Thread: Compression scales

Hi there,

What's it from? I assume the 0.5Kg dosen't need to be ultra mega super doopa accurate? Can you use a known mass to calibrate it? I'm thinking you go into the shed with the SWWMBO kitchen scales and look for a lump of steel that weighs close to 0.5Kg and have a tinker using the weight.

Short of knowing the spring constant and then compressing it the required distance to create the force of 4.9N, it's probably the easiest way.

Just a thought….

Simon

Get plastic container that can hold more than 500ml of water, maybe a 1 liter coke bottle... and a set of kitchen scales.

Fill until it reads 500grams including the bottle.... then use that to adjust the screw.

If you want to measure the force, then add water until it compresses the spring the required amount, then weigh it.

You might be able to sling the bottle underneath with a wire hook of some sort.

Ray

Originally Posted by SAISAY

I nee to know how to set a spring so it takes 0.5 kg to compress it.
It has a screw on top to adjust the pressure on the spring.

Image 6.jpg
I imagine something like a vernier that measures pressure instead of distance
Thank you for any help

For this task I would use my trusty 30 year old spring scale:
DSCF0635.JPG

This is a Swiss Pesola 0-2.5kg precision spring scale. They made them in several dozens of different ranges. An inexpensive and useful measuring tool that does not need batteries. It is perfect for setting forces in mechanical devices similar to the one on your picture. Here weighing a shellite bottle for demonstration.

This is the maker's website: http://www.pesola.com/e/

But I am sure you will find many other makers. In some parts of the world they call them a fish scale.

I am sorry that you seem to have misunderstood the question.
I need the compression load, not the extension load.
The extension load would be so easy but the compression is so very difficult.
How much of a turn of the screw is equal to a force of 500 grams to push the spring upwards?

Sorry!

OK. Take the spring out and rig up something so that you can place it on a set of kichen scales. Measure the spring compression in mm when you apply approx. 500g to it. Or as Ray suggested, use a known mass (500ml water) and measure it's compression from the weight of that water. Then when you put it back on the fixture, screw the nut until it compresses the spring by the same amount.

Can't be rocket science.

Simon

If all you have is a spring balance or a set of luggage scales you can use this setup.

attach a piece of string to the scale and tie a knot in it so a washer can be threaded onto the string
Thread the spring trough the string so that it sits on top of the washer and read the value of all this on the scale and measure the uncompressed length of the spring
Then add "stuff" equal to 500g to the top of the spring and remeasure the compressed length of the spring.
Put the spring bag into to jig and screw the length of the spring down to the required length.

BTW the force needed to compress a simple iinear helical spring by a short distance is usually the same as the force needed to stretch it the same distance so using any compression method would be just as good.

You could just hang a cord down thru the spring with a pin to hold it across the top of the spring. Sit the spring on a suport with a hole for the cord. Hang a container on the cord and pour water in. Use a caliper to measure the compression.

Dean

Hi,

Check out a Neuses spring tension gauge on the net. They come in various sizes so you would need one to measure 0-700gms. Pretty cheap and pretty accurate.

Mark