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Discussion Starter #1
Like many, I have been doing a lot of studying and learning of 4 link rear suspsensions and what makes them work. I intend to do my own 4 link soon.

But during a recent run, I noticed that some guys with revolver shackles had a tendancy to lift the nose easier on climbs than those without (all leaf sprung). And I got to thinking that perhaps the revolver shackle was making the antisquat number go through the roof as it opened up. (the setups and makes of the rigs were very similar, so I am somewhat ruling out higher centers of gravity and other differences).

But my problem is I'm not quite sure how to calculate the antisquat for a leaf sprung vehicle. (Yes, I have searched and read and haven't seemed to stumble upon that fact yet). Does this act like a converging link setup? If so, then a fairly arched spring would put the angle of the "converging link" scenario high and make the antisquat percentage pretty high. And the more you opened the revolver, the more that percentage would increase and effectively want to raise the nose (per previous discussions on this forum).

Does the collective agree? Anyone with a suggestion on calculating antisquat with leaf springs? Am I right in assuming they act like converging links?
 

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four_by_nut said:
Like many, I have been doing a lot of studying and learning of 4 link rear suspsensions and what makes them work. I intend to do my own 4 link soon.

But during a recent run, I noticed that some guys with revolver shackles had a tendancy to lift the nose easier on climbs than those without (all leaf sprung). And I got to thinking that perhaps the revolver shackle was making the antisquat number go through the roof as it opened up. (the setups and makes of the rigs were very similar, so I am somewhat ruling out higher centers of gravity and other differences).

But my problem is I'm not quite sure how to calculate the antisquat for a leaf sprung vehicle. (Yes, I have searched and read and haven't seemed to stumble upon that fact yet). Does this act like a converging link setup? If so, then a fairly arched spring would put the angle of the "converging link" scenario high and make the antisquat percentage pretty high. And the more you opened the revolver, the more that percentage would increase and effectively want to raise the nose (per previous discussions on this forum).

Does the collective agree? Anyone with a suggestion on calculating antisquat with leaf springs? Am I right in assuming they act like converging links?
Let me help you........those type of folding shackles suck. Hows that?

On to your next question. To find the antisquat of a leaf sprung vechicle here is what you do.

Use the equation DH/EL
D=Length of spring
H=COG Height
E=Height of the roll center @ the center of the axle
L=Wheelbase
 

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Also, to find the roll axis/rollcenter just draw a line that intersects both eyes of the spring in the side view.
 

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Re: Re: Antisquat Calculations and Revolver Shackles

PIG said:


Let me help you........those type of folding shackles suck. Hows that?


Hmmm yes but a lot of their problems can be sorted out by the use of centre limiting straps on both axles.

This doesnt help with an articulated senario but it definately helps in a straight climbing situation.
 

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Re: Re: Re: Antisquat Calculations and Revolver Shackles

gon2far said:

Hmmm yes but a lot of their problems can be sorted out by the use of centre limiting straps on both axles.
This doesnt help with an articulated senario but it definately helps in a straight climbing situation.
Oh chit.............. Please don't start the whole limitstrap bandaid fix thing to compensate for a chitty suspension set up.

Euros.....:rolleyes: ........................
 

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Bollocks ive got to leave the office now but:

Sorry Pig im not a euro im a brit

Yes Revolvers are a band aid suspension set up no way are they hard core.

However not everyone is a hard core fab artist!

If you are running Revolvers then centre limiting straps are a very usfull addition to life.


Now I wouldnt like to see what could be a deacent and interesting thread de-railed by the usual Revolvers arguments. The anti squat question gets masses of discussion time in relation to link suspensions but rarely seems to get considered in leaf sprung applications.

For a long while i have been thinking that the front half of a leaf spring acts as an (imperfect) radius bar and that increasing the arch of the spring ie. lift springs would increase the potential for anti squat problems. This would also add to wheel hop problems as the axle articulates and the angle of the spring from axle pad to spring eye increases.

What can be done about this sh!t.

Sorry if that doesnt all make sence its typed in a bit of a rush.


You can flame me but I wont Know it for another 10 hours:flipoff2:
 

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gon2far said:
Bollocks ive got to leave the office now but:

Sorry Pig im not a euro im a brit

Yes Revolvers are a band aid suspension set up no way are they hard core.

However not everyone is a hard core fab artist!

If you are running Revolvers then centre limiting straps are a very usfull addition to life.


Now I wouldnt like to see what could be a deacent and interesting thread de-railed by the usual Revolvers arguments. The anti squat question gets masses of discussion time in relation to link suspensions but rarely seems to get considered in leaf sprung applications.

