What is the best resource for information on mechanical springs?

In summary, the lateral stiffness of a compression spring can be calculated by using a plot found in an older edition of the Handbook of Spring Design, or by using a hot rodder or solve for alpha method.
  • #1
hermano
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Hi,

Is there a simple formula to calculate the lateral stiffness of a compression spring when both ends stay in parallel (see figure)?
244775
 
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  • #2
Get a copy of the SMI Fundamentals of Spring Design, or an older edition titled Handbook of Spring Design. It has a plot showing exactly what you need. Buy a copy for only $25.00: https://smihq.org/store/ViewProduct.aspx?id=8088348.

It's a worthwhile addition to your library, and dirt cheap compared to projects like a square meter of vacuum plate.
 
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  • #3
Thanks. I will take a look at it.
 
  • #4
There is another dynamic typically not apparent. The spring tries to twist and rotate on both ends when compressed. These things work even if only used on one end. They can tilt and they have a row of needle bearings to permit rotation and no binding.
Hyperco Hydraulic Spring Perch
1872.jpg




These precision devices allow the spring end coils to tilt up to 4 degrees as the spring is compressed, reducing the bending loads on your shocks by as much as 96%. This reduction in side force and friction allows more force and energy to be directed to the car's mechanical grip while reducing wear on your shocks.
This model has a special 1.5" x 16 tpi female thread to fit the eyelet (shaft end) on Penske 8760 racing shocks. It is designed to replace the spring perch to minimize bulk. Installing a hydraulic perch at one end of the spring will reduce shock bending loads significantly; however, hydraulic perches at both ends of the spring will provide optimum performance.

 
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  • #5
excellent video on spring stress i n spring design

As far as I can tell from my limited research, coil springs will rotate while being compressed in the vertical direction. I know this from experience over decades of auto racing. This rotation or twist is known as "indexing".
The usual method is to mechanical fix one end of the spring if it becomes a major problem. The deeper you ding into this you find it is not "indexing" it is called "Ratcheting" and lots of things effect it. Are both ends of the spring parallel ground and flat? Is one end fixed? Is the free end riding on bearings?

I have found three solutions to find out how much the spring ratchets.

Hot rodder method - Take a random sampling of 10 springs and mark one of the coil's OD. Then compress the spring and measure how far around the coil it travels. My question is “Why Bother”. In racing ideally you want the spring to compress without any side thrust and minimum of friction at the spring ends when compressing. That’s why we use hydraulic spring perches and worry about other handing aspects. Look carefully at the video of the hyperco perch above. You can see the coil spring twist during compression. Look just below the E and note the white spot moving side to side. It looks like 1/8" but you can see it move laterally.

Solve for Unwinding Method - Spring Design by Wahl as reference to rotation during compression and gives the formula. The angular deflection (unwinding) of the ends for compression spring due to axial loading is given in page 249 of Mechanical Springs, A. M. Wahl 2nd Edition 1963. Therefore, the maximum torque will be the torque to prevent it. For this you need to treat the spring as a torsion spring and calculate the torque that will create/negate this deflection. However, the axial force, coefficient of friction and spring diameter create a moment that may be smaller than the maximum moment.



Solve for Alpha Method -
As close as I can figure this is about the Spring end condition (Alpha) for spring buckling evaluation.
see video below at 45 minutes
This is as far as I can take this subject without looking like a complete fool so hopefully the real Engineers here will provide more insight.
 
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  • #6
For precision spring function applications such as high performance pressure relief safety valves there are spring washers with a ball and socket center pivots installed on both ends of the spring to minimize resistance to the above discussed end rotation.
 
  • #7
Ranger Mike said:
Mechanical Springs, A. M. Wahl 2nd Edition 1963
This book is THE reference for springs. If it's not in this book, you will not find it anywhere. And it's still in print. If the SMI book does not answer your questions, get this book.
 
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What is the best resource for information on mechanical springs?

The best resource for information on mechanical springs would be engineering textbooks and journals that focus on mechanical engineering or materials science. Online databases such as Engineering Village and Google Scholar can also provide a wide range of articles and research papers on this topic.

What are the different types of mechanical springs?

There are several types of mechanical springs, including compression springs, extension springs, torsion springs, and flat springs. Each type has its own unique design and function, and can be made from a variety of materials such as steel, titanium, and plastic.

How do I determine the appropriate size and material for a mechanical spring?

The size and material of a mechanical spring will depend on the specific application and load requirements. Factors to consider include the amount of force needed, the space available for the spring, and the environmental conditions it will be exposed to. Consulting with a mechanical engineer or using spring design software can help determine the best size and material for your specific needs.

What are some common uses for mechanical springs?

Mechanical springs have a wide range of applications, such as in automotive suspension systems, door hinges, and shock absorbers. They are also commonly used in household items such as mattresses, trampolines, and toys. In industrial settings, they can be found in machinery and equipment for various purposes.

How do I properly maintain and care for mechanical springs?

To ensure the longevity and effectiveness of mechanical springs, it is important to regularly inspect them for wear and tear, and replace them if necessary. Keeping them clean and lubricated can also help prevent corrosion and extend their lifespan. It is also important to use springs within their specified load and temperature limits to avoid damage. Consulting with a mechanical engineer or following manufacturer guidelines can provide more specific maintenance instructions for your particular springs.

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