My 8x8 idea

[Chicken Drumstick]

Just a thought on the chassis front again.

But what do you think of taking a 127/130 chassis and chopping it where it starts to dip down both, front and rear. Then simply flip the middle section over, box it and weld it all back together?

Sort of something like this:

[Gremlin]

Sorry to be blunt about this, but you are making more work for youself by hacking up a chassis like that!

The esarco i saw had straight chassis members, with land rover spring buckets and raduis arm mounts welded on.

Have look here http://www.pirate4x4.com/forum/showthread.php?t=355327

G

[steve b]

I'll get some pic's as soon as I can sort it

If I can find the orig article later I'll post up copies of it

..I'm in Suffolk . Have a look in the video shack for one of Forestgrumps threads called Troy I think . It's a 6x6 RRC with electric rear steer air susp. with a lift up middle axle , its not on the road now but is , again, not far from me

cheers

Steveb

[B reg 90]

Re Chassis - Do what LR do. Get 2 of 200" long C sections of 2mm steel folded. Slide into each other and run a weld allong the top n bottom - one chassis rail. Only difficult bit is getting/finding a folder/press 200" wide.

Alternatively use the series chassis method - lazer cut 4 sides and weld to make a box.

Either way you will need a bespoke chassis as you will be way off a standard configuration. If you compomise on the chassis it will make the whole vehicle a compromise from the start.

Adrian

[steve b]

Or just use rectangular rhs of an appropriate scale - isn't the Ibex frame made of box section?

cheers

Steveb

[Chicken Drumstick]

Sorry to be blunt about this, but you are making more work for youself by hacking up a chassis like that!

The esarco i saw had straight chassis members, with land rover spring buckets and raduis arm mounts welded on.

Have look here http://www.pirate4x4.com/forum/showthread.php?t=355327

G

Cheers. Actually that's a SS300 I think it's a bit different to an Esarco with Dana axles and Ford engines and transmissions.

That said I don't disagree with what you are saying. I just have little or no idea where or how I could fab up an entire chassis from scratch of this scale, my worry would be needing to build a jig first to make sure it's all the right dimensions and angles.

My thinking was, if I had a 130 chassis as an entire vehicle, the engine would be in (although I'd look at changing it to a Tdi, but probably after it was running). So by cutting it up, it would have some of the work done already. And would at least be straight and the right widths and such. I could just fab up some wooden rails to line the wheels up with to make sure they were laterally located correctly.

That said, this is all good info and exactly why I thought about posting it here.

If I was to fab an entire chassis, do you have any pointers?

[FridgeFreezer]

As soon as you cut the chassis, it's not straight anymore, so that's a bit of a fallacy. They're not straight from the factory either.

I'm sure John Foers would knock you up an 8x8 Ibex if you asked nicely.

[Night Train]

Me like!

I would start with the four axles laid out where I wanted them and then fit the suspension and transmission parts to work out locations and clearences and then place two lengths of box section onto it to and weld on the locating points for the suspension and transmission.

No point messing with Land Rover parts that are all the wrong shape, just use your donar chassis for some brackets and the required dimensions for the cab and other mounting positions.

It should all work out ok. No need to steer the middle axles as the whole vehicle would pivot on the mid point between them regardless. The tyre scrub will be a small price.

The alternative would be to steer the front two axles one way and the rear axle the opposite way and it will all pivot on the third axle. It will take a bit of thought to get the Akermann angles and relative steer angles correct so you reduce tyre scrub rather then increase it.

I would keep it all mechanical drive using the dog clutches in the transfer boxes to isolate one pair of axles when on the road. Maybe worth making some sort of interconnected high/low selector so both transfer boxes stay in the same gear. Scary bangs and crunches if you get it wrong.

Look forward to seeing it take shape.

[longlandy]

If we're veering off the original a bit, I'd suggest looking at Mr Van Snorkel's 6x6 landy with the articulated rear bogie (a-la Scammel), this sort of layout seems very highly regarded for its off-road ability.

Once again Simon makes a good point about steering, front-axles steering seems to be the popular method for most trucks although presumably the first-and-last method gives a tighter turn at the expense of stability.

arcticulated rear bogie as is in comman with all double drive trucks is the most sensible way as it allows the weight and drive to be transfered correctly when on a approach angle etc .I think I would make a dedicated transfer box instead of joining multiple lt's

[Chicken Drumstick]

As soon as you cut the chassis, it's not straight anymore, so that's a bit of a fallacy. They're not straight from the factory either.

lol, very true. Just probably straighter....

