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PostPosted: December 1, 2006, 12:32 am 
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Joined: August 15, 2005, 10:13 pm
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Location: Charleston, WV
Click to download. It's from the Yahoo group site. It has a pretty cool diagraming feature, I didn't put in any info, I just viewed the example. I assume that units of measure are inches since the tire height in the example is 20.

http://www.locostusa.com/yahoo/Wishbone_setup.exe

If you have trouble getting it to run on a new system read this:
http://filext.com/faq/run_old_program_xp.php

Below is how I came up with the balljoint locations needed to use this program:

Quote:
The first step is to decide what wheel and tire size you are going to run and work from there. Bolt the Spindle to the wheel/tire combo with ball joints in place and then clamp everything into your intended static alignment on a hard level surface. You want 7 or so degrees of caster and a degree or so (depending on the car's prupose) of negative camber. Once you get it where you want it you need to carefully measure the height from the ball joint centers to the ground. (meaure it several times, it needs to be accurate) Next you need to set up a reference object to symbolize the midline of the chassis on the inside of the wheel/spindle/tire (I used a big carpenter's square) that is exactly 90 degrees to the ground. It also needs to be the distance of 1/2 of your track measurement from the center of the tire. Then you need to measure the distance horizontally from the vertical reference point (symbolizing the chassis midline) to the center of the balljoints. You now have the X and Y coordinates you need to allow you to play with the program and get meaningful results.

While everything is still clamped into place measure the steering arm joint center's location. You'll need that later to set up your steering system. Also measure track width.


The other "chassis points" are wide open. Put them wherever you want ot achieve the roll center you want. I know this all may sound confusing and tedious, but it's really simple once you see the big picure. The hard part is accurately measuring the fixed points that you cannot change, which are the balljoint locations on the factory parts. Once you get these numbers nailed down you are off and running.


Q: So what's this Fore and aft business?
A: The X field is fore and aft. Visualize an A arm from above. There's two pivots on one end and a balljoint on the other. The fore/aft numbers represent how far these two pivots are apart. The + (forward) is how far one pivot is in front of the balljoint and the - (rear) is how far the other is behind it. Obviously there will be one in front and one behind. Typically the one behind is the larger dimension since that is the direction of the load when a tire hits something.


Once you have all the numbers you just plug them in and go to it. All you are really doing is trying to properly locate the upper chassis pivot point. You want your lower chassis point the same height as the lower balljoint height so no work is needed with that other than moving it in and out and you are going to put it where it provides the best mounting point on your chassis. This will be decided primarily by your chassis width.
Getting that upper chassis pivot in the right place is the holy grail. Where you put it dictates how your suspension works. Moving it around changes your roll center, camber curve, the whole nine yards. Try and get a roll center that isn't too far below your center of gravity and aim for a camber curve that matches your desired range of suspension travel.

It's been debated how important it is to have your roll center stay put and not move relative to the chassis when the chassis is in roll can the wheels in bound etc. I worked extra hard to make sure my roll center moved very little as the suspension moved. A good test for this is the skewed roll. Roll the chassis a few degrees and then introduce some bump and see what happens. If you ever want to get a visual of what's going on hit F6 and look at the graph.



That should be enough to get you started.

I hope this helps!


Attachments:
File comment: Here's a sample set of numbers from a file based on a Miata front upright bolted to a stock Miata wheel/tire combo set to the stock Miata front track.
nastfr1.jpg
nastfr1.jpg [ 151.16 KiB | Viewed 29187 times ]
measuring.jpg
measuring.jpg [ 100.55 KiB | Viewed 44166 times ]
wishbonepic.JPG
wishbonepic.JPG [ 97.61 KiB | Viewed 44164 times ]

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Last edited by chetcpo on November 26, 2007, 9:57 pm, edited 6 times in total.
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PostPosted: December 2, 2006, 2:19 pm 
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I used it to layout my front suspension. Pretty straight forward and it allowed me to find the sweet spot for my steering rack, and for the camber gain ect. Since with my design the lower arms could not be parallel to the ground I was able to find the spot with the best reaction.
Dale


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PostPosted: December 3, 2006, 2:07 am 
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Location: Charleston, WV
Well I broke out my drafting equipment from college and drew up the front and rear views of my chassis complete with the spindles and ball joint locations. I then selected the obvious suspension attachment points on the chassis and measured them from the ground and chassis centerline to get their coordinates. After that I fired up the Wishbone program and put the numbers in.

