Outer Limits 4x4 Board

Carlton posted this image (apparently from the RTA site):


I can understand this for chassis rails that are C shape like FJ40, maybe even a double C shape like Hilux. But my question is regarding the Sierra chassis, which is a single length of RHS bent to form the arches. Is it okay to weld to the top surface? I want to make a chassis tie-in for a roll cage and I will plate the chassis with 4mm or 6mm plate first. Do you think an engineer would have problems with this?

As per comments from several people that i have heard this week - "talk to the engineer first"

Yes as it is still the top and bottom flanges that provide the bending capacity of the section.

Like Greg says... ask the engineer that will be approving the mods first.

greg wrote:As per comments from several people that i have heard this week - "talk to the engineer first"

Also look at how the crossmembers are fited to the rails, drilled through the wall of the rail and welded from both sides, but ask engineer first.

p/s morning N*A*M*

JK and 2car are both mech. engineers and both say no. where is that auto_eng dude, he is actually in the loop, and will have some input for sure...

edit: JK may be civil/structural enginner now I think about it?
<-- loadbearing member

so which is stronger at the chassis?

this is an under the body cage support so the load will be from top down

My guess would be the one on the left - assuming as you have stated, that force will always be from directly above...

However, again - if you are going to get it engineered, talk to them first - you never know - they may insist that you put crush tube inside the chassis or something - and obviously it would be nice to hear this before going ahead and doing it.

Also, check out the roll cage rules on the vicroads site - there's heaps of rules about where your A and B pillars need to go etc...

Cheers

N*A*M wrote:so which is stronger at the chassis?

this is an under the body cage support so the load will be from top down

The left would be stronger, but more likely to cause cracking in the chassis rail.

the one on the left could still be done without welding to the flanges. from memory, that is kinda how the toyota spring hangers are done, except upside-down.

Wendle wrote:edit: JK may be civil/structural enginner now I think about it?
<-- loadbearing member

Yep...

Wendle wrote:the one on the left could still be done without welding to the flanges.

Sure could. You could extend the channel down either side and still weld to or bolt thru the webs. The vertical loads would bear on the flange or be taken by the weld on the webs.

If you are going to place huge loads on this area of the chassis rail it would only be thru rolling your truck in which case a cracked or bent chassis is the least of your worries.

Being for a roll-bar, the vertical load is going to be negligable unless you actually roll. All you want to do is locate it and prevent it from moving around or vibrating. A bolted connection with crush tubes thru the chassis webs would be good as you could still remove it easily if you have to.

A slightly oversized hole thru the web would ensure that the vertical load would be taken in bearing against the top flange rather than in shear thru the bolt in the webs.

bubs' posts keep disappearing ROFL.. he had a reply straight after my last post and now it hath vanished!


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JK: will this lintel hold up to 2000kg point load with a load bearing member as drawn at each end

only two today dude, i thought i would double check before posting it back up, the hangers do have the tags but with out looking i can't tell you for certain wether toyota weld across the chassis

Wendle wrote:bubs' posts keep disappearing ROFL.. he had a reply straight after my last post and now it hath vanished!

... BS filter...

Wendle wrote:____________________
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JK: will this lintel hold up to 2000kg point load with a load bearing member as drawn at each end

yep as long as I'm not one of them...

DirtPigs wrote: A bolted connection with crush tubes thru the chassis webs would be good as you could still remove it easily if you have to.

if done with a bit of finesse this would also give you a massive strength gain due to the friction of your plate against the chassis.

Wendle wrote:

DirtPigs wrote: A bolted connection with crush tubes thru the chassis webs would be good as you could still remove it easily if you have to.

if done with a bit of finesse this would also give you a massive strength gain due to the friction of your plate against the chassis.

Yep but make sure you use fully tensioned Grade 8.8 bolts or the friction grip is negligable.

Wendle wrote: ___________

JK: will this lintel hold up to 2000kg point load with a load bearing member as drawn at each end

i thought this was your new sig line when i first saw it
it should be!

