Some spy shots of the 6x6 AMG G-Wagen thing

[FridgeFreezer]

I was at Brooklands Mercedes Museum on Sunday and they had that 6x6 G-Wagen thing there for some sort of press event, so I risked a stint in the cooler by evading the guards, jumping the barriers and waving my camera underneath it for as long as I thought I could get away with, all in the name of science. I thought people might be interested in what's going on underneath.

Apologies for blurriness.

[HoSS]

A bit weird to have portals, but then have those silly brackets that ruin clearance and will catch every rock...

[Michele]

Those silly brackets keep the portal boxes in place I believe, and there's still plenty of clearance left...
Nice air tanks.

[HoSS]

Sure, but compare with the Volvo solution, the supports/swivels are almost entirely within the wheels, neater.

[elbekko]

Interesting, so the rear axles aren't connected?

[Cynic-al]

I'd have one for the school run.

[discomikey]

if land rover were to actually design the defender with a quality over cost head on....?

mmmmmmmm

thats had proper DFX meetings behind its design for sure!

[Maverik]

Interesting, it looks like the front axle anti roll bar is clamped onto the radius arms... some great pictures well done fridge.

[tomcat404]

looks like the car is also running CTIS in the hubs from the silver pipework going into the middle of the box? ( I have been wrong before though)

[Cynic-al]

looks like the car is also running CTIS in the hubs from the silver pipework going into the middle of the box? ( I have been wrong before though)

I believe it does.

[FridgeFreezer]

I've been trying to work out the plumbing, there seem to be more pipes than things to do, the CTIS pipe across the rear axle confuses me as there are rubber hoses down the arms to each wheel too.

[Jamie_grieve]

Great pics Fridge!!

The CTIS pipes and tanks look big enough for the job too, not just a gimmick. It takes a lot of air and large pipes to operate CTIS effectively.

Looks like at least the rear portals have intermediate gears in them too for greater tooth contact than the usual suspects. I think the fronts might not..? Merc transfer cases used to have the front drive going the opposite way, wonder if the axles are bought in units, I can't make out if the tags are like ZF or something?

Looks like an interaxle diff on the centre axle too so no windup in the rear bogie like a Volvo.

It's of slightly heavier construction than the Volvo C304 but without any form of load sharing on the rear axles this must limit the payload to somewhere closer to what two axles can handle?

The rear springs are very short and not a lot of movement before the hollow bump stop will start to restrict upward travel. Off road ability wouldn't be affected too much in normal circumstances but at the extremes of summits on steep ground the rear axle would be unloading the front one significantly. No load sharing would also give rise to higher roll angles heavily loaded and more likely to break through soft ground or detonate an AV mine. On the plus side, high speed handling would be infinitely superior. In forty years we might be able to play with these the way we play with Volvo's now!!

[Jamie_grieve]

The silver pipes going into the middle of the hub are for the CTIS I'd say as they go into the middle of the hub through the block on the cover you can see, the back plastic / rubber 'pipes' look to be for the brakes. Are they hand brake cables going to the callipers perhaps? It looks like black plastic pipes coming from the air tanks but it's hard to say. Having the CTIS pipe across the axle might be one way of slowing down a rapid loss of air from one tyre and the easiest way to balance the pressures for normal driving. I'm guessing there's one air tank per wheel for lots of storage . Packaging and redundancy might be why not one large central tank.

[Ex Member]

I can't make out if the tags are like ZF or something?

The tags say "LeTech". The internet says the axle set costs around $90000 USD.

http://www.lennartz-technik.de/Start.2+M52087573ab0.0.html

[Soren Frimodt]

Wow Fridge, great job! i soo love that car and would part with several limbs for it haven't you guys seen the TopGear episode with it? They actually explain a lot of the tech. AFAIR the CTIS can air up all the tyres in a minute! Which is quite impressive. And it has 5 diff locks

[ejparrott]

Interesting, so the rear axles aren't connected?

looks to me like it drives through the lead trailing axle to provide power to the trailing axle, with a step across gearbox feeding the lead

[Ex Member]

I "assume" he meant not connected by suspension. So they are not load sharing at all. It makes for a poor setup in off road situations.

[discomikey]

The silver pipes going into the middle of the hub are for the CTIS I'd say as they go into the middle of the hub through the block on the cover you can see, the back plastic / rubber 'pipes' look to be for the brakes. Are they hand brake cables going to the callipers perhaps? It looks like black plastic pipes coming from the air tanks but it's hard to say. Having the CTIS pipe across the axle might be one way of slowing down a rapid loss of air from one tyre and the easiest way to balance the pressures for normal driving. I'm guessing there's one air tank per wheel for lots of storage . Packaging and redundancy might be why not one large central tank.

if the tyres were to be permanently cross linked you would have much falling over around corners and on side slopes, maybe there is some sort of valving system to isolate the tyres side to side for normal use

[FridgeFreezer]

Jamie - I didn't get the impression that any part was of more robust construction than the Volvos, these axles are ultimately "normal" ones with bolt-on portals (albeit very thoroughly done) whereas the Volvos / Mogs etc. are designed for the job. The 3rd axle takeoff was certainly bigger, but I suspect that's because of how it's grafted on rather than superior strength.