But I do take everyone's points though.

I'm sure John Foers would knock you up an 8x8 Ibex if you asked nicely.

but for how much! Think I'd quite like the satisfaction of doing it myself too.

[Gremlin]

I know its a ss300, it was just to point out the chassis design

Well i am no expert,but logic tells me to go this route.................first build a rolling chassis

All you need are some hollow section, a flat floor and 4 axles to start of with. 8 matching tyres are also a must to get over any clearance issues.

Line up every thing making sure every thing is square, spot weld the axles to the hollow sections. Then set your drive train over the axles and see where it should roughly live. For now forget the 2nd tc, see to that later.

Then get another pair of RHS to use as the chassis rails, then continue off from there............. well putting simpley.......... work as if the axles are at full bump. You will have to build it around the components, keep it simple as possible.

See where the raduis arms will end up, also take care of the pinion angles. The esarco i saw had the all 4 diff pinions pointing upwards towards the transfercases. Once the axles are in place and you have a rolling chassis then see what ride hieght you want, and weld on the spring buckets.

anyway that the way my logic would be, i am not saying things will work fine my way............

The other option is to do the engineers way, and have everything measured up and CAD designed, take it to a cnc machine shop and have it all cut to have a nice build a 8x8 kit...................

G

[Gremlin]

damn nitetrain beat me to it!

[Chicken Drumstick]

I know its a ss300, it was just to point out the chassis design

Well i am no expert,but logic tells me to go this route.................first build a rolling chassis

All you need are some hollow section, a flat floor and 4 axles to start of with. 8 matching tyres are also a must to get over any clearance issues.

Line up every thing making sure every thing is square, spot weld the axles to the hollow sections. Then set your drive train over the axles and see where it should roughly live. For now forget the 2nd tc, see to that later.

Then get another pair of RHS to use as the chassis rails, then continue off from there............. well putting simpley.......... work as if the axles are at full bump. You will have to build it around the components, keep it simple as possible.

See where the raduis arms will end up, also take care of the pinion angles. The esarco i saw had the all 4 diff pinions pointing upwards towards the transfercases. Once the axles are in place and you have a rolling chassis then see what ride hieght you want, and weld on the spring buckets.

anyway that the way my logic would be, i am not saying things will work fine my way............

The other option is to do the engineers way, and have everything measured up and CAD designed, take it to a cnc machine shop and have it all cut to have a nice build a 8x8 kit...................

G

Thanks. All sounds like good advice

I think what I need to do is go off and start collecting all the items I think I'll need to get to a rolling chassis and maybe sketch out a few more accurate designs and plans to work from.

I've also been having a think about the comments concerning it being noise heavy under braking and descents. I was thinking that what you'd want to do would be set the brake bias to axles 2 & 3, with lesser braking force on axles 1 & 4. Surely this would stop it wanting to tip forward as much, yet still provide stability under braking on the road?

[muddy]

I would go for a straight box xection chassis, most box comes in 7.5m lentgths (12x12 anyone ) with the front two and rearmost axles steering, i notice in that image it looks like axle 3 is a sailsbury whilst the others are rover types? this would lend itself well to being 8x2 if you really wanted as the sailsbury would handle the power i would have thought.

Maybe by using a viscous transfer box between axles 3 and 4 you could brake the 3rd axle during hard lock to encourage the vehicle to scrub round it abit like kubota's bisteer system for an even tighter lock.

You can buy ready to weld radius arm brackets, spring seats off the shelf now i beleive which pretty much removes the need for a doner chassis.

Interesting project.

[Night Train]

Don't worry about braking for now, you will have all sorts of issues before you get there.

It might be good to have a disc braked front and rear axle for the front two axles and then drum braked on the rear two, or you could be selective about the caliper size with discs all round.

With unconnected coil spring on each axle you will get axle loading and traction issues on uneven ground. Stay within standard Land Rover weight limits and it may not be an issue but if you had, say, the front axle on a high kerb then it will take more of the load while unloading the second and third axles. They would then have reduced traction leading to both transfer box diffs needing to be locked.

Also if cresting a peak in a 4x4 both axles will stay on the ground. In an 8x8 you could find it balanced on just one of the middle axles so you will have to be careful of the axle loading in that case.

This is why I designed my 6x6 to have three inverted and fully pivoting, load balancing leaf springs. One front wheel could be lifted 3', or a back one 2', without compressing the springs as they just pivoted on bushings keeping all the other wheels on the ground.

It is not so easy with eight wheels but long travel low rate coil springs would keep the tyres on the ground.

