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PostPosted: Thu Oct 30, 2014 3:19 pm 
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Joined: Fri Feb 13, 2009 10:11 am
Posts: 848
Location: Hoppers Crossing
Hi all, had some time to profile the NOS springs, can't do old springs yet as I have lent my hydro pump out. I'll do the old ones in the next month or so as I'm going to change both of the front suspension arms (my NOS L/H arm arrived from Canada today!).

I've created a simple test rig out of a few things lying around in my workshop/garage. The only things I bought was the two pulleys (don't buy Zenith brand ones, as they are crap) and a digital weighing scale that can measure up to 45kg from Super Cheap Auto for ~$11.

Here is some pictures of the setup:
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I created a simple MS Excel spreadsheet to calculate both the initial tension and the spring rate.
To measure spring, I stretched the spring 1" and took a reading in pounds, and then again at the 2" mark.

This is the excel spreadsheet:
Image

Here is a spring calculator that I entered the spring measurements into. I guessed the material as hard drawn... don't know if correct, but didn't make much difference:
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Conclusion:
I think my NOS spring has not lost any significant initial tension, and very closely matches the values from the spring calculator. It will be very interesting to see what the old springs measure, when I get them of the car. My methodology is a bit crude, mainly because the Zenith awning pulleys have poor bearings (or lack thereof) and using a digital weighing scale has readability issues as the value jumps around as well as me not providing an even tension.

Let us know what you think, and if anyone want to drop off or send me an old tired spring, or a copy of the Excel file just PM me.

Cheers. Jim

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PostPosted: Thu Oct 30, 2014 4:36 pm 
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Joined: Fri Apr 29, 2005 9:46 am
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Location: Under the bonnet son!
Mooooved!

I think I'm going to have to make a nice cup of tea before I sit down and digest all that data!

i will be keen to see how the old springs stack up, especially in a graph side by side for comparison. It would be a big ask to get more than an inch of travel I suppose? It must be quite difficult and dangerous with the set up to pull it much further.

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All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.


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PostPosted: Thu Oct 30, 2014 4:47 pm 
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Joined: Fri Feb 13, 2009 10:11 am
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Location: Hoppers Crossing
Thanks Mick. I moved it 1 and 2 inches. The spring calculator thing said max would be around 3.67" so I wouldn't go more than 3" to be safe. With the 4:1 ratio of the pulleys and the initial spring tension it would be a ~24lb pull, manageable but difficult to do holding the tension steady. Reminds me of when my Dad gave me a bullworker (remember them). LOL

I guess the good thing is I've got measured figures very close to the calculated values. Yeah!

I'll try and add a graph into the screen shots for you.

Jim

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