[missingsid]

Reminded me of Bill's good work under there! IIRC

The front axle drop boxes particularly?

Not impressed with the hockey stick with the clamps for the anti roll bar!

Great photo's if they are rushed then I'd like to see ones where you take your time!

[dirtydiesel]

Nice technical spy work Ju,

Digging out my merc anorak.... the front axle looks like a near stock 460 gwagon axle with the addition of what looks like 2 gear portal boxes, the rear axles look to have bigger diffs with more webbing in the casting than 460/463 rears they look more like ones I've seen under the bigger srw sprinters, interestingly the rear portal boxes look like their 4 gear units as well,

I wonder if they've used a 463 transfer box (conventional front prop shaft rotation) with a 460 (reverse rotating diff) to get the front axle to drive the right way because they couldn't squeeze 4 gear portal boxes in with those huge calipers. All though if the were they would be running on the coast side of the front r&p. I'm not sure if they ever offered 4.11:1 ratio in 460's though so the r&p could be bespoke for these axles.

The anti-roll bars clamped to the radius arms is a standard g wagon thing,

The axle tag is in the same location as most merc axles, and it clearly give the ratio as 37:9 = 4.11:1

[FridgeFreezer]

I did try to see the gearbox/transfer but the bash plate was properly in the way and I didn't bring any tools

[RustyNissanPrairie]

The tags say "LeTech". The internet says the axle set costs around $90000 USD.

http://www.lennartz-technik.de/Start.2+M52087573ab0.0.html

Some nice stuff on their website

[Jamie_grieve]

if the tyres were to be permanently cross linked you would have much falling over around corners and on side slopes, maybe there is some sort of valving system to isolate the tyres side to side for normal use

Not so, it's normal practice, indeed essential to run with the CTIS open on a so equipped vehicle in order to be able to adjust it. There are valves at the wheels to isolate it for storage or air loss due to a puncture. Another advantage of CTIS having all the tyres the same pressure is that they are all the same rolling radius and less likely to scrub when the diffs are locked or the rear bogie doesn't have an interaxle diff like many Russian trucks. If the system is at say, two bar then all six wheels will have two bar regardless whether the vehicle is on a side slope. It's air, not hydraulics. True if it were hydraulic and there was no pump so no pressure then you would get the scenario you describe but add a pump then even with hydraulics it wouldn't happen. It's hard to get your head round but think of a range rover with air suspension similarly plumbed in.

Jamie - I didn't get the impression that any part was of more robust construction than the Volvos, these axles are ultimately "normal" ones with bolt-on portals (albeit very thoroughly done) whereas the Volvos / Mogs etc. are designed for the job. The 3rd axle takeoff was certainly bigger, but I suspect that's because of how it's grafted on rather than superior strength.

That's interesting, it all looked very heavy in the pics but I know you know what you're looking at.

The two thicknesses in the axle tubes looked very reinforced and the portal housings looked wide and if they do have 4 gears in there that would be stronger too.

It's hard to gauge the size of the chassis and it's construction which again looked heavier than the Volvos. Even the shafts and UJ's looked bigger but it's hard to tell.

I don't suppose it's even fair to compare it to a Volvo from 40 years ago but they are kinda similar too.

The braces on the portals do look a bit of an afterthought

[bill van snorkle]

I will have to read through O'teunico's 6x6 thread again, because I'm certain I've seen the same rear bogie design but with the coil springs mounted on centrally pivoted balance beams to give load sharing. Perhaps load sharing was on prototypes for the Australian military, who are replacing their 6x6 LandRovers with Mercs of the same design minus the portals and with drum brakes on the rear in place of discs.

Interesting that the diff ratio is 4.11:1. This would probably indicate that the portal ratio is not very deep as even 1.5:1 would yield a final drive ratio of close to 6.17, likely a bit low for a vehicle with so much engine.

Although the portal braces may appear like an afterthought, they are very necessary for portal assemblies designed to bolt onto most standard non portal swivel housing assemblies, due to the enormous additional leverage that the drop boxes exert on swivel, balls, pins, bearings, axle housing etc. Bolting a 4" portal on is equivalent to changing from 31" tyres up to 39" tyres as regards leverage.