A question of process...custom seat lug

[Jacob_Curtis]

I am making progress on frame shaped object No.3 and have an interesting problem.
I made a custom seat lug from a turned down piece of .065 4130. It fits a 31.7 seat tube and 31.7 top tube.

When I brazed the bits together I ended up with a big internal fillet, normally this is great. However since this is going to be used as a lug these internal fillets don't allow a good mating of the top tube to the seat tube.

Should I just hog out all the material so the tube tube can pass through the sleeve there and directly contact the seat tube?
Or is it worth trying to just remove the internal fillet so I can retain the entire sleeve portion on the seat tube?
Or should I scrap it and start over using some no-flow on the interior of the lug?

lug.jpg

[Clockwork]

Should I just hog out all the material so the tube tube can pass through the sleeve there and directly contact the seat tube?

lug.jpg

I like this option and it's the easiest. This is how pre-made lugs are anyways.

-Joel

[e-RICHIE]

I like this option and it's the easiest. This is how pre-made lugs are anyways.

-Joel

^ this.
the two tubes that are mating have to mate, so anything that causes a gap between them has to go atmo.

[Jacob_Curtis]

This then leads me to ask, what about brazing the sleeves onto the top tube and seat tube with brass, then miter and fillet braze as normal ?
I imagine this would be only marginally heavier, and perhaps also only marginally stronger?

[e-RICHIE]

This then leads me to ask, what about brazing the sleeves onto the top tube and seat tube with brass, then miter and fillet braze as normal ?
I imagine this would be only marginally heavier, and perhaps also only marginally stronger?

it sounds like you are borrowing trouble atmo. are you doing this to be creative or to solve a problem by making a part that doesn't exist commercially?

[Jacob_Curtis]

I am really just exploring the process. This is the first time I've experimented with this sort of construction.
Building bikes at this point is just an exercise in pushing what else I can do with the materials. I've been working with precious metals and steel in jewelry and knives for some time, but only recently bicycles.

The bike is going to be a 29er for a hefty fellow and I thought a little extra material at this junction couldn't hurt.

In my limited knowledge of available castings I am unaware of anything that would work on this same situation.

[e-RICHIE]

I am really just exploring the process. This is the first time I've experimented with this sort of construction.
Building bikes at this point is just an exercise in pushing what else I can do with the materials. I've been working with precious metals and steel in jewelry and knives for some time, but only recently bicycles.

The bike is going to be a 29er for a hefty fellow and I thought a little extra material at this junction couldn't hurt.

In my limited knowledge of available castings I am unaware of anything that would work on this same situation.

it's your third frame. if you can fillet that faux lug, i would suggest bagging the exploration and
simply make the frame connections with brass atmo. no need to make a lug just to make a lug.

[Mark Kelly]

A way to think about this is to ask yourself "What's carrying the stress?"

Imagine the brazing material as glue - a thin layer of glue between two strong materials is a strong bond. A thick layer of glue is a weak bond. Adding extra glue outside the joint doesn't do much to help.

[Dornbox]

This then leads me to ask, what about brazing the sleeves onto the top tube and seat tube with brass, then miter and fillet braze as normal ?
I imagine this would be only marginally heavier, and perhaps also only marginally stronger?

I've don a few bi laminates this way and I believe that Edoz still does do his this way and with good results. However, that's a ton of material if you try to do 2 together like this.... I know another cat that does custom lugs like this for raod bikes but for a 29er.... that's a stiff joint and something is going to want to flex and possibly fail unless the joint is beefy and stiffer and stronger than the tube. I had a small fillet fail on me with the same joint do to this exact reason. It can be done but it has to be done right. Allways better to experiment with your own bikes or that of an aware friend ATMO.

Nice looking fillet! -Chris

[Jacob_Curtis]

Mark-
I am not worried about the strength of the method of joining the tubes, but the strength of the item as a whole. A .8mm wall st seems a little light for this application, adding this lug/sleeve or whatever you want to call it effectively increases the wall in a high stress area.

