6082 aluminium heat treating, help?

[Jigantor]

Yep that will work too.
Good luck.
Ji

[Jigantor]

If you are going to over build it why have it post heat treated?
From what I have read most high end mountain bike builders do not post heat treat their frames.
They say stuff like "6061 heat treated to T6 TIG welded frame"
That just means that the material they started with was heat treated.
The only reason for heat treating a frame would be that your design was running close to the wind and that is why I suggested the engineering input.
Some more advise make it out of round or oval.
Square section is stronger than round for the same depth member but square will hurt more during an accident.

Ji

[Jigantor]

Actually, just thinking about it, I would buy a cheap mountain bike from Wall Mart and convert it.
You get a mono shock, forks, handle bars, steering head, seat and post, aluminium frame........
The shock and forks would cost you more than the bike if you bought them seperately.
Still a great project and you still get to TIG weld aluminium.

Ji

[dusse123]

I would buy a bike and convert it if i could but this is my design here so that wouldnt work.
ski bike (1).jpg

What would you consider over built for my purpose? 2-3mm?

[Jigantor]

Are you going to have a rear shock?
The rear ski post connections will be in shear (not the best for load carrying nor for accidents, looks kinda sharp).
The thickness of tube really in this case has more to do with weldability.
I would have to know the loads to be able to advise.
That is the problem with new designs.
Most manufacturers fabricating a new device over build then test it to death. Once something lets go or bends they see where the loads are high and reinforce the next generation.

Ji

[Jigantor]

Just a suggestion.
Can you get your hands on a tube bender?
If so try and bend the rear ski posts like so.

Ji

[dusse123]

the whole point is that there are pivots for the two rear skis so when you lean over both skis will edge. If you are still confused search for north legion smx in images. no shock though, when you say loads do you mean my weight or the forces being applied to the frame.
Thanks for your help man! I cant even begin to tell you how much I appreciate it!

[Jigantor]

Yes I mean your weight including clothes, safety gear, back pack, water........
Also will you be jumping this thing? if so what height and to a flat landing or to a down ramp?
Consider this like a design committee and take on board all the ideas, think about them and then make up your mind.

I have raced motocross since the seventies. The two rear skis look dangerous to me. If you snag a foot it will get ripped back under the frame and could break your ankle. I have done this a few times on my foot pegs and they are designed to fold back.

The two rear horizontal members transferring the seated load to the ski posts will be in bending moment. They will have to be designed correctly as they will carry load and will deflect. Can you instead make another triangle with its apex at the seat post and the legs going down to the skis on a say 30 degree angle.

Ji

[dusse123]

You lost me in both of the last 2 paragraphs

[Jigantor]

Okay I will do a little drawing.

If you don't keep your feet up your toe can get snagged into a rut and left behind as the bike goes over the top of it. your calf hits the frame and break you get a trip to the doctors.

It all depends if you will be wearing skis or just boots when you ride this bike.

Ji