11 replies to this topic

[Bart]

Hey guys, i think this has been disscused before, but i was thinking of having some sheet metal stamped/bent up to form chasss rails which would hug over the existing ones and stitch welded in.
Is this something anyone else have tought of?
I didnt want to go the bolt in kit, i believe welding it in this way is stronger but i need advice

[Toranamat69]

Using SHS steel in beam deflection is very inefficient in terms of how much steel you use to how much you gain in tortional strength.

Have a look at the cross bracing in this chassis.

http://www.hotrod.co...d/photo_08.html

That is how you gain the best tortional rigidity for the weight of the chasis - that's how all good chassis are built.

The CRS kit is built to be a straight bolt in and easy to manufacture. They don't even have any measurements on what sort of improvements they make. Clearly not a very well thought out but easy to fit arrangement.

The vertical sides of the SHS on the CRS kit is what is doing the vast majority of the work, the horizontal sides are doing almost nothing except adding weight.
If you are doing a weld in job, maybe you could start with plating the vertical sides of the chassis and extending the chassis back to join the rear lower control arms.

I think the Torana chassis rails and sill panels could potentially be a good start to doing something like what is in the link above.

I would be reluctant to start doing too much on mine until I have the Mech engineers do a few models for me at work and work out roughly what I might be able to achieve but that is the sort of thing I have in mind for my LX.

I was playing with the idea of some sort of foam filling for a while but young's modulous works against you big time there, steel is far too rigid for just about any other substance to do anything significant so I have thrown that idea out completely.

M@

[Dangerous]

For LC chassis, I've found that the weak points are usually in the front of the chassis rail where the front suspension crossmember bolts in - the rear bolts near the front of the floorpan - not strong enough and too prone to rust, and also the front crossmember trailing arms themselves - they are bolted and welded, but most LC/LJs that have had a hard life show cracks where the trailing part welds onto the transverse member. The rear suspension lower trailing arms can twist as well, so boxing or reinforcing them helps too.

Not much point in reinforcing the body if the front and rear suspension mounts are going to fail first.

[Bart]

something like this perhaps?>>> http://www.mustangsp...ssis/index.html

Edited by Bart, 08 August 2007 - 07:35 PM.

[ls2lxhatch]

This is an extract from the Transport Industry Consultants engineering report on the CRS LC-LJ chassis kit dated 9 Oct 1989. It is supplied with the kit. VIC Roads also have a full copy of the report.

Comparative tests were performed on the standard and reinforced vehicles. It was found that the bending strength of the vehicle is increased by approximately 30%. whilst the torsional stiffness in increased by approximately 40%.

You will find pictures in this thread.
http://www.gmh-toran...showtopic=17766

[Bart]

Using SHS steel in beam deflection is very inefficient in terms of how much steel you use to how much you gain in tortional strength.

Have a look at the cross bracing in this chassis.

http://www.hotrod.co...d/photo_08.html

That is how you gain the best tortional rigidity for the weight of the chasis - that's how all good chassis are built.

The CRS kit is built to be a straight bolt in and easy to manufacture.  They don't even have any measurements on what sort of improvements they make.  Clearly not a very well thought out but easy to fit arrangement.

The vertical sides of the SHS on the CRS kit is what is doing the vast majority of the work, the horizontal sides are doing almost nothing except adding weight.
If you are doing a weld in job, maybe you could start with plating the vertical sides of the chassis and extending the chassis back to join the rear lower control arms.

I think the Torana chassis rails and sill panels could potentially be a good start to doing something like what is in the link above.

I would be reluctant to start doing too much on mine until I have the Mech engineers do a few models for me at work and work out roughly what I might be able to achieve but that is the sort of thing I have in mind for my LX.

I was playing with the idea of some sort of foam filling for a while but young's modulous works against you big time there, steel is far too rigid for just about any other substance to do anything significant so I have thrown that idea out completely.

M@

Toranamat, the cross bracing you are reffering to is the triangulated bits between the outer rail and inner rail? (in the diagram you supplied)
I think you were saying, the inner sills and side part of the rails should be plated? Then cross braced/trianulated between them?

_________ <Floor pan
|___| < Side part of the rail to be plated?
^
Bottom of the rail/closest to the road

Edited by Bart, 11 August 2007 - 11:21 AM.

[Toranamat69]

G'day Bart,

I missed your post until now.

Yes that is the sort of thing I have in mind.
I was also thinking when the diagonal cross bracing goes in between the rail and sill that you could also use steel tube and stagger it vertically so the bit against the inside of the sill could start against the bottom of the floor and end up on the lower edge of the chassis rail and then the next brace forward could start from against the floor on the chassis rail end and end on the bottom edge of the sill and stagger them all the way along rather than just use full height SHS steel.

Could also still be made to be a sort of 'bolt in' kit if you were prepared to weld some threaded tubes into the existing chassis and sills.

I also don't like the rear outrigger bolts on the front subframe as Dangerous mentions above. Long bolts like those used in single shear is a very poor way to fasten things together.

If there is a copy of the CRS engineering report with actual test figures in the kit then why hasn't someone scanned an posted a copy for all to see - so many people ask questions about these things.

I don't dispute the CRS kits will make a difference but I do claim if you can achieve 2 times the improvement for the same weight penalty or achieve the same improvement with 50% the additional weight then their design is lacking.

Of course this is only my thoughts and gut feel from looking at high end chassis.
Until I do some calcs and or measurements I can't prove any of this.

M@

Edited by Toranamat69, 20 August 2007 - 10:56 AM.

[Bart]

thanks mat youve given me a few ideas