amazinmets73

I have already mentioned this...

CAT7RDR

At least the OP does not have to wear a helmet if he rides his bike with a cracked headtube "hard."

3alarmer 

TIG Welding a Titanium Bike Frame

...there was a short afternoon workshop on working with titanium frames, at the NAHBS here about ten years ago.
It's a lot harder to do a good job than you might initially think, if you're mostly familiar with welding steel and aluminum.

Mostly the gas shielding arrangements are more complex, to prevent contamination of the weld.

3alarmer 

https://bicycles.stackexchange.com/q...-advice-needed

With the exception of watching the lecture at NAHBS, I have never considered welding titanium. I guess it's possible that training of the average machine shop welder has progressed significantly, but I'm dubious. I actually did first learn welding at a Votec outside of Charleston, S.C., but they were mostly tuning out welders for the shipyard there. So we ran beads on steel plate with heavy duty stick welder for hours and hours. Maybe Votec education has changed since then too, but it would need to have changed a lot.

It's not just running a bead on your crack, and getting full penetration. There's also the issue of gas shielding the interior of the head tube, as the weld progresses.

If this were easy, there would probably be more people doing it.

Polaris OBark

You could stockpile several pints of your own blood for future transfusions, should the weld not hold.

Koyote

Precisely. This is why the OP's very casual statement below (as well as some other posters' suggestions -- I got a particular laugh at the one who suggested taking the frame to the local high school) is so ridiculous. I've known plenty of people who can weld steel, and even a few who have welding gear in their garages. Titanium is a whole different animal, though. That's why the crack shown in the OP's photo is almost certainly fatal.

reconnaissance

not a lost cause,as this can be TIG welded. Look for a specialty welding shop, take them the frame with the fork and headset removed.

livedarklions

Descent, bump, crack, crash.

livedarklions

I went and checked the tape from 2017, you're either remembering wrong or you're a damn liar:
https://www.bikeforums.net/19850083-post32.html

smd4

Seven pages. Seven...pages.

And my initial question still hasn't been answered in any serious way (Although someone mis-interpreted that question into "advice"). We've got lots of predictions of end-result catastrophic failure, hoped-for good dental insurance, impending death...But no theories about the actual process of frame failure that will lead to all of this.

Seven pages.

"Crack, crash." Uh huh.

What do you think that means? Do you think the crack will propagate the entire length of the head tube? If so, will it then roll open? Or will the front end get so wobbly that the rider will then deicide to stop? Will the crack stop at the reinforcing ring at the top?

Lots of fear mongering. Not much actual thought.

(Why should I be surprised? People still think my rims are going to explode at 140 psi).

amazinmets73

I don't think 140psi is a safety hazard. However please, give your buttocks some relief! 100 psi would be so much more comfortable.

amazinmets73

Just re-read the thread. Don't see a single person advising me to purchase it.

smd4

It's a racing bike, not a Lazy Boy. It wasn't built for comfort.

smd4

I think my favorite is from Ms. Raqball, who initially said (referring to a question I asked):

But then later, seemed to be OK will someone riding the bike (as long as it wasn't ridden "hard"):

GhostRider62

No.

I thought my first response was a nice way of saying, "no"

What is your definition of safety? To me, it is freedom from unacceptable risk. What is risk? It is a combination of the probability of failure and severity of such a failure.

If the front end fails, you are forked.

Were you expecting a professionally done FMEA? If so, my hourly rate is $450

smd4

Guess we're trying for eight pages...

GhostRider62

I guess I am the idiot here.

You got a serious response to foolish question.

Your troll continues.

smd4

You just can't explain to me what this "catastrophic failure" will look like? How is asking this question "trolling?" You can't describe it. Not even a guess. Amazing. Even I wrote down some examples. Why don't you just grab one I wrote and suggest it?

easyupbug 

With a weld shop if you got lucky maybe the bottom cup might seat.

indyfabz

That is why I have him on ignore.

livedarklions

No, but there are plenty of people saying essentially just make sure the dent didn't affect the geometry and if not, it's probably ok. That's an opinion, and it's not "don't buy the bike". So the post I was responding to was either just wrong or a deliberate lie.

Sorry, but this ask for advice then trash people because you don't like the advice troll is absolutely the most annoying bit on BF.

No one really knows what that crack is likely to do because it's not an experiment anyone is currently running. Honestly, you probably won't get hurt if/when the thing goes completely, but it's definitely a possibility. Honestly, at this piouint, I don't care if you break your neck because you know full well you're taking that risk. You want to call people wusses because they won't? You get no good will from anyone at that point. I can't imagine why anyone would want to spend the time to give you reasoned advice after that.

Trakhak

Here's a guy who used the drill-and-clamp method. Maybe you can find a similar clamp of appropriate inner and outer diameters.

Note that titanium is difficult to drill. Look up advice on drilling it properly.

Koyote

Yes, this is right up there with some other bf troll staples:

Did I get a good deal on this Craig's List bike?
No, you got a bad deal.
Well, f--- you!

Does this bike fit me? (Insert photo of person on a bike this is grossly undersized.)
No, that bike looks a wee bit too small for you.
Well, f--- you!

This motorist did something bad to me.
No, that was your fault.
Well, f--- you!

jad3675

Hey, I never said 'high school'; again though, there's nothing magical about welding Ti.
Look - the OP wants to stress relieve the crack and run a worm clamp around it. At that point, even if the local weldor can't run a line of dimes, it has to be a better than not fixing it or using an external clamp. Best case, he's able to fit the headset and the headtube doesn't explode. Worst case, he has wall-art.

GhostRider62

As if we can divine the additional stresses in the steerer tube or know whether it is carbon, steel or heavens forbid, aluminum. The forces are meant to be taken at the crown and bearings, not laterally on the steerer tube as that crack propagates. And how fast will it propogate?

The couple of riders I know with failed front ends required close to a year of rehab.

If the crack was in another location, I might get it fixed but then again I do have such a frame and decided not have it repaired. So, it is a double no for me