The front is still giving me fits, when I get the roll center where I want it and stationary (close anyway) in a skewed roll, I don't get the camber gain I want. Anyway, since the program runs in DOS the only way to show you how it looks was to take pictures.

Here is a pic of the front in a skewed roll. 3 degrees body roll with 1 degree of bump.


Attachments:
File comment: Here are the stats for the lower illustration. Note the 4" or so of lateral movement of the roll center.
DSC00124.JPG
DSC00124.JPG [ 147.46 KiB | Viewed 48632 times ]
File comment: Disregard the upper diagram in the pic, it deals with steering and toe, things I haven't played with yet.
DSC00123.JPG
DSC00123.JPG [ 134.91 KiB | Viewed 48606 times ]

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PostPosted: December 3, 2006, 2:15 am 
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Now the rear was pretty easy in terms of getting the roll center to sit still in a skewed roll. Here are the pics from the program.

I think it is a great program, I could play with it all day. (and did) It may be a little tough to understand if you haven't read any suspension design books, maybe not. Either way it beats the pants off a string computer.


Attachments:
DSC00125.JPG
DSC00125.JPG [ 139.61 KiB | Viewed 48561 times ]
DSC00126.JPG
DSC00126.JPG [ 146.32 KiB | Viewed 48473 times ]

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PostPosted: December 4, 2006, 10:53 pm 
I have tried playing with it a little. The DOS interface for msome reason causes me a lot of eye strain. I think I am going to try to do more testing with it for my suspension.


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 Post subject: suspension design
PostPosted: December 5, 2006, 7:27 pm 
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For the front suspension, try setting your lower control arm at a negative 1 degree, "downward" and see if that doesn't improve the camber curve gain. This will raise the RC, and if you are married to such a low front RC you will have to increase the angle on the uppers. I do not know if, I,m reading this right. the RC is moving cross-car over 4"???
I used the old string method, only took about 300 tries and settled for keeping the RC within a 1/2" radii.
Working the suspension is great winter project, keeps progress moving forward even when it is to cold to be in the shop. Good luck Dave


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 Post subject: Re: suspension design
PostPosted: December 28, 2006, 11:44 am 
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davew wrote:
For the front suspension, try setting your lower control arm at a negative 1 degree, "downward" and see if that doesn't improve the camber curve gain. This will raise the RC, and if you are married to such a low front RC you will have to increase the angle on the uppers. I do not know if, I,m reading this right. the RC is moving cross-car over 4"???
I used the old string method, only took about 300 tries and settled for keeping the RC within a 1/2" radii.
Working the suspension is great winter project, keeps progress moving forward even when it is to cold to be in the shop. Good luck Dave


Your eyes do not decieve you, it really is moving that far. Those are NOT the numbers I settled on. I posted that to illustrate how the program works. I'll post the numbers I settled on if anyone wants to see them.

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 Post subject: Re: suspension design
PostPosted: January 14, 2007, 8:18 pm 
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chetcpo wrote:
Those are NOT the numbers I settled on. I posted that to illustrate how the program works. I'll post the numbers I settled on if anyone wants to see them.

I do I do! I'd also like to know how you get the graphic to come up--I figured out how to get the numbers running, but that string computer simulation graphic eludes me.

Could you make your numbers available in file form? It would save me some typos, I'll bet.

