Building your own bike frames - anyone here ever done it?

[danlb]

According to my research, I am a porn star, but I don't film it.

-Doozer

For research to be valid, the results should be reproducible and witnessed. Try it again, with someone else this time.

I phrased my statement that way because I was curious about the limits of my MIG welder when I looked into buying a TIG model. I did a bit of research into it, and the experts over on welding web (along with other sources) were pretty unanimous about the reason a novice should not use MIG to weld a bike frame.

Sadly, like most of the people here, I have no direct experience in properly welding a bicycle frame. I brazed a broken top tube back to the seat-tube when I was a young teen, but I hardly call that experience.

Dan

[wombat2go]

Here I am just doing basic frame work for special trike design.

I use 4130 tube with OA fillet brazing.
I presently use Flux Coated rods of RB Cu Zn -C ( AWS 5.8 -92)
It has 56 k PSI ( 386 MPa) yield
868 ~ 888 Celsius

The difficulty with it is that the residual flux is like a glass coating and very difficult to remove.
It takes me longer to clean the flux off than to do the joints.

In Australia I used to use a similar flux coated rod called "Manganese Bronze"
but I don't remember having so much difficulty de- fluxing those ones.

What is the normal brazing rod that frame builders would have used?

[softtail]

According to my research, I am a porn star, but I don't film it.

-Doozer

Talk is cheap. I want to see you mig a bike frame that weighs less than you do. Should be an easy task being mig..

[Glug]

There is a simplicity in a bamboo bike frame that makes it appealing. Anyone dabble with those? I haven't had time to dig into it, but I see kits and what not.

[mattthemuppet]

And the finished frame. My sand rail powered by a GSX750CC

cool buggy! That must go like stink with a GSX 750 engine in it. At the risk of derailing the thread (sorry OP!), I can't figure out your front suspension. Is it a simple double wishbone with an adjustable upper shock mount or is there something funky going on with a pivoting upper link? Also, why 3 coil overs per side at the back?

[3 Phase Lightbulb]

cool buggy! That must go like stink with a GSX 750 engine in it. At the risk of derailing the thread (sorry OP!), I can't figure out your front suspension. Is it a simple double wishbone with an adjustable upper shock mount or is there something funky going on with a pivoting upper link? Also, why 3 coil overs per side at the back?

Here is a link to pictures of the front end suspension. http://www.bbssystem.com/viewtopic.php?t=836

I used 3 coil overs in the rear because there is about a 3-to-1 ratio with those rockers. For every foot of wheel travel, there is only a few inches of shock movement so the shock rate is also about 1/3. I also wanted the look of several coil overs with a rocker.

If you want to see all of the details from the initial first cuts of SCH40 pipe until the test drive, there is a chronological index here http://www.bbssystem.com/viewtopic.php?p=10133

[softtail]

Here I am just doing basic frame work for special trike design.


What is the normal brazing rod that frame builders would have used?

Many builders use these consumables:

http://www.henryjames.com/bicyle-parts/bike-frame-building-materials.html?p=2

The gasfluxer is an interesting tool. Puts liquid flux directly in the torch flame. Need to be doing a lot of brazing to justify though..

I would try to get away from the coated rod and switch to a paste if I was you. Yes, the cleanup is a royal pita, and one's health should be protected through the whole process. Luckily, the better the welds ie no over heating, the easier the cleanup. Burnt flux is the worst.

I was a die hard fillet guy for quite a while, but the simplicity and cleanliness of TIG has won me over from a building standpoint. Can't beat the looks of a nice fillet though..

The fellows at Curtis bikes in the UK are in rarefied air re fillet brazing :

https://www.curtisbikes.co.uk/frames/curtis-am7/

[wombat2go]

Softail,
Thanks,
I see the RBCuZn-B filler has manganese + nickel, compared to the RBCuZn-C that I have been using ( manganese only)

I will see if local welding supplier can do it in non-coated.

[754]

I am curious about MIG now. I assume it would be OK for a cruiser type bike? That is not beat hard like off road stuff?
I have grazed frames I rode a lot on bikes 60 years old, and they are holding up good, and I am like 270 lbs.

[kendall]

I have thousands of miles on an old Lambert (yeah, the suicide fork). I really like brazed frames, they are surprisingly strong for very little weight gain.
In my opinion the only thing a lugged frame has over a fillet brazed frame is the artistry that is often applied to the lugs, I've seen some lugs (filed/carved etc to be sure) that would make you tell the Venus de milo to 'getcher ugly azz out of the way' so you can look at those lugs (lugs,(with an L) not jugs(with a J))

[wombat2go]

I would be wary of MIG with 4130.

On the other hand, OA welding of 4130 tube using R45 filler is still an approved method for aircraft.
It does not look too beautiful however ( At least when I do it !)

[softtail]

I am curious about MIG now. I assume it would be OK for a cruiser type bike? That is not beat hard like off road stuff?
I have grazed frames I rode a lot on bikes 60 years old, and they are holding up good, and I am like 270 lbs.

Depends what you mean by 'ok'.

Can mig weld tubes that thin? Control of pre/post flow? Use of a foot pedal? Feed control while welding? Can you get the correct wire? Got a real small and flexible mig handle for getting into the very tight rear joints?

Mig stinks at all that.

Now if I was building some freak bike that took car wheels/tires, with big ol thick tubes and large clearances, then sure... not only sure, but please, as tig is fun and all, but for doing many feet of welds, it can get a bit old.

Dumpsters, bumpers, thicker material, lots of welds, bring on the mig!

But yeah, if a guy just had to prove it could be done, sure you could make a really scabby frame that weighs a ton and would probably cost more in materials that the dime a dozen made in china crusier frames.

[bborr01]

And the finished frame. My sand rail powered by a GSX750CC

Awesome job on the buggy build 3phase. Thanks for sharing it with us.

Brian

[3 Phase Lightbulb]

Awesome job on the buggy build 3phase. Thanks for sharing it with us.

Brian

Thanks, I built that over 11 years ago... Here is a test drive after final assembly back in summer of 2006:

[754]

Ok I meant chopper for cruiser rides, maybe a small motor.
Probably 60 thou tubing, no weight weenie effort..