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Framebuilders Thinking about a custom frame? Lugged vs Fillet Brazed. Different Frame materials? Newvex or Pacenti Lugs? why get a custom Road, Mountain, or Track Frame? Got a question about framebuilding? Lets discuss framebuilding at it's finest.

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Old 04-12-08, 05:05 PM   #1
VaAu
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Main Triangle

Am I correct to assume that the four inside angles of the main triangle should sum to 360 degrees? Mathematically this is tru for a four-side polygon but I'm wondering if frame builders deviate (by say 1 degrees) for some reason I'm not aware of.

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Old 04-12-08, 11:20 PM   #2
Allen
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The sum of the interior angels of a quadrangle is always 360, there is no way around it.
180 (n-2) where n is the number of sides of the polygon.
You could put a bend in one of the pipes to make up for it, but I have not worked with metal and don't know if there is a reason one would want to do such.
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Old 04-13-08, 07:00 AM   #3
VaAu
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Thanks.

The specs provided to me by a lug maker don't sum to 360. I'll request they re-submit specs on assumption they made an error.
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Old 04-13-08, 11:16 AM   #4
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Ask again at Frameforum.net.
They have more traffic from professional frame builders, and you'll get a more informed answer.
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Old 04-13-08, 08:39 PM   #5
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Hi,
Are you talking about adding up the lug angles from the ht/st/bb? Most lug angles are measured in relation to an imaginary vertical plane and can vary according to the design ie: road bike, track bike, amount of bb drop, sloping top tubes.....there is no reason the angles should add up to 360.
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Old 04-14-08, 04:38 PM   #6
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These are the angles I summed:
st/tt + tt/ht + ht/dt + dt/bb/st

tt/ht is actually 180 minus tt/ht
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