yes another post from that mad man...

I’ve been looking over some sites about how to weld up a simple chopper frame as a bit of fun. Many sites go on about TIG welding and how great it is, no doubt that’s the case but I struggle to believe that it’s the only thing to use, after all it’s really only recently that TIG’s have come down in price, but still not low enough for me. Yet that is what some are saying and that MIG welding has little place in frame construction.

I have seen some DIY sites that are using MIG’s and although the welds are not as attractive, certainly seem fine for the job. I intend on using nothing more than a (don’t laugh) 250cc (I said don’t…laugh) engine so have little fear that it might rip apart from the awesome torque and was going to use swing arm rear suspension, so even less stress on the frame and also my arse.

I’m sure there will be many naysayer’s out there who declare I have too little knowledge to risk the lives of my fellow brit’s by attempting this death machine. But I want to have a go.


So any idea’s from this great reservoir of knowledge?

[Edited on 11/1/08 by Mr Whippy]

i think they like tig because it look neater, and chopper frames are largely on show? maybe?

I agree on the aesthetic reasons for the chopper frames, also bike frames, at least old british ones anyway) tended to be made out of high spec steel, or at least high spec for the day, and for that reason they tended to be lugged, pinned and brazed (possibly bronze welded cannot remember off hand).

I would be a bit concerned about creating stress concentrations around the mig weld due to the profile of the weld.

just my tuppence mind

I'd copy the basic dimensions from something modern that handles well. What engine are u planning on using? I remember the welds on my 1980's Jap bikes being like piles of pigeon pooh so shouldn't be that difficult to make something better. Throw in a single rear shock and a brembo caliper on the front and u could have something pretty good. You'd be hard pushed to make something as bad as a Harley anyway.

Welding is welding is welding.

Fred W B

You could think about braising?

Loads of people have welded their own chassis for their Locost - I can't see any difference.

I am assuming you are planning on using steel for this chopper chassis of course.

Not at all mad this one I know a fair few people who've made their own hardtail frame using a MIG welder and none of them fell apart. Obviously being hardtail ie no rear suspension the shock loads are higher as well.

You could probably argue that MIG welding isn't ideal for the application but in the real world it works.

There you go you see, I'm not against all your mad ideas

quote:

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Originally posted by Bluemoon
You could think about braising?

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quote:

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Originally posted by Mr Whippy
I intend on using nothing more than a (don’t laugh) 250cc (I said don’t…laugh) engine so have little fear that it might rip apart from the awesome torque and was going to use swing arm rear suspension, so even less stress on the frame and also my arse.

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you say that tig is expensive i partly agree with that.

on fleebay prices are as low as 200euro for an Tig welder. i'm with you that that doesn't buy you a gas bottle and regulator etc. etc. BUT lower as 200euro for a 140AMP HF unit you aren't gonna pay.


also if you think that with TIG the result will be better/nicer or more secure then i wont try to save those 200+euros.

anyway if you can weld MIG wy doubt??

To build a bike you need to be sure of your welding quality. sow it looks like you aren't that secure... after all WELDING = WELDING.. and its just down the quality wich you generate = strenght.

so my advice spent those 200euros on a TIG unit and weld the chasis that way.
you are looking to doubtfull about your own MIG welding quality and building then a bike is in my eyes a to high risk.

(imagine you ball head rips of or the steering etc. etc.)

if i'm wrong i appolozise its just a question wich comes down (for me) to confidence.

regards,

Tks

[Edited on 11/1/08 by tks]

I've mig welded bits onto an existing frame for a friend who is building one. I don't like choppers personally but if they are done right, not these tarts handbag things with tassels on the handlebars and forks 10' long, they are o.k.

Here is a good website, you can even download plans for the frames.

http://www.chopperhandbook.com/

I watch American chopper and biker build off quite a lot and have noticed that they tend to tig weld the frames and use mig on non structural parts. They seem to use the mig to tack everything in place then finish off with the tig. I guess as stated before this may be for looks.

I wonder if the rollcages made by MK, mac1, mnr etc etc are mig welded?

I never could spell!

Ducati frames are mig welded, nothing wrong in that, especially if you go for mild steel...

MIG's OK

Have a look at a Japanese motorcycle frame from the seventies to see how bad the welding can be before you get trouble.

My Trikes are MIGged

Neil

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Originally posted by trikerneil
MIG's OK

Have a look at a Japanese motorcycle frame from the seventies to see how bad the welding can be before you get trouble.

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well that's good to know and the web site is very good, cheers.

quote:

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Originally posted by locogeoff
brazed (possibly bronze welded cannot remember off hand).

I would be a bit concerned about creating stress concentrations around the mig weld due to the profile of the weld.

just my tuppence mind

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