suspension gods

[redzook]

ok ive drew up this link setup for the rear

ive got a few questions is there enough triangulation(SP?) in the links the keep the rear diff centered or will it want to move side to side under the rig?

and the next question is

what will the rear do squat? lift? i think it will lift a little but unsure but if it lifts i can just lower the upper mounts on the chassis a little cant i ? and it should squat a bit more?

and overall how do u think it will peform?

TIA Tim

[Bush65]

You haven't provided enough info.

Download the 4 link analyser from http://home.earthlink.net/~triaged/Files/ enter your data into that and it will answer your questions and much more.

[POS]

You haven't provided enough info.

Download the 4 link analyser from http:Bootiefablinks@just_ask_SAM_andbe_done_withit/Files.Cum enter your data into that and he will answer your questions and much more.

[POS]

Looks pretty good to me but then again, i know jack!

Like my smartarse comment above, Just ask Sam (Strangerover). What he doesn't know about suspension geometry isn;t worth knowing!!!

[A1]

ok ive drew up this link setup for the rear

ive got a few questions is there enough triangulation(SP?) in the links the keep the rear diff centered or will it want to move side to side under the rig?

and the next question is

what will the rear do squat? lift? i think it will lift a little but unsure but if it lifts i can just lower the upper mounts on the chassis a little cant i ? and it should squat a bit more?

and overall how do u think it will peform?

TIA Tim

Upon advice n knowledge told to me by one of the suspension gods .......u can run less triangulation on the uppers if u run tri'ed lowers aswell as these will also fight the side to side forces on the axle ............so by the looks u have bout 48 deg separation on the uppers this alone would prob be fine if u didnt have tri'ed lowers ...of which your showin so it should be sweet in that aspect .............


Ands thats bout as far as my knowledge goes even tho ive built my 4 link ...........pretty much a copy but a few critical measurements are different i guess wen it eventually gets trail ready i will see how it will react

As POS has said pm StrangeRover .......................ive also got that petersons 4x4 write up on my comp i can send u if you like , it may help...............but hey atleast ya takin the time to draw up the setup properly to get everything pretty much spot on

Dan

[beebee]

As has been said you haven't provided enough info.

However......

It appears that you will have some anti-squat. Although not too agressive, it will be present. You will also have a roll axis that is inclined which will give you axle steer upon articulation.

If you wanted to alter each of these characteristics, then I would suggest mounting your lower links further up the chassis toward the front which would make them flatter when viewed vertically.

Good luck. I'm interested to hear other's opinions.

[redzook]

As has been said you haven't provided enough info.

cool can i ask what other info u/i need?

how long are your links in the lux?

[Wendle]

can you post the side elevation drawing again with the whole chassis showing, and the tyres, gound, and maybe even engine/gearbox roughly drawn in? that will make an educated guess of wether it will suqat or jack up under acceleration possible. allthough it does look already like it will jack up a bit.
the roll axis angle is pretty vicious due to the pitch of the lower links. you could move the lowers up on the axle a bit, losing a bit of seperation, which should be fine with 65hp what size tyres are going on this? (this will lower the ant-squat numbers as well)
the other way to flatten the roll axis would be to move the lower mounts further inboard on the chassis, but this won't be as beneficial, and you will probably run into issues with them colliding with the uppers.
it's good fun playing around with it and working it out anyway, just fawk around with the mounting positions till you are happy with the numbers. get that 4-link analyzer thingie too, it is pretty cool.

[1MadEngineer]

Why don't you just get Sam/Overkill to build it for you, does'nt he do all your stuff anyway?

[hottiemonster]

Why don't you just get Sam/Overkill to build it for you, does'nt he do all your stuff anyway?

lol, they look identical except for the colour

[stumped]

lol, they look identical except for the colour

except for the fact that one is leaf and one is custom coil. oh, one's running hilux diffs, the other is zook. one's a supercharged baleno engine, the other's an EFI sierra engine. one's series 3 rockhopper, one's series 1. so i guess the bodys are the same, and the tyres are the same

[stumped]

is this for a buggy tim, or for ur zook?

[DeWsE]

Why is the diff in the stock position. or is it not?

Don't you want longer wheel base, and don't you already have it with the current setup?

This is a good thread would love to know more

[redzook]

Why is the diff in the stock position. or is it not?

Don't you want longer wheel base, and don't you already have it with the current setup?

