Bilaminate Joints: Actually Building Them

[DanBailey]

So let's chit-chat a bit about the best way to actually build a bi-lam joint. I'm about to embark on some experiments with them and wanted to get some feedback.

What I was thinking is this:

Miter the two tubes. Tack them together with bronze. Tin the joint so that everything is held together without the need for a giant fillet. Clean up everything so the sleeve slides into place cleanly. Build the fillet with the bronze. Clean/finish the fillet. Go through and use 56% silver to fill the area under the sleeve.

I'm trying to visualize any stupid gotchas from doing it this way. Thoughts?

[EricKeller]

braze the sleeve on the tube, miter, braze them together, join like a couple of thick tubes.

You can braze the sleeves on the tubes with silver and then use brass for the fillet, doesn't hurt anything.

[Jayme]

Check out this thread... http://www.velocipedesalon.com/forum...rts-25843.html

[DanBailey]

That thread doesn't really say much about the process of actually brazing them.

[afwalker]

Well I never would have tried Silver on the sleeve first, even though it's easier to get all the way through, THEN done Brass for the fillet,
because I would have worried that the higher heat for brass would have messed up all that silver in the sleeve, but
thanks to Eric Keller, I think I will try this now:) I guess if the silver gets wet, where's it going to go if it's allready in the sleeve, it can't all run away.
cheers
andy walker

[Curt Goodrich]

Don't over think it. Fit it up like a lugged joint and braze it all at once. No need for different fillers. Use the same filler to flow the joint as to lay the fillet.

[e-RICHIE]

Dan -
I clicked through the site (URL is in your Signature...) and noticed you have
a Bilam order in the queue list. Is this the frame you're asking about here?

[Cooper Cycles]

Here's a picture of a bilam joint a did awhile back.


Bilaminate by Cooper Cycles, on Flickr

I've tried it a few different ways and like brazing the sleeves on and then making a fillet. Using good bronze rod (I like the Cycles Design stuff) makes brazing the sleeve easier. I would recommend against using silver for the sleeve and then bronze for the fillet, it will get messy and a chore to clean up (been there done that). If you are using thin tubes, use 56 for the sleeve and 50n for the fillet.

Have Fun,
Travis
Cooper Cycles

[DanBailey]

Dan -
I clicked through the site (URL is in your Signature...) and noticed you have
a Bilam order in the queue list. Is this the frame you're asking about here?

Actually, in a roundabout way, yes. I plan to do at least a good dozen practice joints before I even think about touching one in production. I'm comfortable with both my bronze and silver skills, so I just want to make sure that I find any kinks before I actually put them on a complete bike.

The plan is to take those dozen joints and then take them to my brother, who works in non-destructive testing, so we can get a look at the brazing without destroying them, and then I plan to run all of them through destructive testing. I'm just trying to gain some insight into the best way to approach the construction of the joint before I do that.

[e-RICHIE]

...who works in non-destructive testing
...destructive testing

Can you describe the non-destructive and destructive testing?
I have taken hundreds of brazed joints and pulled them, pushed them, and beat them to death with many tools.
No frame failures I have had (to date) ever resembled the results I saw when done in house.

[hmbatrail]

I mitered the tubes and mitered the lugs separately and did fit separately as I find it easier to work with a bit thinner metal versus really leaning on the file. Brazed up together with fillet and lug braze done in one shot.

It isn't overly difficult, just time intensive with little practical reason to do it. That is simply my opinion mind you.

8302629310_8630f11d44_c.jpg

[Andrew R Stewart]

Tim- Are the butts in the depicted frame longer then the lug/sleeve is? Andy.

[hmbatrail]

No. Lugs are still inside the butted sections.

[DanBailey]

Can you describe the non-destructive and destructive testing?
I have taken hundreds of brazed joints and pulled them, pushed them, and beat them to death with many tools.
No frame failures I have had (to date) ever resembled the results I saw when done in house.

Well, yeah, reality and the "lab" never really match up -- whether in engineering, or in science, right?

For the NDT portion of it, my brother will either do an industrial x-ray or an industrial CT scan to look at the interior of the weld.

For the destructive portion, I'll be doing what Wyganowski taught me to do, which is to put the joint in a vise, stick a cheater bar in the tube and wrench it around until it fails. If it breaks away from the weld, then I'll cut the area apart to take a look at the guts.

[DanBailey]

Brazed up together with fillet and lug braze done in one shot.

It isn't overly difficult, just time intensive with little practical reason to do it. That is simply my opinion mind you.

Ideally, this is the route I'd go, but I have zero experience in bronze-brazing lugs. Thus, my whole two-stage approach using items I'm comfortable with.

[Eric Estlund]

experience

Not to be "that guy", but I'd say keep going with the fundamentals for a bit before venturing into "non-standard". Bilam is a term that best describes a couple of different end results, all achieved through what amounts to some fundamentals added together.

Have fun working through a few different approaches and getting a feel for what works for you. And maybe get hell bent on getting the stuff down that challenges.

[DanBailey]

Not to be "that guy", but I'd say keep going with the fundamentals for a bit before venturing into "non-standard".

Well yeah, obviously, it's a case of experience. There's nothing about a bilam joint that seems overwhelming -- based on what I've done in the past with silver and bronze. My question was more of a "what's your process?" than anything else. I already plan to build a dozen (or so) test joints and put them through some rigorous testing before I move on to putting them on a client frame. Really, from what I can tell this is more or less a fillet brazed joint with a section of lug sleeve worked into it -- it's important to get it right, sure, but we're not landing men on the moon here, either. My only point of concern has been filling in the area under the lug sleeve and without having bronze brazed a lug before, I posited a possible solution.

What I'll probably do is try a couple via the approach I mentioned in my initial post, try a couple the way Andy Walker mentioned above, and I'm going to PM Tim for a little clarity on how he's approaching it (doing both lug and joint with bronze or using silver/bronze in tandem) to see if it makes sense to try a few his way, too.

[e-RICHIE]

I would do what CPG suggests - one pass and one pass only, and all with brass (no rhyme intended) atmo.

[anon.]

My only point of concern has been filling in the area under the lug sleeve and without having bronze brazed a lug before, I posited a possible solution.

I wouldn't worry too much about getting full penetration under the sleeve.