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Dusterbd13
Dusterbd13 MegaDork
1/18/18 10:46 a.m.

Sitting on my desk are 8 coilover springs of various colors. No numbers on any of them. 

Whats the best, most accurate way of testing them at home to see what rates they are? I tried standing on them and having the wife record the compressed lengh with my 200lb ass on top, but that was far less than successful. 

Ive found some simple online calculators, and when plugging in the same numbers, i get different answers.

Honestly, i just want to know roughly what they are before I test with them.

GTXVette
GTXVette Dork
1/18/18 10:52 a.m.

Odd There are no numbers, Spring rate tool is just a Lever to Compress it over a Scale. Don't start reading numbers until it is Compressed 1"

Dusterbd13
Dusterbd13 MegaDork
1/18/18 10:57 a.m.

I think the bathroom scale maxes at 300lb.i. had the thought of loading the scale, a couple of 2x4s and the springs in my press. 

GameboyRMH
GameboyRMH MegaDork
1/18/18 10:58 a.m.

Yeah you were on the right track, you just have to upgrade the equipment. Maybe to a pole with a wide base and some barbell weights.

I can tell you from experience that trying to measure by dimensions is a recipe for disaster, no matter how careful you are.

NOHOME
NOHOME UltimaDork
1/18/18 11:00 a.m.

Be careful..a 1" loaded spring that tips out of your compression rig is going to go places.

Driven5
Driven5 SuperDork
1/18/18 11:06 a.m.

Safest and easiest to get a 'close enough' number is to just break out a caliper and start measuring.  The equation for spring rate is k=(d^4*G) / (D^3*N*8) where k is the spring rate, d is the wire diameter, G is the modulus of rigidity (~11.2*10^6 psi for steel), D is the diameter of the coil (center to center on the wire), and N is the number of active coils. 

If measuring by force, the first and last 10% or so are not normally valid.  You should be doing all of your measuring in the middle 80% of its travel.

akylekoz
akylekoz HalfDork
1/18/18 11:10 a.m.

Compress to a given height, record the force value, compress a given distance say 1" record the second force value.  The difference between the two is your lbs/".

I have a digital/hydraulic spring tester that any one can have for shipping or pick it up in GR MI.

This is for if you don't know what your wire material is.

And I agree with the above comment.

 

GameboyRMH
GameboyRMH MegaDork
1/18/18 11:17 a.m.
Driven5 said:

The equation for spring rate is k=(d^4*G) / (D^3*N*8) where k is the spring rate, d is the wire diameter, G is the modulus of rigidity (~11.2*10^6 psi for steel), D is the diameter of the coil (center to center on the wire), and N is the number of active coils. 

This is exactly the approach I must recommend against. It's just too easy to get wrong. For example, even if you managed to get a set of perfect measurements, you could use this on a chrome-silicon alloy spring and get it all wrong.

GTXVette
GTXVette Dork
1/18/18 11:30 a.m.

In reply to akylekoz :

Sir I will take you up on that . Lets get Db13's address and then he can send it to me. Michel Get the Cost to your place and I will get some money up.

44Dwarf
44Dwarf UltraDork
1/18/18 11:40 a.m.

https://www.facebook.com/media/set/?set=a.487230128050086.1073741834.100002893081629&type=1&l=cb8fab7b4b

I made my own tester only part i had to buy was the $12 jack.

The key is realizing a 1.125 bore cylinder has 1 Square inch area thus no conversion is needed PSI is reading is direct.  Before I made this i used my 30ton press with a smaller range gauge and a adapter to have a bar go through the spring so it could not lunch out sideways.

akylekoz
akylekoz HalfDork
1/18/18 11:52 a.m.

In reply to GTXVette :

Add @gmail.com to my profile name, send me an e-mail and I'll send you some pics.  If you pass this test you are worthy of what I am offering.  

 

Dusterbd13
Dusterbd13 MegaDork
1/18/18 11:55 a.m.

In reply to akylekoz  and gtxvette :

Yall are awesome. I leave to go back under a dash and wind up with 50% of a spring rating rig. 

28001 is my zip code. Ill send it/drive it to gtx when these are rated, along with his set of springs.

Keith Tanner
Keith Tanner MegaDork
1/18/18 11:56 a.m.

Keep in mind that the first inch may read differently than subsequent ones. Measuring one inch experimentally will not necessarily give you the average rate.

Details

I would go by calculation to get in the ballpark, then start actually testing to see how the car works on certain springs. I've been able to match expected results between experiment and calculation.

GTXVette
GTXVette Dork
1/18/18 11:58 a.m.

on the way.

modernbeat
modernbeat Dork
1/18/18 12:02 p.m.

http://vorshlag.com/forums/showthread.php?t=6570

 

Vorshlag will still rate your springs for free. And, I've updated our rig so we can more easily test long, OEM springs.

Driven5
Driven5 SuperDork
1/18/18 12:20 p.m.
GameboyRMH said:
Driven5 said:

The equation for spring rate is k=(d^4*G) / (D^3*N*8) where k is the spring rate, d is the wire diameter, G is the modulus of rigidity (~11.2*10^6 psi for steel), D is the diameter of the coil (center to center on the wire), and N is the number of active coils. 

This is exactly the approach I must recommend against. It's just too easy to get wrong. For example, even if you managed to get a set of perfect measurements, you could use this on a chrome-silicon alloy spring and get it all wrong.

Unless you've got something really exotic, I believe there most common spring alloys are all in the same 11.0*10^6 to 11.5*10^6 range. So that should mostly be a non-issue. Accurate dimensions just require a cheap Harbor freight caliper. The least accurate part is the number of active coils, but even that isn't hard to get close enough. I've only done it a couple of times a number of years ago, but don't recall having any problem getting in the right ballpark.

GTXVette
GTXVette Dork
1/18/18 12:21 p.m.

Keith,

I must have mis told ? I ment start checking after the First inch of Compression, as you know the first inch is the Base number 2-3-4 inches tell the tail.

Keith Tanner
Keith Tanner MegaDork
1/18/18 12:49 p.m.

We're saying the same thing. The first inch is not good information.

Trackmouse
Trackmouse UltraDork
1/18/18 12:53 p.m.

Wouldn’t this be really easy to just go buy some hyper co springs?

Dusterbd13
Dusterbd13 MegaDork
1/18/18 12:59 p.m.

In reply to Trackmouse :

Challenge car.  Still may happen though. 

akylekoz
akylekoz HalfDork
1/18/18 1:28 p.m.

Info on the tester sent, it's a few thousand dollars worth of old test equipment that I can't bring myself to scrap or bring home.

Dusterbd13
Dusterbd13 MegaDork
1/18/18 1:29 p.m.
akylekoz said:

Info on the tester sent, it's a few thousand dollars worth of old test equipment that I can't bring myself to scrap or bring home.

Holy berkeleying E36 M3!

 

You sure about this??????

Keith Tanner
Keith Tanner MegaDork
1/18/18 1:30 p.m.

Just measure them with calipers, stick the best option on the car and work from there.

akylekoz
akylekoz HalfDork
1/18/18 2:05 p.m.

Um, yeah I don't need another glorified shop press in my garage.

Did you see the pictures?  The part numbers are current, just Ebay them when you are done.

GTXVette
GTXVette Dork
1/18/18 4:57 p.m.

Tony , That thing Is AWESOME, But HOLY MOLY, Huge. Let me Study the pics to see If we Can send the Measuring Components With out the Press, I mean Yea I would like to have it and would put it to good use, But like you I have a Press and I can only Guess what that may Cost to Ship South. I'll Let you know in the 'Morrow.

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