Q for Ti builders: how do these miters strike you?

[wallymann]

builder will remain anonymous, but to me these look REAL gappy.

http://sphotos-a.xx.fbcdn.net/hphotos-prn1/67843_300396596728016_32981974_n.jpg

[54ny77]

http://www.huffingtonpost.com/huff-wires/20080609/fbn-giants-strahan-retires/images/fcec3620-7194-4fd6-9512-2ed208e968d0.jpg

[dave thompson]

At least the air gaps are consistent.

[happycampyer]

That's the ti equivalent of the Domane—those gaps will allow the seat tube to move fore and aft a few millimeters, giving the frame a small amount of shock absorption. Same with the chainstays. Pivotless suspension of sorts.

[54ny77]

Bet your builder can burn a mean hole in paper with his glasses under the hot desert sun.

http://media.lonelyplanet.com/lpi/23239/23239-8/681x454.jpg

[fatallightning]

look like hell. builder shouldn't remain anonymous ATMO

[cnighbor1]

the seat tube doesn't appear to in the correct position
if tilted forward than it fits tight
stays may be not angled correctly in photos
if moved a bit could fit fine

[Sketchy]

Not bothered by the gap between the DT/ST, assuming the ST is going to be welded underneath. The ink on the stays bothers me more. Clean that crap off!

[Peter P.]

Maybe that was just a hurried mock up to take a photo?

Unless there was a caption under the original photo that said otherwise, you might want to give the builder a break and maybe just conclude the builder was not wise to post pictures which could be construed as shoddy assembly and damage their reputation.

Without seeing the web page of the original photo and any accompanying text, I'd be willing to give the builder a "pass" on that one but I certainly won't deny it raises questions and makes me leery.

[EnginCycle]

Well since no builders seem to be talking I will give my feelings.

The tubes are not prepped for welding so the branding on the chainstay will go away before welding (IMO).

The gap on the counter miter is too big for me (not my ability but my standards of quality). It could easily be welded (except for the gases that will come pouring out of it and make it harder) but it will require much more heat and filler which could potentially pull the tubes together more than wanted and have an effect on the end products QC. The chainstays are just a poor miter. Chainstay miters can rotate on the shell and still remain proper since it is a perpendicular miter. Moving the chainstays will not correct the error. It appears to be done with the wrong cutter and was a larger radius than needed.

Lots of bikes in the world started out with poor miters. They are easy enough to overcome but the better the miter the more consistent the heat added and the more predictable the outcome.

If the point of this thread was that is your bike and you are concerned then why not ask the actual builder. If the reason was you found the photo and wanted to show the world then I am curious why keep out the maker? It all depends on how you got the photo. Either way this is a difficult topic. I try to document as much of my work as possible so people can see my QC.

-Drew

[mike p]

I quess I agree with Drew. I weld for a living but have never welded a bike frame in my life. Most of my welding is heavy structural steel or pipe welding, but welding is welding. To me the gaps are nothing that can't be overcome by a competent welder but they go to the overall quality and workmanship of the craftsman. 90% of welding is the prep work before you ever strike an arc. Even though I believe a sound weld could be made of those miters I wouldn't hire that guy.

Mike

[avalonracing]

Come on... Tell us.

And where can I get a bottom bracket like that?! ;)

[Jason E]

I'm with Peter P. This pic does not really tell us anything. Maybbe he saw an email from you as he was first getting the tubes in and wanted to get you a quick pic.

Too much unknown to criticize someone. If you have issues with a bike you are having built, you need to call or go see the builder.

[wallymann]

not my bike, just something i found whilst perusing the interwebs...was interested in how critical tight miters are to Ti, more for self-education than anything -- hence leaving builder anonymous.

...
If the point of this thread was that is your bike and you are concerned then why not ask the actual builder. If the reason was you found the photo and wanted to show the world then I am curious why keep out the maker? It all depends on how you got the photo. Either way this is a difficult topic. I try to document as much of my work as possible so people can see my QC....


Too much unknown to criticize someone. If you have issues with a bike you are having built, you need to call or go see the builder.

