NS Dev
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 posted on 11/9/06 at 09:19 AM |
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Anti-Squat
Saw mention of much debate over anti-squat on another thread.......
so thought I would put the cat among the pigeons and start a fresh debate!!
What is the concensus here (for those with "unusual" suspensions as the std book version doesn't allow for much alteration!)
I will voice my opinion later
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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Volvorsport
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| posted on 11/9/06 at 09:47 AM |
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yes , i made mine so that it had some .
www.dbsmotorsport.co.uk
getting dirty under a bus
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Syd Bridge
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| posted on 11/9/06 at 10:35 AM |
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quote:
Originally posted by NS Dev
Saw mention of much debate over anti-squat on another thread.......
Hey Nat,
WHich thread, where, why was I not told????
Regards,
Syd. 
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TimC
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| posted on 11/9/06 at 11:48 AM |
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Matt @ Procomp's your man on this subject!
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NS Dev
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| posted on 11/9/06 at 12:03 PM |
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As far as I can tell with my limited knowledge, anti-squat is a very difficult subject.
Simple theory dictates that the more you have, the more directly vehicle weight is transferred to tyres to create traction.
Conversely, experience in very traction-limited conditions (grasstrack) where a race is usually won or lost in the drag for the first corner,
PRO-squat geometry has worked very well for me!!!
I have found that the benefit of this is that the rear suspension is wound up by the initial start, cushioning the initial shock to the tyres, then
releasing that shock progressively as the dampers allow the springs to unwind again.
maybe this is not a scientific solution but it seems to help get off the line exceptionally well. With anti-squat, the shock into the tyres can
actually be felt on launch, followed by soaring wheelspin which requires throttle feathering to limit.
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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procomp
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| posted on 11/9/06 at 01:32 PM |
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Hi right as you know i use geometry witch works verry verry well IE 200bhp locost style will do verry quick o-60mph and indesantly quick o-64 feet
time with is capable of leaving two black lines for 22.5 feet if you use to manny revs of the line all with a open diff and a driver with a sensative
right foot.
Know the question is why dose that geometry work and is it actually antisquat. Dose anti squat exist.
This is a can of worms and should be an enjoyabe debate.
cheers matt
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Syd Bridge
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| posted on 11/9/06 at 02:09 PM |
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No no no no no! I will not get drawn in to this.
You debate all you like, I'm off!
Cheers,
Syd.
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JoelP
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| posted on 11/9/06 at 02:30 PM |
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i believe that cars car be designed so that they dont dive or squat, but its debatable how useful this is for any given application. For circuit
racing on tarmac in a light car id not bother myself. Drag racing may be a different issue.
[Edited on 11/9/06 by JoelP]
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C10CoryM
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| posted on 11/9/06 at 04:44 PM |
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Well lets looks at drag racing where the launch is all important.
Years ago when the gasser cars were around they realized that weight transfer onto the rear wheels gave them more traction. Weight transfer is
visibly seen in squat so they thought the more squat the better. Problem is after about 60ft the car unsquats suddenly and unloads the rear tires.
My camaro was like that, would come out of the hole good then blaze the tires at the 60ft mark (not a drag car). It is incredibly difficult to launch
a car like that.
So, later on someone figured out that the whole opposite/equal reaction thing applies to cars. If you try to lift the back of the car up using the
power of the engine, the tires are going to get forced into the ground just as hard. Add weight transfer to it and you get some major loading of the
tires. Because you are using the engines torque to gain traction it is a fairly smooth loss of traction as you get going faster and unload a bit.
Pro drag cars generally run at LEAST 100% antisquat. If you watch them launch from behind you can usually watch the back end come up.
If you want an example you can take a hotchkis (leaf sprung) camaro into the 9s with stock rear suspension and Cal-tracs and DOT slicks. Try doing
that with no antisquat.
So why dont road race cars use antisquat? Well they do.... when they can. Not many modern road cars with solid rear axles anymore and IRS
won't gain much antisquat. The 4th gen camaro with solid rear had a torque arm for anti-squat. The torque arm is about the simplest way to
think of anti-squat. The shorter the arm, the further away from the COG and the more antisquat you get (also from leverage). Problem is you get
brake hop if its too short.
