Outer Limits 4x4 Board

What thickness steel should a rear bar be made from? I was thinking 3mm This is the mockup so far.





Any thoughs or better ideas? The ends will just finish at the edge like a normal ute rear bar. It will have 2 spare wheels or 1 spare and a recvery gear box.

the price of steel is done by weight so the thicker you go the more dear it gets.

3mm will probably be fine but a good hit will bend it.

5mm starts to get up in weight and it'll take a bit more of a hit to bend it.

I think at the end of the day it's up to you, after all it's your money.

You could also do a combo 5mm flat bar for the top and 3mm for the side but will need a but weld, use gussets along the bar also for some extra strength, right angle will be the quickest to weld then setup but will weigh more than flat bar.

3mm is thick enough, most commercially made bars are 3mm. What makes the bar strong is the geometry, ie where the mounts are, gussets ect. If you expect to hit the bar in a certain angle make sure the pressure will push to something to support the bar.

As above.... 3mm is heaps, and just use Geometry. Any more and its going to tranfer the stress t the chassis anyway and bend it instead.
what you have there at the moment just wooden work

I wouldn't even make it from 3mm. That bar by itself will bring you over GVM and the structures shape is significant already and the design reinforces itself with the lip on the back. Keep in mind that your chassis wall is probably half that thickness and half the depth. The vulnerable part will be the corners, but you can reinforce that section. When you look at what the bar will impact on, the bottom is protected by the tow hitch arrangement and the wings will have strength through cross section.

If it was me, I'd be winding it right back to about 1.6 and reinforce the corners with something a bit thicker to stop ot from folding..

Done/doing the front and rear bars on the 40 out of 4mm....front bar is small enough that weight wasn't a issue, but now the rear bar is all welded up I was bit surprised by how heavy it was. Still easily lift it by myself, but once the tow bar bits go on, and a tyre carrier, and spare, it'll be a pretty heavy setup.

Your design looks sweet but 98 lux

2.5 to 3mm will be fine on your design. if you can fold the sections rather than welding laser cut flats etc it will be stronger. the more folds, the stronger the area.

zagan wrote:5mm starts to get up in weight and it'll take a bit more of a hit to bend it.

Holy shit, 5mm would be massive overkill imho.

joeblow wrote:2.5 to 3mm will be fine on your design. if you can fold the sections rather than welding laser cut flats etc it will be stronger. the more folds, the stronger the area.

A lot of that looks like it could even come out of RHS like this.

another option yes

RHS for the win

Find some the right size for the look you want. Far less work than trying to finish off welded plate.

RHS is usually a higher grade steel too, eg 250mpa for steel sheet and 350mpa for RHS. Other grades are available but these are most common.

nastytroll wrote:RHS is usually a higher grade steel too, eg 250mpa for steel sheet and 350mpa for RHS. Other grades are available but these are most common.

True, but that just means it can flex further without staying bent. Most designs are limited by stiffness or buckling where higher strength has no benefit.

I made my rear bar from SHS, came out good, plus i made sure it was all fully sealed so i can use it for an air tank. Just welded in a plate and some air fittings today actually, tested it to 9bar for a max normal working pressure of 7bar, worked great. Well worked great when i went over it with soapy water, found the numerous pinhole leaks, drilled em out then welded em again.