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TREK style seat lug with seatstay sockets

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TREK style seat lug with seatstay sockets

Old 03-03-17, 04:23 PM
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Panthadad2
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TREK style seat lug with seatstay sockets

I just picked up this used 1993 Trek 750 and love the lug style with seatstay sockets. I'm looking into building a lugged touring bike and would love to use this style of lug if I can find it. Two questions:

1) Can the stay angle vary a little from the pre-cast angle of the socket? How much?
2) Anyone know if this style lug is even available out there? I've poked around a little and seen something vaguely similar from Long Shen and Ceeway, but not really.
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Old 03-03-17, 06:37 PM
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When you use thousands of lugs a year you get special treatment. Like non other use clauses in the contract with the lug manufacturer. That is the case with these and the other version that Trek used. My understanding is that Trek had a few versions, differentiated by the socket wall thickness (and perhaps internal tube end aspects), tube diameters and the stay spread. The pictures looks like the mountain bike version For each version they has a couple of each lug with different angles. My late wife's 1984 720 clearly had the seat stays entering the seat lug sockets at a few degrees off the lug's angles.


The market for over the counter lugs is not very large so no surprise that the range is not as great as what you once saw in production.


As to who far can one stretch" lug angles- it depends of a variety of aspects. How deep is the socket, how snug does the tube fit (and what filler you hope to use), will you bend the socket with a solid bar and then reshape the fit, will you cut a wedge out of the lug and braze/weld it back together? And there are other considerations.


Generally for a cast lug with an intended silver filler with no cutting but some grinding, 2 or 3 degrees of angle change is often thought as being achievable. I've gone as far a 6 degrees but used bronze as the internal gaps grow pretty large. But what any one tube/socket allows for is part of the discovery builders go through. Andy.
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Old 03-03-17, 11:25 PM
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Thanks Andy. Very helpful reply.
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Old 03-03-17, 11:32 PM
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There's a very nice system from Italy, with a cast seat lug that has the upper end of what would be a seat stay cap, then is relieved and drilled. The actual cap, or plug (they made both) is formed and radiused to pocket into the lug yet free to move to meet stays coming form a range of angles. When brazed up, it looks like and is as strong as a single cast assembly.
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Old 03-04-17, 12:03 PM
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This one is new and not sure of the availability. It's from Llewellyn and may be available from Nova.


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Old 03-04-17, 01:46 PM
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An investment is a wax, or plastic replica of the part you want made. now with 3D printers that part can be a one off.

then a mold a (A refractory clay-plaster) is poured around the piece, and the investment is burned out in an oven at high temperatires , plastic just takes a little longer.

Then a steel foundary pours the molten metal in..
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Old 03-04-17, 08:58 PM
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Reddog3: That's a nice clean looking lug. Definitely a possibility. I looked on the Nova and Llewellyn websites and didn't see that one; doesn't mean it wasn't there though. I'll have to look harder. Thanks for posting the pic.
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Old 03-04-17, 09:10 PM
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Originally Posted by fietsbob View Post
An investment is a wax, or plastic replica of the part you want made. now with 3D printers that part can be a one off.

then a mold a (A refractory clay-plaster) is poured around the piece, and the investment is burned out in an oven at high temperatires , plastic just takes a little longer.

Then a steel foundary pours the molten metal in..
Didn't even think about the advances in 3D printing that could open up possibilities. Good idea. I'm no mechanical engineer so I'd have to hire that one out. But if I ever decide to build multiple frames, or for anyone who is, seems like that could be a great way to create something unique. Pretty cool stuff.
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Old 03-05-17, 12:01 PM
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Tig welding can make lugs too, it is a bit of extra effort, of course.

Plain steel filler wire can be brazed over to make the joints smooth.
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Old 03-05-17, 01:12 PM
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A 3-D printer could certainly make a one-off wax for a cast lug, but there more factors that need to be taken into account when designing the wax, e.g. it has to be slightly oversize to account for shrinkage when the metal cools. How much oversize depends on a number of factors including what type of metal, how thick it is, etc. This is where it helps to have someone experienced in precision casting.
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Old 03-05-17, 01:17 PM
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Originally Posted by Panthadad2 View Post
Reddog3: That's a nice clean looking lug. Definitely a possibility. I looked on the Nova and Llewellyn websites and didn't see that one; doesn't mean it wasn't there though. I'll have to look harder. Thanks for posting the pic.
Looks like Ceeway has that one, or one similar to it:



Lugs
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Old 03-05-17, 01:55 PM
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I know I have seen a seat lug with seat stay sockets riveted to each side with large diameter hollow rivets so that the seat stay angle could be adjusted by rotating the socket around the rivet, then when the seat stays are inserted in the sockets and correctly positioned at the rear dropout in the frame fixture, the socket is brazed to the lug using brass filler at the correct angle. The rivet hole is then filled with brass filler and filed smooth.

I've looked online and can't find it, but I know I didn't dream it.
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Old 03-05-17, 10:38 PM
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Stan, I know what you mean. There was a lug with separate pieces for the stays. Personally, I just attach the stays the way I want without a special lug.
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Old 03-06-17, 08:53 AM
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[QUOTE=JohnDThompson;19420274]Looks like Ceeway has that one, or one similar to it:

Thanks for the reference John.
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Old 03-06-17, 10:03 AM
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Investment cast seat stay tips will work at any angle, so on any sized frame..
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Old 03-06-17, 10:41 AM
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Originally Posted by fietsbob View Post
Tig welding can make lugs too, it is a bit of extra effort, of course.

Plain steel filler wire can be brazed over to make the joints smooth.
I admittedly have zero TIG welding skills. Plus I love the lugged look and have at least some experience there. So lugs it is . Maybe someday I'll get some TIG training.
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Old 03-06-17, 05:43 PM
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Originally Posted by Panthadad2 View Post
I admittedly have zero TIG welding skills. Plus I love the lugged look and have at least some experience there. So lugs it is . Maybe someday I'll get some TIG training.


What about fillet brazing with bronze? Andy
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