Glue and lugs
07-26-10 | 08:04 AM
#26
Senior Member
Joined: Jul 2007
Posts: 84
Likes: 0
Alan frames
Alan frames were aluminium tubes in aluminium lugs and almost all their frames were under tremendus pressure because all the lugs were the same angle for a 54cm frame and if you built a different size frame, the lower head tube lug and the bottom bkt angles were wrong so the tubing would be bowed.
I thought the problem in gluing metal tubes and lugs is that the epoxy is more rigid and brittle than the relatively flexible steel or aluminum tubes. Hence the occasional failure of those glued al. frames? The Alan frames used glue and screws in the joints, that may have stiffened the joint...
Or perhaps better epoxies are more compliant, like brazing filler?
Anyway, here is a video of Colnago gluing carbon tubes in carbon lugs: https://www.youtube.com/watch?v=MRt4p...layer_embedded. My guess is that carbon is generally stiffer, and perhaps has similar properties as epoxy?
Or perhaps better epoxies are more compliant, like brazing filler?
Anyway, here is a video of Colnago gluing carbon tubes in carbon lugs: https://www.youtube.com/watch?v=MRt4p...layer_embedded. My guess is that carbon is generally stiffer, and perhaps has similar properties as epoxy?
07-26-10 | 10:45 AM
#27
Banned
Joined: Jun 2010
Posts: 43,586
Likes: 1,380
From: NW,Oregon Coast
Bikes: 8
I think they had a few different lugs , or at least machined the tapered thread into the lug for a given angle for each size.
Had 2 AlAn's, the 2 ends of the tube were threaded opposite directions I presume , like a turnbuckle ,
so as the tube was rotated it pulled itself into the Lugs at either end.
Being on the wrong side of the Atlantic meant getting the frame back to get what was a pretty cheap repair
as Quoted by the factory in Italy .. was no longer affordable .. air freight priced by Volume more than weight.
Had 2 AlAn's, the 2 ends of the tube were threaded opposite directions I presume , like a turnbuckle ,
so as the tube was rotated it pulled itself into the Lugs at either end.
Being on the wrong side of the Atlantic meant getting the frame back to get what was a pretty cheap repair
as Quoted by the factory in Italy .. was no longer affordable .. air freight priced by Volume more than weight.
07-29-10 | 04:42 AM
#28
Senior Member
Joined: Jun 2010
Posts: 212
Likes: 0
From: South Australia
Bikes: Aegis Aro Svelte
Epoxy bonds to aluminum better than steel. It is a matter of fact. Alot of the mid 90's Trek bikes were aluminum lugs 7000 series aluminum tubes/carbon tubes.
The actual reason for glueing aluminum rather than welding is the heat affected zone. Aluminum alloys can get over 25% of the stiffness/strength from the heat treatment alone.In order to properly construct an aluminum frame it must be welded then heat treated. Obviously with gluing this is not a problem. Trek only did it with the better frames & tubing.
The bond area should be a minimum 50% of the diameter of the tube. 1 1/2" tube needs a 3/4" deep lug.
The actual reason for glueing aluminum rather than welding is the heat affected zone. Aluminum alloys can get over 25% of the stiffness/strength from the heat treatment alone.In order to properly construct an aluminum frame it must be welded then heat treated. Obviously with gluing this is not a problem. Trek only did it with the better frames & tubing.
The bond area should be a minimum 50% of the diameter of the tube. 1 1/2" tube needs a 3/4" deep lug.
Thread
Thread Starter
Forum
Replies
Last Post
exmechanic89
Bicycle Mechanics
44
09-26-23 08:54 AM
