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Discussion Starter #1
Hey all,

I posted this in the desert section and got nothing

Can someone explain whats going on with TrophyTruck suspension when they accelerate hard on asphalt, the rear squats but also leans to the right side with the front left wheel and chassis lifting quite a bit.

Is it a combination of low antisquat and torque roll?

cheers
 

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Discussion Starter #3
Answered in the other section.
Thanks Frank,

reason I ask, Is im currently building my Land Rover 110. I have re linked the rear. I set my AS to 50% and am a little concerned about some potential off roading situations. Like steep climb with a step up. Just wondering if it will be inclinded to unload and lift the front left.

I know I only have 1/10th the Hp of those TT but at 65-1 low there will be some torque there.
 

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this place is really dead hey...... I remeber a time when this would have had 3 pages of flaming within 24hrs :flipoff2:

btw how do you post pics these days? still have to pay? Fuck that! after 3 years of not being able to log in, no response from multiple contacts to admin, creating new account etc, im not risking the dough for the sounds of silence....
 

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04 Wrangler Unlimited, 67 F100
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this place is really dead hey...... I remeber a time when this would have had 3 pages of flaming within 24hrs :flipoff2:

btw how do you post pics these days? still have to pay? Fuck that! after 3 years of not being able to log in, no response from multiple contacts to admin, creating new account etc, im not risking the dough for the sounds of silence....
The question was answered. :homer: Do you want 3 pages of duh? That felt like an old-school pirate answer so why not throw in some black text?

When the new software rolls out later this month photograph hosting is supposed to be free.
 

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this place is really dead hey...... I remeber a time when this would have had 3 pages of flaming within 24hrs :flipoff2:

btw how do you post pics these days? still have to pay? Fuck that! after 3 years of not being able to log in, no response from multiple contacts to admin, creating new account etc, im not risking the dough for the sounds of silence....
try doing a regular reply instead of a quick reply, see if the attachment paperclip is there.

shortly pictures will all be free, but please respond if you are able to upload a picture now

i'm curious
 

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Discussion Starter #7
try doing a regular reply instead of a quick reply, see if the attachment paperclip is there.

shortly pictures will all be free, but please respond if you are able to upload a picture now

i'm curious
Yeah I tried the regular reply, if i scroll right down, bottom left is a box with can and can nots. I can NOT post attachments.

I have instagram but im not here to get more followers.

ITs a LR 110, will be on 33s for DD and 35 for play. 110" WB, built LR axles and housings front and rear. New fabbed Radius arms +12" long over stock up front. They will be bored for Nissan Patrol/Toy Crusier axle bushes (specificly Superpro Polyelast hybrid bushes) Long arm re link rear. They are stock linked, wishbone upper, I stuck with a wishbone design , re using an extended ball joint (higher RC) due to chassis width/triangulation. I put as much triangulation on the lowers as possible (from frame to axle flange). Has a crappy 2.8 TD but that will stay because money. LT230 t/case with either +30% or +49% low range gear set (I have both) with a centre ATB diff. Not wild by any means due to being road legal down here and we have many regs.

cheers
 

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Discussion Starter #8
The question was answered. :homer: Do you want 3 pages of duh? That felt like an old-school pirate answer so why not throw in some black text?

When the new software rolls out later this month photograph hosting is supposed to be free.
Slow down there buckeroo....

The original question was answered (thanks). But no discussion of low AS in relation to trail rig and specificly steep stepped climbs and front ends (left side more so) unloading...

fuck your black txt
 

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Another factor with tire lifting is the fact that with 26 inches up front and 30+ in the back, sway bars don't have much effect. Bars small enough in diameter to survive 45 degrees of twist will not have much anti sway force around ride height. People figure that with so much wheel travel, there is no chance one side will be at full bump and the other at or near full droop. Well it does, as they quickly learn when their bars break. Next time you are at a big race, look around at contingency and you will see a lot of trucks with some kind of extension added to the sway arms to reduce angular twist in the bar. My own truck's front bar will twist 36 degrees at full articulation with 21 inches of front travel. For comparison, a stiff bar on a sporty road car is designed to move 5 to 7 degrees at 50% yield stress. I calculated the bar diameter needed to survive in my case and found 50% stress was only 3/4 inch dia, not enough sway bar to do anything. So I gambled and went with a 1.0 inch bar, which will hit 80% of it's 160,000 psi yield strength. So far so good, so maybe it hasn't fully crossed up yet, or it's fatigue life is nearly used up, or maybe the bar was just conservatively rated. I figured it's life would be short, so I had 4 made at the same time.
 

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For rock crawling, people around here have said 50% AS or less is best. On rocks and roots, you want minimum jacking or lifting of the back end, as that shifts weight forward and reduces traction. Search general 4x4 for anti squat and you will hit the mother load. Getting under 50% is hard though, as the upper link mount at the frame needs to be so high that you risk the instant center of axle swing flipping to behind the axle. That causes a big change in wheelbase through the stroke, lengthening at bump. This causes a strange pushing sensation when the suspension strokes under power, like you are being bumped from behind by another truck.

Edit: the first time I said the wheelbase shortens at bump when the IS is behind the axle. It actually lengthens, which forces the truck forward like a bump from behind.
 

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Discussion Starter #11
For rock crawling, people around here have said 50% AS or less is best. On rocks and roots, you want minimum jacking or lifting of the back end, as that shifts weight forward and reduces traction. Search general 4x4 for anti squat and you will hit the mother load. Getting under 50% is hard though, as the upper link mount at the frame needs to be so high that you risk the instant center of axle swing flipping to behind the axle. That causes the wheelbase to shorten at bump, causing a strange pushing sensation when the suspension strokes under power, like you are being bumped from behind by another truck.
I will probably run a rear sway bar, but as the front is based off stock radius arms (only longer) it basically is already a sway bar. Ill just try and match the rear to front for roll stiffness.

