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Spring strength?

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NutmegCT

NutmegCT

Great Pumpkin
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Turning to the wisdom of the BCF!

How do I measure the strength of a spring?

Examples from the old reed organ I'm restoring.

https://photos.app.goo.gl/eCEvyjGNVpopx8Rg7

All are "compression" springs. As you pump the bellows closed to provide vacuum, the springs are compressed. They expand to re-open the bellows.

My fumble-brain idea was to put the tip of a spring's leg on a bathroom scale, then push down the other leg and see what the scale reads when the legs were as close together as I can get them.

Your wise counsel is requested!
Thanks.
Tom M.
 
Would a fish scale do what you want?
 
Thanks Greg. These are compression springs (not extension springs). If the "strength" is measure by compressing the spring, I don't think a fish scale would work (it measure downward pull by gravity). Main thing - is the strength officially measured by the force (in pounds) that it takes to fully compress the spring? or is there another measurement needed?

Edit: this video tells me how to measure the dimensions of a coil spring:

https://www.youtube.com/watch?v=4OuUbGDtt5E

But it says nothing about how strong the spring is!

I think I need a scale using Newtons, not pounds. (?)
 
Did they measure in Newton meters when that organ was made?!?

I think you could rig up Greg's suggestion with a stop at the upper end to pull the spring against.
 
DrEntropy said:
Did they measure in Newton meters when that organ was made?!?

I think you could rig up Greg's suggestion with a stop at the upper end to pull the spring against.
Click to expand...

Certainly do-able! But what would the scale be measuring? You hang the spring on the scale, it shows the weight of the spring. You pull down on the spring, and the scale shows an increase. The more you pull down on the spring, the bigger the increase.

But what is the strength/force of the spring?

Inquiring minds want to know!
 
Make up a fixture so the scale is tensioning the spring from the bottom, fixed to a bench at the top. Scale will give you a reading in pounds/ounces at full compression. Subtract the weight of the spring and you at least have a value to compare with other springs.
 
Automotive coil springs are measured in lbs/in, as in how many pounds does it take to compress the spring one inch.

The next question is how do the springs in your photo "compress?" I assume the upper two compress by pushing the two legs closer together. A postal scale measuring in ounces would probably be appropriate. Measure how much force it takes to push the ends together by one inch.

It's not clear to me how the two lower springs in your photo work, but it's the same idea.
 
Thanks John. I figured that compressing the legs would be a good comparative measure. But my goal is to figure out how each of the springs is "rated" - in other words, is the top spring called a "10 pound" spring, or "2 pound", etc.

Each of the four springs is compressed by moving the tips of the legs upward and inward toward each other.

I can measure the force needed to compress each spring by one inch, but that doesn't tell me the actual "rating" of the spring - unless *all* types of springs use the one inch as the common factor.

Thanks.
Tom M.
 
Thanks again. Looking at that page with the formulas, there's a lot more to the calculation than just measuring how much force is needed to compress (or expand) the spring one inch.

Yikes.
 
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