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PostPosted: Mon May 21, 2012 2:36 pm 
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FYI~~~ I got the DOS based Wishbone suspension program to work w/little problem over two years ago! Used it to re-engineer my K1 Attack car for a different rack & pinion unit [Honda Prelude] from what my car's original design called for..... and the results have worked perfectly for me! :D


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PostPosted: Thu Feb 28, 2013 1:38 pm 
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I don't know if this is possible, but it may be helpful to have a setting that where you would not enter the explicit lengths of the control arms instead the program only uses your uprights and frame dimensions, and would therefore tell you what control arm lengths you need. It is somewhat frustrating if you're designing from scratch and you only know your track measurements,etc.


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PostPosted: Thu Feb 28, 2013 1:55 pm 
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freetors wrote:
I don't know if this is possible, but it may be helpful to have a setting that where you would not enter the explicit lengths of the control arms instead the program only uses your uprights and frame dimensions, and would therefore tell you what control arm lengths you need. It is somewhat frustrating if you're designing from scratch and you only know your track measurements,etc.

I agree, but Wishbone is what it is. The math is good but the input can be tough to get together. The Wishbone Input Generator was developed as a front-end to Wishbone to do the kind of thing you suggest. It is specifically for Wilwood Mustang II spindles and a Car9 frame type, but the frame type could be creatively adapted for other configurations. viewtopic.php?f=5&t=13442&p=138964&hilit=wishbone+input+generator#p138964

There are also other suspension design programs that you may find helpful.

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My Car9 build: viewtopic.php?f=35&t=14613
"It's the construction of the car-the sheer lunacy and joy of making diverse parts come together and work as one-that counts."

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PostPosted: Thu Feb 28, 2013 3:04 pm 
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seattletom wrote:
freetors wrote:
I don't know if this is possible, but it may be helpful to have a setting that where you would not enter the explicit lengths of the control arms instead the program only uses your uprights and frame dimensions, and would therefore tell you what control arm lengths you need. It is somewhat frustrating if you're designing from scratch and you only know your track measurements,etc.

I agree, but Wishbone is what it is. The math is good but the input can be tough to get together. The Wishbone Input Generator was developed as a front-end to Wishbone to do the kind of thing you suggest. It is specifically for Wilwood Mustang II spindles and a Car9 frame type, but the frame type could be creatively adapted for other configurations. viewtopic.php?f=5&t=13442&p=138964&hilit=wishbone+input+generator#p138964

There are also other suspension design programs that you may find helpful.


Oh crud. I actually wrote my post referring to the Vsusp program. I've never even used wishbone


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PostPosted: Thu Feb 28, 2013 4:28 pm 
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freetors wrote:
Oh crud. I actually wrote my post referring to the Vsusp program. I've never even used wishbone

Wishbone will give you the a-arm lengths, but first you need to give it the inboard and outboard pivot points (that's what the Windows Input Generator creates.) You can find a link to the Windows version of Wishbone and copy of the Wishbone definitions from the original DOS version earlier on this thread. See March 24, 2012 post for both.

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My Car9 build: viewtopic.php?f=35&t=14613
"It's the construction of the car-the sheer lunacy and joy of making diverse parts come together and work as one-that counts."

Ultima Spyder, Northstar 4.0, Porsche G50/52


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PostPosted: Tue Aug 19, 2014 9:05 pm 
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The Windows adaption of Wishbone is here - viewtopic.php?f=26&t=11985


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PostPosted: Tue Aug 19, 2014 11:49 pm 
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kf2qd wrote:
The Windows adaption of Wishbone is here - viewtopic.php?f=26&t=11985
Peter, thanks for reposting this link. Wishbone is my go-to 3D suspension analyzer tool. And the price is right (free!)

I've been running Wishbone extensively for the past several weeks for both front and rear bump-steer analysis. Its been a huge help.

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Cheers, Tom

My Car9 build: viewtopic.php?f=35&t=14613
"It's the construction of the car-the sheer lunacy and joy of making diverse parts come together and work as one-that counts."

Ultima Spyder, Northstar 4.0, Porsche G50/52


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PostPosted: Mon Dec 01, 2014 4:42 pm 
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I kind of tripped over this program by accident & haven't found anywhere else with folks taking about using it.

