End of the world

[Antichrist]

The LR3 uses what they call "Cross Link" to prevent what you are illustrating. Basically a valve connects the two air springs on each axle and makes them behave as a solid axle. ie, one side compresses and the air flows to the other airshock and it extends.

So the coil sprung LR3's have air springs as well? That's what I was trying to find out, but I haven't been able to find any info on the coil sprung versions.
In any case, that was what my original post about IFS/IRS and electronics was addressing. That sort of suspension is fine on things like the LR3, RR and whatnot, but I don't think relying on something like that in a Defender replacement is a wise move.

That's too funny! You must be proud of those, although I think some CAD experts might not think they are perfect... Firstly, it look like a uncomfortable ride, with the elliptical wheels.

LOL not really, but then again, I've done worse on a napkin discussing things during a meal.

And why's the transfer box on the ground when you bump off the ledge?

You mean you can't tell you're looking at it from the rear and that's the diff? lol

In any case, I only posted that one as a joke. That's why I said the one from the shop manual was a bit better.

 

[muskyman]

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[KevinNY]

I was referrring to the regular LR3 Tom, I have no idea about the coil versions.

 

[muskyman]

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[R_Lefebvre]

No, it was somebody else, and definitely related to the guy buying a coil spring version, it might have been on LRO. One group of "experts" was criticizing his LR3 for being too complicated. Then he told them he had the coil spring version, and another group of "experts" criticized him for not getting the good parts. Something like that. It was tragically funny.

and unless you drive your DII like a mini van this matters how?

Tom's drawings seem to suggest some kind of disadvantage based on IRS suspension movement and diff heights. It's a straw man argument, because IRS suspensions don't carry the diff at the same height as a live axle. There are disadvantages to IRS. Diff clearance isn't one of them.

 

[muskyman]

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[Antichrist]

Tom's drawings seem to suggest some kind of disadvantage based on IRS suspension movement and diff heights.

I included my drawing merely because I thought it was funny in it's crudeness.
However, Land Rover's illustration has the same implications, and is a much nicer illustration.

 

[R_Lefebvre]

No, I know it's funny. But I was referring to LR's drawing too. It's not like no solid axle truck has ever damaged it's diff on the ground, or that nobody makes diff guards. IS vehicles *can* be designed for what you want to do with them. Most IFS trucks are not. Mind you, not many SFA trucks are either.

 

[michaelgroves]

It is true that a solid axle lifts the whole axle when the wheel goes over a bump, thus hopefully clearing the diff over any corresponding obstructions . Independent suspension will only necessarily lift the body (and the diff), when the suspension reaches the bump stop.

However, this apparent advantage of solid axles might be offset if the diff is higher off the ground in the first place (and it often is).

I don't particularly like the sound of this "cross-linking" of the pneumatic suspension. It sounds all well and good off the road, but how come it doesn't induce extreme body roll when cornering, for example? More electrickery needed, I would guess?

 

[michaelgroves]

I used a similar idea to the "cross-linking" on the rear "tandem" of my Defender 6x6. I had Air-Lift air bags in all four rear coils, and I linked the two left-hand bags together, and the same with the right. The idea being that when the front (middle, that is) axle went over an obstacle, the air forced the rearmost axle down - and vice versa. It made the rear tandem behave more like a bogey (which would have been a better design from some points of view). I did consider interconnecting all four air bags, but decided against it because of the body roll issue. The main reason for fitting the air bags in the first place was to reduce body roll while on the road, but allow full axle articulation off the road, by simply deflating the bags, either partially or completely.

 

[R_Lefebvre]

It is true that a solid axle lifts the whole axle when the wheel goes over a bump, thus hopefully clearing the diff over any corresponding obstructions . Independent suspension will only necessarily lift the body (and the diff), when the suspension reaches the bump stop.

However, this apparent advantage of solid axles might be offset if the diff is higher off the ground in the first place (and it often is).

I don't particularly like the sound of this "cross-linking" of the pneumatic suspension. It sounds all well and good off the road, but how come it doesn't induce extreme body roll when cornering, for example? More electrickery needed, I would guess?

I was thinking the same thing. I'm guessing that there's a valve for the crosslink that opens and closes depending on where the terrain selector switch is. Also, bodyroll might be largely controlled by massive swaybars? And finally, I thought I remembered seeing that the "cross linking" is actually RF to LR, and LF to RR.

 

[muskyman]

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[R_Lefebvre]

Huh, not a bad idea.

 

[Alaska Mike]

In consumer applications, there are strength issues with independent suspensions, as there are added flex joints (of varying types). I've seen this quite a bit on H1s and, to a lesser extent, Toyota pickups.

There's also the greater expense in properly lifting the vehicle.

IFS has certain advantages (ride quality among them), and there have been quantum leaps forward in IFS design since the early days. IRS? I still haven't seen a good 4 wheel drive example.

 

[Ron B]

I don't particularly like the sound of this "cross-linking" of the pneumatic suspension. It sounds all well and good off the road, but how come it doesn't induce extreme body roll when cornering, for example? More electrickery needed, I would guess?

I considered this when converting my truck to all bags. Thought it might not be a good idea on steep side-slope situations unless, as previously mentioned, there was a way to defeat it. But I was trying to keep it simple and use as little "electrickery" (love that term!) as possible so there would be less to fail on me in the boonies. I have each bag individually controlled with it's own pneumatic switch. Works well...but its IS so not alot of wheel travel anyway!

A great discussion, love reading this stuff.