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# Rectangular Spring to Circular Spring Conversions?

## Rectangular Spring to Circular Spring Conversions?

(OP)
Whats the easiest way to use a diameter that equates to a rectangular springs width and length.

I have a spring in hand that we paid a good chunk of change to produce 10 of. Thing is we would like to make it with a smaller solid height using various spring calculators on the internet. The problem is they all need a diameter. Well, I don't have a diameter, I have a square rectangular spring. Since we could not figure it out we just paid a company to redesign our spring and what came back had about half the compression value of the old spring we sent in. This leads me to believe that A. they did not know what they were doing or B. square spring design is very difficult.

Anyone have any ideas?

### RE: Rectangular Spring to Circular Spring Conversions?

It looks like a spring used inside a gun/hand gun magazine.

Do you have a drawing of the "square spring"?
How many coils?
Free length?
wire diameter?
Square dimensions (width and length of the square section)?
Bend radius at the square corners?
Spring deflection vs. spring force (or force/s at specific deflection/s?
Spring wire material?
Working environment?

### RE: Rectangular Spring to Circular Spring Conversions?

[B] is more nearly correct than is [A].
Consider also [C], you do not know how to ask for what you want, implicit in the undefined term "compression value". Israelkk has given you a decent list of defined parameters with which to start.

What you have appears to be a magazine spring of obround configuration, apparently made from round wire, and tapered. To analyze such a thing, you have to analyze each coil individually, because none of them are identical. ... and as each coil flattens and becomes inactive, you have to analyze the stack of remaining coils all over again. Not easy.

Springs with a lot of taper are often used where minimum shut height is important, but yours does not appear to have enough taper to allow any coils to nest in the same plane when compressed.

It might be cost effective for you to rent an onsite designer or engineer with very strong experience in spring design to help you develop your product. Internet spring calculators are not going to work for you; they make too many assumptions that are not applicable in your case.

Mike Halloran
Pembroke Pines, FL, USA

### RE: Rectangular Spring to Circular Spring Conversions?

(OP)
Thanks for the replies guys.

I actually do have a drawing that was made in solidworks. Its a drawing of the exact spring that we have now that does in fact work but it is not ideal (solid height is to high). See attached png drawing.

The spring must be 17-7 Steel. In the revised spring we are just trying to make a smaller solid height.

Is there is a program that we can build a oblong spring in that would estimate our springs output? Everything that I have found online only does circular springs.

### RE: Rectangular Spring to Circular Spring Conversions?

kdoske

The drawing you provided is lucking the load deflection requirement. Even if you do not know how to calculate the spring you have you sill can measure the force/s at the deflection points the at two different compressed points (this will define the spring rate too). I noticed that 3 coils are smaller than the rest of the coils. How this spring is loaded? Can you provide a sketch?

As I understood you are looking for an equivalent round coils compression spring. Can you define your requirements:

Maximum outside coil diameter
Minimum inside diameter
Maximum solid height
Spring compressed length at first load point and the load to compress to this point
Spring compressed length at second load point and the load to compress to this point

Can you tell us where are you located (State, Country)?

### RE: Rectangular Spring to Circular Spring Conversions?

I'm not aware of any canned spring program that can do this type of spring. Certainly the Spring Manufactures Institute Advanced Spring Design 7 program can not. You could use a general purpose FEA program, I expect it would take a lot of nodes as there is a huge change in stress across the wire.

To make a significant change in the solid height, you need to taper the spring so that each coil can nest inside the previous coil. There are spring manufactures who make springs like that for gun magazines, I would contact one of them.

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