Details on butting of 93 Ti

mtbmaniac

New member
Hi, I'm wondering if anyone would know, possibly needs info straight from the welders.
My 93 Ti externally welded butted frame, has an extra (machined?) outer butting about 1 cm from the BB shell on the bottom tube.
My question is, was this particular butting intended to surround the bottom tube completely? Or was it intended to go in a certain direction, e.g. right (driveside) or left, or straight (top or bottom). Or was it intended to be centerred (equal amount of butting all around?)
Am maybe shooting in the wild, but finally got to taking my second hand one apart to rebuild, and the engineering part of me is just got extremely curious how it was designed and intended, seeing / feeling this butting.
Thanks.
 
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I-ROBOT

Active member
Hello
I've been away from the site for a bit and just seeing this now. The first versions of the second generation of Titanium Fat Chances (I call it that since the first generation was the version created by Gary Helfrich who wound up taking his ideas and founding Merlin Metal Works) had "butting" created by welding sleeves onto the downtube and chainstays. The headtube had inserts that were welded into straight gauge tube and the seat tube also had a welded insert at the top. These were done on the '91 and '92 models. Chris got the idea to machine the exteriors of the down tube, top tube, and chainstays for the '93 model. At the time, Merlin was experimenting with chemical milling to create butting in their tubes but I don't know if they used that in production or not.

The machined tubes provided the stiffness of of traditional butted tubes (as was common with steel bike frame tubing produced by True Temper, Tange, Columbus, and others) and it drastically reduced the amount of welding that was required for each frame. Granted. machining all the tubes was a fairly arduous process since we did not have a modern CNC lathe. The overall weight of the frame was also cut considerably, close to a half pound if I remember correctly. Also the frames just looked cleaner and not as bulky.

As far as the dimensions of the butting goes, I'm not sure how Chris came up with the diameters, lengths of butts, tapers, etc. I know he had some sort of Excel program that worked out angles and lengths of tubes for each size of model we produced.

I have a '91 that was a warranty return. I repaired it and Chris said I could have it when Somerville shut down. I wish I could find a '94 as those are the pinnacle of Somerville craftsmanship and my personal zenith as a frame welder.

And, yes, the '93 and '94 models came with a top tube sticker that said "FEEL MY BUTT"

Hope this helps
Scott
 

newsboy

New member
do you have pics of the 1991 fat ti? never saw such an early one. only saw 1-2 from 1992.
i know that gary h made some experiments with ti at his fat time. ;) but haven't known or seen that he welded some external sleeves to the tubes. but what i know is that mike a made some external sleeves at his frames (chain-/seatstaytubes)/forks at one-off titanium before the catalogue pics from fat in 1993. but i wasn't there...

as i like pics...
stuff i got from mike a. some fat sleeves details
fat_chance_titanium_downtube_20210202_007.png

fat_chance_titanium_downtube_20210202_005.png

fat_chance_titanium_headtube_20210824_001.png

fat_chance_titanium_headtube_20210824_004.png


one-off titanium frame & fork from 1991
one_off_mtb_lf_20190914_022.jpg

one_off_mtb_lf_20190914_024.jpg

one_off_mtb_lf_20190914_011.jpg


one_off_mtb_lf_20190914_023.jpg

another one-off fork
merlin_ashley_039.jpg


cheers
ashok
 

mtbmaniac

New member
Lovely details Ashok.

@Scott: The reason why I was asking is that it seems that the machined butting closest to the BB on the downtube, about 1 cm from the BB shell, is not centered completely, rather it is slightly more butted on one side. I was wondering if it was intentional, eg to stiffen on one side. Or if it was just by accident ;) :D
 

I-ROBOT

Active member
I doubt that was intentional. More likely just the way the machining came out. We only had an old lathe and I'm sure it was not as precise as a modern-day CNC lathe. Probably some tool run-out. We couldn't afford to throw away any tubes that the machining came out a bit off-center.
Good eye in noticing it though.
I like the cut away of our '91 Ti frame. I never saw the inside of one and wondered just how good my purging set-up was. Looks pretty good.
Here is my '91
ti frame.jpg
 
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