For a long while i have been thinking that the front half of a leaf spring acts as an (imperfect) radius bar and that increasing the arch of the spring ie. lift springs would increase the potential for anti squat problems. This would also add to wheel hop problems as the axle articulates and the angle of the spring from axle pad to spring eye increases.

What can be done about this sh!t.

Sorry if that doesnt all make sence its typed in a bit of a rush.


You can flame me but I wont Know it for another 10 hours:flipoff2:
Dude, you are hilarious..............I was just trying to break your balls a little.
 

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Discussion Starter #8
PIG: Thanks for the info. I will definately file that one away in my archives.

And I notice, 144 views and only 2 people commenting. Hopefully my use of the term "Antisquat" didn't make people think "Oh chit.......another one of THOSE discussions."

I'm just wondering if anyone else has seen the revolver cause an additional problem with climbing inclines as I seem to have seen.
 

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Discussion Starter #9
Re: Re: Antisquat Calculations and Revolver Shackles

PIG said:


Let me help you........those type of folding shackles suck. Hows that?

On to your next question. To find the antisquat of a leaf sprung vechicle here is what you do.

Use the equation DH/EL
D=Length of spring
H=COG Height
E=Height of the roll center @ the center of the axle
L=Wheelbase
OK. So let's say I have 4" Superlift springs for a Wrangler (49" long??) with revolvers.

D=49"
H=32" (estimate)
E=4" (4" lift spring, where stockers are assumed flat)
L=95"

Then, AS=413% ?? Right? (I multiplied by 100% to get to that).

AND......if the revolver starts to open up, then the roll center increases. So if a revolver opens up 9", then the roll center is now at 13". Which makes for AS=127%??? Correct? Or is the roll center based on the spring eyes ONLY and not on the frame mount? If it is spring only, then the AS won't change as it opens up. Correct? But you are still at 413% AS!!!
 

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Re: Re: Re: Antisquat Calculations and Revolver Shackles

four_by_nut said:


OK. So let's say I have 4" Superlift springs for a Wrangler (49" long??) with revolvers.

D=49"
H=32" (estimate)
E=4" (4" lift spring, where stockers are assumed flat)
L=95"

Then, AS=413% ?? Right? (I multiplied by 100% to get to that).

AND......if the revolver starts to open up, then the roll center increases. So if a revolver opens up 9", then the roll center is now at 13". Which makes for AS=127%??? Correct? Or is the roll center based on the spring eyes ONLY and not on the frame mount? If it is spring only, then the AS won't change as it opens up. Correct? But you are still at 413% AS!!!
Try again dude....... E is measured from the ground.
 

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Re: Re: Re: Re: Antisquat Calculations and Revolver Shackles

PIG said:


Try again dude....... E is measured from the ground.
really?? I don't know much about this crap, and I know you do, so I'm just checking to make sure that's what you meant to say. the reason that doesn't make sense to me is that then the numbers would change based on what size tires you're running...:confused:
 

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Re: Re: Re: Re: Re: Antisquat Calculations and Revolver Shackles

BrettM said:


really?? I don't know much about this crap, and I know you do, so I'm just checking to make sure that's what you meant to say. the reason that doesn't make sense to me is that then the numbers would change based on what size tires you're running...:confused:
So does the COG..........see how that works?

DH/EL, think about it.
 

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Re: Re: Re: Antisquat Calculations and Revolver Shackles

four_by_nut said:


OK. So let's say I have 4" Superlift springs for a Wrangler (49" long??) with revolvers.

D=49"
H=32" (estimate)
E=4" (4" lift spring, where stockers are assumed flat)
L=95"

Then, AS=413% ?? Right? (I multiplied by 100% to get to that).
So you're saying on a stock leaf spring, E would equal 0 and the formula doesn't work because stockers just shouldn't worry about antisquat yet. And correct me if i'm wrong, but tire size does effect the percentage. Well from looking at the picture drawn up of the 4 link, tire size would matter in determining the instant center (may not be correct term, but point C2 if you saw the last AS post.)
 

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Discussion Starter #14
OK. So let's rework that.

Let's assume the following:

1) 4" Superlift springs in Wrangler length (D=49")
2) H is at 36" sitting on 38" tires
3) E is 18.5 (Tire radius loaded) + 4 (4" lift over flat stock) + 5 (spring eyes above main spring and spring perch and 1/2 of axle tube diameter) = 27.5"
4) L is 95" (Stock Wrangler)

AS for 4" springs = (49*36)/(27.5*95)*100%=68%
AS for stock springs = (49*36)/(23.5*95)*100%=79%

So.............the more arch, the lower the antisquat???

