can't be repaired.

I assume it is a carbon steerer and forks? If so find out if they were involved in the crash. This is a much bigger problem. The damage to carbon fibre is irreparable and can be completely undetectable and this can suddenly fail on you. I'd replace them ASAP.

I'll leave my personal opinions out of it as far as whether or not this was a purchase I would have made. That said, your buddy's TIG welding is good quality. I've been a Nuclear Certified welding inspector for 26 years, and our company makes products for both the Nuclear Power market and the Military. I would keep an eye on any distortion caused by the weld repair. You don't want to end up with an out-of-roundness issue that distorts the bearing races. Also, you might want to consider some sort of nondestructive weld examination after the repair. The only problem is the frame is probably painted, so doing a liquid penetrant examination of the areas might not revel much, unless there are tiny cracks, invisible to the naked eye, that are coming through the paint as well. A dye check might reveal this.

The other thing to check, since this has been involved in a crash, is the overall general frame alignment. If you're involved with race cars or something like that, this should be sort of simple. But I'd loop a long string around the head tube and extend the ends out to the rear drop-outs. Then you can take some measurements from the string to various spots on the frame, side to side, to determine if there is any misalignment from the crash. Back in the 1980's I was involved in several bike crashes while racing, one of which snapped the fork on my bike and cracked the head tube. It was enough to change the angle of the head tube in relation to the top tube. I'd check that angle on yours as well, and compare it to the published specs for the bike. If that's been compromised, the bike will not steer or track very well, since the rake and trail will have been affected.

Oh, BTW...you might want to drill holes just past the end of both those cracks before weld repair, jus to stop them from propagating. Without that, the heat from the TIG torch might cause them to spread. I figured you probably knew this anyway, but wanted to mention it just in case. And have your friend excavate the cracks a bit, open them up to get good weld penetration, rather that just a cosmetic repair by covering them up. I only say this because you'll surely want to grind off all the excess weld reinforcement after the repair, so make sure you have good weld bead penetration. And clean the area good to avoid contamination problems. Washing the aluminum surface first with alcohol or acetone might help too. Maybe even go with .045" or even .030" wire and lower amperage to lessen the chances of blowing away the tubing wall during weld repair.


Good luck and let us know how things turn out!

Edited by max 2005-03-22 12:04 PM

That is why I love this site! Where else would you be able to get that kind of indepth analysis for free? Max, that was truly impressive.

Whoops, I hit the submit button too many times. Over excited!

Edited by mlaugustine 2005-03-22 1:38 PM

For anybody who's bored with what's now turning into a welding & fabrication thread, I apologize.

Max, thanks! All good suggestions. I'm an engineer and a former aircraft tech myself. I have a TIG here at the house and I do pretty much anything I need to (that's my welding on the control arms in the first pic), but for gorgeous aluminum work, I turn to Tracy (see 2nd pic).

I always stop drill and vee out cracks before welding; I have done quite a bit of this with cast iron blocks that are prone to re-cracking after welding. The crack prep, along with preheating and post-weld slow cooldown, seems to work well. I have one V6 block repaired that way that's currently making 1200 HP.

The dye penetrant seems to work OK on anodized parts; doesn't work well on painted or powdercoated surfaces. I don't know what Felt does to their frames..I'll have to clean the area around the weld anyway.

I will probably face and ream the head tube after welding before re-installing the bearing cups. I'll take some pictures when I do the work.

For anybody who's still reading this and thinks I'm insane, I enjoy fabrication and welding work; see my web site (www.secondhandsix.com) for some past and current projects.

Kendall, it sounds good to me. You got a pretty decent handle on the situation. The weld repairs I'm not scared of. Anything can be repaired. The frame was welded originally! Actually the weld metal will be stronger than the parent metal, due to the fact that the tensile and yield strength of the deposited weld is higher than the aluminum base metal. The only caveat with aluminum is because of its modulus of elasticity that it is not very forgiving when it has gone past it's yield point and repairs made by "cold forming" tend not to work very well, as they would on steel.

I'd just keep a good eye on the general frame alignment, that would be my biggest worry. You might even want to set it up on some sort of jig and take some reasonably precise measurements to see how the alignment is. The original cracks in the head tube suggest a mild shock to the frame. Anything real drastic, like it might have been slammed into a wall at high speed would have resulted in permanent buckling of the top and down tubes for sure. It appears that's OK.

And yes, I agree on the paint removal in the area of repair. That'll let you at least do some sort of inspection on the metal surrounding it. The dye check isn't much good unless the paint is removed anyway. If you don't have dye checking materials, a "poor man's substitute" can be made by painting the area with kerosene, letting it soak into any potential cracks for a few minutes, wiping off as much of the excess with dry rags, then dusting with talcum or baby powder. That'll at least let you see any micro-cracking!

I'd sure be interested in any photos you might take of your repair work. Let me know if you have any, and perhaps you could just email them to me!



Edited by max 2005-03-23 1:32 AM

uuhhh....does this mean I'm NOT getting those wheels?