I wont have near that travel. Coil springs and 12"shocks are my limit.

Ill have to do the dig up again, I remember the likes of "Bigger Valves, Triadged, GOS, StrangeRover etc back in the day.

regarding the sway bar info you talked about, To me its more of a chassis reaction that im seeing and hearing about. I used the TT as an example because most people have seen videos of it and it paints a picture, but I imagine thats where the similarites stop. Im concerned about a step up on a climb, and instead of the front starting to climb that step, the chassis lifts at front, with some twist down to the right, unloading the front left wheel. I think the direction of twist is torqu reaction to the gears in axles etc. But why the lift instead of forward?

Can you describe more the "instant centre of axle flipping behind it" Im not picturing that?

I can say, cycling my suspension on the link calc, that it looks like my WB gets longer in bump, that being due to the +5 degrees axle roll axis I have at ride height (yes yes I know, think of all the burning nuns )
 

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The instant center is an imaginary point in space, the center of the arc the axle swings in through it's motion. It is found by drawing lines through the links and projecting them forward. Where the lines meet is the center of the arc of motion. But the lines move as the axle moves, so the arc center is constantly changing. It is called the 'instant' center because it is only the center of the arc for the particular moment you are looking at or sketching. Normally the lines converge in front of the axle. When the upper link frame mount is raised, usually to reduce anti squat, it is possible for the imaginary lines of the links to meet behind the axle. The arc of movement may be a mirror image of what you expect or it may move in an S curve. I made a sketch on the back of an envelop to illustrate. We will be able to post pictures soon.

Wheelbase is longest where the links are closest to horizontal, which is typically ride height. My wheelbase loses an inch at bump and 2 inches at droop, and that is with an instant center probably 8 feet in front of the axle. But with a reversed IS, the effective arc radius may much shorter, meaning the change in wheelbase is greater. You can take out your springs and move it through the range, mapping the axle track on cardboard or use a plumb bob to make marks on the floor.

Another thing to keep in mind is a TT is a very rigid structure, triangulated in every way. There is no chassis flex like a production vehicle. If a regular fullsize pickup with 5 or 6 inches of wheel travel was as rigid, it would lift tires off the ground on the slightest rough terrain. It's the first thing people notice when they cage a truck - they need full lockers front and rear or the tires off the ground mean no forward motion.
 

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Discussion Starter #13
The instant center is an imaginary point in space, the center of the arc the axle swings in through it's motion. It is found by drawing lines through the links and projecting them forward. Where the lines meet is the center of the arc of motion. But the lines move as the axle moves, so the arc center is constantly changing. It is called the 'instant' center because it is only the center of the arc for the particular moment you are looking at or sketching. Normally the lines converge in front of the axle. When the upper link frame mount is raised, usually to reduce anti squat, it is possible for the imaginary lines of the links to meet behind the axle. The arc of movement may be a mirror image of what you expect or it may move in an S curve. I made a sketch on the back of an envelop to illustrate. We will be able to post pictures soon.

Wheelbase is longest where the links are closest to horizontal, which is typically ride height. My wheelbase loses an inch at bump and 2 inches at droop, and that is with an instant center probably 8 feet in front of the axle. But with a reversed IS, the effective arc radius may much shorter, meaning the change in wheelbase is greater. You can take out your springs and move it through the range, mapping the axle track on cardboard or use a plumb bob to make marks on the floor.


Another thing to keep in mind is a TT is a very rigid structure, triangulated in every way. There is no chassis flex like a production vehicle. If a regular fullsize pickup with 5 or 6 inches of wheel travel was as rigid, it would lift tires off the ground on the slightest rough terrain. It's the first thing people notice when they cage a truck - they need full lockers front and rear or the tires off the ground mean no forward motion.
First off, thanks for your replies.

I always get IC and convergence point mixed up.

As for my rear IC, at ride it is well off forward into the ether somewhere. At full bump it is just in front of front axle centre line. Now at full droop, the Link calc has it going backwards for some reason???

BTW, how low are the RCs on TTs? are we taking axle centre line, lower?

My rear roll centre height is 23" on a 33" tyre
 

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Discussion Starter #14
As far as the wheelbase lengthening during bump, I thought that would be somewhat desirable on the rear.

Maybe it is if the IC doesnt swing but only by the links arcs?

As you are traveling forward, especially at speed, the force of a bump is not only upward but rearward. So if the axle travels up and rearward it is following the path of force somewhat. Im pretty sure its what go fast Ultra 4 solid front axle rigs try and design in and its harder in the front as they are leading arms, not trailing (btw all links that mount to the chassis forward of the axle are trailing, for some reason Pirate decided that only links with coil overs etc mounted to them were trailing arms. :flipoff2:)

So why does the IC flip? whats going on there?
 

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Leaf springs move the axle backward when they flatten in bump, so it's not automatically a bad thing. I may not be able to explain the IC without a sketch. Hopefully picture posting will be coming soon.
 

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Discussion Starter #16
try doing a regular reply instead of a quick reply, see if the attachment paperclip is there.

shortly pictures will all be free, but please respond if you are able to upload a picture now

i'm curious
Well I pulled the trigger and went ahead with my design. I got my uppers and cross member fab'd and burnt in.

IMG_2363.jpeg
 
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