6x6 Perentie performance off road?

[Outback]

How do the Perentie 6x6 perform off road?

[PeteFox]

Pretty much the same as a 4x4 but with bigger turning circle. Its not really meant to be a go anywhere vehicle, just to go where a 4x4 can but with a much bigger payload.
It is however much lower geared than a 4x4 and you can crawl along at walking pace.
Pete

[TK_Co]

Pretty much the same as a 4x4 but with bigger turning circle. Its not really meant to be a go anywhere vehicle, just to go where a 4x4 can but with a much bigger payload.
It is however much lower geared than a 4x4 and you can crawl along at walking pace.
Pete

I got mine bogged when I was just trying to get to my mates place. It's needs lockers. I think I need to to the rear suspension travel straps off the rear axles, but I'm a bit scared as I can't really work out what the point if them is.

Do you know what the purpose of them is? I thought maybe something to do with air lifting ?


Just catching the perentie bug.

• 1990 Perentie 6x6 Air Defence GS
•2013 Range Rover Sport

[JDNSW]

Have a look on here for the "Simpson Desert Eejits Tour", I think the report is called. One of the vehicles in this tour was a 6X6 and it was reported to be as capable as the others (from memory a couple of 110s, a 130 and a Discovery), except for turning circle, and riding better on rough surfaces.

As well as turning circle, the greater width is likely to pose problems on some narrow tracks.

John

[Blknight.aus]

Comes down to the steerer driver or operator


I can put one almost anywhere you might reasonably want to go and quite a few places you probably shouldn't if you decide to lob the three rules out the window.

If it's the gs or dual cab winch version and its got the full ces and or some of the other gear I'd carry in any normal four by four they become nearly unstoppable unless you overload them.

And then with enough chains and shackles you can half track them.

[isuzurover]

...It's needs lockers. I think I need to to the rear suspension travel straps off the rear axles, but I'm a bit scared as I can't really work out what the point if them is.

Do you know what the purpose of them is? I thought maybe something to do with air lifting ?

...

Yes lockers are needed.
The travel straps are a hangover from the series landies. The idea is they are there to protect shockies and/or stop the propshaft reaching the end of its travel. They are pointless and need to be removed.

For offroad work the rear suspension design is too stiff and far from optimal. You can improve things by fitting softer rear springs (removing leaves).

[holeyhardtop]

http://www.aulro.com/afvb/multi-state-reports/203738-2014-edjits-simpson-desert-centreing-tour.html


also worth a look:


http://www.aulro.com/afvb/queensland-reports/208986-qld-landy-lizards-sand-perenties-fraser.html

[303gunner]

Yes lockers are needed.
The travel straps are a hangover from the series landies. The idea is they are there to protect shockies and/or stop the propshaft reaching the end of its travel. They are pointless and need to be removed.

For offroad work the rear suspension design is too stiff and far from optimal. You can improve things by fitting softer rear springs (removing leaves).
The beauty of the rear suspension design is the rocker beam that gives a superbly supple and smooth ride over broken ground, for what is in essence a heavily sprung 2t load carrying truck with rigid springs.


The drawback to the rear suspension design is the rocker beam which (in combination with the limiting cables) only gives 40mm of articulation before hitting the chassis rail. Once hard up against the chassis, the rear axles lift off the ground and you have to engage CDL and 6x6 to gain drive.

[TK_Co]

The beauty of the rear suspension design is the rocker beam that gives a superbly supple and smooth ride over broken ground, for what is in essence a heavily sprung 2t load carrying truck with rigid springs.


The drawback to the rear suspension design is the rocker beam which (in combination with the limiting cables) only gives 40mm of articulation before hitting the chassis rail. Once hard up against the chassis, the rear axles lift off the ground and you have to engage CDL and 6x6 to gain drive.

Thanks to you both. And yes, I agree it's limiting !! I literally have to engage 6x6 to get out of my concrete driveway because it's a bit of a slope then flat. I just sit there and spin the tyres.

So in summary, removing the suspension travel straps won't do any damage to the vehicle ?


Just catching the perentie bug.

• 1990 Perentie 6x6 Air Defence GS
•2013 Range Rover Sport

[TK_Co]

Suspension travel strap

[isuzurover]

So in summary, removing the suspension travel straps won't do any damage to the vehicle

no.
But it won't transform the vehicle either.

Those springs are about 1000lb per inch. So on flat ground you need 2t to compress the rear end 1 inch.

