REVIEWS DEALS BIKESHOPS TRAILS

gusset/ doubler questions

2404 Views 15 Replies 10 Participants Last post by becik, Feb 11, 2010

becik

Discussion Starter · Jan 17, 2010

Excuse my poor English....
I'm planning to do something pretty similar to Santacruz or intense...

I'm still definitively not a welder of big experience.
And I'm working with aluminum.

Thickness: ?? would you go same as the tube or thicker.

But the real question to me is may be more of a welding sequence,
If I go with the idea that the "doubler" is the same thickness as the tube (or sheet metal) and welded or tacked to the tube and mitered properly, then when welding let's say the doubled DT to the HT there is no proof that it is going to be stronger since I will have problem to weld properly both "layer" of DT at the same time. So I guess, in that case the doubler should be thicker and I'll be relying only on the doubler.

But, if I'm sticking with same thickness what about welding everything "sans doubler" and add the doublers in a second pass (over some existing weld)

Merci de votre interet.

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becik

Discussion Starter · #2 · Feb 6, 2010

Ok,
Since, I haven't got much from you guys, I thought I should share what I have...
I did some more research.. On the wonderfull web.
And came with this

It look like the way to do is weld the portion of the tube that will receive the doubler to the
HT.
Then weld the doubler on the tube (DT),
And, finish with the weld that will run from the TT to the DT...

What do you think. ?

themanmonkey

· #3 · Feb 6, 2010

Fist things first, the term you want to use in English is gusset, not doubler. All the examples you have are for aluminum, are you building aluminum? If you're building with steel research what Keith Bontrager did with his frames. It's been discussed quite a bit in the archives.

Thylacine

· #4 · Feb 7, 2010

themanmonkey said:
Fist things first, the term you want to use in English is gusset, not doubler. All the examples you have are for aluminum, are you building aluminum? If you're building with steel research what Keith Bontrager did with his frames. It's been discussed quite a bit in the archives.

He did a better job than you did! :skep:

Roadsters

· #5 · Feb 7, 2010

I'm not even a frame builder, but I try to dress stylishly so I'll offer some thoughts. Using a tapered lug for inspiration, you could taper the thickness of the pieces down their entire length, so at the end that's nearest the head tube or seat tube they are they same thickness as the wall thickness of the tubing they're being added to, and at the other end they are as thin as you can make them. The reasoning here is that we want stresses traveling down the tube to dissipate gradually rather than being concentrated at the ends of the pieces you add.

AZ BAD BOY

· #6 · Feb 7, 2010

becik said:
Excuse my poor English....
I'm planning to do something pretty similar to Santacruz or intense...

I'm still definitively not a welder of big experience.
And I'm working with aluminum.

Thickness: ?? would you go same as the tube or thicker.

But the real question to me is may be more of a welding sequence,
If I go with the idea that the "doubler" is the same thickness as the tube (or sheet metal) and welded or tacked to the tube and mitered properly, then when welding let's say the doubled DT to the HT there is no proof that it is going to be stronger since I will have problem to weld properly both "layer" of DT at the same time. So I guess, in that case the doubler should be thicker and I'll be relying only on the doubler.

But, if I'm sticking with same thickness what about welding everything "sans doubler" and add the doublers in a second pass (over some existing weld)

Merci de votre interet.

This is going to be your biggest problem with your project (I'm still definitively not a welder of big experience). Aluminum is the hardest material to weld out of all common metals. If you're thinking on using a MIG with a spool gun or something similar you need to reconsider this project.

Assuming you have at least decent TIG welding skills you'll want to weld the tubes all the way around before adding the gusset/doubler. I would make the gusset out of 1/8" material. Whatever you do, don't sand down any welds to make them look better. This is never an option with aluminum, especially if you can't weld both side of the joint (in and out).

If you need any other advice you can always PM me.

Good luck,

BB

Teague

· #7 · Feb 7, 2010

AZ BAD BOY said:
This is going to be your biggest problem with your project (I'm still definitively not a welder of big experience). Aluminum is the hardest material to weld out of all common metals.

BB

Thats just your opinion. Aside from issues with cleanliness, i actually found aluminum to be easier than steel or stainless (which require much smaller beads, and much more finesse with the filler rod), once i got the hang of it. Just my opinion

Roadsters

· #8 · Feb 7, 2010

AZ BAD BOY said:
Whatever you do, don't sand down any welds to make them look better. This is never an option with aluminum...

It sounds like you've never looked at the filed welds on any aluminum Klein.

Live Wire

· #9 · Feb 7, 2010

Roadsters said:
I'm not even a frame builder, .

Hmmm:skep:

j-ro

· #10 · Feb 7, 2010

Roadsters said:
It sounds like you've never looked at the filed welds on any aluminum Klein.

Kleins and cannondales run two passes to build it up enough to then smooth and shape.

A gusset is a lap joint or flat weld. If you shape it or file it smooth you will be left with an insufficient weld profile, You might as well not put anything there to begin with

Aluminum depends on a larger weld structure for its strength than steel.

Linnaeus

· #11 · Feb 7, 2010

I'm w/ Teague, I think Al is pretty easy to TIG. But I've never done any analysis on my joints so who knows how they would fare structurally.

becik

Discussion Starter · #12 · Feb 10, 2010

4

OK guys thank you for the replies.

I will use the term "gusset" the next time.

May be I should have said, but for this project I won't be the welder.
I'm more a machinist and a designer than a welder,
So I'm relying on some good friends who defenitly knows how to weld aluminum better than me. (one use to weld for DEVINCI and the other is working with XPREZO.)

I know for some of you, it is an offence (not to weld my frames myself..)
but I'm still working on my skills.
The next frame will be from my hands 100%... I swear.

For the interested.
this is what should look like my actual project.

And this is what the monocque is looking.

The welds ...

from the inside

I am actualy working on my jig and the machinig of the linkage.
I'll keep you informed if you want to know the progress but I'm realy (I mean, I have two kids and a whife and a real job and prefer to play ouside...) not progressing that fast...

Tx

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zipzit

· #13 · Feb 10, 2010

becik said:
For the interested.

And this is what the monocque is looking.

Wow. I'm very impressed. How did you form the shell? If I had to guess you made two male forms either in metal or wood, then pressed / hammered the aluminum to fit? Doesn't that work harden aluminum too much? Or do you have access to a high tonnage hydraulic press?
--zip

j-ro

· #14 · Feb 10, 2010

looks nice man, keep us posted!

Teague

· #15 · Feb 10, 2010

I may not be an expert on aluminum bike frame welding, but that sure seams like a lot of burn through.

becik

Discussion Starter · #16 · Feb 11, 2010

I build two form bloc, one male for each side. (CNC machining again)
This time I used MDF wood, since I won't go production with this. but usualy we use aluminum.

I'm fortunate to have acces to an hydromorming press at work.
I took this picure with my phone... next time I'll bring the camera.
And I'll show you the process.

-lay the sheet metal (6061 condition 0) On the rubber with the form bloc over it and in good position.
-put the pressure (in my case 60 ton) on the form bloc so the rubber force the sheet metal against the form.
-release pressure.
-finish forming with a lot of tender hammering and patience.
-trim to hachieve perfect fit.
-clean
-weld
-miter.

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