The book 4 link (+ panhard) actually does allow for some antisquat. If you angle the arms up a bit and raise the sideview IC you are gaining
antisquat. Simplest way to think of how that works is to think the tires move forward first and try to drive under the car lifting the back. Also
the twisting axle is trying to push against the lower link will lift the back if the lower link is pointing upwards. Anytime the tires are lifting
the back of the car up, the tires are getting pushed into the ground just as hard. Add to it the fact you are hard on the gas and are transfering
weight to the rear and you can see why it works.
For loose surface racing I have no idea. I would guess its very likely that other factors are more important.
If Ive missed of screwed anything up let me know. Id hate to lead people the wrong way.
Cheers.
"Our watchword evermore shall be: The Maple Leaf Forever!"
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Gav
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| posted on 11/9/06 at 08:32 PM |
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quote:
Originally posted by C10CoryM
If you watch them launch from behind you can usually watch the back end come up.
No that i know, however from simple observation i thought that was due to the rapid acceleration of the tyres which increases the tyres diameter hence
the the backend raising?
[Edited on 11/9/06 by Gav]
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C10CoryM
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| posted on 11/9/06 at 08:45 PM |
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quote:
Originally posted by Gav
quote:
Originally posted by C10CoryM
If you watch them launch from behind you can usually watch the back end come up.
No that i know, however from simple observation i thought that was due to the rapid acceleration of the tyres which increases the tyres diameter hence
the the backend raising?
[Edited on 11/9/06 by Gav]
I used to have a great rear view slow-motion shot of a rail car launching. You can watch the tires wrinkle and get shorter while the chassis is
raising up. I will try and find it again. Its pretty cool to see. But yes, as the car goes down the track the bias ply slicks get taller just like
when they do the burnouts.
Cheers.
"Our watchword evermore shall be: The Maple Leaf Forever!"
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procomp
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| posted on 12/9/06 at 07:05 AM |
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HI right now what C10CORYm is describing is exactly what i have and what i have been thinking for some time one interesting thing is are you
measuring 100% at the point of the COG along the wheelbace or at the front axle center as i have seen both used to calculate the % of squat.
Inorder to take the best advantage of this we have had to spend a lot of time developing dampers to work with the coilover spring setup at the rear
aswell.
And also some people say that it really only works whilst getting of the line i find that by adding a bit more to the inside of the car perdomently
the right for the uk circuits this helps keep the wheel on the ground and resist axle lift due to torque out of the tighter corners. And when wet it
dose seem to be able to get the torque down to the ground better than the other cars on the grid wich are running no antisquat but they are also of a
shorter wheelbase.
cheers matt
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NS Dev
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| posted on 12/9/06 at 09:07 AM |
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quote:
Originally posted by C10CoryM
Well lets looks at drag racing where the launch is all important.
Years ago when the gasser cars were around they realized that weight transfer onto the rear wheels gave them more traction. Weight transfer is
visibly seen in squat so they thought the more squat the better. Problem is after about 60ft the car unsquats suddenly and unloads the rear tires.
My camaro was like that, would come out of the hole good then blaze the tires at the 60ft mark (not a drag car). It is incredibly difficult to launch
a car like that.
So, later on someone figured out that the whole opposite/equal reaction thing applies to cars. If you try to lift the back of the car up using the
power of the engine, the tires are going to get forced into the ground just as hard. Add weight transfer to it and you get some major loading of the
tires. Because you are using the engines torque to gain traction it is a fairly smooth loss of traction as you get going faster and unload a bit.
Pro drag cars generally run at LEAST 100% antisquat. If you watch them launch from behind you can usually watch the back end come up.
If you want an example you can take a hotchkis (leaf sprung) camaro into the 9s with stock rear suspension and Cal-tracs and DOT slicks. Try doing
that with no antisquat.
So why dont road race cars use antisquat? Well they do.... when they can. Not many modern road cars with solid rear axles anymore and IRS
won't gain much antisquat. The 4th gen camaro with solid rear had a torque arm for anti-squat. The torque arm is about the simplest way to
think of anti-squat. The shorter the arm, the further away from the COG and the more antisquat you get (also from leverage). Problem is you get
brake hop if its too short.