[303gunner]

I've been considering remaking the rocker beam in a different form, rather than a straight horizontal beam, instead an inverted "V" shape. This would give the dual benefit of slightly raising the rear end and allowing more angular rotation of the beam before hitting the chassis (or possibly not even hitting the chassis at all!).


Removing the straps/cables should be OK provided you check the extended lengths of the shocks at full articulation.

[TK_Co]

Thanks guys, I think I'll give it a go before the excursion next weekend. I do know they are very strong springs!! I had 4.5 ton on the back and it took the load beautifully. Which is great if ur trying to carry a small planet around all the time. Not so good for the mrs when going over a bump or speed hump.

One think I've considered gunner, is putting the leaves over the axle housing rather than under. The spring carriers have very little clearance and foul when in soft sand.

If your playing around with suspension, maybe you could look at doing that?...then tell us how you did it :)


Just catching the perentie bug.

• 1990 Perentie 6x6 Air Defence GS
•2013 Range Rover Sport

[Dervish]

One think I've considered gunner, is putting the leaves over the axle housing rather than under. The spring carriers have very little clearance and foul when in soft sand.


That would give you a lot of lift, but I think it might put too much angle on the rearmost driveshaft UJs. That shaft is very short; you can see the flange where the shaft starts at the very bottom left of this terrible photo.

http://i940.photobucket.com/albums/ad246/OreganoM1/IMG_8864_zpsac1cf3c7.jpg

I think 303's idea has legs and will probably make the most of the Perentie design, which is unfortunately quite constrained.

One of the things to keep in mind is that the articulation available is related to the load the vehicle is carrying. Very lightly loaded, the rocking beam sits like this:

https://www.aulro.com/afvb/

So the middle axle doesn't have far to droop. Carrying load you'd have more articulation. It would be interesting to see how much difference in articulation loading the back of the vehicle up until that beam was level would make. 303: maybe part of your video?

[isuzurover]

A better option for those doing mods would be to swap to a setup which allows the axle group to tilt as a single unit. E.g. buggy spring setup usind a single inverted spring pack per side, which can pivot in the centre and is rigidly fixed to each axle.

[Blknight.aus]

Stick a camelback and 6 point on it?

[TK_Co]

Stick a camelback and 6 point on it?

There's lots of ideas. Maybe someone should start a 6x6 suspension thread? I see there are some companies (6x6 Australia, MDT, off-road trucks Australia) that specialise in 6x6 and 6x6 suspension. Has anyone changed the suspension on there 6x6 yet?


Just catching the perentie bug.

• 1990 Perentie 6x6 Air Defence GS
•2013 Range Rover Sport

[PeteFox]

One of the things to keep in mind is that the articulation available is related to the load the vehicle is carrying. Very lightly loaded, the rocking beam sits like this:

http://i940.photobucket.com/albums/ad246/OreganoM1/IMG_8863_zps4273533a.jpg

So the middle axle doesn't have far to droop.

I've just a look at the rocking beam on my 6x6 and it doesn't look like the photo above. I may be an optical illusion from the angle the photo was taken but the beam seems to be pointing down at the front end . On my 6x6 the beam is sitting absolutely level, on level ground with a light load. The gap before the beam contacts the chassis is about 30mm each side but this gap (that ultimately restricts articulation) is right at the pivot point and the axle(s) centre is 450mm away from the pivot. I'm not able to do the maths right now but this should give a reasonable amount of articulation. The axle straps are the limiting factor on mine, and not the rocker arm contacting the chassis. There are no marks on my chassis to indicate any contact here.

I am considering lengthening the straps but I wouldn't remove them entirely due to the risk of catastrophic damage to the rear tailshaft if it were to separate at the spline. A few measurement up on jacks would be a good starting point.

The main issue I have had off road is the rear end 'pig rooting' in loose going up-hill. This thing is really no good on round river rocks or unpacked loose ground or ploughed paddocks. Skipping on the middle axle seems to set the rear axle off with causes the middle axle to bounce and on it goes......Sort of like a see-saw on steroids. Foot of the throttle seems to be the only fix.
Pete

[Blknight.aus]

Your vehicle.probably doesn't have the rear axle.ha gong from its check strap because the wheel.is removed.

On level ground unloaded you can drive the vehicle with one axles wheels removed without drgagging the other axle, that's part of what the check straps are for

For your off-road problem first check your cdl is engaging and that you are not cross axling the rear pair when you drive.