This is a good thread would love to know more

the diff has been moved back 3.6 more then a lwb with where my front diff is the wheel base will stand at 100.7

[redzook]

can you post the side elevation drawing again with the whole chassis showing, and the tyres, gound, and maybe even engine/gearbox roughly drawn in? that will make an educated guess of wether it will suqat or jack up under acceleration possible. allthough it does look already like it will jack up a bit.
the roll axis angle is pretty vicious due to the pitch of the lower links. you could move the lowers up on the axle a bit, losing a bit of seperation, which should be fine with 65hp what size tyres are going on this? (this will lower the ant-squat numbers as well)
the other way to flatten the roll axis would be to move the lower mounts further inboard on the chassis, but this won't be as beneficial, and you will probably run into issues with them colliding with the uppers.
it's good fun playing around with it and working it out anyway, just fawk around with the mounting positions till you are happy with the numbers. get that 4-link analyzer thingie too, it is pretty cool.

cool ill work on the chassis with a motor an gearbox later this arvo when i get home from work

can some 1 explain to me what the roll axis is?

yeh i could move the lower links to the top of the diff it would get me a bit more clearance to

dont know what size tires yet 35's maybe 37's

cant move the lowers in any more as tcase/driveshaft will be in the way

keep the help coming [/b]

[Wendle]

cool ill work on the chassis with a motor an gearbox later this arvo when i get home from work

can some 1 explain to me what the roll axis is?

yeh i could move the lower links to the top of the diff it would get me a bit more clearance to

dont know what size tires yet 35's maybe 37's

cant move the lowers in any more as tcase/driveshaft will be in the way

keep the help coming [/b]

your roll axis is an imaginary line that runs front to back. it is the hinge pivot that the axle swings around (for want of a better description) if it is horizontal you have no roll steer. if it is higher at the front (like yours will be) you get roll oversteer (common in lifted 4x4's) if it is higher at the rear you get roll understeer. with the setup you are contemplating the roll axis will be a line drawn from the imaginary point where the lower links would intersect at the front of the vehicle (if projected forwards) to the point where the uppers would intersect (if projected rearwards). kinda hard to describe, but i hope that makes sense.
your setup, i think, will behave much nicer, and be more fun to drive, if you could maybe lift the lowers up 50mm on the axle, and maybe lift the uppers some as well. getting the links flatter and slightly closer to parallel, will move the instant centre forward and down, lowering your anti-squat % as well as flattening the roll axis, which is quite steep.
just play around with it and see what you can physically fit in there and get to work. what you have drawn there is nearly identical to what i run, except mine is scaled up a bit in size and has less ride height. it works well if you can make it fit without compromising too much.

congratulations on starting the first real technical thread that has been on outerlimits for a very long time

[Bush65]

If you download the analyser you will find out what info you need and it will answer most of your questions.

Including what you have provided, you need:
Heights from ground to the ends of the links.
The height to the centre of gravity (you will have to make an informed best guess unless you are capable of taking the needed measurements at aweighbridge).
The wheelbase.

(1) The height of the centre of gravity affects how much the load on the suspension changes during acceleration/braking.

(2) The traction force (between tyres and ground) is transferred through the links from the axle to the chassis. The rear lower link pushes upwards and forward against the chassis during acceleration. How much up depends upon the slope from the mount at the axle to the mount at the chassis. The rear lower links, pull the chassis (how much up/down again depends upon the slope).

If the combined upward forces from the links at (2) exactly balances the load change at (1) the load carried by the springs wont change therfore the vehicle wont squat or lift (this is called 100% antisquat). If the combined upward forces from the links at (2) is greater than the load change at (1) (from too steep an angle of the lower links) the load on the spings is reduced and so the springs lift the rear (antisquat is more than 100%).

In solving both the weight transfer (1) and the link forces (2), the weight and acceleration are required, but these are cancelled out when calculating the antisquat. It is usual to use a graphical method to determin the antisquat.

There are 3 roll axii. Front axle, rear axle and body.
Slope of the rear roll axis affects bump steer. Slope up toward front results in understeer, down results in oversteer and level is none).
Front bump steer is not so important.

The rear roll centre is the point where the rear roll axis intersects a vertical plane through the rear axle. Similar for the front roll centre.

The line connecting the rear and front roll centres is the roll axis for the body. If the unsprung centre of gravity is above this roll axis the body will flop over on cross slopes/ highway cornering. A high roll centre (closer to c.o.g.) is benificial.

