Ever designed your own?

Got a general MTB question that doesn't fit anywhere else? Here's the place.
PashleyRider
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Re: Ever designed your own?

Postby PashleyRider » Tue Jan 15, 2013 18:54 pm

Learning to weld neatly will be the biggest hurdle, especially MIG with thin materials. I have been doing it for about 5 years now (as a hobby) and i'm still far from great although i only really ever do automotive stuff.

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bluechair84
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Re: Ever designed your own?

Postby bluechair84 » Wed Jan 16, 2013 08:42 am

I've been reading about welding alu, it sounds like TIG welding is prohbitively expensive and MIG can make a bit of a mess as PO says /\ , I'd like to do alu rather than a steel frame. Is it harder to make strong joints with a MIG welder?

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Woodmonkey
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Re: Ever designed your own?

Postby Woodmonkey » Wed Jan 16, 2013 15:35 pm

you'd be better off designing it, getting all the tubes cut etc then taking it to someone who can weld. i used to work with a guy who made saracen frames when the were still made in coventry by hand, but any decent welder would do it.
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RockmonkeySC
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Re: Ever designed your own?

Postby RockmonkeySC » Wed Jan 16, 2013 16:04 pm

bluechair84 wrote:I've been reading about welding alu, it sounds like TIG welding is prohbitively expensive and MIG can make a bit of a mess as PO says /\ , I'd like to do alu rather than a steel frame. Is it harder to make strong joints with a MIG welder?


MIG welding aluminium is not good. It will be messy and mechanically useless. The only way to weld aluminium for bike frames is TIG but that takes time to learn to do well.
For steel it's easy to make a MIG weld look pretty with no strength at all. MIG isn't really suitable for small tubes, it takes half an inch of welding before you start geting any penetration so half your weld is useless. TIG is much stronger, you can control it better and the weld will be much cleaner with less impurtities which will cause cracks.
Brazing can also be very good for steel frames, possibly stronger than TIG because it allows the joint to flex more without cracking.
I worked as a welder & fabricator for several years, it takes no time to learn to make a tidy weld. It takes a years of welding full time with regular testing to learn to weld properly. Pipe and tube joints are the most difficult to do properly because you are working with metal as a liquid and as you get to vertical and overhead positions you are fighting against gravity to get the weld where you need it in the root of the joint.

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bluechair84
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Re: Ever designed your own?

Postby bluechair84 » Wed Jan 16, 2013 19:46 pm

Crap. Looking like the ambition is a dead end... This is very sad news.

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Re: Ever designed your own?

Postby RockmonkeySC » Wed Jan 16, 2013 20:50 pm

bluechair84 wrote:Crap. Looking like the ambition is a dead end... This is very sad news.


Could always try this:
http://www.thebicycleacademy.org/

Learn to do it properly.

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bluechair84
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Re: Ever designed your own?

Postby bluechair84 » Wed Jan 16, 2013 20:59 pm

RockmonkeySC wrote:
bluechair84 wrote:Crap. Looking like the ambition is a dead end... This is very sad news.


Could always try this:
http://www.thebicycleacademy.org/

Learn to do it properly.


This could be interesting, I'll have a good look at that. Cheers

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captainfly
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Re: Ever designed your own?

Postby captainfly » Thu Jan 17, 2013 01:48 am

I think a good place to start would be modifiying a cheap hi tensile steel frame (second hand old bike) to get an idea for geometry (plus you get your bb shell head tube and dropouts etc.) and it is a lot easier to mig weld and is quite forgiving especially if you uses plugs when you weld it, look up rat rod bikes for frame moding, have fun dude.
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RockmonkeySC
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Re: Ever designed your own?

Postby RockmonkeySC » Thu Jan 17, 2013 10:10 am

captainfly wrote:I think a good place to start would be modifiying a cheap hi tensile steel frame (second hand old bike) to get an idea for geometry (plus you get your bb shell head tube and dropouts etc.) and it is a lot easier to mig weld and is quite forgiving especially if you uses plugs when you weld it, look up rat rod bikes for frame moding, have fun dude.


