Subject: Re: spring winding

From: [email-masked] (Ron Ginger)
Date: Thu, 12 Sep 1996 18:32:26 LOCAL

>In article <[email-masked]>, [email-masked] (John Morton) says:
>>

>>Music wire comes with a spring temper.  You should not have to do
>>anything to it.  Springback is obviously an important consideration in
>>trying to arrive at what you want - you just have to experiment to make to
>>the proper compensation.

you can save a lot of the expirement by looking up the mandrel size in 
MACHINERY HANDBOOK. There is a chart relating wire size, desired dia and 
mandrel. Ive made a few and they come out very close to what I need if I just 
follow the table.

Ron Ginger
my signature is http://www.ultranet.com/~ginger

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From: [email-masked] (mark eisinger)
Date: 14 Sep 1996 18:51:08 GMT

In article <[email-masked]>, [email-masked](J.A.Harvey) says:
>
>In <[email-masked]> [email-masked] (mark eisinger) 
>>example  2.1" OD spring wound with 0.100 wire
>>
>>           2" - 0.100
>>           ----------   x 100%  = 19%
>>             0.100
>>
>>           2" - ( 2"x 19% )  = 1.62 or 1 5/16" drill rod
>>
>Mark:
>
>Is that a typo? 1.62 would be 1 5/8" Yes?
>
>Jim Harvey
>[email-masked]
>http://hre.com/
Ooooops <red face on> yes that should 1 5/8" 

Mark Eisinger

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From: [email-masked] (mark eisinger)
Date: 12 Sep 1996 23:13:37 GMT

In article <[email-masked]>, Mike Rehmus <[email-masked]> says:
>
>After reading Kozo's HSM article, I too tried the music wire approach.
>
>I quickly found three problems:
>
>1.  The relaxed size of the coils I made using his method were larger
>    than predicted by the nomographs.
>2.  The tension placed on the wire as it is wound has a huge effect on the spring.
>    Should probably use a weight to maintain tension on the wire.
>3.  The music wire that comes in coils, packaged in the yellow boxes (Precision Brand)
>    is not precision even though they brag about their tight tolerances.  I have found
>    up to 0.002" variation between boxes of the same nominal size.  This has a great
>    effect when the wire you need to use is nominally 0.01".  Moral of this story is
>    to take a micrometer with you when you buy spring steel wire.
>
>Best regards,
>
>Mike Rehmus
>
If you calculate the spring index, you can you that number to predict the growth
of the OD. Take the mean diameter of the desired OD divided by the wire diameter.
take that number to be a percentage of the mandrel undersize to get the
desired finished OD.   

(OD-d)/d=spring index   ie. 2" - .100
                            ----------  =  19
                              .100

19 expressed as a %     ie.   19%

19% of 2"= 0.38 reduction of mandrel thus

2" -0.38=  1.62  therefore use a 1  5/8" 

You'll be real close to the desired OD, Of course fine tuning will be
required to get exact OD. Remember to stress relieve the springs before
use.

Mark
Spring maker by trade
Search the the web for Dendoff Springs, we've beeen there for 90 years!

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From: [email-masked](J.A.Harvey)
Date: 14 Sep 1996 03:08:17 GMT

Mark:

Jim Harvey
[email-masked]
http://hre.com/

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From: [email-masked] (mark eisinger)
Date: 13 Sep 1996 23:37:37 GMT

>my signature is http://www.ultranet.com/~ginger

You can calculate mandrel size by using the following formula.
It uses spring index to calculate the reduction of mandrel
size to get the corect OD.

      meanOD - wire diameter
      ----------------------  x  100%  = mandrel reduction %
           wire diameter

     meanOD - (meanOD x Mandrel reduction %) = corect mandrel

           2" - 0.100
           ----------   x 100%  = 19%
             0.100

Remember to stress relieve the spring before use. Also stress
relieveing changes spring diameters, so experiment a little.

Mark
Spring maker by trade

---

From: [email-masked] (dal wagner)
Date: 18 Sep 1996 19:11:41 GMT

In article <[email-masked]>, [email-masked] (Rrice2) says:
>
>I have recently reviewed Kozo Hiraoka's article in an early HSM on spring
>winding, preparing to make a spring I need. he stipulates the use of cold
>drawn steel music wire. I have searched the MSC catalog, and do not find
>cold drawn music wire listed. I have a bit of music wire that I bought at
>a good local hardware store, and have tried to wind spring with it, but
>find it does not retain its dimension. i.e., a compression spring quickly
>becomes short and compacted.
>
>I seem to recall something about hardening and tempering springs, but
>can't recall where I saw it. My question is: Do springs made of "common"
>music wire requier haredning, and do you do it the usual way, by heating
>to a bright red, quenching and then heating again to a lower temperature?
>
>Any help apreciated.
>
>Roy Rice.
###########################################################################

Dal Wagner replies:
 
Roy
The diameter of your mandrel won't have too much effect on the performance 
of the spring. If it expands 1/64 or 1/32 or 1/16 when removed from that 
mandrel the effect on spring characteristics is marginal unless your working 
with a very small outside diameter springs .
As a matter of fact if the spring expands the problem you experienced with 
compacting would be improved not made worse. Commercially this is not 
desirable because customers require their springs to be a specific sizes and 
within certain tollerances for obvious reasons.
 