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PostPosted: March 13, 2007, 10:38 pm 
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keeps crashing for me


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 Post subject: Suspension design
PostPosted: March 20, 2007, 5:05 pm 
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Location: Anchorage Alaska
Well, Chetco, it has been over a year hasn't it?
Have you found the numbers you were looking for?

Great program, thanks for posting it.
I am just starting the design process and am interested in how others are doing who have used the Wishbone program.

Any updates anyone?

Freezing in Alaska
JagLite


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 Post subject: Re: Suspension design
PostPosted: March 20, 2007, 6:29 pm 
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Location: Charleston, WV
JagLite wrote:
Well, Chetco, it has been over a year hasn't it?
Have you found the numbers you were looking for?

Great program, thanks for posting it.
I am just starting the design process and am interested in how others are doing who have used the Wishbone program.

Any updates anyone?

Freezing in Alaska
JagLite


Yeah I have the numbers I'm looking for, I just need some time to spend fabricating. Also, FWIWI just started on my suspension design about 4 months ago. :P

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 Post subject: Suspension design
PostPosted: March 27, 2007, 5:34 pm 
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Well, DUH. :roll:

I looked at the date of your first post and for some reason I read 2005 instead of 2006 so I thought it was over a year. Must be a leap year for my brain. Or is it the long cold dark winter nights up here in Alaska I wonder. Glad I have a heated garage!

I have been having fun playing with the inboard locations and comparing the results. So far, I have not found anything that is very good though. I'll keep playing with it. Boy does it suck up the time too! It is like a time vortex. I sit down at the computer and next thing I know is 4 hours have zipped by.

I am interested in how others are doing with the program. How tight are you able to confine the RC and the IC? I can get one or the other close but not both. I am not so concerned with camber change as my car will only have 2.5" total movement. ( 1.5" up & 1" down, FSAE car )

JagLite


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PostPosted: March 28, 2007, 10:52 am 
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Location: Lanark Highlands, ON
violentblue wrote:
keeps crashing for me


I had a problem with the software too. Not being a Windows guy I didn't have a Windows box lying around to run the software. I couldn't get it to work in Linux under Wine so I cobbled together an old boat anchor Windows machine to run the software.

Whenever I would switch to the graphics mode to view the suspension the screen would go blank. I messed around with all the custom settings to try to get it to work with no joy. Then I tried swapping out the display card (was ATI Rage XL, now NVIDIA 5800) and it worked right away.

The old ATI card is a peice of junk and wouldn't go into the low res graphics mode that this software uses. Garbage.

So, if it "crashes" when you hit F6 try a different display card.


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PostPosted: April 2, 2007, 6:57 pm 
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Darth V8r wrote:
violentblue wrote:
keeps crashing for me


I had a problem with the software too. Not being a Windows guy I didn't have a Windows box lying around to run the software. I couldn't get it to work in Linux under Wine so I cobbled together an old boat anchor Windows machine to run the software.

Whenever I would switch to the graphics mode to view the suspension the screen would go blank. I messed around with all the custom settings to try to get it to work with no joy. Then I tried swapping out the display card (was ATI Rage XL, now NVIDIA 5800) and it worked right away.

The old ATI card is a peice of junk and wouldn't go into the low res graphics mode that this software uses. Garbage.

So, if it "crashes" when you hit F6 try a different display card.


Should have just went down to the local library :)

Great program, it will help a ton on my front suspension design (which is coming up quickly on my to-do list.)

Anyone have a good suggestion for a suspension book that I can pick up at the local Barnes and Noble?

Thanks!


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PostPosted: April 2, 2007, 9:06 pm 
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timman_24 wrote:
Anyone have a good suggestion for a suspension book that I can pick up at the local Barnes and Noble?


Race Car Vehicle Dynamics by Milliken and Milliken (SAE Press). Excellent book once you get past the sticker shock. My only quibble is that solid front axle suspensions are left as an exercise for the student. I've had my copy for over 10 years... and it looks the part.


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