Raise your idle speed using the ha d throttle so the engine sits. At about 1000rpm let it walk and if you need to lower the tyre pressure.

Setting the vehicle up on the right line with the right engine power and gear with the right loans and tyre inflation is key to getting the best out of your 6*6

[PeteFox]

Sorry guys having some issues with photo uploads

Guys I have been doing some measurements with my 6x6 to work out the range of movement of the rocker beam and therefore the axle. some of these measurement will be load dependent. My vehicle was grossing approx. 4.0 tonne when I made the measurements and was on level ground.

The amount of vertical movement in the rocker arm at the point where it would contact the chassis is approx 25mm

https://dl.dropboxusercontent.com/u/23520961/IMG_1412_m.jpg

and this point is 38mm distant from the pivot point as shown
https://dl.dropboxusercontent.com/u/23520961/IMG_1411_m.jpg

This is a an angular movement of 41deg. This is a large angle and I don't think that any restriction in suspension oscillation will be down to a restriction here. This angle allows for movement at the axle which is 465mm from the centre pivot of 305mm

The amount of axle drop possible with the axle straps in place is approx. 65mm
https://dl.dropboxusercontent.com/u/23520961/IMG_1413_m.jpg

However the gain in oscillation in removing these will not be anything like 300mm because upwards movement of each axle is restricted by the rubber bump-stops above each axle
https://dl.dropboxusercontent.com/u/23520961/IMG_1416_m.jpg
but this will be dependent on the load.

clearly there are a lot of factors at work here.
Pete

[303gunner]

Your calculations of 41 degrees of rotation are based on the wrong contact point. The point that the rocker beam contacts the chassis is directly above the rear shackle of the intermediate spring when the rear axle is at full droop. You can see in the picture below that the rocker only has to move 45mm for the beam to contact the chassis. In fact you can see a wear point where this happens, with a thud. I could place a square of conveyor belting there to soften the blow, but it would further reduce the limit of travel.


https://www.aulro.com/afvb/images/imported/2016/04/34.jpg (http://s162.photobucket.com/user/303gunner/media/IMG_6535.jpg.html)






The suspension initially flexes due to the rocker beam action, with the springs themselves principally flexing under load, not articulation. For the 45mm gap to the chassis to close up, the opposite end of the rocker beam needs to drop 45mm. For rule of thumb purposes, we will say the axle is located approximately halfway along the spring, so 45mm of deflection at the shackle end is about 22.5mm at the axle (if we can say there is some deflection of the spring itself, we might be generous enough to say as much as 30mm at the axle).




And here it is:
https://www.aulro.com/afvb/images/imported/2016/04/35.jpg (http://s162.photobucket.com/user/303gunner/media/IMG_6536.jpg.html)



This is the limit of articulation. You can't make it out in this picture, but the rear wheel is suspended in the air and the tyre can be turned by hand. The rear axle is doing very little to support the load, and absolutely nothing to provide traction. If the rear axle were to be engaged, the drive torque would go straight to the suspended wheel without some form of traction aid (air locker, Detroit, truetrac, etc)


https://www.aulro.com/afvb/images/imported/2016/04/36.jpg (http://s162.photobucket.com/user/303gunner/media/IMG_6537.jpg.html)


The rocker beam is hard up against the chassis and any articulation must now come from deflection of the springs. As pointed by others, the springs are designed to support a 2 tonne payload and don't deflect easily.


https://www.aulro.com/afvb/images/imported/2016/04/37.jpg (http://s162.photobucket.com/user/303gunner/media/IMG_6538.jpg.html)



The limiting cables are next to useless. Although they are now close around the axle tube, they are loose and in no way taut or restricting the travel of the axle (cable can be jiggled by hand). That is being done by the rocker beam being hard up to the chassis, and that ain't moving any further!


https://www.aulro.com/afvb/images/imported/2016/04/38.jpg (http://s162.photobucket.com/user/303gunner/media/IMG_6539.jpg.html)

[Blknight.aus]

If the rocker arm is touching the chassis it means the strap is installed wrong and has been installed as supplied instead of being set to length or its been stretched.

[303gunner]

So it's supposed to have even less articulation? :o

[TK_Co]

So it's supposed to have even less articulation? :o

So, we now know that the rear suspension set up is poor at best, what are we going to do to fix it ?? :)

Both gunner and black night seem to have a lot of knowledge on the suspension. As does a lot of other people on here.


Just catching the perentie bug.