Heat treatment is necessary to remove the residual stresses aquired by the 
spring when it was wrapped around the mandrel. This is particularly true for 
tightly wrapped small ouside diameter springs with relatively large wire 
sizes. The lack of heat treatment shouldn't effect the compacting of the 
spring. It is however necessary to prolong the life of the spring and if 
longevity is important the heat treatment must be done. It is done 
commercially almost without question.
The fact that your spring is permenantly "setting", you refer to this as 
"shortening and compacting", is caused by one condition only. The loads are 
too high for the spring you have produced. 
 
Every type of spring material you select, and there are many of them, have a 
limit to the amount of "twisting stress" you can place on them. As strange 
as it might appear, the wire in a compression spring is not exposed to a 
bending action when a load is placed on it. If you could look at a cross 
section through the wire you would in fact see the wire twisting or being 
"torqued". 
Compression springs fail when the twisting torque you place on this wire 
produces a stress that is greater than a value we call the  "ultimate shear 
strength" of that wire. Each different type of wire has a different value 
for this "ultimate shear strength." Once you exceed the value of this stress 
the spring will partially collapse and will never return to it's original 
length. This is what is happening to your spring.

When you design a spring however you don't even want to come close to this 
ultimate value unless your spring is being designed for a single shot 
application where weight and size are paramount. Because you want to avoid 
these high stresses, designers have a "safe allowable shear stress" that 
they design to. This design value is much lower than that nasty ultimate 
shear stress. To complicate matters this value is not the same for each
 material selected. The safe value changes depending on the type of service 
the spring will be exposed to such as LIGHT, AVERAGE, or SEVERE. It also 
changes with  every different wire diameter selected. 
Hope I'm not losing you! It isn't something easy to understand nor to write 
about.	

The following conditions can cause a spring to "set":

1. The wire diameter is too small.
2. The spring outside diameter is too small.
3. The spring material is not tough enough i.e higher value of ultimate 
   shear strength required.
4. Two few coils in your spring.  Working coils equally share the loads. 
   More coils means less load per coil.
5. The spring is being compressed too far.

Any of the above 5 items can be changed. Changes however have a ripple 
effect that effects many of the other characteristics of a spring.
Example
If you increase the wire diameter, the spring will give more force for the
same deflection but because you changed the wire diameter the allowable 
stress you can put on the wire increases but not proportionately. 
(Trust me this does mean something)

All of the conditions that make for a good spring work in concert. You  
simply cannot change one parameter of the spring without paying a price 
somewhere else.
You would have to be extremely lucky to come up with a workable spring 
simply by experimentation.
  
Many large spring companies actually have catalogues for their "stock" 
compression springs that if you wish you can order single unit quantities. 
You may pay $15 for that single spring but it's cheaper than paying a setup 
charge at a custom spring manufacturer, and from the sounds of things, a lot 
cheaper than winding one in your basement. 
Once you get a suitable prototype you can make your own and wind away for 8 
hours down in your basement. ( Don't forget that  heat treatment). I guess 
it totally depends on how many springs you want.

The information required to properly design a spring is as follows:

1. In the springs initial operating position do you require any 
   precompression on the spring. If so how many pounds . If you don't 
   require precompression the force on the spring in this position will be 
  zero.
2. What is the required length of the spring when it is in it's initial 
   operating position.
3. In the springs final compressed position how many pounds force should the 
   spring produce?
4. In the final compressed  position what should the spring length be?
5. Do you have a preference for an inside or outside diameter and if so what 
   is this dimension.
6. Do you have a material preference. Normally cost is the consideration and 
   the cheapest material    to do the job is used. You can't always get your 
   preference however . Music wire for instance has a limit to the maximum 
   wire diameter that is produced.
  Spring materials that are typically available more or less in order of 
  cost are:
  ASTM A229 Steel oil tempered
  ASTM A228 Music wire
  ASTM A227 Hard draw steel
  ASTM A401 Chrome silicon
  ASTM A313 Stainless 302
  ASTM A231 Chrome Vanadium
7. The type of ends you wish on your spring i.e ground and squared ends, 
  plain ends, plain ends ground, and squared ends.

If you want to send me answers to 1 through 7 privately by e-mail I'll
return you a spring specification that will work for your application. I 
have written windows based, object oriented sofware for this application 
that permits me to input the above items and get an answers immediately. I 
use the sofware strickly for my own purposes . It isn't for sale.

Had a look at that basic spring program  someone mentioned in another thread 
related too this article. Wasn't aware that MicroSoft still ships GWBasic, 
QuickBasic or what ever it is now called along with the DOS package any more. 
I didn't look at the program in too much detail but have the following 
comments: 

It would appear that this program does calculate the maximum stress on the 
spring wire but it doesn't indicate if that stress level is safe.
If using that program I would advise investigating if, for the wire size, 
material and service factor selected that the  maximum stress that it 
calculates is in fact lower than the allowable stress. If you don't you 
might have some more "flatened springs" that won't recover. 
The Constant called "G" found within the first few lines of this program 
represents a value called the Shear Modulus of the spring material. The 
value for music wire is questionable and the value for the generic material 
called "spring wire" is probably an average figure for several different 
materials.

Hope my discussion assisted more than it confussed.

Regards,

Dal Wagner