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Thunderbird IRS - Wishbone program
http://www.locostusa.com/forums/viewtopic.php?f=5&t=13686
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Author:  V8bug [ May 22, 2012, 9:40 pm ]
Post subject:  Thunderbird IRS - Wishbone program

Hi all,

I am in the parts collecting phase/planning and I am trying to figure out the rear suspension on paper right now. I am going to use a thunderbird IRS, but I have no stock control arms to go off. I have been playing with the wishbone program, and I think I am close. I would just like to see what you guys think, steer me in the right direction.

Image

thanks,

-Matt

Author:  V8bug [ May 22, 2012, 9:56 pm ]
Post subject:  Re: Thunderbird IRS - Wishbone program

picture came out small for some reason, perhaps this is better:

Image

Author:  horizenjob [ May 23, 2012, 1:09 am ]
Post subject:  Re: Thunderbird IRS - Wishbone program

Here's a diagram MaxLessica drew for his version of a Ford IRS on his car. You can get the heights and lateral offsets here.

Edit: I thought you were looking for exact upright dimensions, but it seems you have them? Your numbers look OK, but it would be nice to see what it says for 1" bump and 2 degrees roll...

Author:  V8bug [ May 23, 2012, 8:37 pm ]
Post subject:  Re: Thunderbird IRS - Wishbone program

thanks for the info Horiz, more info the better. Here is 1" bump, 2 roll. I am trying to keep the RC lateral near zero, what is acceptable limits for RC lateral?

Image

thanks,

-Matt

Author:  horizenjob [ May 24, 2012, 12:08 am ]
Post subject:  Re: Thunderbird IRS - Wishbone program

I would basically ignore the lateral movement of the roll center.

It's fine to look at the combined bump and roll, but better to start with each by themselves. You may not even have that much suspension travel, especially on a car for the track. Could you post each please?

I'd say you are in the ballpark but the front matters too.

Author:  seattletom [ May 24, 2012, 2:51 pm ]
Post subject:  Re: Thunderbird IRS - Wishbone program

Matt,

A little while back, I ran a series of Wishbone runs using Max's geometry as shown in the drawing posted by Horizenjob. A summary sheet with the Wishbone results is shown below. It shows pretty good RC height control in roll and a decent camber curve. Note the tire size may be different from yours. Hope this is helpful.

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