Roll cages and tube chassis

[God mode restorations]

Afternoon everyone.
I have watched a lot of videos and do lots of research in to this particular subject. I love the engineering and fabrication that's involved. My question is for both cds and chromolly tubing. When you guys welding them in wherever it's tig or mig .do you weld the tubes in two half's once it has been tack in place.or four parts.down one side and then the other.just wondering as a lot of it is out of position welding..cheers.

 

[chevy2]

I've done quite a few tube chassis's and cages in both cds and moly,
I generally get all the fabrication/tube notching done first and apply 3-4 evenly spaced tacks around each joint,
as far as final welding goes, do as much as possible while locked down to a jig if you're using one,
With the welding process, do maybe 1" stitches and move from joint to joint,
A bit like the torqing down sequence on a cylinder head to keep the heat and distortion at bay, especially with moly.

 

[God mode restorations]

So would you then weld top to bottom of one side of the tube so you would have two final welds on one tube.or if it has been tack in four places would you then weld from tack to tack.

 

[chevy2]

With fishmouthed tube joints the welded area most likely to cause distortion is the most acute/tight angled part of the joint,
Leave all those till last as by the time you get to these they'll be enough weld on all the other areas to keep it square and true,
For example, on a roll cage main hoop that has welds where it meets the sill bars at the bottoms and welds that join to the A post tubes that run along the top of the door frame,
once again, looking at the hoop through the screen, start with the non acute parts of a tube joint with say a 1" long pass to the top right joint,
then an inch to the bottom left joint,
An inch to the bottom right joint,
An inch to the top left joint and so on,
use this principle through out the whole frame/chassis and remember, acute joints last,
do as much while locked down to a jig, weighted down to a level surface also works well,
you'll get to a stage where theres some areas you cant get access to due to the jig etc,
you'll need to release or raise it then but if you continue the last welds with the same cylinder torque sequence all should be good.
I built the moly frame on this a few years back without a jig, simply locked/weighted it down during the build,
It was only chassis'd from the firewall back but i've just a new moly front chassis to also without a jig,
you need to put the hours to ensure its constantly true and level,
It must have worked as it ran 8.60 quarters at over 150mph in street trim,
200lb ish lighter and the two hair dryers are adding another 500hp to the 900+ it had,
Should be fun

[/URL][/IMG]

 

[God mode restorations]

With fishmouthed tube joints the welded area most likely to cause distortion is the most acute/tight angled part of the joint,
Leave all those till last as by the time you get to these they'll be enough weld on all the other areas to keep it square and true,
For example, on a roll cage main hoop that has welds where it meets the sill bars at the bottoms and welds that join to the A post tubes that run along the top of the door frame,
once again, looking at the hoop through the screen, start with the non acute parts of a tube joint with say a 1" long pass to the top right joint,
then an inch to the bottom left joint,
An inch to the bottom right joint,
An inch to the top left joint and so on,
use this principle through out the whole frame/chassis and remember, acute joints last,
do as much while locked down to a jig, weighted down to a level surface also works well,
you'll get to a stage where theres some areas you cant get access to due to the jig etc,
you'll need to release or raise it then but if you continue the last welds with the same cylinder torque sequence all should be good.
I built the moly frame on this a few years back without a jig, simply locked/weighted it down during the build,
It was only chassis'd from the firewall back but i've just a new moly front chassis to also without a jig,
you need to put the hours to ensure its constantly true and level,
It must have worked as it ran 8.60 quarters at over 150mph in street trim,
200lb ish lighter and the two hair dryers are adding another 500hp to the 900+ it had,
Should be fun

[/URL][/IMG]

Awsome car...thank you very much for your very valuable information. .cheers.

 

[normspanners]

200lb ish lighter and the two hair dryers are adding another 500hp to the 900+ it had,

Would have thought it should have had rear tyre warmers instead of front ones