Richard-
Not sure I follow, why shouldn't I be trying new things? All these things that I am creating at this point are just experiments, I have no deadlines or paying customers.
I can certainly understand an emphasis on mastering the basics, but if I'm going to bother putting the torch to something other than some scraps to practice on it begs the questions why not?

[Mark Kelly]

Second half of reply - I have no idea why the software didn't let me post them together.

I cannot see why brazng sleeves onto the tubes, mitreing and brazing the joints wouldn't work.

Weight penalty marginal, strength increase significant. In my bond line analogy, you've got twice the area of thin bond between strong materials.

[Kumo Cycles]

Not sure I follow, why shouldn't I be trying new things? All these things that I am creating at this point are just experiments

Does the hefty fellow you are building the frame for feel the same re the experiment? He may not be paying but best not to take risks right?

[Jacob_Curtis]

Does the hefty fellow you are building the frame for feel the same re the experiment? He may not be paying but best not to take risks right?

I suppose I used the word experiment loosly, Its not going to be a case of cross my fingers first time he hits the trail. If I'm not comfortable with the work or for some reason he isn't we'll just have a big huffy frame to toss off the porch.

[e-RICHIE]

Richard-
Not sure I follow, why shouldn't I be trying new things? All these things that I am creating at this point are just experiments, I have no deadlines or paying customers.
I can certainly understand an emphasis on mastering the basics, but if I'm going to bother putting the torch to something other than some scraps to practice on it begs the questions why not?

i guess because it pays to focus, and it also can pay dividends to focus. what's more important - making that frame or making that lug? they're not separate from each other. the task involves joining two pipes, and with two frames under your belt it seems the shortest distance between two points should be the one taken. in your scenario, or in the one that i am sensing here, you want to create art and make a frame. if you're asking for advice, all of mine would be directed at learning you how to make that frame. with so little time at the bench, the last thing i would consider is branching out into the extracurricular stuff. i think of the lug making and the bi-lam stuff as internet driven exercises in making things taking the most circuitous route available. it's fine. but since you're the one who ran the filler into the area that the tube miters want to be, it's more like fine for a project well in the future.

again - my reply is based on my interpretation of your 1s and 0s.

[Jacob_Curtis]

i guess because it pays to focus, and it also can pay dividends to focus. what's more important - making that frame or making that lug? they're not separate from each other. the task involves joining two pipes, and with two frames under your belt it seems the shortest distance between two points should be the one taken. in your scenario, or in the one that i am sensing here, you want to create art and make a frame. if you're asking for advice, all of mine would be directed at learning you how to make that frame. with so little time at the bench, the last thing i would consider is branching out into the extracurricular stuff. i think of the lug making and the bi-lam stuff as internet driven exercises in making things taking the most circuitous route available. it's fine. but since you're the one who ran the filler into the area that the tube miters want to be, it's more like fine for a project well in the future.

again - my reply is based on my interpretation of your 1s and 0s.

I find you allusions to the creation of 'art' interesting. I have spent the last 3 and a half years working towards a BFA. I'm not going back in 2012, just over a semester shy of graduation. I grew sick of the attitude in the program. The emphasis was always on making art, or having some kind of artistic statement. I wondered how I was supposed to achieve this in all these different mediums I was required to be exposed to. I couldn't find the motivation in printmaking, painting, or photography. So little emphasis was placed on techniques or practices. I ultimately chose to concentrate in metals and jewelry, and while this wasn't much better I managed to weasel my way into the engineer dept machine shop for a bit and spend some time off campus working with a blacksmith.

I have no desire to create 'art', I won't want to sell my work, I don't want to show my work for any purpose other than to find ways to improve upon what I am doing.
In a perfect situation I'd be apprenticing with one of the dozens of frame builders I tried to contact before I got into this whole frame shaped object mess, or working somewhere here in the states working my way up from sweeping the floors at a larger frame building operation.

I just want to know more, I can't help myself. I started wrenching on bikes, then building wheels, this seems like a logical step.
So I'll take what I can get, If I can't stand in your shop or someone else's I'll at least try to glean as much as I can here.

