Spring rate tester

Many of you are talking about red, blue,  white and even black springs from different manufacturers.

But what do you know about the spring tension rate, length and so on compared to each other and then compared from brand to brand? 
Simple answer.  NOTHING AT ALL!

All you do is accepting your own feeling and personal opinion or maybe the opinion from an other person.
To make an end to all guessing and discussions we are going to test and publish all springs we can lay our hands on and provided by manufacturers.
The values will be mentioned in N/mm the higher the number the stiffer the spring.
Remember that preloading a spring on a car only adjust the ride height not the spring tension!
For softer or harder springs you need to use different springrate!

At the moment we use a prototype spring rate tester made by Fred Waasdorp from www.tekoma.nl

How do we test?

	We have two weights. In this case one of  561 grams (small) and one of 817 grams (large). The pole and the inside hole of the weights are treaded with Teflon oil to have less possible friction.
	We place the spring over the pole and center it.
	We place the small 561 gram weight on the spring and let it bounce a little until it stops. Then we tab with our fingers a few times on the black plate so the weight comes free from the pole and friction is not affecting the measurement. This small weight will remove all unsprung load and is our starting point for the first measurement (zero level).
	Then we use a caliper to measure the length to the top of the small weight and the top of the pole. For the measurement we call this value X1
	Then we place the large 817 gram weight on top of the small and also let them bounce a little. Then we tab with our fingers a few times on the black plate so the weight are is free from the pole and friction is not affecting the measurement. Then we measure again the length to the top of the large weight and the top of the pole. For the measurement we call this value X2 So this second weight determines our compression in mm.
	Then we calculate the difference in mm the large weight has compressed the spring. I spare you that calculation there for someone has made an Excel spreadsheet where I only have to fill in the X1 and X2 values and the necessary K value in N/mm comes out!!!!

Together with the weight and the compression in mm of the spring we now can calculate the spring tension in N/mm.

The formula is F=K . x

F is the load on the spring (in this case the weight [kg] *g
(9.81m/(s*s)))[N]
K is the spring constant (stiffness) [N/mm]
x is the compression given the load F [mm]

Pre-load the spring with the small weight and use that position/compression as (zero level) reference, add the larger weight and read the position/compression x in relation to the reference position value K will then read :

K=(0.817).(9.81)/x [N/mm]

Example:
First measurement (ZERO LEVEL) is 69 mm with small weight.
Second measurement is 55 mm with extra large weight added.
So 69 mm - 55 mm is 14 mm compression.

The stiffer the spring, the higher the K number will be and the other way around.

The above stated K value measurement is only valid for the "regular" wound springs we are using. 
If the springs have coils with variable spacing (progressive springs), the K value then will vary with the compression.

All values measured can change from spring to spring a little but are inside the measurement tolerance.
We only measure brandnew springs.

For those who like to measure their own springs they can order this spring tester. 
Price 1 piece @ 35 Euro
Price from 3 pieces @ 25 Euro
For more info and ordering mail at this email address only springtester@twf8.ws

Special thanks for their help on this project goes to David Andriessen, Stein Rimestad, Peter van Marion and Fred Waasdorp.
Thanks guys, without your help this all was not possible.
I also like to thank sofar Mr. David Wu from Hong Nor Taiwan and Mr. Tony Lin from GS-Racing Taiwan for the kind and quick support and supplying the springs for the  measuring.

If your required spring is not tested ask the distributor, manufacturer to send me one!
Companies that are interested to have their springs rate measured and published can get in contact at info@twf8.ws

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