Anyway, while playing around with it after taking some quick measurements off an SCCA Formula 500 car I came up with a couple curiosities & am wondering if I've got an old "buggy" version, or if anyone else has encountered these...

1st up is that you can't enter a number outside a range of +/- 10" for the X-value of the upper foreward mount... lower forward mount, no problem... but I really would need another inch-ish forward for the upper mount.. so obviously any results I get from it aren't going to be perfect.

Not sure if it's related to that, but while changing the X-value for that mount there's always a "ghost" value of 0.00 just to the right of it.

Image

Another bit of wierdness is that on the "Dimemsions" screen (F5) the front & rear leg lengths of the upper arm are reversed... the front leg should be the longer of the two... the lower arm legs are represented correctly though.

Image
Image

However, they are drawn correctly on the diagram (F6) screen.

Image

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PostPosted: Wed Dec 17, 2014 3:40 pm 
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today i dipped my toe in the wishbone water.

looking at the previous post, i am confused as to where you take the chassis mounting pivot dimension from, reading the instructions it would appear that you use the chassis centerline?

in the illustration chart these dimensions are shown as 6.88, 4.75, 7.00 and 5.88, if as i stated, the dimension is taken from the center of the chassis, these would appear to be on a very narrow car with the front lowers only 9.5 apart, is this the case?

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PostPosted: Wed Dec 17, 2014 4:47 pm 
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john hennessy wrote:
looking at the previous post, i am confused as to where you take the chassis mounting pivot dimension from, reading the instructions it would appear that you use the chassis centerline?
John, the following has been working for me:

X = Distance fore and aft of front wheel centers, positive forward
Y = Distance above ground plane
Z = Distance outboard from chassis centerline

Note this takes a little bit of translation if one is going back and forth with Vsusp.

Dix wrote:
Another bit of wierdness is that on the "Dimemsions" screen (F5) the front & rear leg lengths of the upper arm are reversed... the front leg should be the longer of the two... the lower arm legs are represented correctly though.
Dix, I recall seeing this leg length reversal in the Windows version of Wishbone, so it must have carried through from the old DOS version.

BTW, the Windows version is much easier to use. The instructions, explanations and such have been extracted from the original version and posted. There is a link to the files a few posts back in this thread.

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Cheers, Tom

My Car9 build: viewtopic.php?f=35&t=14613
"It's the construction of the car-the sheer lunacy and joy of making diverse parts come together and work as one-that counts."

Ultima Spyder, Northstar 4.0, Porsche G50/52


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PostPosted: Thu Dec 18, 2014 10:28 am 
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john hennessy wrote:
looking at the previous post, i am confused as to where you take the chassis mounting pivot dimension from, reading the instructions it would appear that you use the chassis centerline?

Correct.... measurement is from chassis centerline outward.

john hennessy wrote:
in the illustration chart these dimensions are shown as 6.88, 4.75, 7.00 and 5.88, if as i stated, the dimension is taken from the center of the chassis, these would appear to be on a very narrow car with the front lowers only 9.5 apart, is this the case?

Again correct.... the chassis is an SCCA class called "Formula 500".... think of an Indy/F-1 style open wheel car without the wings & fancy aero scaled down to 55" wide with an 80" wheelbase.... power is a 500cc snowmobile engine & drivetrain (CVT-type belt drive)

Image


seattletom wrote:
Dix, I recall seeing this leg length reversal in the Windows version of Wishbone, so it must have carried through from the old DOS version.

BTW, the Windows version is much easier to use. The instructions, explanations and such have been extracted from the original version and posted. There is a link to the files a few posts back in this thread.

Thanks for confirming the "bug"... even though the leg lengths are reversed on that screen, everything else appears to make sense & has confirmed my suspicions so it was worth the time spent with it... I will check out the Windows version though... thanks for the tip.

I've always felt the nose-dives when on the brakes hard was a bit excessive... even if the -32% anti-dive is only a "ball park" figure (given I can't be perfectly accurite with the upper front mount location) that explains it.

Along with not enough Ackermann & even swapping to 18" tires doesn't get the front RC where I'd really like to see it... that being below ground but still up a bit higher than it shows above.

Looks like the rear suspension isn't the only thing I'll be working on. :mrgreen:

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PostPosted: Thu Dec 18, 2014 1:22 pm 
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Quote:
1st up is that you can't enter a number outside a range of +/- 10" for the X-value of the upper foreward mount...


