[SEL] Need Spring Help

[Curt]

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





Rob Skinner wrote:

>
> On Oct 19, 2006, at 2:23 PM, Paul Maples wrote:
>
>> Folks I am going bonkers trying to find a source for this spring:
>>
>> http://i52.photobucket.com/albums/g36/wheelterrapin/ 
>> StoverRebuild87B.jpg
>>
>> I have been working with McMaster Carr for two days and they  
>> seemingly don't want to help me. I have sent them the same picture  
>> as the one above of the spring and dimensions and have ask them to  
>> please give me a part number of a spring that they have that will  be 
>> comparable to the one in the picture. All they do is refer me to  the 
>> spring section of their catalog which I tried to use but  without 
>> success.
>>
>> Can someone tell me where I can go to find one of these springs? It  
>> is for my fuel pump on the 1905 Stover I am working on.
>>
>> Thanks,
>>
>> Paul
>>
>
>
> Hi Paul,
> Jeff Allen was peddling springs on ebay a while back.  Wasn't he?   
> Maybe I dreamt it.  It can't hurt to ask him.  Buy a bucketful, find  
> something close, keep cutting it until it doesn't work anymore and  
> then add one coil.
>
>
>  
>   Rob Skinner
>   1721 Brookdale Avenue  •  La Habra, CA 90631 • 562.694.2301
>   rskinner at rustyiron.com  •  http://www.rustyiron.com
>
>
>
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>