Spring Winding

[putputman]

I can't think of a better place to get help on winding springs.

I have built many model engines, but have always been able to find workable springs at the local ACE Hardware "Ace is the place" or some other place. I am in the process of building a "New Holland" and it has numerous springs of many different sizes. I think it is impractical to purchase a coil of music wire for each size of spring required. I am going to attempt to make some springs with the music wire I have on hand. Some is several thousands smaller or larger in diameter. 1st attempt at making springs.

I have downloaded the article on "How to make springs" Lot of information there but leaves a lot of trial & error.

Questions:

How important is the size of music wire etc. for springs on these little model engines. I can understand the importance if you are making production springs for a customer or a product.

Do you people follow through with the heat treat process or use them as they are wound?

I used Marv's program to calculate the mandrel size. (works great)Does the tension or drag you put on the wire have any effect on the size of the spring?

Need a lot of help on this one!!

 

[TinkerJohn]

I’ve made several small springs for IC engines. (Mostly the Upshure type). The booklet you downloaded is a great help.

When making springs I’ve tried to stay as close to specs as possible. However when I’ve substituted with something next size up or down I did not notice a difference. I just ‘stretched’ the spring and it worked OK.

Here is a link to the Enco catalog that has a music wire assortment at the bottom of the page. It may be what you need to get a good assortment started. BTW: I keep my spring wire (1 ft lengths) in hot water PCV pipes with one pipe cap glued on, the other loose and it works super and takes up very little space.

http://www.use-enco.com/CGI/INPDFF?PMPAGE=755&PMCTLG=00

As for heat treating…never did it for the model engines so far.

My time is mostly spent working on the intake valve spring on IC engines and getting the spring limber enough! Good grief…those things are touchy.

---TinkerJohn---

 

[rleete]

While I have never made a spring, I did a lot of research on extension and compression springs a few years ago for a project. What I found was that there is huge overlap in all the sizes. You need a certain amount of force, there are literally dozens of ways to get that. Narrowing it down by a single paramater (OD, wire diameter, length, etc) still gives you lots of choices.

What I mean is, you get one specific spring rate in a certain wire size. Over a specific length, you get a certain force. So, changing the spring length or diameter can give you that same force with a smaller or larger wire size. Conversely, changing length or mandrel diameter can adjust the force.

Sorry of that is all "well, DUH. We knew that." stuff. What I'm trying to convey is that there is really no reason to get a bunch of different sizes for similar springs. Just another coil or one less on the same size wire will adjust the force, as will the diameter mandrel you wind it over. So, you ought to be able to get a quite wide range of springs from a single size wire.

 

[GailInNM]

If you keep everything else the same, the spring rate of a spring will vary as the fourth power of the diameter of the wire.

For example, if you change from 0.010 wire diameter to 0.012 wire diameter then the spring rate will change:

0.012/0.010 = 1.2
1.2^4 = 1.2 x 1.2 x 1.2 x 1.2 = 2.07
or about 2 times the spring rate.

To get back to a spring with the same specifications as the original, we can change either the number of turn or the diameter of the spring.
The spring rate is proportional to the number of turns, so in our example we would have to increase the number of turns by 2.07 which is just close enough to doubling for our purposes. Of course if we can not fit the increased length in our design that may not be possible.

So maybe we can change the diameter of the spring. The spring rate varies inversely as the cube of the diameter of the coils. In our examble we want to reduce the spring rate by 2.07. The cube root of 2.07 is 1.27 so we multiply the diameter of the original spring by 1.27 and we are back to where we started.

The two methods can be combined if necessary. Say that there is enough room to increase the spring diameter by 15 percent or1.15 times the original diameter. Then 2.07 divided by 1.15 cubed = 2.07/(1.15 *1.15 *1.15) = 1.36 Now if we multiply the original number of turns by 1.36 our spring has the same performance as the original.

For a quick look at the spring formulas go to:
http://www.leespring.com/engguide4.asp?mypdfstr=C1

If you don't have a math bent, then you can find a commercial spring from a catalog with the properties of the original and then find a similar spring with the new wire size. This can be frustrating as there are so many possible possibilities.

One such commercial catalog is at:
http://www.leespring.com/browse_catalog.asp?springType=C

This can be time consuming as there are over 500 pages. Not shown on the catalog main page is the number of turns, but you can find that by clicking on the part number for a more detailed spec on the spring.

Gail in NM,USA

 

[firebird]

Hi putputman

Don't know if this helps but if you go over to a work in progress and look at my small boiler project on pages 12 & 13 where I made the safety valve you will see I wound a spring from bronze wire.

Cheers

Rich

 

[jack404]

http://home.earthlink.net/~bazillion/springs.html

i reckon this is the best at home spring making guide online

cheers

jack

 

[putputman]

Thanks for all the replies. I'm finding out there is a lot more to springs than I thought.

Thanks Tinker for the source on music wire assortments. I looked high & low and could only find coils or tubes of 100 of one size. I'll order them soon.

I did wind a few springs this week end. I tried to hit a 3/8 I.D. and used Marv's formula to start with. Each time I wound another spring, the dia. would change using the same mandrel. I am convinced the tension you put on the wire has a great effect on the spring dia.. I was clamping the wire between two pieces of TFE clamped in the Aloris toolholder. I think as the wire passed through between the TFE it would wear the plastic & lost tension.

I am going to make a spring loaded brass tentioner that should give me more control.

I am also convince that most of the springs on these little engine are probably not that critical, with the exception of the intake valve spring. That one is more trial & error than anything else.

Always something new to learn with this hobby.