Shortest recommended butt at HT/TT and HT/DT junctions
07-31-19, 06:25 PM
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Shortest recommended butt at HT/TT and HT/DT junctions
Any recommendations on tube end butt length minimums using standard 25.4 and 28.6 tubes and 1" head tube. Lugs are the joining method.
07-31-19, 07:30 PM
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Tube walls? Rider size? Builder's skill? Andy
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AndrewRStewart
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07-31-19, 07:47 PM
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shortest remaining length of full size butt is 30mm according to Columbus. 50mm would be nice.
07-31-19, 08:42 PM
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As I see it the big thing is where the HAZ ends up WRT the butt. transition. IIRC the various posts and articles about this lugs need longer time at temp and thus the HAZ drifts away from the joint. Ideally the HAZ is within the thick end of the tube.
Having said that and being a guy who works with small frames I have pushed the butt trimming so that only a cm (or so) of thick wall extended past the lug tip more then once with no issues. Andy.
Having said that and being a guy who works with small frames I have pushed the butt trimming so that only a cm (or so) of thick wall extended past the lug tip more then once with no issues. Andy.
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AndrewRStewart
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08-01-19, 08:53 AM
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Short butt lengths are a curse. I'm glad there are some options with longer butt lengths now.
I didn't know I was short until I realized that the two head lugs on my travel bike almost touch.
I didn't know I was short until I realized that the two head lugs on my travel bike almost touch.
08-01-19, 02:03 PM
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what tube is 25.4 7/4/7? I thought there was only Kaisei. Have you estimated what your remaining butt will be?
08-01-19, 07:27 PM
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With that thin a thick end (as thin as "normal nice tubing" was in the center a few decades ago) I would also be concerned about the thick end being a bit longer then the lug tang is long. But as I tried to say it's all about the trade offs and the willingness to accept less weight for less lifespan. Andy
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AndrewRStewart
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08-02-19, 05:24 PM
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Yes, Keisai is the tube I am intending to use.
I put this out there because on my daily rider built in 2001, I used a really short butt on the TT and DT, if recalled correctly they are around 50mm. That tubing is 9-6-9, so much thicker, and the frame has about 20,000 miles on it without trouble. Am not sure 7-4-7 can handle that short of a butt at those two joints.
The lugs are Henry James on the daily rider, but will be Long Shen on the new frame since HJ is no longer doing lugs, or at least does not have them available for this application.
I put this out there because on my daily rider built in 2001, I used a really short butt on the TT and DT, if recalled correctly they are around 50mm. That tubing is 9-6-9, so much thicker, and the frame has about 20,000 miles on it without trouble. Am not sure 7-4-7 can handle that short of a butt at those two joints.
The lugs are Henry James on the daily rider, but will be Long Shen on the new frame since HJ is no longer doing lugs, or at least does not have them available for this application.
08-02-19, 05:51 PM
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50mm of the thick part is fine