[simonr]

What about using the same suspension system as the sojourner mars rover http://www.robothalloffame.org/mars.html

For the rear six wheels? There is some good video on YouTube of a Lego implementation of it. That alone makes me think it could be pretty good off road!

For steel / box section, try Parker Steel or IS&G who can supply pretty much anything!

Si

[FridgeFreezer]

Ref the braking, most vehicles are biased towards the front for good reason - because that's where the weight goes when to anchor on. Biasing toward the back end would not solve this, you'd just be skidding along with the back wheels locked waiting for the crash - and hill descent would probably not end well.

Unless the thing is going to be carrying heavy loads then you're going to need quite supple springs as you have twice as many axles supporting the weight, in fact with cab-over and a flat bed you're going to have trouble keeping the back end planted & not just bouncing round. A mate of mine took the body off a V8 RR and plonked a GRP hot-rod body on (weight: about 20kg) and it was absolutely rock hard because the RR body is so heavy.

Have a look at some 8x8 trucks on YouTube - search "Tatra 813", "KOLOS", "MAN KAT" or "Euro truck trial" to see how they get on - they're very capable but also show issues to be considered like how long half of the wheels spend in the air.

Two straight beams as chassis seems logical and simple, it's how almost all trucks are built. If you place them the same distance apart and make them the same width as LR then you can use standard LR x-members, outriggers, engine mounts, etc. although quite frankly if you're undertaking this sort of project then having to make an engine mount should be well within your capability, it's just a bit of steel after all.

[hedley]

A very interesting idea, one I have been working on myself for the last 5/6 years...

My plan was not to do a straight 8x8 as this would take massive engineering, but a 6x6 based on a standard lwb which would be a lot easier to build and possibly easier to get iva'd etc, then use the extra trasnfer box output to drive a powered trailer.

[hedley]

A very interesting idea, one I have been working on myself for the last 5/6 years...

My plan was not to do a straight 8x8 as this would take massive engineering, but a 6x6 based on a standard lwb which would be a lot easier to build and possibly easier to get iva'd etc, then use the extra trasnfer box output to drive a powered trailer.

[hedley]

A very interesting idea, one I have been working on myself for the last 5/6 years...

My plan was not to do a straight 8x8 as this would take massive engineering, but a 6x6 based on a standard lwb which would be a lot easier to build and possibly easier to get iva'd etc, then use the extra trasnfer box output to drive a powered trailer.

[Chicken Drumstick]

Ref the braking, most vehicles are biased towards the front for good reason - because that's where the weight goes when to anchor on. Biasing toward the back end would not solve this, you'd just be skidding along with the back wheels locked waiting for the crash - and hill descent would probably not end well.

Unless the thing is going to be carrying heavy loads then you're going to need quite supple springs as you have twice as many axles supporting the weight, in fact with cab-over and a flat bed you're going to have trouble keeping the back end planted & not just bouncing round. A mate of mine took the body off a V8 RR and plonked a GRP hot-rod body on (weight: about 20kg) and it was absolutely rock hard because the RR body is so heavy.

Have a look at some 8x8 trucks on YouTube - search "Tatra 813", "KOLOS", "MAN KAT" or "Euro truck trial" to see how they get on - they're very capable but also show issues to be considered like how long half of the wheels spend in the air.

Two straight beams as chassis seems logical and simple, it's how almost all trucks are built. If you place them the same distance apart and make them the same width as LR then you can use standard LR x-members, outriggers, engine mounts, etc. although quite frankly if you're undertaking this sort of project then having to make an engine mount should be well within your capability, it's just a bit of steel after all.

Thanks for the suggestions and I agree about making the braking rear biased would be wrong, I was thinking more "mid" biased as you have 4 axles to chose from.

[discomikey]

me like. why not start with a 101 chassis and lengthen it? i think theyre more flat like a series chassis also other parts could be used for the cab configuration. just my 2p

[landroversforever]

What about some sort of antiroll bar type thing, but working between say, axles 1 and 4, should stop the tendency to want to roll forward and make the brake bias setting up a bit easier?

[FridgeFreezer]

It's not so much about roll as weight transfer, might be worth asking a truck tech how they balance the brakes on the 4-axle tippers. You'll need the brake balance to be right to pass the SVA/IVA.

[landroversforever]

It's not so much about roll as weight transfer, might be worth asking a truck tech how they balance the brakes on the 4-axle tippers. You'll need the brake balance to be right to pass the SVA/IVA.

Thats what I meant, the weight transfer making the truck tip forward.