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bluespanner

6x6 axles

22 posts in this topic

They work by poking a diff pinion in the back to take drive up from the crownwheel - as such not 100% perfect as the rear axles will be locked together rather than having a differential between them, ISTR in articles about the Carmichael etc. it was said the proper 6x6's did scrub because of this.

Not complex to make, but hard to get right & reliable.

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Is it my imagination, or do they have the diff for the 3rd axle up side down..??????

looks like. The offset of the pinion left them no other choice, I think, and the rearmost axle needed to turn the same direction as the others.

Anyways, I´m afraid that the crown wheel (alternatively the pinions) of the middle axle will be the first to fail. I think the forces going through them, when turning two axles should be too much.

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I think its a carp design having thought about it, that first diff is going to be under a massive amount of stress

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Is it my imagination, or do they have the diff for the 3rd axle up side down..??????

IIRC If the input to the first axle is clockwise then the output on the rear of it will be anticlockwise thus the second axle diff needs to be upside down to drive the wheels correctly.

Axles coupled with a through drive are better used with the pair of axles on a common suspension hinge point in the middle like trucks as the suspension travel of each axle separately as in a coil and radius arm system will soon tie up the prop-shaft as the front axle moves up and the rear moves down.

Marc.

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I build proper 6x6 splitter boxes, anyhow a pal of mine was too mean to buy one off me so he bought a pair of these off ebay from those engineer without brains fools.

The design is flawed anyway, but the workmanship on these is a disgrace cardboard to shim the second pinion , cereal packet gaskets, hacked and ground faces , not machined no diff pegging etc etc

He promptly sold them off back on ebay to portal rover in whose hands they failed almost immediately.

I contacted the builders and told him he was a disgrace but I got no comment

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hi if you really want to go straight through you should look at the hypoid diffs with large hypoid offset eg Ford 9", someone in the US markets them for 6wd, the input pinion is extended and passes under the diff center so eliminates the need for second pinion. We used to make a drop box arrangement but discontinued due to other pressures, Foley now make and sell an improved version of our early design. I never did like the design with a second pinion out of the rear, it is very inefficient to try to drive a pinion with the crownwheel and creates huge stresses. Regards Ian Ashcroft

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hi if you really want to go straight through you should look at the hypoid diffs with large hypoid offset eg Ford 9", someone in the US markets them for 6wd, the input pinion is extended and passes under the diff center so eliminates the need for second pinion. We used to make a drop box arrangement but discontinued due to other pressures, Foley now make and sell an improved version of our early design. I never did like the design with a second pinion out of the rear, it is very inefficient to try to drive a pinion with the crownwheel and creates huge stresses. Regards Ian Ashcroft

I was thinking of that idea at one time though I didnt believe the market big enough to justify development and the lack of space (in length) for a clutch mechanism

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I bought a set of these axles and did NOT have success with them - off road they stripped the centre diff out soon as the strain came on. I tried to make it work, had the rear diff face pegged, had holes elongated to try and set the crown wheel and pinion to a snug fit - nothing worked. The guy I bought them from just gave me a lot of abuse and dismissed me as an off road freak ! Why would you have a 6x6 if not for off road ? !!

In the end I went to Paul Folley who built me a beautiful centre diff transfer box which works a treat. It has selectable 6/4 wheel drive and is fitted with a Kam LSD.

A straight through diff sounds nice, but in reality, unless you have a good space between the 2 rear axles, you end up with a very short prop shaft, and this limits the travel on you suspension before the 2 halves come apart. What we have is a long shaft, HD wide yoke, and free wheeling hubs on the rear axle. With this set up we have max articulation off road and a static rear drive line when on the highway - rear axles free wheel and centre diff out of gear.

If you would like to ask me about the set up, or anything to do with it, please contact me. Hughie www.portalrover.co.uk We have done it and learned by the mistakes !

Portalrover - torque of the north.

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yes you bought them off my neighbour, who bought them off engineers without fears, I told him to chuck them in the scrap but It sounds like you bought them.

Mr foley paid a engineering firm to build your diff to Mr ashcrofts design, he couldnt build a thing!

