Finally taken some pictures.

[roguevogue]

Front axle fitted with fixed, converging radius arm/a-frame thing. Also showing prop shaft adapter to match the rover shaft to the Toyota input flange. The front diff is conveniently 1/2" shorter than a Rover unit.

Hydraulic assist ram on the back of the axle casing. B)

Front panhard rod bushes replaced with spherical bearings, I have been having problems with metalastic type bushes giving up.

Rear radius arms mounted on Nth Degree Gyro joints.

Rear axle showing diff-lock actuator and guard. Again showing drive flange adapter, the rear diff is about an inch longer than the Rover unit so the rear prop is shortened.

Rear axle from underneath showing reverse a-frame, again mounted on a gyro joint.

All mounted with x-springs.

I built a controller for the lockers using four 5 terminal relays, I got the wiring diagram from the internet.

Switch panel on the centre console with switches for lockers, winches, welder, air compressor and lights. Missing switches are for front locker and work lights.

Finally, just in case you were in any doubt about who my new favourite sponsor is, here's one of my new vinyl. (The grey paint is only primer). B)

[GBMUD]

Cool - I like the front suspension set-up. Are we going to see it actually do something some time soon?

Chris

[bishbosh]

Looks really impresive Nick.

Is that first photo misleading? It looks like the prop is almost touching the radius arm wotsit...

[roguevogue]

Only two week away but you won't be there!

[pugwash]

really useful post thanks Nick.

is the hyrdoassist just a single ram on one side? is it effective? seems like a really straightforward way of doing it but seems counter intuitive if you konw what i mean.

[roguevogue]

Looks really impresive Nick.

Is that first photo misleading? It looks like the prop is almost touching the radius arm wotsit...

Shhh! don't tell anyone but it does touch, just, on full articulation, only enough to scratch the paint though. The way it all moves the biggest the gap gets is about 4mm.

You need to bear in mind that all this is experimental and untried!

[roguevogue]

really useful post thanks Nick.

is the hyrdoassist just a single ram on one side? is it effective? seems like a really straightforward way of doing it but seems counter intuitive if you konw what i mean.

I am using a single, double acting ram on one side, attached to the track rod, it is very effective and straight forward, however there are many more experienced, knowledgeable, if not opinionated people you could take advice from.

[pugwash]

if it works, it works! that's all that really matters when you get right down to it doesn't it!

[roguevogue]

if it works, it works! that's all that really matters when you get right down to it doesn't it!

It really is a doddle, just connect hoses from the steering box, one from the bleed nipple and one tee'd into the steel pipe which goes down the side of the box, attach the other ends to the ram.

[will_warne]

Nice write up, Nick. I like what you've done with the hydro assist too - that's a really nice location that you've got. The high track rod's also a nice feature I didn't realise the toyota axles had.

Out of interest, why the reversed A-frame on the rear axle? Is it to raise the roll centre?

[roguevogue]

Out of interest, why the reversed A-frame on the rear axle? Is it to raise the roll centre?

I wish I understood the question. I used the reverse A-frame because it was convenient with the available mountings, nothing more considered than that i'm afraid.

[Hybrid_From_Hell]

I wish I understood the question. I used the reverse A-frame because it was convenient with the available mountings, nothing more considered than that i'm afraid.

Nick,

Lovely lovely work, .............great ideas ....................and nice thinking with "Out of the Box" solutions. B)

2 things :

1 - Wots wrong with the 'tools n fab' forum then - you too posh or are we too rough feryer then ?

2 -Are those 'Jap Cr*p Oil leaks' in the piccies ......or the remains of the landy bits / or old Piggy deposit ?

Looking forward to seeing it in action (even with a reversed frame)

Nige

[simonr]

That looks fab!

I've read a lot about roll centre height - and there does not seem to be any consensus on whether it should be hgh or low? I can see advantages and disadvantages to both.

Will, could you explain what is optimal and why to us?

Cheers,

Si

[JST]

looking good Nick, you coming down for the X-Eng challenge then 16 Jun. see you at HBRO, hope it goes well.

[dollythelw]

sweet, very nicely done

[will_warne]

That looks fab!

I've read a lot about roll centre height - and there does not seem to be any consensus on whether it should be hgh or low? I can see advantages and disadvantages to both.

Will, could you explain what is optimal and why to us?