The book 4 link (+ panhard) actually does allow for some antisquat. If you angle the arms up a bit and raise the sideview IC you are gaining
antisquat. Simplest way to think of how that works is to think the tires move forward first and try to drive under the car lifting the back. Also
the twisting axle is trying to push against the lower link will lift the back if the lower link is pointing upwards. Anytime the tires are lifting
the back of the car up, the tires are getting pushed into the ground just as hard. Add to it the fact you are hard on the gas and are transfering
weight to the rear and you can see why it works.
For loose surface racing I have no idea. I would guess its very likely that other factors are more important.
If Ive missed of screwed anything up let me know. Id hate to lead people the wrong way.
Cheers.
Certainly all sounds like what I understood.
Hadn't thought about the issue with the loss of traction following squat with the "old" type of pro-squat setup.
Can say that on the loose both pro and anti-squat have worked very well, so not an easy answer, certainly not "right and wrong" situation.
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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MikeRJ
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| posted on 12/9/06 at 09:46 AM |
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Surely the only point at which the tyres are being 'pushed' into the ground is during the fractions of a second that the rear end is
actualy moving up (i.e. the reaction force pushes the tyres down).
Once the chassis is raised, I can't see that there will be any extra force pushing down on the tyres. In fact raising the rear end up would
tend to transfer weight to the front, assuming that the cars COG is somwhere above the axle line.
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Volvorsport
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| posted on 12/9/06 at 09:53 AM |
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a trick also used by drag racers - they load the suspension up on one side so if they have an open diff - on launch , they have equal weight on either
tyre , giving really good traction .
so that backs up the unequal side to side setup .
also raising the cog gives more weight transfer to the rear on acceleration , another reason why drag cars sit the arse right up in the air .
[Edited on 12/9/06 by Volvorsport]
www.dbsmotorsport.co.uk
getting dirty under a bus
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NS Dev
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| posted on 12/9/06 at 10:21 AM |
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quote:
Originally posted by MikeRJ
Surely the only point at which the tyres are being 'pushed' into the ground is during the fractions of a second that the rear end is
actualy moving up (i.e. the reaction force pushes the tyres down).
Once the chassis is raised, I can't see that there will be any extra force pushing down on the tyres. In fact raising the rear end up would
tend to transfer weight to the front, assuming that the cars COG is somwhere above the axle line.
good point, hadn't thought of it like that!
at least an interesting debate has started, and for once its one that I don't have a definite "answer" on!
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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procomp
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| posted on 12/9/06 at 11:45 AM |
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Hi yes it should only be acting on the rear whilst momentry in squat but it dose allow the car to leave two black lines equal for a considerable
distance. shurly if it is only momentry it wouldent leave such long lines for such a length.
funnily enough the last time i demonstrated this to a driver was at donnington so i wonder if the two black lines are stil there in the padock as you
go in on the white ish coloured concrete in front of you. If it is there i will show you on sunday Nat.
cheers matt
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NS Dev
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| posted on 12/9/06 at 11:58 AM |
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not sure Matt.
Certainly what you describe will no doubt aid traction exactly as you suggest.
Really difficult to cut to the exact science if it all though.
On the grasser, the long travel means that the shock loading on the tyre is absorbed by the springs compressing, then the dampers allow a controlled
release of that energy, which minimises wheelspin.
Obviously the grasser is mid-rear engined, but (with pro-squat geometry)we can make 0-60mph in 4.5 secs uphill on wet mud, which says something for
traction.............. on the flip side, so can another club members car with anti-squat, so who knows!!!
On tarmac, you have to be REALLY brutal with the car to get any wheelspin at all, normally it just lifts the front clean off the ground and goes off
like a rocket, but never have timed it on hard surfaces. Took it on the kart track at stretton just outside leicester and from a standing start it hit
the limiter in 2nd, which is 72mph, on the straight where the prokarts hit 50mph or so after exiting the corner!!! lol
also know it hits the limiter in 2nd (again 72mph ) in 2 streetlights distance down the road, but again no idea how far that is (and less said about
that the better!!! lol)
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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C10CoryM
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| posted on 12/9/06 at 03:51 PM |
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quote:
Originally posted by MikeRJ
Surely the only point at which the tyres are being 'pushed' into the ground is during the fractions of a second that the rear end is
actualy moving up (i.e. the reaction force pushes the tyres down).
Once the chassis is raised, I can't see that there will be any extra force pushing down on the tyres. In fact raising the rear end up would
tend to transfer weight to the front, assuming that the cars COG is somwhere above the axle line.
