Any thoughts on a spring tester?

[csdilligaf]

  I have so many unknown springs that when I dig around and find something that work in a build I want to know what spring rate I have for later.  I could build something but Summit racing has these for testing valve springs for only $20.  I assume they have 1 sq in of area on the piston and filled with hydraulic oil to read in PSI.  Do you think I can change the gauge to a lower psi and save all the time of making something?  I just want to know the spring rate at my compression length for the hammer spring.  What do you guys use?

[csdilligaf]

  Opps!  the $20 was just for an adapter.  Its more like $128, so that is just at a point I will make my own since I have the gauges anyway.  Does 1 sq in of piston face work or since there is an Oring on the end that will change the area I guess I shoule use the bore dia?

[michaelthomas]

Chip,

You might try a small scale to replace the tester for the poundages you are working with.  Maybe set it up vertically in a drill press or use the DRO on a mill to indicate the amount of compression.

Mike

[csdilligaf]

  I thought about that but thought to measure my spring with a rate of 47 lb/in that my 15 lb mail scale was to small.  So I just tried it with a people scale.  a 2" long spring rated at 47 lb/in with .3 compression was 15 lb.  So I tried it on the mail scale.  It is 9 lb 14 oz.  I think that is good enough.  I can use the mail scale after all.  It does not matter what the number is really as long as I use the same scale and same compression.  But what does it take to convert these numbers into what Gardner Springs numbers are?  Some calculation or would I have to compress it to the maximum when it is solid? 

[michaelthomas]

Chip,

I think the published spring rates are expressed in pounds per inch of compression. 

Mike

[rsterne]

The simple tester I use is like a long, thin eye-bolt (6" long, 3/16" diam) and a piece of angle iron with a hole in it slightly larger than the bolt (13/64").... You clamp the angle iron in a bench vice out to the side, with the hole vertical.... Slide the eye bolt up from the bottom with the eye below the vice.... Slide your spring over the top of the eye bolt, then a washer, then a nut.... When you pull down on the ring, the spring compresses....

On the eye, hang a known weight, say 5 lbs.... That will compress the spring.... If you measure the length of the spring before and after compression, and divide by the weight, you have the spring rate in lbs./in.... It's as accurate as your measurements.... While you are at it, you can also measure the free length and fully compressed length of the spring, and if you use a fish scale instead of a weight, you can measure the maximum force available at coil bind....

Bob

[csdilligaf]

  Hey, I can try that too.  More options is good. 

[rgb1]

Here's one I put together, mostly from scrap box material. The upper and lower aluminum blocks are fastened
to the 3/8 rods with setscrews........the two middle blocks "float". The "tab" behind the lower indicator allows
mounting in a vice. As pictured, the spring under question is on top, the master on bottom, the load is applied
to the upper floating block with the brass knob (3/8 threaded rod). For a master spring, most anything will work
as long as its load/displacement characteristics are accurately known. I'm sure you can figure out exactly how to
use it. Hope this helps.

                                                                                                                                           Ron

[rsterne]

BTW, I just measure between the washer and the angle iron with calipers to get the length of the spring and (by subtraction) the travel under load....

Bob

[csdilligaf]

  OK Bob,  Here is what I got.  2" long spring.  Hang 9.5 lbs and it compressed to 1.75".  Gardner spring rates this spring at 47 lbs.  Does this work out?  .25 / 9.5 = .0263....... I dont get it?  what did I do wrong?  Or did you mean the wieght divided by the travel?  That works out to 38?  closer right

[csdilligaf]

another try on different spring.  Die spring that is in a regulator I have.  Very strong.  I put 92 lbs on a 1.06 long spring and it compressed to 1.005"     so 92/.055=1672    Is that right?

[michaelthomas]

That sounds right, Chip.

[rsterne]

Sorry, yes, divide the weight in lbs. by the length it compresses in inches.... 9.5 lbs. to compress 0.25" is 38 lb./in....

Bob