ideal weight for steel tube space frame? - Page 2

Jac Mac · 12-20-08, 12:30 AM

Shouldnt the 'big' wheels/tyres be on the back?

You might wish to build in a bit of torsional stiffness by replacing many of the somewhat redundant parallel tubes with diagonals in all 3 planes

Eric · 12-20-08, 01:16 AM

Quote:

Originally Posted by jac mac

Shouldnt the 'big' wheels/tyres be on the back?

they are! the rear ones are fatter, and they do look smaller in diameter compared to the front ones...

i get what you mean about more diagonals though. again, i originally intended for this to be a really basic design in the tubing itself with shear panels everywhere, so maybe i could afford to go to smaller tubing. dunno how that'd affect torsional stiffness, but i've read of 200lb backbone frames that basically rely mostly on shear panels for strength. i think, depending on my time this week, i may put time into that now just to see... considering today i spent 6 hours doing really nothing due to issues with individual models that basically undid any work i attempted. those wheels are just about done now!

Kalun D · 12-20-08, 01:26 AM

Quote:

Originally Posted by jac mac

Shouldnt the 'big' wheels/tyres be on the back?

CAD programs don't view in perspective when you're drawing, no matter how close or far everything appears the same size. There is a "perspective" setting but you don't normally use it.

Eric · 12-20-08, 06:07 PM

alright, 4 straight hours of tweaking yielded this:

no more 2"x3", and the diagonals are now 1" square. a few tubes still need to be added to the backbone, and i may put some diagonals in the front box. i didn't change the cutlist since finding all the new lengths will take another 4 hours, and my shoulder was starting to hurt.

edit: oh...and i guess i forgot to mirror a bar or two..

Eric · 12-22-08, 03:23 PM

just finished the new cut list. the current weight is 346 lbs.

Jac Mac · 12-22-08, 04:15 PM

[QUOTE and my shoulder was starting to hurt...[/QUOTE]

You think its hurting now, wait until you have finished cutting, beveling, matching all those tubes prior to welding

Eric · 12-22-08, 07:24 PM

true, but i'll be lifting bars that only weigh 16lbs max rather than having my arm in an odd position that originally felt comfortable for hours. then again...i may have my body in an odd position while welding for hours.

Mike Pass · 12-23-08, 09:24 AM

This may help for reference. This is a chassis I built for a Gilbern Invader a few years ago. It had a Sierra Cosworth 2wd rear axle beam. It was mostly 14swg and weighed 235lbs as in the pic (without the roll cage).
Cheers
Mike

Eric · 12-23-08, 04:54 PM

wow. very nice. looks like you used all 1" square or something close? i like.

did a bit of work today on looking for places where i might want extra diagonals (1" square, of course) for extra stability, but then i had to leave the office early because of freezing rain causing deathly road conditions..

Howard Jones · 12-23-08, 08:21 PM

Go get a 3 foot piece of exhaust pipe. 2" in diameter. Take it over to the band saw and cut it into 2" sections. Make about 1/2 the total cuts at 45 degrees. Weld it all back together into several shakes with a lot of inside 90 degree corners. You now know how to weld thin material. You more than likely will have it at the 2 foot mark.

Mike Pass · 12-24-08, 11:45 AM

Thanks Eric,
The chassis was a mix of many sizes. As it was just about all triangles the bit I found a real bitch was welding the tubes where they met at a very acute ange. I also filled a large bucket with grindings from tidying up my crap welding. Good luck with your project.
Cheers
Mike