# How can I measure the pressure of tiny compression springs

I need to be able to measure the spring pressure and rate of tiny compression springs. Picture the spring that goes in one of those old
pens with the clicker on the end. It would be something very simliar to that.
For those who need to know, these springs are used in carburetors, for the power valve... and I want to be able to match an OE spring to the ones avail in the aftermarket.
I ass-u-me that I would need some sort of super small measuring device to measure the force of the spring at a certain height, then compress it and read the force again, then do some math with the distance I compressed the spring. Or... ????
I am familiar with the type of spring raters used in the automotive world for valve springs, and suspension springs... now maybe that has tainted my mental picture of the way this needs to be done with the small stuff.
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http://en.wikipedia.org/wiki/Hooke 's_law
snipped-for-privacy@hotmail.com wrote:

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snipped-for-privacy@hotmail.com wrote:

A clear tube a bit bigger than the spring.
Some small weights a bit smaller than the tube, but not much (perhaps turned on a metal lathe). Not too short, or they will jam in the tube.
A scale, a bright light if your eyes are not young, and a magnifying glass if your eyes are really old. Or get fancy and figure a way to mount the whole setup on an optical comparator?
Perhaps a fixture to hold the tube and the scale upright.
Drop in spring, measure relaxed length. Drop in weight, measure compressed length. If you like, drop in another weight, measure compressed length. Repeat until you've satisfied your curiosity, plot the results. Relaxed and one weight "should" give the spring rate if the spring is in the linear region. More points either characterizes the real spring better, or confuses you; if the latter, stick to two points, since you always get a nice linear curve-fit from that ;-)
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If you have an "original" spring and want to determine how close the "aftermarket" spring's rate is as compared with that one, couldnt you squeeze one against the other?? I'm assuming these springs are very easily compressed so their rate is a very low number and cant be measured with household scales.
Jerry
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Wagner Instruments (etc.) force gage.
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On 15 Jan 2007 16:25:15 -0800, snipped-for-privacy@hotmail.com wrote:

Ecnerwal's solution sounds good. I have used a dial indicator on the quill of a mill and a straingage postage scale (Sunbeam, about \$25 at Office Max) to measure rates of small springs.
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Were it me, I'd cobble up an adaptor that allowed the pan of a gram balance to compress the spring (in a pocket or around a telescoping rod) and alongside a measuring scale.
Then you can apply weight until the spring is fully compressed, and you'll have both the pressure and solid compression distance. If the springs are "healthy", the partial compression pressure will be linear from solid.
LLoyd
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Cheap drill press, the smaller the better. Make sure it has a usable quill depth indicator with the degree of accuracy you need. A quill stop is also handy.
In inexpensive digital scale, such as reloaders use, or a postage scale. Make sure it reads in the units you want - ounces, grams etc.
Arbor - Turn a small shaft with on OD that will slip into the spring, and a shoulder bigger than the spring. Clamp into chuck.
Set scale on DP table. Slip spring onto your arbor. Compress spring a predetermined distance appropriate for the spring size. Observe scale reading.
I use a similar setup to check oil pump check valves for Mazda rotaries.
snipped-for-privacy@hotmail.com wrote:

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With the warning that the normal units for a reloader's scale are *grains* -- not to be confused with *grams*. They are quite different. If the reloader's scale will switch to other units -- fine, but I suspect that for safety reasons they would not have a grams scale on the same device used for measuring powder in grains.
The units program tells me that there are 15.432358 grains in a gram.
Otherwise, this sounds excellent.
Enjoy,         DoN.
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I need a stand for a roper whitney #10 punch - anyone have one they would care to offer me at an attractive price? I also need some 1/4 inch punches - next stop, Roper Whitney and get the stuff new, but thought I'd check here first to see if someone had them just lying around spare
bill to email me, go to www.wbnoble.com and find my email - don't reply to this message, it won't work.
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When I worked for Winchester and Ramset we designed a lot of small springs and used in our labs small, commercially available benchtop spring testers which were like small arbor presses with associated force gages and usually a rule like a pocket scale for measuring displacement. Names like Hunter, Dillon, Chattillon and Wagner come to mind. These things tend to be rather more expensive than one might think. I'm sure one could rig up their own tester using a suitable force gage or transducer and dial indicator(s) or linear displacement transducers for less cost and achieve any degree of accuracy required, particularly if the springs under consideration fall within a narrow range of sizes. Here's a Google search on "spring tester" small: http://www.google.com/search?hl=en&lr=&q=%22spring+tester%22+small
Tip: Inform yourself on the effects of spring buckling and its frictional effects on spring force and hysteresis, also the effects of compression spring end treatment. Wahl's book on mechanical spring design and behavior is good. http://www.google.com/search?hl=en&lr=&q=wahl+mechanical+spring+design&btnG=Search
David Merrill

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On Tue, 16 Jan 2007 15:50:35 GMT, "David Merrill"
I think Ive a couple spare Chattillons hanging around, along with a stylus force gage from an old record player.
Gunner
"Deep in her heart, every moslem woman yearns to show us her tits" John Griffin
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