Cheers,

Si

Si, I can see both sides too and can never decide whether a high or a low centre makes most sense. That was why I was wondering whether the reversed A-frame had been done for handling reasons of for packaging in case Nick understood it better than me and could explain it. I wasn't trying to judge it or e cleaver but rather learn something from a skilled engineer. As it is, Nick's answered my question

[simonr]

I can see both sides too and can never decide whether a high or a low centre makes most sense.

Thanks Will - what are the pros and cons? Sorry for hijacking your thread Nick - but I think we potentially all have something to learn here!

Si

[will_warne]

Si, as I understand it a higher roll centre will reduce the effect of torque on the axle trying to lift a wheel during acceleration and bring the roll centre closer to the vehicles CoG meaning you'll have less weight transfer over rough ground which'll help stability. A lower roll centre should have its pivot point near to the centre of the axle meaning the vehicle should have less steering effect during articulation and there should be less resistance to articulation meaning better stability. As most of the effects seem to be dependent on stability at speed I tend not to be too sure about the relevant effects on a low speed vehicle. Is what I'm saying OK or am I talking gibberish?

[simonr]

Thanks Will, that's very helpful.

I don't quite follow this bit though:

axle meaning the vehicle should have less steering effect during articulation

Surely to reduce the roll-steer, you either need the roll centre at one end or the other of the panhard rod or make the radius arms really really long?

And

meaning you'll have less weight transfer over rough ground which'll help stability

Why is that? Lots of people say 'it will handle much better' if you do this, but can you quantify why and how much?

Si

[will_warne]

Thanks Will, that's very helpful.

I don't quite follow this bit though:

Surely to reduce the roll-steer, you either need the roll centre at one end or the other of the panhard rod or make the radius arms really really long?

And

Why is that? Lots of people say 'it will handle much better' if you do this, but can you quantify why and how much?

Si

Hint of sarcasm?

First point is me explaining badly! The way I've imagined the differance (rightly or wrongly) is to compare a sea saw with a fairground pirate boat (those ones that swing back and forwards) and assuming the vehicle is setup with an A-frame or Watts linkage and radius arms. The sea saw being the low roll centre (right on the centre line of the axle) and the pirate boat being the high roll centre. When articulating, with the high roll centre the axle will effectivly be moving like a pendulum and so will be offset to one side of the vehicle. Whether it has a real effect I don't know - I may be spirting out as much s**t as a someone the night after rather a lot of beer and vindaloo. You're the one who's read a fair bit on it - I know very little about it.

The second one - mass moving (or more correctly accellerating ie a force) about a centre resulting in a moment. Quantify, yes I could but my mechanics is rusty and, as much as I'd love to, I've got to get back to learning about biosynthesis of secondary metaboloids and physical organinc chemisty. As you've said you've read about this and I know you know the answer. I was simply being curious and trying to maybe learn something when I asked initially. Next time I won't!

[Daan]

Si, as I understand it a higher roll centre will reduce the effect of torque on the axle trying to lift a wheel during acceleration and bring the roll centre closer to the vehicles CoG meaning you'll have less weight transfer over rough ground which'll help stability. A lower roll centre should have its pivot point near to the centre of the axle meaning the vehicle should have less steering effect during articulation and there should be less resistance to articulation meaning better stability. As most of the effects seem to be dependent on stability at speed I tend not to be too sure about the relevant effects on a low speed vehicle. Is what I'm saying OK or am I talking gibberish?

I personally dont think the roll centre height has an effect on drive torque. But a higher roll centre gives us better stability, allowing us to fit softer springs which improve travel and have better weight distribution over our four wheels on uneven ground.

A low roll centre is more for f1 boys, (on road level or below). The trade off is that these cars have a very high rollstiffness, achieved by stif springs and anti roll bars. I think the whole story about roll steering or resistance to articulation is largely a case of bad design, or people lifting a car sky high without looking at geometry. And even if all this has an effect: does it make a blinding bit of difference? I dont think it does myself.

I have been involved in Rallycars and their suspension quite a bit, and always the endresult of lots of testing was: a higher rollcentre improves the car, in terms of handling and grip.

My 2p worth on suspension.

Coming back to the toyota conversion: I had and still have the same plan, interesting to see how you get on, it look well engineered.

Daan

[nas90]

Nick, why use Toyota axles? Stronger come with lockers as standard? or why?

[reads90]

Nick, why use Toyota axles? Stronger come with lockers as standard? or why?

