Defender Cross Member fabrication

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S

SDR597

New Member
Posts
13
Location
Forest of Dean, Gloucestershire
Has anyone on here made a rear cross member from scratch?

Mine is rotting through and all the threads I have read seem to point out that replacement ones are 'off limited quality'.

With this in mind I was considering fabricating one from scratch, A piece of 150 x 75mm x 4 or 5mm wall box seems to look like a good starting point and then plasma the ends to the profile of the 'proper LR version'.

I can then cut holes in the box to allow chassis legs to slot into and be welded into position.

It all sounds fairly simple, but what are the pitfuls I should watch out for?

Also any advice on things that I should build into such a design (I was thinking of building in recovery and jack points). This will obviously be a HD version and therefore I am conscious of keeping weight down)

Any advice would be welcome as I am new the LR thing and it was the previous owners use of chequer plate that meant I didnt see this coming before I purchased (that said I am not too scared of most jobs providing a I can leave my wallet alone!! - I know I am tight, but there is still a recession on in our house regardless of what the TV tells the kids!!!)

Thanks

Steve
LR 90 200 TDI.
 
Its basic metalworking. I've not done it myself but my mate made his own out of scrap 3/8" sheet steel. He folded the correct section at work (any decent machine shop will do this for you) then cut and welded the rest. He even made it follow the original shape so that mud flaps etc would fit. Captive nuts and jacking tubes etc. were welded to the inside of the section before he welded the back braces in. It was then welded to the chassis before the whole thing went off for a galvy dip. It is probably the strongest piece of his chassis.
 
Mark Evans shows how to do it on the series A 4x4 is born shown on discovery channel, I think you tube has it or try Mark Evans website. Looked simple,but I cant weld so stumped at the 1st hurdle lol
 
there's a standard sized RSJ that's perfect for this, saves having to do any folding and it'll be far stronger than any home fabricated jobbie
 
hughesy said:
Next time I need one I'll definitely make it myself. All the bought replacement ones I've seen are rubbish.
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This pretty much substantiates what I've seen, I'm an engineer and like to think I can weld (once I find the metal under the rust). So I'll sketch one up ready for fabricating at work.

I'll look into using a piece of channel, but can't help thinking a box section will allow me to position it better by plasma cutting slots for the chassis members to slot into, 150 x 75 x 5mm is a standard size, and it'll be easy to profile the ends to look tapered as per OEM. Its just a matter of holes to be cut in then and for that I may weld tubes into the holes to ensure the internals are not exposed to the real world.

From my observations most of the holes are generic and not required on my 200 TDI. So I'll only put jack points and tow bar mounting holes into the new fabrication.

I'll make the cross member up and post some pictures when its done, but I have to make the most of the snow in my new (to me!) Landy first.

Fitting may be a little while off, but I like to get things ready in plenty of time as thats a commodity I struggle with.

Once made and proven i'll put some basic manufacturing drawings up as well.

Well I was gonna make a new front bumper in my spare time anyway - so a couple of hours welding was expected!!!
 
Aye there's definitely a market fo a decent heavy duty one. Spose it's only as strong as the welds that hold it to the rest of the chassis though.
 
hughesy said:
Aye there's definitely a market fo a decent heavy duty one. Spose it's only as strong as the welds that hold it to the rest of the chassis though.
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If its made with sleeves that slide over the existing chassis rails then the strength is in these and not just the welding. If it was designed properly you could probably make a bolt on one which would be attractive to those peeps who dont/cant weld or who dont use the vehicle for regular heavy towing.
 
Shifty1962 said:
If its made with sleeves that slide over the existing chassis rails then the strength is in these and not just the welding. If it was designed properly you could probably make a bolt on one which would be attractive to those peeps who dont/cant weld or who dont use the vehicle for regular heavy towing.
Click to expand...
True. Probably needs a lot more thought put into it than is immediately obvious. One of the big downfalls of the mass produced ones I've seen is that instead of having the extensions made from two "C" sections welded together, like the original chassis, they're made from four flat pieces of plate welded along the corners. The welding is rubbish and they don't look like they'd stand up to any abuse at all.
 
hughesy said:
True. Probably needs a lot more thought put into it than is immediately obvious. One of the big downfalls of the mass produced ones I've seen is that instead of having the extensions made from two "C" sections welded together, like the original chassis, they're made from four flat pieces of plate welded along the corners. The welding is rubbish and they don't look like they'd stand up to any abuse at all.
Click to expand...
Its the same old story of things being made down to a price that is attractive but at the expense of quality. Why over engineer something when a cheaper mass produced item will do the job most of the time. You definitely get what you pay for and I'd be looking at making my own.
 
I have just fabricated one from sheet - had a local forge bend it up into channel and then fabricated the rest with the welder, in all cost me around £30 which is a fraction on what a replacement would have cost and is a lot stronger as well.

The best reason I can se for using channel over box section is that it is easier that way to ensure that everything is coated against rust - and you can easily jet wash it off. The problem with box section is that it will fill with muddy water, which will sit in there and gradually rust your new cross member from the inside out...

Top tip, when you come to re-fit the rear tub, bolt the five fixing tabs to the tub before welding them to the chassis - that way everything lines up perfectly. ...and remeber, it's a Land Rover so there wasn't anything precise about the way it was built in the first place (being designed to be fixed by a squaddy in a field with nothing but a hammer in has tool kit) so you don't need to measure and cut to the nearest thou...!

Good luck.
 
Thanks for the tips. Box is looking favourite - any 'holes' I cut into it will be with tubes welded in and thus mud tight! I can also fit a thread bung for squirting waxoil in or letting unexpected water out

Once I draw it up I'll post a 3D design (luckily I can design it in 3D first and then update the design after I discover where LR went 'off piste' with their design for you guys).

If its successful hopefully you can use it to get one made - I'll look at adding some bolt on tabs for the non welding community - should be easy although limited in strength.

Once I made mine it will probably become obvious how to do it better again !!! (and no its not an offer to practice on someone elses).

Off to Strata Florida this weekend just to put more water on the existing rust first though! Then need to win favour back with wife as she's starting to hate the thing!! (I suspect this must be a common problem).
 
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