MIG weld is not suitable for bike frames. It WILL fail. Even a skilled welder wouldn't be able to get a good MIG weld on small diameter, thin wall tube. You can't get enough heat in to it to get any fusion. The weld will basically just sit on the surface.

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captainfly
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Re: Ever designed your own?

Postby captainfly » Thu Jan 17, 2013 17:45 pm

Fair comment I am not a welder and have only ever done bits and pieces mostly sculptural work, but have built some tubular works with plugs and mig welds it's just easier than arc welding.
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cooldad
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Re: Ever designed your own?

Postby cooldad » Thu Jan 17, 2013 20:11 pm

captainfly wrote:Fair comment I am not a welder and have only ever done bits and pieces mostly sculptural work, but have built some tubular works with plugs and mig welds it's just easier than arc welding.

Yeah, but were you riding your sculptures down bumpy hills?
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Woodmonkey
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Re: Ever designed your own?

Postby Woodmonkey » Thu Jan 17, 2013 23:21 pm

Weren't alu frames originally joined with silver solder?
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RockmonkeySC
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Re: Ever designed your own?

Postby RockmonkeySC » Fri Jan 18, 2013 19:12 pm

MiG is very easy to learn to use as long as you only need a weld that looks nice and has a little strength. If you want a mechanically good weld it's actually easier to learn to use TiG or MMA (stick).
When I used to build pressure vessels we used to TiG weld in the root of the joint to get the penetration and good fusion and then blast in a really hot MiG weld just to fill it up. And for pipe work (simila to bike frames) TiG or gas welding is actually easier to do properly than MiG.
Silver solder can be very strong when done well (not easy) and so can brazing.

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bluechair84
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Re: Ever designed your own?

Postby bluechair84 » Fri Jan 18, 2013 20:16 pm

can you use gas welding and welding rods on alu? Or just steel?

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Re: Ever designed your own?

Postby RockmonkeySC » Fri Jan 18, 2013 21:48 pm

I have never gas welded aluminium but it can be done. I would have thought its very difficult. With TiG it takes ages to heat up then you have to move quickly or it will melt and burn through, especially with thin aluminium. I always used TiG with a foot control for the amperage to keep control of the heat.

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bluechair84
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Re: Ever designed your own?

Postby bluechair84 » Sat Jan 19, 2013 10:13 am

Well, cheers for all this. I'll start to read up on gas welding and see how expensive it is to try. I won't be able to give a project like this a try until I'm in a new place with a bigger yard but I'll have plenty of time to learn and plan.

RockmonkeySC
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Re: Ever designed your own?

Postby RockmonkeySC » Sat Jan 19, 2013 19:12 pm

Try a evening course at your local college. Gas welding kit is expensive, TiG is probably cheaper, I have seen 200A TiG welders for about £200, plus rental of a bottle of argon, a second hand grinder, a few tungsten tips and some wire.

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bluechair84
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Re: Ever designed your own?

Postby bluechair84 » Sat Jan 19, 2013 19:24 pm

Yeah I'll look into a welding course I think. I don't want this to become a financially explosive passtime though. I thought TIG was the expensive option? I'll keep looking into it. If TIG is cheaper than gas, and it creates stronger, neater welds, it would be the obvious avenue to go down.

dmorton
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Re: Ever designed your own?

Postby dmorton » Sun Jan 20, 2013 14:30 pm


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bluechair84
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Re: Ever designed your own?

Postby bluechair84 » Sun Jan 20, 2013 17:44 pm

dmorton wrote:How about this, pricey though:

http://www.downlandcycles.co.uk/frameBuilding.htm


Cheers, steel only though. I'm reading lots of mixed messages on various places, some suggest that self teaching alu isn't that bad, but most agree that getting it professional quality is extremely hard. But I'd like to go down the alu route really


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