Determining ball joint rate
Determining ball joint rate
(OP)
We are designing a suspension system for a small car. It is a double a-arm suspension, and we are trying to determine the spring rate, and one of the values that we need is the ball joint rate.
How do I find this value?
Any help would be appreciated.
How do I find this value?
Any help would be appreciated.





RE: Determining ball joint rate
What do you mean by the "ball joint rate"?
Jay Maechtlen
http://home.covad.net/~jmaechtlen/
RE: Determining ball joint rate
You should ask the manufacturer of the balljoint. Or test them yourself.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Determining ball joint rate
Is it the result of the value of the motion ratio. I.E. starting spring rating*motion ratio=the spring rating that I buy.
RE: Determining ball joint rate
Now, that is not an especially helpful answer, but since I strongly suspect you are an FSAE student then that is fair guidance.
Real engineers check the sensitivity of their models to the factors in them. If you told me that the calculation of wheel rate showed a significant contribution from ball joint radial stiffness, I would laugh at you.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Determining ball joint rate
Confusion may be coming from some of the spring suppliers, like the one linked below, which openly refer to ball joint rate. They also may or may not mention that any significant wheel offset needs to be factored in also.
http://www.proshocks.com/calcs/imotion.htm
RE: Determining ball joint rate
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Determining ball joint rate
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Determining ball joint rate
As for the spring, short travel not much, long travel like crazy.
Or another way to look at it, for a given spring, it changes the ball joint rate.
The term "ball joint rate" is fairly new to me too.
RE: Determining ball joint rate
RE: Determining ball joint rate
One of the off-road shock makers has a suspension calculator that includes MR correction for shock angle. Although probably sufficient most of the time, the ACF does assume travel that moves eqauadistance from level.
http://www.swayaway.com/Suspension%20Worksheet.htm#
RE: Determining ball joint rate
The spring load would be the wheel load - unsprung times the linkage ratio.
-Joe