Coil Spring Alteration 1

[overwound]

Assume: any car with original coil spring front suspension in new, unused condition. When a coil is cut to change the ride height, how does the loss of one coil affect the capacity of the spring, assuming the rear suspension is lowered the same amount? How does it affect the spring rate? Is the load carried, divided equally by all active coils? I have seen people cut a coil from a spring, takingout 1-1/2 inches of space, yet it drops the car sometimes 3 inches. Why? Everyone I have asked uses the by guess and by golly method of determining the results. I am not satisfied with that answer. If anyone here has some concrete knowledge on this topic, I would appreciate your opinion. Thanks!

 

[GregLocock]

With a simple parallel wound spring chopping one coil out has no effect on its load capacity. Its rate will increase in inverse proportion to its length(ie remove 25 % of the coild and the rate will increase by 33%).

The change in ride height is equal to the change in length of the spring /in the laden condition/ divided by the motion ratio of the suspension. the motion artio is a geometrical property of each particular suspension, except for beam axles.



Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[overwound]

Thank you very much for your answer .... and for referring me to the forum rules. I apologize for my misuse of this forum, and respectfully withdraw my login.
Take care.
Goodbye.

 

[Bribyk]

That's just his signature, the forum rules part wasn't aimed at you personally ("SIG:".)

Coil spring rate, k = d*G/(8*NC^3) where;
d is wire diameter,
G is Modulus of Rigidity (typ. 30 X 10^9 psi for steel)
N is number of active coils (neglect ends), and
C is coil diameter.

So, if you reduce the number of coils and keep everything else the same, your spring rate will increase.

 

[GregLocock]

Sorry about that, you asked a sensible polite question, my SIG certainly was not intended as a comment.



Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[NormPeterson]

Long term basis, isn't some consequence of increased energy per unit volume possible?


Norm