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majority of the 6 wheel RR carmicheals were only 6x4 [not 6x6] the rearmost axle was undriven just there to carry the extra weight, none were 6x6 while in service, & only went out of service because the requirements changed, from petrol to diesel, fire vehicle had to have all wheels driven & had to carry more fire fighting media & be dual purpose aircraft crash rescue & domestic appliances with full breating apparatus for all the crew.

doubt those axle would last even under a standard vehicle.

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I aggree, they are being sold with no drive disconnect the chances of them winding up and going bang is very high

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yes you bought them off my neighbour, who bought them off engineers without fears, I told him to chuck them in the scrap but It sounds like you bought them.

Mr foley paid a engineering firm to build your diff to Mr ashcrofts design, he couldnt build a thing!

Who ever Foley commissioned, made a good job of it, and it works well. The set I bought off ebay were scrapped. Good money down the drain - to say nothing of the time and abuse !

LRO have asked to do a feature on the vehicle, so that will be out in a few months. I have just had a Swedish 4x4 magazine come over and do an article, so it appears that when it is done properly, there is a lot of interest.

I have learned the hard way, but I am more than willing to assist any other who want to know the pit-falls I have come across.

www.portalrover.co.uk Torque of the North.

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...

LRO have asked to do a feature on the vehicle, so that will be out in a few months. I have just had a Swedish 4x4 magazine come over and do an article, so it appears that when it is done properly, there is a lot of interest.

I have learned the hard way, but I am more than willing to assist any other who want to know the pit-falls I have come across.

www.portalrover.co.uk Torque of the North.

I got the Swedish magazine, 4 Wheel Drive, today. Haven't had time to read the article yet, but they had some really nice pics of the car and yourself (I suppose?) in it.

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the rear diffs upside down because the second pinion on the middle diff would spin the other way,

so the rear diff is upside down to rectify this otherwise the rear axle wouls spin backwards

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I saw a nice conversion fitted to a truck in Belgium which was essentially a chain drive 'drop box' which sandwiched between the prop shaft and flange of the middle diff and transferred the drive to a second prop shaft which passed over the top of the middle diff. There was a cable operated dog-clutch which disengaged the rear-most axle and a certain amount of metalwork to stop the whole thing rotating. I believe the chain drive and clutch were Suzuki Jimny transfer box parts.

Anyway, I think that's how I'd do it. I would consider scrubbing the clutch and replacing the drive to the rear with a Freelander viscose coupling unit to take up the speed differences. OK, this looses some torque - but I wonder if it gains more in other areas.

Si

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I think I'd go diesel electric...

3 motors as inputs to each diff. Alternator in place of the gearbox.

All sorts of advantages with using the most efficient engine speed/electronic lockers etc etc. Lots of fun to be had!

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There was a type of clutch I saw on a BMX bike where, if you held the pedals stationary, the bike would freewheel forward or backwards, but if you pedaled forwards or backwards, it would turn the wheel that way.

With something like that, you could turn the rear axle with a hydraulic motor and just engage it when you need a little extra drive?

Si

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I saw a nice conversion fitted to a truck in Belgium which was essentially a chain drive 'drop box' which sandwiched between the prop shaft and flange of the middle diff and transferred the drive to a second prop shaft which passed over the top of the middle diff. There was a cable operated dog-clutch which disengaged the rear-most axle and a certain amount of metalwork to stop the whole thing rotating. I believe the chain drive and clutch were Suzuki Jimny transfer box parts.

Anyway, I think that's how I'd do it. I would consider scrubbing the clutch and replacing the drive to the rear with a Freelander viscose coupling unit to take up the speed differences. OK, this looses some torque - but I wonder if it gains more in other areas.

Si

Done like that I would have the through drive to the third axle live and the clutch on the chain drive in the drop box.

I suppose it could be rigged up with a centre diff from a Land Rover transfer box.

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I bought 2 sets and they both broke the first time they went off road.

You can not set up the pinion and crown wheel in the middle axle. It howls on the road and strips when under load.

I have the solution now, but it is not cheap !

www.portalrover.co.uk

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