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 Post subject: Determining Spring Rate
PostPosted: Wed Apr 10, 2019 4:49 am 
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Joined: Mon Oct 26, 2009 5:57 am
Posts: 137
I have some unmarked coil springs.. is there a way to estimate what their rating is when you down have 1,000lbs of weight around to load them? thanks


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PostPosted: Wed Apr 10, 2019 5:11 am 
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Joined: Fri May 10, 2013 6:18 pm
Posts: 53
Put one of your scale pads on your press with the spring on top of it. Zero the scale, compress it an inch and see what sort of pressure takes?

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Bowie

EP 2004 RX-8 #13


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PostPosted: Wed Apr 10, 2019 5:31 am 
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Joined: Mon Feb 04, 2013 9:13 pm
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There is a formula online that is pretty accurate.Just google it and give it a try.


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PostPosted: Wed Apr 10, 2019 5:56 am 
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Joined: Mon Oct 26, 2009 5:57 am
Posts: 137
This is interesting.. I do have electronic scales and a press - I will check them that way and also do the same with this formula that came up from google:

HOW TO RATE COIL SPRINGS

Spring Rate = GD^4/8ND^3

G=Torsional Modulus for Steel = 11.25x10^6

D=Wire Diameter in Inches

N=Number of Active Coils

D=Mean Coil Diameter in Inches

8=A Constant for all Coil Springs

I will post what I get. thanks


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PostPosted: Wed Apr 10, 2019 6:45 am 
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Joined: Fri Dec 23, 2011 6:59 am
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Location: Spring Hill, FL.
You can also use a reference spring on known good value . Esp to baseline your scale deal .

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Mike Ogren/Protech Racing, http://www.FWDracingguide.com http://www.ogren-engineering.com/ 352.428-8983 mogren@tampabay.rr.com


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PostPosted: Wed Apr 10, 2019 3:18 pm 
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Joined: Fri Nov 13, 2009 5:51 pm
Posts: 721
Crude, but amazingly accurate. Requires 2 people and some beer.

Make 10 : 1 lever arm of 2" x 4" steel tube or 4" x 4" wood. Mark 10 : 1 ratio points with magic marker or equivalent (saw cut slot). 8' or 10' worked for me. Make pad to fit under bathroom scale (3/4" plywood or 2" x 12"wood). Place spring on driveway near tow vehicle or trailer. Place piece of angle iron centered over spring, and put lever arm over angle iron on spring and under tow vehicle or trailer frame, making sure contact points are on 10 : 1 mark (or saw cuts). Use spacers as required to make lever arm nearly horizontal but pointed up. Place angle iron on far end 10 : 1 mark, and put bathroom scale and pad centered on angle iron. Bit of jockeying necessary. Compress spring 1" by pushing down on bathroom scale (most tricky part). Note reading. With 10' bar, 30# to 80# all that's necessary. (300# - 800# spring rate)

Scale reading times 10 equals spring rate.

Neighbors already know you're nuts!

Don't let spring slip out from under lever arm. Don't ask. Band aids and more beer!

RJS


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PostPosted: Wed Apr 10, 2019 3:51 pm 
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Joined: Thu Oct 03, 2002 10:34 am
Posts: 2865
Location: Wauwatosa, WI
No beer required (until after hours), go to local race perp shop and use their spring tester.

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David Dewhurst
CenDiv Milwaukee Region
F Prod #14


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