The antisquat will come into play anytime there is acceleration. Much more noticable at low speed/high torque situations of course. Anytime the axle
is trying to twist from acceleration it will also be trying to lift the rear of the car. It is not the weight transfer that gives antisquat, it is
the twisting of the axle.
That being said, at 100mph with only a couple hundred hp you won't notice any effects.
Antisquat will also not max out until you lift the front wheels, run out of torque, or lose tire grip. For drag racing the ideal launch is the front
tires barely in contact with the track. This means that 100% of the cars weight is on the drivewheels. Doesn't get much better than that so
long as it stays straight .
For autoX antisquat is a great thing. Our local autoX used to be low speed, tight courses due to lack of space. Top of 2nd gear max speed. At such
low speeds it was all about getting on the gas out of the corner. Especially if you were dumb enough to try running a heavy V8 camaro(me!).
Antisquat will allow you to get on the gas a LOT harder in those situations. Low speed/high torque and you bet its noticable.
Again, I really doubt there is enough traction in loose surface racing for antisquat to be a major factor. The dirt oval track guys use antisquat
(pullbars) but they actually have pretty good traction on that packed clay.
No luck on the video. Ill keep looking.
Found a doodle here of the basis of 4link antisquat. I can look through my books for more pics if people need them.
I am no expert but living where HP and fuel are "cheap", cars are heavy and drag racing is god I can't help but pick up a thing or
two about traction .
Cheers.
"Our watchword evermore shall be: The Maple Leaf Forever!"
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BKLOCO
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| posted on 12/9/06 at 06:00 PM |
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quote:
Originally posted by MikeRJ
Surely the only point at which the tyres are being 'pushed' into the ground is during the fractions of a second that the rear end is
actualy moving up (i.e. the reaction force pushes the tyres down).
Also you would actually get the phenomenen known in skiing terms as "unweighting" at the point where the car reaches its topmost travel.
Thereby reducing the down force on the tyres.
Experience is what you get when you don't get what you want!!! 
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MikeR
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| posted on 12/9/06 at 06:20 PM |
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now thats a concept i understand - except there are two ways to do it in skiing.
Jump up (top most travel = lack of traction)
squat down (as you drop down, you actually reduce the weight on the skis during the drop down)
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Steve Morten
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| posted on 12/9/06 at 10:25 PM |
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I've spent the last year or so biulding anti-squat into my Sylva Striker for autotesting and it really does work. The article I found most
interesting is this one:
http://www.afcoracing.com/tech_pages/4link.shtml
On a 4 link axle if you slope the trailing arms up towards the front of the car then as the axle pushes forward, the arms will push down at the back
forcing the tyres into the ground. Just try holding a stick against the wall with your hand and pushing if you angle the stick up towards the wall
then your hand will go down.
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Steve Morten
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| posted on 12/9/06 at 11:04 PM |
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------------------------------------------------------
Surely the only point at which the tyres are being 'pushed' into the ground is during the fractions of a second that the rear end is
actualy moving up (i.e. the reaction force pushes the tyres down).
Once the chassis is raised, I can't see that there will be any extra force pushing down on the tyres. In fact raising the rear end up would tend
to transfer weight to the front, assuming that the cars COG is somwhere above the axle line.
------------------------------------------------------
The above isn't true. All the time you accelarate the c of g is trying to push the back of the car down, so the anti-squat can try and conteract
that and give the tyres more bite.
If you get to the point where the back of the car is raising then you've gone to far.
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MikeRJ
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| posted on 13/9/06 at 02:22 PM |
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quote:
Originally posted by Steve Morten
The above isn't true. All the time you accelarate the c of g is trying to push the back of the car down, so the anti-squat can try and conteract
that and give the tyres more bite.
Ok, look at it another way:
Anti-squat (and anti-dive) effectively increase suspension rate under acceleration (braking).
Unless you are driving on silky smooth tarmac, high suspension rates generaly do not give the best traction or braking. Accelerating out of a bend
and having the rear suspension stiffen itself up doesn't sound like a great idea.
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Steve Morten
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| posted on 13/9/06 at 05:01 PM |
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Mike,
You're quite right, it's all about compromise. If you didn't have suspension at all then you wouldn't need anti-squat but the
tyres wouldn't be in contact with the ground much.
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