[SEL] Need Spring Help

[Rob Skinner]

On Oct 20, 2006, at 5:24 AM, Curt wrote:

> Paul,
> Forget McM Carr. Get online and find Century Spring. You can also  
> order a catalog from them. Trust me, you WILL be impressed with  
> their huge selection of springs in stock. Now, before making any  
> assumptions, do you know how to figure the k-rate of the existing  
> spring you have? The free length, the OD, and the k-rate are the 3  
> most important factors when searching for a replacement spring. The  
> free length and OD are obvious and these will be the first two  
> entries in the catalog pages. The k-rate is very important also.  
> This defines the spring preload, and the load at full deflection.  
> Depending on the type of spring will define what kind of weight  
> scale you should be using to determine the k-rate. If you are  
> measuring an exhaust spring, you should use the bathroom scale. If  
> you are measuring an intake valve spring or a fuel pump spring,  
> perhaps a trip to the post office to use the letter scale is more  
> appropriate. The idea is to use a scale that has the appropriate  
> weight range, so that when you deflect the spring, say 1/2 its'  
> length, you'll have decent weight numbers to look at. Lets consider  
> the exhaust spring example. With luck you might be able to deflect  
> one of these stiff springs a 1/2" by hand. With an assistant, place  
> the spring on the bathroom scale, and measure the free length with  
> a machinist scale. Lets say it is 3" long (free length). Have your  
> assistant compress the spring some reasonable distance, say a 1/2"  
> or 3/4" (even better would be 1"). Whatever the amount, do not  
> compress it so much that you are anywhere close to bottoming out  
> the loops on each other. Whatever compression length you settle on,  
> record the scale reading in pounds for that compression distance.  
> Lets say it was 50# at 3/4" of compression. You will calculate the  
> k-rate, by taking the 50# and dividing it by 0.75" . This gives you  
> a k-rate of 67#/inch. When you start searching in the catalog, the  
> k-rate will be the third column, after the OD and free length.  
> Knowing this data, you will be able to pick out a replacement  
> spring, that will be very nearly a duplicate of the original.
> To check yourself for accuracy, perform the weight check several  
> time and perhaps at a couple of different deflection amounts and  
> weight readings. Calculate the k-rate for all the combinations you  
> measure and they should all result in the same k-rate.
>
> If you are measuring a very soft compression spring, use a light  
> scale, perhaps at the post office or the Pitney Bowes mail scale at  
> work. You'll run the test the same way, except remember, you'll be  
> measuring in ounces. You'll need to convert the ounces to pounds  
> before calculating the k-rate (#/in) .
>
> Good luck with this.
> Curt Holland
> Gastonia, NC
>




Jeez Louise, Square Nuts!

K rates, bathroom scales, assistants and slide rules?
You should be making toilet seats for the government.



   Rob Skinner
   1721 Brookdale Avenue  •  La Habra, CA 90631 • 562.694.2301
   rskinner at rustyiron.com  •  http://www.rustyiron.com