• 1990 Perentie 6x6 Air Defence GS
•2013 Range Rover Sport

[Patrol 32]

I got mine bogged when I was just trying to get to my mates place. It's needs lockers. I think I need to to the rear suspension travel straps off the rear axles, but I'm a bit scared as I can't really work out what the point if them is.

Do you know what the purpose of them is? I thought maybe something to do with air lifting ?


Just catching the perentie bug.

• 1990 Perentie 6x6 Air Defence GS
•2013 Range Rover Sport

TK Having driven these a lot I can tell you they need lockers a lot less than they need the driver to understand how to drive the vehicle. Did you engage six wheel drive? If you must go and spend money on this truck, install an after-cooler. If you must have lockers I suggest you look at Ashcroft's Automatic Torque Biasing diff centres (Ashcroft Transmissions UK). We tried ARB and they were no good.

[Patrol 32]

Your calculations of 41 degrees of rotation are based on the wrong contact point. The point that the rocker beam contacts the chassis is directly above the rear shackle of the intermediate spring when the rear axle is at full droop. You can see in the picture below that the rocker only has to move 45mm for the beam to contact the chassis. In fact you can see a wear point where this happens, with a thud. I could place a square of conveyor belting there to soften the blow, but it would further reduce the limit of travel.


https://www.aulro.com/afvb/images/imported/2016/04/34.jpg (http://s162.photobucket.com/user/303gunner/media/IMG_6535.jpg.html)







The suspension initially flexes due to the rocker beam action, with the springs themselves principally flexing under load, not articulation. For the 45mm gap to the chassis to close up, the opposite end of the rocker beam needs to drop 45mm. For rule of thumb purposes, we will say the axle is located approximately halfway along the spring, so 45mm of deflection at the shackle end is about 22.5mm at the axle (if we can say there is some deflection of the spring itself, we might be generous enough to say as much as 30mm at the axle).




And here it is:
https://www.aulro.com/afvb/images/imported/2016/04/35.jpg (http://s162.photobucket.com/user/303gunner/media/IMG_6536.jpg.html)



This is the limit of articulation. You can't make it out in this picture, but the rear wheel is suspended in the air and the tyre can be turned by hand. The rear axle is doing very little to support the load, and absolutely nothing to provide traction. If the rear axle were to be engaged, the drive torque would go straight to the suspended wheel without some form of traction aid (air locker, Detroit, truetrac, etc)


https://www.aulro.com/afvb/images/imported/2016/04/36.jpg (http://s162.photobucket.com/user/303gunner/media/IMG_6537.jpg.html)


The rocker beam is hard up against the chassis and any articulation must now come from deflection of the springs. As pointed by others, the springs are designed to support a 2 tonne payload and don't deflect easily.


https://www.aulro.com/afvb/images/imported/2016/04/37.jpg (http://s162.photobucket.com/user/303gunner/media/IMG_6538.jpg.html)



The limiting cables are next to useless. Although they are now close around the axle tube, they are loose and in no way taut or restricting the travel of the axle (cable can be jiggled by hand). That is being done by the rocker beam being hard up to the chassis, and that ain't moving any further!


https://www.aulro.com/afvb/images/imported/2016/04/38.jpg (http://s162.photobucket.com/user/303gunner/media/IMG_6539.jpg.html)


Team, The suspension does look tired, particularly the position of the shackle bushing washers. These look off centre. Have you had a look to see if your rear suspension bushes are warn? Also Gunner is right (must be a spanner) in that the axle restraint straps (the steel wires which are looped around the axle and fastened to the chassis) are there to limit articulation droop and protect the universal joints and dampers. As Gunner stated check these have not been stretched. Have you tried jacking the intermediate axle up to its limit while the vehicle is on a flat level surface (out of gear, front wheels chocked) with the rear axle free to hang? this may give you an unbiased view of how the suspension should be working. The read assembly is load sharing and should not allow the load beam to touch the chassis under normal circumstances. Having driven these a lot, they are awesome off road, and although a truck and not a rally car, they will go pretty much anywhere. Have driven across parts of the Hamersley Range in WA in a fully laded (5.6 tons) six wheeler with absolutely no problems what so ever.

[123rover50]

Mine was a prototype and came with difflocks centre and rear, no check straps. I put freewheel hubs on the rear axle and if I get crossaxled only need to lock the centre diff (g,box).
Only put the FWH in, in really rough stuff.
Just in case , I have a hydraulic winch as well.:D
I wonder why they did not continue with the lockers.