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I just skimmed through this thread 'cos i gotta go to work now so i appoligise if i'm repeating something here but sounds to me like simple case of centrifigal force, the same you experience when cornering and rounding a round-about.
The higher the mound, lower the dip, ect. the higher the cars COG the more pronounced this effect will be.
just a thought!!
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jeep97tj wrote:So no 1 else has this problem with air shocks? could it be because i have the air shocks sitting so low that there is not enough pressure in them?
When it happens the low side is just about fully compressed and the high side is nearly full extended, theses are with 16" shocks .
sounds like lots of anti-squat compounding the problem. i could easily be wrong though.
i run very little pressure in my shocks (about 85psi in the rear giving about 75mm bump travel) and don't have any torque lift. my crownwheel does spin backwards though, that helps..
With a 3 link (2 lowers, 1 upper) + panhard suspension, you can arrange the offset of the upper link to cancel the torque reaction.
The offset is related to the diff ratio.
The side to which the upper link is offset, depends whether the height of the chassis mount for the upper link is higher or lower than the height of the axle mount.
For the rear suspension the upper link is in tension, during acceleration.
If it is higher at the chassis mount, offset the upper link to the left, so that it is pulling the chassis down on that side.
If it is lower at the chassis, offset the upper link to the right, so that it is pushing the chassis up on that side.
With the front suspension, the upper link is in compression during acceleration (tension during braking, which is more important for front). So offset for torque reaction should be to right if chassis mount is higher.
Don't be to concerned about the offset v/s diff ratio, it is more important to get the side correct and angle correct.
Yer i tryed winching down and it did help a little but so does winching down the front.
This is a pic of how it is set up at the moment
The blue lines and the red dot are the current setup
The red lines and the blue dot are the purposed setup
The lower green dot is the current upper arm mount position
The lower is the purposed.
Now my Qs are
Is my drawing right, are all my lines in the right position?
Will moving my upper arm up only 2" bring my anti squat back to roughly 0%?
and lastly is this the best way to go, or can some one else see a better option, besides throwing it away and starting again?
Thanks Shane
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i would be moving them up even more if i was in your position. even if you have to put a bend in them to clear the fuel tank. that way you should be able to have it behaving relatively neutral through most of the droop travel.
damm i suck at this supension thing, i thought the point in which the line going from the front tyre met the cog was 0%
Who can tell me where 0% is on the pic. I want to mount the arms at 0% on a adj mount with say 4 holes below and 2 above.
100% is a neutral value. anything over 100% will lift under acceleration on level ground. anything under 100% will squat under acceleration on level ground. it's all a bit here and there though, as we are guessing our centre of gravity for the most part. and it all changes with wheel travel and incline anyway.
i can't get my head around 0% as a value, it might be mythical. both links being parallel to the ground and each other may give you 0%, as there is no calculable instant centre. but maybe not
my instant centre is out in front of the car and down near the ground, and still reads in at around 25%.
I reckon that 1000ft/lb of torque is wrong. V8 supercars don't even put out that much.
That is because they don't have the gearing of a 4x4. You can get unimogs with 2L engines that have 10000ft.lbs of torque.
I did realise that there may be a twisting force through the driveshafts which was large (1000ft/lb possible yeah) however that is only thanks to the gearing, the engines are not putting out that much at all (330Nm of my Patrol = 243ft/lb).
I wonder if this geared torque is actually applicable to the phenomenon or is it just the engine's torque output we should be considering. It's not like we are all of a sudden getting more torque or something for nothing... To do this, we are losing rotational velocity (RPM).
yer the fronts are 1" over and the rears are just full.
I dont understand how more oil would help, It may slow it down but will still torque over??
Isnt that like thinking stiffer shocks will hold u up on side slopes??
If you dont want to try adding more oil then you will have to cut your links off and start again......if it was me I would just add more oil and see what that does.
Try this....add an excessive amount of oil. Support the rig 2 inches below ride height, drop the gas, totally fill with oil until you carnt fit any more and then regas. The suspension will be as stiff as a mo fo. It will ride really rough and you wont get the torque lean.
I dont think your antisquat is causing your torque lean (it will still lean even if you had 0% AS). All your high AS will be doing will be causeing your rear suspension to unload when you apply the throttle which will lift the rear up and mean that the shocks will have a softer spring rate which means that your rig will torque lean more.
What you need is stiffer springs and to get this you need to add more oil.
Strange Rover wrote:
I dont think your antisquat is causing your torque lean (it will still lean even if you had 0% AS). All your high AS will be doing will be causeing your rear suspension to unload when you apply the throttle which will lift the rear up and mean that the shocks will have a softer spring rate which means that your rig will torque lean more.
What you need is stiffer springs and to get this you need to add more oil.
Sam
Yep I see what u are saying now
I have 4"-5" in the rear and about 3" in the front.
I reckon that 1000ft/lb of torque is wrong. V8 supercars don't even put out that much.