[wallymann]

i guess they tack, then do the full-up welds in a 2nd pass. wonder if the 2nd pass is "free" or left in the jig.

anyway the DT-ST gap is pretty massive still, but the others seem to have been tightened up a bit:

http://brown-snout.com/cycling/misc/432222_300403186727357_262509422_n.jpg

[Ahneida Ride]

Well....

I've seen what they look like when Mr. Bedford does em ...

and they don't look anything like that ....

[David Kirk]

I think a few things are possible -

First is that the tubes may not be well positioned in the photo and the miters may be better that they appear. One would have to wonder why anyone would set up the tubes poorly so that they looked like that and then take and share the photo. That doesn't make much sense to me.

Or........ the miters are what they look like - not good. I would say that if they are as they appear in the photo that they are unacceptable. Now a good welder could fills those gaps and make it work............but just because you can doesn't mean you should.

dave

[rice rocket]

Bigger filler rod and a competent welder can overcome that pretty easily.

edit: You should see some of the miters I've made (though on 1018 steel) and a good welder was able to gap. I'd say it was a good 1/8". :)

[fogrider]

i guess they tack, then do the full-up welds in a 2nd pass. wonder if the 2nd pass is "free" or left in the jig.

anyway the DT-ST gap is pretty massive still, but the others seem to have been tightened up a bit:

http://brown-snout.com/cycling/misc/432222_300403186727357_262509422_n.jpg

with the tubes tacked like that, how can the seat tube be welded completely to the bb?

[wallymann]

almost looks like both the DT and ST are mitered at their interface, hence the big gap? cant find any "tweener" pics to show what was/not welded or tacked to the BB shell under that gappy miter.

with the tubes tacked like that, how can the seat tube be welded completely to the bb?

[pbarry]

with the tubes tacked like that, how can the seat tube be welded completely to the bb?

Right. IMO, ST and BB should be welded as a unit, then jigged up with the rest. A good framebuilder would have knocked off the "ears" of the lower DT/BB mitre to get a closer fit. The gap in the third mitre: DT/ST is less of a concern. Chainstay mitres could have been cleaned up with a half round file and a bit of jig adjustment.

Hope this was a production frame, then I'd excuse the play fast/get it done feeling from the images. If it's a one-off for good money, things should be tighter than a....

[Chance]

For all we know this frame could have been used for education or training purposes. Maybe it’s just to show someone/students what not to do. Or was deliberately botched to show poor quality control or what not to buy. A picture off the internet without context leaves too much information missing to make anything out of it in my opinion.

[EnginCycle]

Right. IMO, ST and BB should be welded as a unit, then jigged up with the rest. A good framebuilder would have knocked off the "ears" of the lower DT/BB mitre to get a closer fit. The gap in the third mitre: DT/ST is less of a concern. Chainstay mitres could have been cleaned up with a half round file and a bit of jig adjustment.

Hope this was a production frame, then I'd excuse the play fast/get it done feeling from the images. If it's a one-off for good money, things should be tighter than a....

I want to explain this to others.

The counter miter was cut too short. Plain and simple. The "ears" as you are referring would not move the counter miter towards the ST. The reason you round off the corners is to clear the radius of a weld that would be the ST/BB. I am of the opinion that a bicycle should enter the fixture once and that maximizes the tolerances of using the BB face as a datum. I put the BB/ST in the fixture and weld the front and back just enough to clear the counter miter for the DT. I then put the DT in the fixture and when the bike is finished the ST will have a complete weld including under the counter miter.

The short miter could have resolved IF there was an ability to lower the DT on the HT. If you re-mitered the BB portion of the DT it would close the gap on the counter miter.

Next concern is about your comment on the "jig adjustment". What are you talking about here. That is not a way to fix anything. The fixture is the fixture and all adjustments are to be made (to the parts) so the parts mess together without any forcing. There is no adjusting the fixture.

Sorry to be harsh but I hate when bad information is passed over as fact on the internet.

-Drew

[jpw]

i'm reminded of why i chose to buy Serotta ti.