[redzook]

well ive drew up another one its lost abit of quality since i made it smaller.

and if i have understood what the roll axis is (thanks wendle) i think i have got it alot flatter(just higher at the front)

i also THINK it will have around 100% AntiSquat but i should be able to make it less then that buy just moving the upper links at the chassis end higher?

so as it stands the
lowerlinks are 38.6"
lowerlinks are 33.2"
Vseperation at the diff is 8"
Vseperation at the diff is 4.1"

tell me what u think

btw the tires are 35's

[Bush65]

Redzook,
From a glance, it looks like your antisquat is well under 100%.

Re roll axis, this is determined graphically by drawing a line between 2 points for the suspension that stay fixed on the vehicle centreline when the axle articulates.

For a 4 link setup like yours:
In plan view (looking from above), project the upper links to their intersection (above the axle in your case). This intersection is 1st point.
In plan view, project the lower links to their intersection (somewhere way in front of the vehicle in your case). This intersection is 2nd point.
Project both points to the elevation (side view).
Draw a line that connects both points in the elevation. This line is the roll axis.

Adjust the horizontal separation of the lower links at the chassis until the roll axis is flat. This is the advantage of this type of double triangulated 4 link setup (also known as james link, after desertoy on pirate who was first to use it).

With lower (or upper) links that are parallel (in plan view) the intersection point is at infinity. In this case draw the roll axis (in elevation) through the intersection of the upper links, but parallel to the lower links.

With suspensions that have a panhard rod, 1 of the fixed points is on the panhard rod at the centreline of the vehicle.

With A frame (such as rear upper of rangie), 1 of the fixed points is at the pivot at the apex of the A frame.

[redzook]

Redzook,
From a glance, it looks like your antisquat is well under 100%.

Re roll axis, this is determined graphically by drawing a line between 2 points for the suspension that stay fixed on the vehicle centreline when the axle articulates.

For a 4 link setup like yours:
In plan view (looking from above), project the upper links to their intersection (above the axle in your case). This intersection is 1st point.
In plan view, project the lower links to their intersection (somewhere way in front of the vehicle in your case). This intersection is 2nd point.
Project both points to the elevation (side view).
Draw a line that connects both points in the elevation. This line is the roll axis.

yeh wendle explained what the roll axis is and if i read it right this is the roll axis?

it is alot flatter the the setup that i first posted

u still think its not flat enough?

[Bush65]

That last pic where you drew the projections of the links and the roll axis is more revealing. When I looked at the previous pic, I thought the intersection of the lower links would be further forward.

Your roll axis should be ok, but flatter is better providing you are not compromising something more important.

Now find the instant centre at the intersection of the upper and lower links in the elevation. Then draw a line from where the rear tyre toches the ground, through the instant centre, to a point above the front axle.

Compare the height of this line at the front axle to the height of your centre of gravity. If they are the same height you have 100% antisquat. If the height of this line at the front axle is 80% of the centre of gravity, you have 80% antisquat. 80% antisquat is a good amount to aim for.

[redzook]

Compare the height of this line at the front axle to the height of your centre of gravity. If they are the same height you have 100% antisquat. If the height of this line at the front axle is 80% of the centre of gravity, you have 80% antisquat. 80% antisquat is a good amount to aim for.

i knew how to get squat and anti squat

but i dunno where my COG is

id say it would be pretty close to 100% Anti Squat (as a guess id say the COG would be pretty close to where the line crosses through the front tire)
so if i just move the uppers higher on the chassis this should give me more squat.

im pretty happy with this setup just when i make it ill make the uppers adjustable.

can any one see anything wrong with it now?

[Wendle]

that looks good man, better than most. looks like your projected line to the instant centre is at about 950mm off the ground where it crosses the line of the front axle? compare that to a guess at the height of your centre of gravity (meaure the height to the top of your bellhousing, or water pump pulley, or something similar is as good a guess as any), i reckon you are looking at 85-90%, at a very rough guess.

[Bush65]

I would try and get the roll axis level.

Yours is a little up towards the front. This could be an advantage in some offroad situations, but will oversteer on the road (not as safe as neutral or slight understeer).

[Axel Von Gardan]

Hey,got any pictures of 4 links moded to MQ/MK Patrol?

[Spartacus]

is this what happens when the lowers arent triangulated?

http://www.tufftruck.com.au/gallery/v/2 ... hubby4.jpg

this is similar to the way i have to set mine up due to pinion and chassis
clearance.

is their anyway to counter rearsteer?