V8 supercars dont have 35:1 gear reduction in low range first gear
" If governments are involved in the covering up the knowledge of aliens, Then they are doing a much better job of it than they do of everything else "
Everyone has been talking about one side of Newtons equation (for every action there is an equal and opposite reaction), how about this for the other side. Would the tyre size have an effect on the amount of torque twist induced, as in the bigger the tyre the more pronounced the twisting moment force?
Trying to visualize it fom the oppsite perspective, the tyres turning a stationary driveshaft through the diff and inducing the axles to twist WRT the chassis, obviously it would be easier with large tyres, but more difficult with small wheels. In other words bigger tyres will induce more torque twist.
George Carlin, an American Comedian said; "Think of how stupid the average person is, and realise that half of them are stupider than that".
jeep97tj wrote:That would cause front to back twist loading up the arms and there mounts. The torque twist we are talking about is side to side.
Would also cause side-side twist along the driveshaft, which is braced at the far end by the (stationary) drivetrain, in the same manner as a twisting force along the driveshaft from the transmission would twist the diff/axle if the wheels were staionary (difference in perspective viewpoint) My point was would the tyre size affect the amount of torque twist?
Putting it another way, with two identical vehicles, one with 30's one with 44's stitting staionary with engine maitaining position (auto trans) on an uphill slant, will the 44's have more torque twist than the 30's??? My logic would say yes due to more torque along te driveshaft/axle to counter the larger tyre diameter. If the effect is produced "statically" it would also be apparent with changes in torque from accelleration/decelleration.
George Carlin, an American Comedian said; "Think of how stupid the average person is, and realise that half of them are stupider than that".
Just curious, are we taking the sprung COG to be level with the top bellhousing bolt. Seen a few threads in pirate and some people there have said that this is a good approximation. I spent my CAE tut drawing lines over you car this morning too
Layto....
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hotrod4x4 wrote:Damkia , i would imagine the weight of the 44's would help control the effects of torque twist , not make it worse
The weight of the tyres is unsprung weight, the torque twist exists in the interface between the sprung weight and the unsprung weight. The tyre weight is not really relevant.
A "left of field" factor could be the procession forces on the wheels when a wheel does leave the ground and spin up, and hit the ground and slow down. I would imagine that the forces could resolve detrimentally in some cases.
Edit (typo): Should read precession
Last edited by DamTriton on Tue May 02, 2006 11:24 pm, edited 1 time in total.
George Carlin, an American Comedian said; "Think of how stupid the average person is, and realise that half of them are stupider than that".
lay80n wrote:Just curious, are we taking the sprung COG to be level with the top bellhousing bolt. Seen a few threads in pirate and some people there have said that this is a good approximation.
Layto....
Yep
DAMKIA u have gone to far for me, I will just sit and listen now
hotrod4x4 wrote:Damkia , i would imagine the weight of the 44's would help control the effects of torque twist , not make it worse
The weight of the tyres is unsprung weight, the torque twist exists in the interface between the sprung weight and the unsprung weight. The tyre weight is not really relevant.
A "left of field" factor could be the procession forces on the wheels when a wheel does leave the ground and spin up, and hit the ground and slow down. I would imagine that the forces could resolve detrimentally in some cases.
Edit (typo): Should read precession
Exactly my opinion. Others will dissagree. Any excessive resultant anti/squat value will create an interuption in the torque load as soon as traction is broken. What I'm saying is that a high antisquat value is fine until a tyre slips. Once that tyre slips, the anti squat is neutralised causing the sprung weght of the vehicle to compress the suspension. This compression of suspension increases the contact pressure on the tyres resulting in more grip. Now this extra new found grip causes the suspension to load up again - but more aggressively this time. What you end up with is similar to a leaf spring vehicle wrappin/bouncing its rear end.
Actually....re-reading you post I see that you're getting at the decelleration forces of the tyre opposing the afformentioned resultant values and turning anti-squat into squat. Unless you're turning massive tyres with lots of weight, I wouldn't think the result would be significant. If so however, it only adds to the scenario that I have proposed.
So i changed my rear supension set up to less anti squat, It climbs so much better, befor i had to hit the steep climbs with a bit of speed so buy the time it started to hop i was at the top any way, now i can crawl all the way to the top
But im still geting the torque roll .
So my only option left is to add more oil??
I am thinking of filling the rears 1" over full of oil like the front??
What sort of oil level do others run there shocks at??
Thanks Shane
PS Red is befor, Blue is now
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jeep97tj wrote:But im still geting the torque roll .
So my only option left is to add more oil??
I am thinking of filling the rears 1" over full of oil like the front??
it should be less severe now than it was before, yeah?
no that you have isolated your issue, try adding a bit at a time, go 1" over take it for a quick spin on a known problem climb. if it still feels nasty keep adding a bit at a time untill you are happy with it.
each time you add oil you are going to be losing a part of your travel that the car is now trying to squat into, so play around with it and find a compromise that works for you.
the suspension under acceleration is now opposing the pinion trying to climb the crown wheel, so any increases you make to your spring rate now will have much bigger improvements to it's behaviour than they would have before.
so i appoligise if i'm repeating something here but sounds to me like simple case of centrifigal force, the same you experience when cornering and rounding a round-about..
