The answer Paul is that you've misapplied the math of coil springs. The more
coils you've got total, the *softer* the spring is. The formula is:
Spring rate = (wire diameter^4)/(number of active coils*coil
diameter^3)*1500000.
Since the number of coils and the coil diameter are on the bottom, if you
increase them, you make the spring rate softer. As you discovered with your
springs. The softer spring you installed has more coils then the stiffer
spring, as one would expect.
All those units can indeed be measured with a ruler and by counting on the
fingers, as I described.
The number 1,500,000 comes from the metal properties of an automotive coil
spring. They are all essentially the same type of tempered steel. No brass or
aluminum springs are used in automobile suspensions, especially not Spitfires.
And in the case of cutting ones own coils, the steel stays exactly the same
because we're always dealing with exactly the same spring.
So, indeed the real world does match up with the math, and cutting springs can
be quantified as I described previously. It's also safe for engineers to
continue using this formula in designing springs for automobiles. :-)
PS, how goes the vibration resolution?
>>> "ptegler@cablespeed" <ptegler@cablespeed.com> 02/13/02 07:35AM >>>
OK..plug this into your formulas...
I just lowered my front end by using earlier MKIII
springs. The taller 'uninstalled' 1500 spring has
11 coils and is rated at 180 lbs. The shorter
MKIII spring has 12 coils and is rated at 150 lbs.
BOTH use the same gauge wire for the spring.
If the shorter spring has more coils for the distance
why isn't it stiffer? A 'fewer wind' longer spring should
technically be easier to compress but it's the reverse in
this instance. Do the 'straight up' coil calcs and they don't
follow the 'real-world' results of these two springs.
photos of the springs at
http://teglerizer.com/triumphstuff/75w_newfrontsprings.htm
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