I think the best idea so far is to go with the four crush tubes and bolts.

Not sure what state you are in but in QLD there are no modification codes for modification to chassis on light vehicle (those with a GVM under 4500 kg) so these modification have to be treated using a heavy vehicle code. These state the rules above but generally the certifiying officer gets to make up his/her mind. The picture and information in the first post also appears in the heavy vehicle code which is a national code unlike light vehicle codes that vary state to state.

Seeing a zook is such a light vehicle I wouldn't have a problem with it if it was welded to the chassis so long as you didn't weld all the way to the edge of the web, considering the gearbox/transfer mount on a zook is welded across the rail from factory.

The only way to be 100% sure is to ask the engineer who is putting there name on it. As soon as the decision involves personal judgement you can only get the answer from the horses mouth. Not all engineer agree on what is ok.

Generaly it is best to steer away from welding on the webbing as shown in the picture. This comes from the heavy vehicle background where the chassis has to endure a significant amount of flexing and often chassis rails can be made form a high tensile steel that is heat treated. These heat treated rails don't respond well to being welded at the best of times especially when all the stress is concentreated on the edge of the web. Mounting to the middle of the chanel is better. Harder to push your finger through a piece of paper than rip it from the edge.

Don't just consider what will happen with a direct load on the bar but also consider the stress on the weld when the chassis rails are flexing relative to each other.

Hope this helps..

just to clarify... the | is the web and the -- is the flange?

Sorry mate. It and hour and a half after beer o'clock and looks like I buggered the terminology. I'll try and clear this up.

I think the best idea so far is to go with the four crush tubes and bolts.

Not sure what state you are in but in QLD there are no modification codes for modification to chassis on light vehicle (those with a GVM under 4500 kg) so these modification have to be treated using a heavy vehicle code. These state the rules above but generally the certifiying officer gets to make up his/her mind. The picture and information in the first post also appears in the heavy vehicle code which is a national code unlike light vehicle codes that vary state to state.

Seeing a zook is such a light vehicle I wouldn't have a problem with it if it was welded to the chassis so long as you didn't weld all the way to the edge of the flange (top), considering the gearbox/transfer mount on a zook is welded across the rail from factory.

The only way to be 100% sure is to ask the engineer who is putting there name on it. As soon as the decision involves personal judgement you can only get the answer from the horses mouth. Not all engineer agree on what is ok.

Generaly it is best to steer away from welding on the flange as shown in the picture. This comes from the heavy vehicle background where the chassis has to endure a significant amount of flexing and often chassis rails can be made form a high tensile steel that is heat treated. These heat treated rails don't respond well to being welded at the best of times especially when all the stress is concentreated on the edge of the flange. Mounting to the middle of the chanel is better. Harder to push your finger through a piece of paper than rip it from the edge.

Don't just consider what will happen with a direct load on the bar but also consider the stress on the weld when the chassis rails are flexing relative to each other.

Hope this helps..

N*A*M wrote:just to clarify... the | is the web and the -- is the flange?

In the above pics yes.

For square or rectangular hollow section it depends on which axis you are bending it about.

For an I beam, the web is the part that joins the two flanges. Same with a C section (correctly termed a channel).

I posted this pick in the other thread this one originated from but i will also add it here.

This is a stock rear spring hanger from a early 4Runner.

One of the shock mounts on the rear is also welded right across the top as is the rear bump stop pad.

If you look closely this has 4 welds right across the bottom.

hmm... okay let's say i go with the crush tubes idea

is the pic below illustrative of what you guys mean?

is it acceptable to drill an oversized hole so the crush tube slips through and then weld to the tube to the webs from the outside, then grind it flat? would 2 holes be sufficient?

if you are going to go the full channel like that, it is probably better to leave a bit of a cavity.. say the chassis is 75mm wide, cut you crush tubes at 85, and have the channel folded to 85 internal. leaves you room for a nice bit of weldment on each side, and considering were you live, the 5mm cavity should stop the joint becoming too much of a rust trap??
ymmv and shit.. i am only really guessing