I won't deal too much with the ute chop. I think the only decent reason for a ute chop is to allow a wheelbase stretch, but I can see that as some of the inherent problems of the Jimny are due to the high rear COG, I could perhaps see a point. I will take issue with this though:
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I believe that it will actually be lighter then stock with this design.
Nope. It won't be. By the time you close the cab out, make a tray, mount a winch, and run roll over protection, you're going to gain weight overall, for sure. Body panels are light. I reckon you'll have 60kg of tube in the car alone, before the tray is built or the cab is closed out.
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The 2nd part to this is that the bar work design will come out just far enough to be equall to the width of the tyres. The rear tray forming part of the fender. This way If i get wedged between something it is not on the tyres but the bar work. I will be trying to keep the build as light and 'tight' as possible.
I think this is silly, and what turns cars with exo's into trail plugs. So the bar work is the width of the tyres. Now you flop over onto a bank. without your exo, you would have been running on the tyres, but with it, you're now jammed on some bit of tube and busting axles. Jimnys' are capable because they are small. Making them bigger doesn't help. The problem areas are in front of the front door, where you need a vertical bar which is just going to be an anchor, and behind the door, which is where the car pivots to when it's slipping around an obstacle. if you add a bar there, you've just jammed your car on stuff it used to be able to drive easily.
I'll add to the problem - unless you are a NINJA at bending tube and roll your verticals, you won't be 5" wider than stock at the sills, you could be nearly double that. That means you'll be dragging the exo everywhere, especially if it's as wide as the tyres at rest. So to protect the A pillar from a flop (nothing else will get hurt in a flop - your tyres are outside the guards) you've made the car less capable and heaiver, and therefore more likely to flop in the first place.
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3. To confirm it is just 1 3mm plate to be welded to the chassis giving me a 5.5mm thick place to weld on? I was not aware about not welding onto the corner of the box section (and I wont do it - but what is the reasoning for this?
No, a 3mm plate welded to a 2.5mm plate doesn't equal a 5.5mm plate, it equals a 3mm plate preventing damage to the 2.5mm plate. I know this seems like semantics, but you need to understand that the two plates are only joined where they are welded, elsewhere, they are still two separate plates and don't share stresses. That's the point - keeping the doubling plates ideally equal in thickness distributes stress equally and doesn't concentrate it in the thinner part. (the chassis) therefore hastening cracking.
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In explanation for the 5mm plate, As the back will be chopped off I plan to mak the winch plate mounted vertically between the rear chassis rails. For this I will use some folded or welded 5mm plate, I planned to both bolt through the chassis rails (hence the question about welding the plates on to weld 5mm plate to the rails) as well as bolting through. The use of 5mm plate will of course be as minimal as possible but it will be used for front and rear winch, both to be mounted in a similar fashion between the chassis rails and also tied into the bar work used on the vehicle.
Firstly, I challenge that a well designed winch mount needs to be made from 5mm plate. (for a Jimny, not a Landcruiser) A smart winch mount should gain its strength from planes and gussets, not from heavy plate. 3mm should be all that's needed, Where necessary, (like around the mounting bolts) it could be doubled up with another 3mm plate. Think smart not heavy.
There has never been a good reason to weld AND bolt anything ever. if thats what you were implying.
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4. The end story of this is that it must retain on road safety and handling first and foremost safety is always paramount.
Then you won't want to be lowering the roll stiffness at all then, or getting into instant centre, fabricating links etc. the reason Jimny's have most of the suspension compromises they do is in the name of road safety and handling.
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For all I know it is the fact that people dont want to chop the car, or modify it too much that stops the Jimny being more capable (I know its fairly capable) then what can be done with bolt on modifications.
Chopping the back off a car has never made it more capable because it doesn't effect any of the things that have an impact on capability. It makes a car less prone to damage, that's not the same thing. In my opinion the biggest problem with the capability of the jimny is that it wasn't designed as on off road vehicle. It was designed as a Kei class urban car. Principally, the wheel arches are too small, the suspension is designed around an unworkably low ride height (at the sill) , and the car is too wide at the sills relative to its track width, and the rear COG is too high. These problems ignore the driveline completely, but you can't really work around them without building something that's effectively just like a hilux or patrol but more work regardless of what you do with the driveline.
Adding all manner of tube and hacking the back off don't deal with those problems except maybe lowering th COG at the rear, but I fear the result will be moving the high COG forwards rather than lowering it, which wouldn't make a jimny more capable. Sure, you might feel you're able to drive it more aggressively, which might get you further, but that's attitudinal, it's not a measure of the function of the car mechanically. Now if a Jimny was able to run 33's at the same lift height and with the same sill clearance, width at the sill, and COG as a Sierra it would be more capable than a sierra because of the longer wheelbase, better approach and departure angles, and better weight distribution.
Steve.
