Welding onto D4 chassis?

[cjc_td5]

A project of mine has the potential for having to weld a bracket onto the chassis rear cross member. What specific requirements are going to be required so that I don't kill an ECU or 2?

Chris

[Tombie]

You mean an ECU or 21+ [emoji41]

[Tombie]

But seriously you aren't likely to have an issue if:

Anti-Zap onto battery - disconnect aux if you have them.

Clamp Earth as close as possible to the weld site. Keep current as low as suitable.

[cjc_td5]

But seriously you aren't likely to have an issue if:

Anti-Zap onto battery - disconnect aux if you have them.

Clamp Earth as close as possible to the weld site. Keep current as low as suitable.
Thanks Tombie. What do you mean by Anti-Zap?
Chris

[Tombie]

Thanks Tombie. What do you mean by Anti-Zap?
Chris

Surge protection
https://www.aulro.com/afvb/images/imported/2017/03/391.jpg

[cjc_td5]

Could just both batteries be disconnected?

[Tombie]

No.. because the ECUs won't be surge protected.

[Pedro_The_Swift]

http://www.ebay.com.au/itm/like/251965014020?chn=ps
[biggrin]

[incisor]

never having owned one, is the chassis just carbon steel or something fancier?

[theresanothersteve]

I was a boilermaker welder in a previous career.

I wouldn't do it to any vehicle of mine. When you weld you create a heat affected zone alongside the weld in the parent metal. It is the area immediately adjacent the weld penetration. This zone is prone to cracking, exacerbated by the torsional stresses applied to a chassis. That's why they pay engineers the big bickies, working out the shape and placement of welded components so the HAZ does not compromise strength.

Also consider anything other than new material has the potential to be contaminated. You should grind back to bare metal to prepare the weld. This, of course, will remove any form of corrosion protection applied by the factory. It will need to be replaced.

[cjc_td5]

Thanks for the responses. I am aware of the pitfalls re heat, shrinkage & stress concentrations etc. This has to be balanced up against the other option of drilling holes in the chassis, that can cause the same stress concentration issues....

Another option may be nutserts (or similar)?

My first option would be to fabricate up a bracket that wraps around the chassis rail but there is no access behind it without removing the rear bumper itself, and the chassis section has quite large radius corners that make it hard for a bracket to wrap and grip on an edge?

Chris

[nismine01]

I was under the impression that it was forbidden to do anything like this to a chassis.

No drilling holes to fit things and as the last poster said the problems with heat build up torsional tensions etc could cause problems.

Have an accident because something you did caused it and you could be in a heap of trouble. What ever is done really needs an engineers certificate to say it is good.

Regards

Mike

[Tombie]

What kind of item are you looking to fit/mount etc..?

[cjc_td5]

Modifying the spare wheel winch by providing a new chain style winch accessable from underneath the vehicle. Just need a small bracket to mount the winch to the inside of the rear cross member. I'll fabricate up a bracket that wraps around the rail.
C

[LandyAndy]

Chris.
I would look more into exsisting holes in the chassis and making a bolt on conversion.
Andrew

[PeterJ]

"just carbon steel"...........not sure what you mean, but I guess you are referring to low carbon content <0.25%, frequently referred to as mild steel. It will almost certainly not be that, more likely 400+Mpa grade of medium carbon steel with alloying elements and it may not take to welding all that well. Yes, you can stick the bits together but as theresanothersteve commented this introduces all sorts of issues. HAZ in welds are significant stress concentration points, fatigue failures just love :ehand: a good stress concentration to get a start in life. Where you are considering welding, is the chassis member in tension (pulling forces), compression forces, fully reversing (both), torsion, bending, shear, the whole lot probably. Try not to weld it, have a good look at utilising existing attachments and bolt holes. Drilling holes is preferable to welding, but again, they need to be in the right place and suitable corrosion protection applied, rust never sleeps. (not my line it's from a movie [biggrin])

If you must get it welded, get it done by someone who has a clue, go find a LR approved crash repairer they may be on the right page.

Peter

[cjc_td5]

No worries guys. I'm sure by spending some time under there pondering, a fixing solution utilising existing hardware will evolve....[wink11][bigrolf]