[e-RICHIE]

good - my advice is this: re that seat lug you posted about ...

forget frame number three totally and take as much tubing as you can afford and make braze 20 of these lugs. heck, braze 50 of them. no need to carve or decorate the shorelines or file down the fillets; this is all just an exercise. when you have a sense of what it takes to avoid the issue in the OP, you can work through other parts of the process. at the end of the day you'll know more atmo.

I find you allusions to the creation of 'art' interesting. I have spent the last 3 and a half years working towards a BFA. I'm not going back in 2012, just over a semester shy of graduation. I grew sick of the attitude in the program. The emphasis was always on making art, or having some kind of artistic statement. I wondered how I was supposed to achieve this in all these different mediums I was required to be exposed to. I couldn't find the motivation in printmaking, painting, or photography. So little emphasis was placed on techniques or practices. I ultimately chose to concentrate in metals and jewelry, and while this wasn't much better I managed to weasel my way into the engineer dept machine shop for a bit and spend some time off campus working with a blacksmith.

I have no desire to create 'art', I won't want to sell my work, I don't want to show my work for any purpose other than to find ways to improve upon what I am doing.
In a perfect situation I'd be apprenticing with one of the dozens of frame builders I tried to contact before I got into this whole frame shaped object mess, or working somewhere here in the states working my way up from sweeping the floors at a larger frame building operation.

I just want to know more, I can't help myself. I started wrenching on bikes, then building wheels, this seems like a logical step.
So I'll take what I can get, If I can't stand in your shop or someone else's I'll at least try to glean as much as I can here.

[Jacob_Curtis]

Never thought I'd need to do brazing practice to MINIMIZE internal fillets. It was the other way around just months ago.

I'll get to work on my practice fillet batch.
sax_max_2.jpeg

Aside from that I am quickly learning to value this place and the folks that contribute here.
Thanks e-richie and others.

[edoz]

This then leads me to ask, what about brazing the sleeves onto the top tube and seat tube with brass, then miter and fillet braze as normal ?
I imagine this would be only marginally heavier, and perhaps also only marginally stronger?

That's worked fine for the ones I've done. There's also the benefit of mitering both tubes at the same time.

[Thylacine Cycles]

I find you allusions to the creation of 'art' interesting. I have spent the last 3 and a half years working towards a BFA. I'm not going back in 2012, just over a semester shy of graduation. I grew sick of the attitude in the program. The emphasis was always on making art, or having some kind of artistic statement. I wondered how I was supposed to achieve this in all these different mediums I was required to be exposed to. I couldn't find the motivation in printmaking, painting, or photography. So little emphasis was placed on techniques or practices. I ultimately chose to concentrate in metals and jewelry, and while this wasn't much better I managed to weasel my way into the engineer dept machine shop for a bit and spend some time off campus working with a blacksmith.

I have no desire to create 'art', I won't want to sell my work, I don't want to show my work for any purpose other than to find ways to improve upon what I am doing.
In a perfect situation I'd be apprenticing with one of the dozens of frame builders I tried to contact before I got into this whole frame shaped object mess, or working somewhere here in the states working my way up from sweeping the floors at a larger frame building operation.

I just want to know more, I can't help myself. I started wrenching on bikes, then building wheels, this seems like a logical step.
So I'll take what I can get, If I can't stand in your shop or someone else's I'll at least try to glean as much as I can here.

I assume a BFA is a BA (Fine Arts).....and you're complaining about the 'art' quotient???

I do sympathise though. It's not like 'Framebuilding' is something you can traditionally study anymore, either academically or through an apprenticeship.

Did you consider going to UBI, or Dave Bohms' course?

It seems insane to spend all that money doing a Bachelors and not finishing. Anyone looking at you as a prospective employer isn't looking at that as a plus. You just have to suck it up and finish. I understand the sentiment - I had the same issue in both High School and University, where the final years had nothing to offer me that I didn't already know and were a huge drag, but in the grand scheme of things you'll look back and be glad you got those pieces of paper.