One comment on the tire diameter increase and CG relation. This shows that the CG is going to increase at the same rate as the roll center increases (1/2 the diameter increase). So the AS stays the same reguardless of the tire diameter increase. Right?

So are we getting anywhere?

Thanks for the clarity here. This really does help me to completely understand the relations involved.
 

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Re: Re: Re: Re: Antisquat Calculations and Revolver Shackles

PIG said:


Oh chit.............. Please don't start the whole limitstrap bandaid fix thing to compensate for a chitty suspension set up.

Euros.....:rolleyes: ........................
dude, i am running a springover with a dodgy ass wrap bar that is causing me to hop and bounce all over the place

what should i do to stay with leaf springs, and get less antisquat
any ideas?
 

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PIG said:


Dude, you are hilarious..............I was just trying to break your balls a little.
Cheers Pig I'll take that as a compliment then shall I:flipoff2:

"""""dude, i am running a springover with a dodgy ass wrap bar that is causing me to hop and bounce all over the place""""

BJ

Arn't you already running the centre limiting strap "band aid fix" and finding it a help in reducing axle hop?


I dont make any claim to be a whizz with the maths and a page full of figures turns my brain to soup but is four_by_nut correct when he says-

So.............the more arch, the lower the antisquat???

I would have thought the opposite (but I confess to not having done the maths). In a simplistic sort of way I would have thought-

The more arch in the spring the more axle hop problems caused by anti squat.

The flatter the spring the more axle hop problems caused by spring wrap.

Yes I know its very simplistic and a combination of the two things is going to be happening all the time.


:D
 

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ok so PIG how would I go about finding the COG height on my rig? Without having to roll it over anyway. (yeah I know about the camshaft centerline guesstimate rule thing)
 

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four_by_nut said:
OK. So let's rework that.

Let's assume the following:

1) 4" Superlift springs in Wrangler length (D=49")
2) H is at 36" sitting on 38" tires
3) E is 18.5 (Tire radius loaded) + 4 (4" lift over flat stock) + 5 (spring eyes above main spring and spring perch and 1/2 of axle tube diameter) = 27.5"
4) L is 95" (Stock Wrangler)

AS for 4" springs = (49*36)/(27.5*95)*100%=68%
AS for stock springs = (49*36)/(23.5*95)*100%=79%

So.............the more arch, the lower the antisquat???

One comment on the tire diameter increase and CG relation. This shows that the CG is going to increase at the same rate as the roll center increases (1/2 the diameter increase). So the AS stays the same reguardless of the tire diameter increase. Right?

So are we getting anywhere?

Thanks for the clarity here. This really does help me to completely understand the relations involved.

I hope you folks can help me (this topic is interesting, and I am never too old to learn something new)?

I imagine the equation quoted is from Milliken (what is the reference source)?

Did this equation come with any basis for application (initial design conditions)? What I am interested in is what the author assumes for the design basis and/or other conditions that must be met to apply the equation properly?

On the question of more arch providing more anti-squat? Given the equation, and only a change in spring arch with the spring eyes parallel to the ground, yes. This change placed into the equation assumes the shackle length is not lengthened to allow the longer spring to work, or the shackle is lengthened but the eye height is compensated for by raising the shackle mount to (re)level the rear spring eye. These are ideal restraints to allow the equation to remain valid (not very realistic).

Back to your question. Old 60's era drag racers employed high arch leaf packs to reduce the AS% (they also leveled the spring eyes by raising the front end an equal amount -- the early high boy Gasser look demanded by factory mount rule restraints). When they started to rake the chassis for aerodynamic efficiency they had to learn better ways to get a leaf to hook up (one reason why I ask the initial conditions demanded for using the equation). The same sort of rules regulating leaf mount changes in Modified Stock crawling competition make this topic a worthwhile exploration.

Oh, and a change in tire size will slightly change the AS produced by the equation (a small decrease in AS for an increase in tire height, and the resulting increase in CG height). Spreadsheet the equation and play around some to search the results of changing one or another factor. This makes it easy to plug in the respective increase in H&E for a larger tire, and watch the resulting change.

Leafs may suck, and revolvers may suck, but some competitors are limited to leafs, so is it preferred to dismiss leaf design questions because the basic design limitations (well ;) ) suck ?

Happy Trails!
 
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