MIG weld Aluminium to Steel

Joined
Nov 22, 2021
Messages
8
Location
Southampton, UK
Hi,

For my Warrior Trike project I need to weld my steel frame parts to the aluminium bike parts - for example welding the mountain bike bottom bracket to the steel trike frame.
From what I've read, you can't weld aluminium to steel as the melting temperatures are very different. Any advice on how to get around this - I have a MIG welder.

Thanks
Tim
 
Joined
Apr 16, 2017
Messages
396
Location
Winnipeg, Manitoba
You read correctly, aluminum and steel cannot be welded together. For a bottom bracket follow Brads advice and find a cheap used steel parts bike and use its parts. I got lucky and picked up a bunch of parts lately, included in them is a few steel tubes of the correct I.D. The right size pipe can be used with a cartridge bearing for the bottom bracket. I have a couple of those that don't need to be threaded into the BB. Next time I head outside to the garage I'll take a picture and include any part nos, etc that I can find. It's minus 30 C here know and with the wind expected to feel like minus 40 so the house is a nice warm place for me to stay in at the moment. Tomorrow s/b a bit milder so I will head outside then.
 
Joined
Oct 19, 2012
Messages
2,008
Location
Wakefield, UK
The effort involved in getting around the issue simply isn't worth the effort and involves making very complex bracketry in steel to clamp the aluminium. Vastly better to buy a steel donor. Forget about welding aluminium with a MIG - it simply won't do it. You need an AC pulsed TIG for that.
 
Joined
Jan 16, 2011
Messages
594
Location
Vilvoorde / Flanders / Belgium
Aluminium and steel can't be welded. Not with any real result.
Brazed, maybe. Explosion cladded, yes.

Welding aluminium is a pain in the behind whatsoever.

My advice, get a steel bottom bracket.
 
Joined
Nov 22, 2021
Messages
8
Location
Southampton, UK
Thanks all! I wish the instructions had mentioned this. I guess in the US steel frames are more common. Here in the UK they are pretty rare now. I'm off down the scrap yard next week to see what I can find.
Happy New Year.
Thanks
Tim
 
Joined
Oct 19, 2012
Messages
2,008
Location
Wakefield, UK
Steel is still in plenty of use at the lower end of the market. Try freecycle.org too. I've had several free donors from there.
 
Joined
Apr 16, 2017
Messages
396
Location
Winnipeg, Manitoba
Well not really milder out (minus 29) out but I needed to head outside to try to start our vehicles so I brought the BB pipe and cartridge in. The Pipe has an internal diameter of 1 3/8" and a length of 2 13/16" The cartridge had no external markings on it but is a type that does not require the BB to be threaded. BB do come in a variety of lengths such as 68, 73 on up to 120mm for my fatbike. I've included a picture
 
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