Maybe you need to rebase your numbers? The program probably has some opinion about where the origin should be. Or am I missing what you are saying?

Quote:
even if the -32% anti-dive is only a "ball park" figure (given I can't be perfectly accurite with the upper front mount location) that explains it.


I don't really use Wishbone, but maybe I should before I finish my car. So does this mean the car has 32% pro-dive? You can intuitively check this by looking at the car and seeing wether the spindle is moving up and down vertically or if it also moves forward and back while moving vertically. If the spindle moves backwards while it is rising, that is pro dive and if it moves forward while rising that is anti dive. Hmmm, I guess you can also use brake torque to resist dive. Then you would also look to see if the spindle is following an arc as it goes up and down. That would happen if the upper and lower wishbones are not parallel the way they are mounted. Then you would want to consider wether the brake torque is adding or subtracting to a force around that arc.

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PostPosted: Fri Dec 19, 2014 4:20 pm 
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horizenjob wrote:
Maybe you need to rebase your numbers? The program probably has some opinion about where the origin should be. Or am I missing what you are saying?

I think I get what you're saying (basically move all the other measurements back an inch?) but given that the program is fixed on using the front axle CL as it's zero base for the X-value that's not possible... in other words, there's no way to have the program assume that the front axle CL is "-1"... so just moving all the other values back an inch would throw many of the calculations off.... unless I'm missing something.


horizenjob wrote:
I don't really use Wishbone, but maybe I should before I finish my car. So does this mean the car has 32% pro-dive? You can intuitively check this by looking at the car and seeing wether the spindle is moving up and down vertically or if it also moves forward and back while moving vertically. If the spindle moves backwards while it is rising, that is pro dive and if it moves forward while rising that is anti dive.


Actually, it's easier than that... using this diagram as a "mental guide image"...

Image

If you just look at the measurements in my 1st post above, you can tell the upper arm mounts at a more forward-down angle than the lower... placing the instant center forward of the front axle... so you then draw your imaginary line from the instant center to the tire contact patch... in order for it to intersect the CG line you'd continue it rearward... so now it's below ground level where it intersects the CG line... meaning negative anti-dive... or "pro-dive".

I got a similar negative value when I calculated the rear anti-squat as well... & there are other aspects of the rear suspension I'm not crazy about... which was the beginnings of this whole project.

The good news is that the Windows version fixes the bug that doesn't allow you to enter a value above 10 for the length of the upper forward arm... being able to enter the correct value of 10.75 brought the calculated anti-dive to -30.5% (-23% w/18" tires)... an improvement, but I'd still be looking to make it closer to 0.

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PostPosted: Sat Dec 20, 2014 12:26 pm 
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BTW... since I'm on the subject of anti-dive & this program... I didn't see this mentioned anywhere in the previous pages, so I should point out to everyone... the above diagram showing the anti-dive/anti-squat geometery is actually not correct.... it is however, I believe, how the program is calculating it... that being, the 100% line being drawn between the front tire contact patch and the center of gravity.... given the age of the original program, I'm assuming this to be the case because it's an old (& often used back then) error.

That is only going to be accurate if your CG location as a percentage of the wheelbase is the same as your front brake percentage.... now, in my case that's actually not that far off... so the anti-dive percentage the program generates is actually in the same ballpark for me (front brake bias = 58% / rear weight bias 57%).

The actual amount of anti-dive is dependant on the percentage of the total amount of braking force generated by the front tires... the correct way to diagram it is this...

Image

So, for the program to generate an accurate result it would have needed a front brake percentage input for use in the calculation.

Also, the way the descriptions are wirtten, I'm assuming it was also intended to be capable of calculating the anti-squat percentage of an independant rear suspension... well, unless you have 4WD that result isn't going to be in the same zip code, let alone ballpark.

The 100% line for a RWD vehicle runs from the rear tire contact patch to the CGH at the front axle.

Image

The reasoning is the same as for anti-dive... in the case of RWD, 100% of the acceleration force is generated by the rear wheels... so the 100% line = 100% of the wheelbase at CGH.

I figured I'd point this out as a potential pitfall to anyone using it... unless your front brake percentage is at least VERY close to your rear weight percentage, the anti-dive figure is not going to be anywhere near correct.

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