They are stronger standard than land rover are after the maxi drive treatment.

They also come in serveral differant ratios already . So they do 4.1, 4.3, 4.7 and with factory lockers

Strong axels which are cheap to pick up

[Bush65]

The roll centre is at the point where the roll axis intersects a transverse, vertical plane at the centre of the axle. The roll axis passes through 2 points of the suspension, which are fixed when the axle articulates.

With the A-frame + parallel trailing arms, of rover coil sprung rear suspension, one of these fixed points is the A-frame ball joint, the second point is where the parallel trailing arms converge, ie. at infinity. So the roll axis passes through the ball joint and is parallel with the trailing arms. Since the ball joint is more or less at the centre of the axle, it is also the height of the roll centre.

BTW, height of roll centre does not affect roll/bump steer. This is caused by the slope of the roll axis, either roll understeer or roll oversteer depending if the roll axis slopes up or down. If the roll axis slopes up toward the front, the drooping wheel moves forward, while the wheel that is pushed up, moves back, thus steering the axle.

With a panhard rod, one of the fixed point on the roll axis is at the panhard on the centreline of the vehicle. With a watts linkage it would be the pivot point of the watts link.

For good road handling, the front roll centre should be lower than the rear roll centre.

For what we do with our 4wd vehicles off road, reasonably high roll centres are better for stability on cross slopes.

With a low roll centre, when the unsprung weight (body etc) leans over on a cross slope, the centre of gravity, being much higher than the roll centre, moves well over to the downhill side, making stability much worse. In extreme cases, the body flops over. This is usually made worse because the angle of the trailing arm on the uphill side becomes steeper, due to the body roll, and tends to push that side of the vehicle up more than the flatter trailing arm on the downhill side.

The down side of very high roll centres (for us) occurs when driving hard, up a steep rough track at a reasonably high speed (often necessary on timed stages). With high roll centres the sprung weight (body etc) shifts to one side, relative to the tyres during articulation. At high speed the inertia due to the acceleration of the side shifting sprung weight, has an effect like increasing the roll stiffness making it harder for the axle to articulate and maintain good traction (keep the tyres in contact with the rough ground).

[will_warne]

The roll centre is at the point where the roll axis intersects a transverse, vertical plane at the centre of the axle. The roll axis passes through 2 points of the suspension, which are fixed when the axle articulates.

With the A-frame + parallel trailing arms, of rover coil sprung rear suspension, one of these fixed points is the A-frame ball joint, the second point is where the parallel trailing arms converge, ie. at infinity. So the roll axis passes through the ball joint and is parallel with the trailing arms. Since the ball joint is more or less at the centre of the axle, it is also the height of the roll centre.

BTW, height of roll centre does not affect roll/bump steer. This is caused by the slope of the roll axis, either roll understeer or roll oversteer depending if the roll axis slopes up or down. If the roll axis slopes up toward the front, the drooping wheel moves forward, while the wheel that is pushed up, moves back, thus steering the axle.

With a panhard rod, one of the fixed point on the roll axis is at the panhard on the centreline of the vehicle. With a watts linkage it would be the pivot point of the watts link.

For good road handling, the front roll centre should be lower than the rear roll centre.

For what we do with our 4wd vehicles off road, reasonably high roll centres are better for stability on cross slopes.

With a low roll centre, when the unsprung weight (body etc) leans over on a cross slope, the centre of gravity, being much higher than the roll centre, moves well over to the downhill side, making stability much worse. In extreme cases, the body flops over. This is usually made worse because the angle of the trailing arm on the uphill side becomes steeper, due to the body roll, and tends to push that side of the vehicle up more than the flatter trailing arm on the downhill side.

The down side of very high roll centres (for us) occurs when driving hard, up a steep rough track at a reasonably high speed (often necessary on timed stages). With high roll centres the sprung weight (body etc) shifts to one side, relative to the tyres during articulation. At high speed the inertia due to the acceleration of the side shifting sprung weight, has an effect like increasing the roll stiffness making it harder for the axle to articulate and maintain good traction (keep the tyres in contact with the rough ground).

Thanks John, that's a really good write up

Just getting my head around the last point... Is the weight shift due to the torque of the engine causing the sprung weight to roll? The further away from the CoG the roll centre is the more it resticts this rolling effect and the less weight will be transfered to one side of the vehicle during acceleration?