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 Post Posted: Wed Feb 04, 2009 6:40 pm 
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Beretta wrote:
want-a-be wrote:
Beretta wrote:
John, You need to set your shocks some where in the middle of there travel.

My shocks are set to 16 1/2 inches at ride height now that has nothing to do with if the spring is compressed or not... O:)  I have 125lbs spring on my car now and they are not compressed at all if I let the suspension hang....


 How much does your car weigh in at?  How much of that is on the rear tires?

Don






Don, my car weighs 2135 race ready without me in it. With 1020 of that is in the rear...Why do you ask???


Hang on Barry, he's calculating  to compair your mentioned spring rate =;  =;  =;

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 Post Posted: Wed Feb 04, 2009 7:05 pm 
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Quote:
Don, my car weighs 2135 race ready without me in it.


That's just not fair!  =;


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 Post Posted: Wed Feb 04, 2009 7:09 pm 
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I was thinking your car was around that kind of weight,  and thought the 125# springs seemed a bit high for the weight.  course thats jmo.  When I was racing my car was a few hunderd pounds lighter and I was running 95# springs in the rear.  Chassis worked great.  I usualy run the 125-135 pound springs in car that weight about 2800-3000#s.

 I know they aren't the same.  But I know the Prostock guys were running 75# springs in the back and they have to weight in at 2200#s.

Don

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 Post Posted: Wed Feb 04, 2009 7:42 pm 
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Here's a hint. Static weight is a whole different ball of wax than dynamic weight.
Where does all that weight go when the front wheels are off the ground?  :-$

And what about rear wing?


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 Post Posted: Wed Feb 04, 2009 7:47 pm 
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To the back,...but if the chassis is working properly, the rear of the chassis should be separating.  Forcing the tires into the ground.

Don

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 Post Posted: Thu Feb 05, 2009 6:10 pm 
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Haven't visited this forum for a long time. This thread looked interesting, but I wonder which 4link program is being used. There's a free spreadsheet available at my site (Page 13). Of course, they should all give the same answer. It's high school algebra. I do notice, however, that few (if any) of the other spreadsheets allow the user to position the rear pivots in front of (or behind) the axle centerline.

In all this talk of the 100% antisquat line, some might have missed the fact that this is but one of an infinite number of constant percent antisquat lines. All of these lines intersect at the rear tire patch, so, in side view, they look much like a Japanese fan.

It's the percent antisquat that is important, not the location of the instant center (IC). There are practical limits, of course. You couldn't very well have the IC one inch in front of the rear axle centerline, for instance.

There are other practical limitations. If the upper and lower links are close together, in side view, the loads will be very high. And, if the rear locating points are very far from the housing, bracket strength becomes a consideration. Flexibility and bushing or Heim clearance can also affect the outcome. In other words, there's always room for common sense.

An asymmetrical adjustment should also be considered. There's no "law" saying that left and right link setups should be identical. The driveshaft torque is acting to unload the right rear and load the left. The link loads are proportional to the driveshaft torque. It makes perfect sense to use those link loads to cancel the effect of the driveshaft torque. This would mean a higher percentage antisquat on the right side than on the left, with the average at or about 100%.

Launch video can help in suspension setup, but the only accurate procedure is to use a traction dyno. More on this at my site.

Almost forgot: Since the front of the car will always rise on launch, a static antisquat value slightly over 100% will commonly "end up" at 100% as the link front mounting points come up with the nose of the car. This is probably nit-picking, but I've found that somebody's always bringing this up. Come to think of it, I've a spreadsheet at my site which calculates the optimum ratio of upper and lower link lengths to compensate for this effect.

http://home.earthlink.net/~whshope
over 130,000 visitors


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 Post Posted: Thu Feb 05, 2009 10:22 pm 
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BillyShope wrote:
Haven't visited this forum for a long time. This thread looked interesting, but I wonder which 4link program is being used. There's a free spreadsheet available at my site (Page 13). Of course, they should all give the same answer. It's high school algebra. I do notice, however, that few (if any) of the other spreadsheets allow the user to position the rear pivots in front of (or behind) the axle centerline.

In all this talk of the 100% antisquat line, some might have missed the fact that this is but one of an infinite number of constant percent antisquat lines. All of these lines intersect at the rear tire patch, so, in side view, they look much like a Japanese fan.

It's the percent antisquat that is important, not the location of the instant center (IC). There are practical limits, of course. You couldn't very well have the IC one inch in front of the rear axle centerline, for instance.

There are other practical limitations. If the upper and lower links are close together, in side view, the loads will be very high. And, if the rear locating points are very far from the housing, bracket strength becomes a consideration. Flexibility and bushing or Heim clearance can also affect the outcome. In other words, there's always room for common sense.

