Welding to chassis

[barney1587 Lurker Find all posts View Profile Close barney1587]

Have finally found a local fabricator that can build a set of steps for my toy, only concern is that the attachment method is to weld bracket to chassis & bolt steps on. I have searched Qld Transport website (along with other states) & can't find definitive answer whether its legal to do so or if insurance is affected (don't have side airbags so no probs there) Keen to hear if anyone else has researched this problem. Would prefer to have bolt-on brackets only worried bout the limited space above chassis not allowing for bolts to fit through.
cheers, Barney

[leachy_9 Advanced Member Find all posts View Profile Close leachy_9]

Re: Welding to chassis

Barney,
I can't help with the legality of welding the chassis. But my sliders bolt on, bolts under and over chassis and while it is a tight fit, it is achievable. I have never had any issues with the top bolts hitting on the body.

Leachy

[foxclan Avid PP Poster! Find all posts View Profile Close foxclan]

Re: Welding to chassis

Hi Barney
I did see a post from a member that lived in the U.K. I think, He had a Three door 120 series and had some side steps/sliders fabricated.
These steps had very neat almost laser cut, bolt on attachment brackets on them.
I can remember MickL explaining the concept of crush tubes when bolting through the chassis.
Might search the build up threads to try and find this particular post.
Regards troy

[Guest Close Guest]

Re: Welding to chassis

Might search the build up threads to try and find this particular post.
Regards troy

Here it is. Did the search for you. Now go back and finish your packing :lol:
viewtopic.php?f=18&t=6389

[foxclan Avid PP Poster! Find all posts View Profile Close foxclan]

Re: Welding to chassis

Thats the one Andrew.
Top marks mate.

[barney1587 Lurker Find all posts View Profile Close barney1587]

Re: Welding to chassis

Thanks for the replies,will go back to the drawing board on the "bolt on bracket" idea. Leachy, any chance of some pics of your bolt ons to give me more ideas of spacings, brackets etc. Was blown away by the link to the earlier post fom CroyNyax & his custom steps - the brackets were excellent (wonder how much for freight from the UAE ???)
I like the idea of the bolt through concept & great tip on using crush tubes - looks like this job is going to take longer than I thought.
Thanks again,
Barney

[Guest Close Guest]

Re: Welding to chassis

Do note that drilling a new hole or welding something onto the chassis will weaken it. If you drill a hole, you will get a stress concentration factor around that hole. If you weld, you will get an area called the Heat Affected Zone (HAZ) and this area will have its strength reduced. Without doing Finite Element Analysis (FEA) it would be hard to say which is the better way to go. Plus we don't have all the engineering design loads that the Toyota engineers worked with when they designed the chassis. So just be careful when taking the risk.

As for the crush tubes, it is better that the crush tube is flush with the external surface of the chassis, as opposed to being proud of it. There will be more weld prep around the crush tube so that it can be flush. When the crush tube is flush, the load is spread between the crush tube and the chassis. As opposed to having the load all on the weld holding the crush tube.

If you are bolting vertically up into the chassis, then the hole to drill at the bottom of the chassis is the external diameter of the tube. The hole at the top of the chassis should be the internal diameter of the tube. So the tube is inserted from the bottom of the chassis and only welded at the bottom. You just need to make sure that the length of the tube is exact so that the unwelded end of the tube is touching the inside of the chassis.

[samo Addicted PP Member Find all posts View Profile Close samo]

Re: Welding to chassis

hey barney have a look here as well if ya already havent, might give you some ideas. cheers samo
viewtopic.php?f=18&t=3741

[AJ120 Out of control poster! Find all posts View Profile Close AJ120]

Re: Welding to chassis

Hi Barney, if you are worried about the clearance whan bolting on sliders, i know i was, take a look at this. viewtopic.php?f=18&t=5400&start=20 I have plenty of clearance on mine.

Cheers Andrew

[barney1587 Lurker Find all posts View Profile Close barney1587]

Re: Welding to chassis

Hey Andrew,
Looks like you know your way round the engineering department !!! Great advice on crush tube use (have cut & pasted your reply into my 4WD info "keeper" file) I would have cut crush tubes to same length as overall width of chassis but what you have suggested makes heaps of sense. Thanks also to Samo for the link to your sliders construction. This is exactly the type of bracket idea that I had rattling round in my head. Will PM you for a few more details if you get a chance.
cheers & thanks to all,
Barney

[Guest Close Guest]

Re: Welding to chassis

Looks like you know your way round the engineering department !!!

It appears that my profession is slowly leaking out.

Now if you did cut the tube the same width as the chassis, the advantage is that the top end of the tube won't move when you weld the bottom end. However, after welding, the crush tube and the chassis needs to be fairly close and flush with each other, with the tube slightly inside of the chassis being the ideal case. So the bolt compresses the chassis a little bit until it reaches the tube.

[mjrandom Out of control poster! Find all posts View Profile Close mjrandom]

Re: Welding to chassis

The only thing I have to add is that unless you know exactly what grade of steel the chassis is made from and whether it has been heat treated DO NOT weld the chassis.

HAZ and stress concentrations are one thing, softening or hardening the base material is entirely another. Many truck and trailer chassis have a sticker saying heat treated do not weld. No idea what Toyota does. Of course it is possible to pre-heat, weld (with the correct electrode or wire) and post weld heat treat just about any grade of steel but you need the right gear and the right procedures. I have access to all that gear (bar the factory info) and wouldn't even think about it. And getting a sample of chassis tested for chemical composition doesn't give you how it has been heat treated.

Go carefully.

[samo Addicted PP Member Find all posts View Profile Close samo]

Re: Welding to chassis

in my opinion because the prado is mass produce you would probably find the chassis is just a std low carbon steel, eg 250gr i doubt it would be of a hi tensile nature because of the extra cost, as for chassis strength it would come down to the way it is constructed, have a look at the way the chassis rails r constructed eg they r not a std butt weld fit up , more of an overlap of 2 sections, eg 1 fits into each other then welded longitudinally, ie to create a double thickness on the top and bottom flanges, as for HAZ you cant do much about that but you can minimize the effects by preheating the parent metal as well as the attached piece, usually by just heat a little till the surface moisture has disappeared depending on thickness, the thicker it is the more preheat is needed, eg moisture at the tip of the flame has gone and formed around the outer edge of the preheat flame, also if it cools naturally will bring the parent metal back near its std compostion, when you start quenching and tempering you make it harder and more brittle, and as for weld metal eg mig wire it usually as a tensile strength of 480Mpa, std 250g mild steel is around 410Mpa so the higher strength wire is used to allow for greater joint strength. cheers samo

[mjrandom Out of control poster! Find all posts View Profile Close mjrandom]

Re: Welding to chassis

Samo, all you say is right and without making this into a masterclass on welding there are a few things to consider like most MIGs especially in the hands of infrequent users suffer from a lack of penetration. Weld looks great but falls off. Preheat helps but it is technique that ultimately makes it a good weld. Stick welding can result in heavy undercut which leads to cracking. Most people wont have low hydrogen electrodes which are what should be used. HAZ is no issue on mild and low carbon steels but can be a huge consideration in low to medium chrome steels under fatigue or high temperatures. And so on. My view is that there is no need to weld so why take the risk?

Michael

[samo Addicted PP Member Find all posts View Profile Close samo]

Re: Welding to chassis

you r right mjrandom, there r ways around welding to the chassis, some manufacturers have different ideas eg ATS bolt on and Macquarie 4x4 r weld on, just all depends on what you want, good to see that ppl with different backgrounds can offer information at various levels keeps it real. cheers samo