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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.

 04-12-08, 05:05 PM #1 VaAu Member Thread Starter   Join Date: Apr 2008 Bikes: Posts: 37 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) 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. Thanks
 04-12-08, 11:20 PM #2 Allen Senior Member   Join Date: Sep 2005 Bikes: Posts: 4,758 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) The sum of the interior angels of a quadrangle is always 360º, 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.
 04-13-08, 07:00 AM #3 VaAu Member Thread Starter   Join Date: Apr 2008 Bikes: Posts: 37 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) 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.
 04-13-08, 11:16 AM #4 Allen Senior Member   Join Date: Sep 2005 Bikes: Posts: 4,758 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) Ask again at Frameforum.net. They have more traffic from professional frame builders, and you'll get a more informed answer.
 04-13-08, 08:39 PM #5 Live Wire  Framebuilder   Join Date: Dec 2007 Bikes: Posts: 541 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 3 Post(s) 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. __________________ Instagram: http://www.instagramhd.com/profile/m..._custom_cycles http://www.matthewscustomcycles.blogspot.com/
 04-14-08, 04:38 PM #6 VaAu Member Thread Starter   Join Date: Apr 2008 Bikes: Posts: 37 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) These are the angles I summed: st/tt + tt/ht + ht/dt + dt/bb/st tt/ht is actually 180 minus tt/ht