An asymmetrical adjustment should also be considered. There's no "law" saying that left and right link setups should be identical. The driveshaft torque is acting to unload the right rear and load the left. The link loads are proportional to the driveshaft torque. It makes perfect sense to use those link loads to cancel the effect of the driveshaft torque. This would mean a higher percentage antisquat on the right side than on the left, with the average at or about 100%.

Launch video can help in suspension setup, but the only accurate procedure is to use a traction dyno. More on this at my site.

Almost forgot: Since the front of the car will always rise on launch, a static antisquat value slightly over 100% will commonly "end up" at 100% as the link front mounting points come up with the nose of the car. This is probably nit-picking, but I've found that somebody's always bringing this up. Come to think of it, I've a spreadsheet at my site which calculates the optimum ratio of upper and lower link lengths to compensate for this effect.

http://home.earthlink.net/~whshope
over 130,000 visitors



Uuuhh oooo, who called the BIG DOG in here???? =;  =;  =;


 Hi Billy, funny, I was at the other site where Edvanced engines Ed had posted a long thread in the 4 link forum and I saw your inputs also.  A lot of this is all starting to sink in, in the mind of how it all works so to be able to think it thru and be able to make the best adj. possible to get the best results.  I know I have a long way to go with the tuning aspect, but I think I have a start on it better now than before.  I know you have a website, I need to go find it and read up on it, and that (fan explaination was perfect) =D>  =D>  =D>  it is sometimes hard to believe the I/C lifts up, up on an angle, and then forward in motion after the initial hit and the tires start to move, neet stuff and "johnny 5 wants more innnnnnnnnnput" =;  =;  =;   Thanks for your time here, much needed for me. ;-)

John

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 Post Posted: Fri Feb 06, 2009 6:48 am 
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This stuff is making my head spin ](*,)  ](*,)  #-o

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 Post Posted: Fri Feb 06, 2009 8:23 am 
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I have the utmost respect for Billy. If he says the chicken can pull the train hitch him up. If he says it's Christmas, hang up your sock.

He puts a book basis to what you know is going on in your car , if you pay attention to it. It's good to be reassured. Any time I disagreed with Billy, he always changed my mind. There may have been other factors that brought me to my first conclusion, but they affected the results not caused them.

I suggest everyone read his blog and see how the laws of Physics do agree with what your car tells you.

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 Post subject: reply
 Post Posted: Fri Feb 06, 2009 9:59 am 
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Beretta wrote:
This stuff is making my head spin ](*,)  ](*,)  #-o


Xanex, that's the ticket ;-)

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Last edited by Elkyman on Wed Feb 18, 2009 9:52 am, edited 1 time in total.

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 Post subject: 60's
 Post Posted: Fri Feb 06, 2009 9:59 am 
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Beretta wrote:
This stuff is making my head spin ](*,)  ](*,)  #-o


Barry what are your best 60 ftr's to date?????

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 Post subject: Re: 60's
 Post Posted: Fri Feb 06, 2009 10:26 am 
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Elkyman wrote:
Beretta wrote:
This stuff is making my head spin ](*,)  ](*,)  #-o


Barry what are your best 60 ftr's to date?????




1.200 with an old worn out set of Goodyears and that was it's 2nd pass with the car and never repeated it again O:)  O:)  O:) .....Now with the Hoosier's that are the wrong compound I guess it's never better than 1.23 =P~  =P~

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 Post subject: Re: 60's
 Post Posted: Fri Feb 06, 2009 10:53 am 
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Beretta wrote:
Elkyman wrote:
Beretta wrote:
This stuff is making my head spin ](*,)  ](*,)  #-o


Barry what are your best 60 ftr's to date?????




1.200 with an old worn out set of Goodyears and that was it's 2nd pass with the car and never repeated it again O:)  O:)  O:) .....Now with the Hoosier's that are the wrong compound I guess it's never better than 1.23 =P~  =P~


1.20's aren't bad at all, quit your complainin =;  =;  =;  how do you think I feel, 1.40 best :-  yeah, a heavy chassis, but man, 1.40 O:)  I would be happy to see low 1.30's with the bigger tires and 4 link setup, but who know's, it may be worse, or better, but that is the tuning to be done...

Doooooon't worry, beeeeeee happy =;  =;  =;

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 Post Posted: Sat Feb 14, 2009 4:45 pm 
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Scott Smith wrote:
I shoot for an IC of 50% of the wheel base. if it's nose heavy a little longer and if it's rear heavy a little shorter.
Bottom bar angle 2 to 7 depending on power level.



Scott, Do you need more angle with more power or less angle?

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 Post subject: Re: 4 link program ???
 Post Posted: Tue Mar 10, 2009 7:53 am 
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For those who haven't already purchased 4link software, there's a free spreadsheet on Page 13 of my site.
http://home.earthlink.net/~whshope
over 130,000 visitors


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