First, I'm still alive after the spring slipped out from under the trailer hitch with 700 lbs of force on it!
Wasn't actually too bad, nuthin hit me!
I used my alignment turntables under the spring eye ends to allow float. This made a %100 difference in repeatablity of the readings.
Here is how I did it:
I first figured the weight on the spring, or "load".
I looked up an old rear weight I had for my 67 with full tank and spare tire-1600 lbs. I subtracted the weight of the 12 bolt rear end with brakes-185 lbs, plus half the springs weight-35 lbs= 220. I didn't figure shocks because they don't weigh much.
I got 1380 lbs rear weight, the weight on one spring is 690 lbs.
I used 700 lbs as my "test weight".
Now, to test a variable rate leaf spring you are supposed to measure the rate one inch above and below the normal ride height.
Then average the two rates to come up with the spring rate at normal ride height.
I decided to use a half inch above and below and measure the difference between them, which would give an automatic average spring rate in lbs per inch.
I got 160 lbs rate at normal ride height with an arch of 3/4" measured from a line between the spring eyes to the top of the spring pack, and measured at the center bolt location.
What was very interesting was the next inch of droop was 80 lbs per inch, the next TWO inches were 80 lbs per inch TOO!
I think the main thing that is happening with this spring is the two main leaf's are providing the 80 lbs, the short leaf is not touching until the last inch, then adding quite a bit of rate, like double the rate.
The front of this spring is VERY stiff and the main deflection is the rear "half".
At full deflection, the center bolt area was about 3/4" higher than the front of the spring about six inches behind the front eye.
I should add, my accuracy could be off by 10 or 15 lbs becuase the guage I used only has 100 lb increments on the dial. I had to guess at the exact numbers.
The hydraulic load cell I used was off my home made coil spring checker.
Check my web page for First Gen Camaro suspension info:
David's Motorsports page
First Gen Suspension Page
67 RS 327
69 Camaro Vintage Racer
65 Lola T-70 Chev 350 Can-Am Vintage Racer
[This message has been edited by davidpozzi (edited 10-24-2001).]
[This message has been edited by davidpozzi (edited 10-26-2001).]