Finalizing the forming of a replacement car window winder spring (special multi-shaped)

[Colin1190]

Hi....I'm in need of some 'process' advice regarding a specially shaped spring (looks like a letter 'S' with an extra soft 'V' added to one end of the 'S'....total length being 60mm..width 5mm on 1.5mm....special UNHEATED spring steel (bought in for this job in hand).....I have formed up 4 pieces ( 2 needed + 2 spares) to the correct shape (as per the rusted/broken original)…..and now need advice on how I can form the 'spring/tension' into these pieces.....I rebuild vintage cars so have experience with the usual workshop environment/tools/gas equip.etc.etc.but have never had to actually make up a 'working' spring. Your advice would be greatly appreciated.....please....cheers....Colin.

 

[ivymike]

if the material properties and cross section of the "beam" are correct, and the shape of the beam is correct in the free state, then you should have the right tension when you deform the spring to install it. A spring has no tension when it's free, and the tension is created by elastically deforming the spring from the free state.

 

[Colin1190]

HI IVYMIKE ….THANKS FOR YOUR QUICK RESPONSEMUCH APPRECIATED !....I GET YOUR DRIFT ABOUT 'FREE STATE' & 'SHOULD HAVE THE RIGHT TENSION'....WHERE I AM CONFUSED A BIT, IS THAT.....THE 'SPRING STEEL' STRIP THAT WAS PURCHASED FOR ME (BY AN ENGINEERING COLLEAGUE') LEADS ME TO UNDERSTAND THAT THIS MATERIAL (IN ITS UNTREATED STATE) NOW HAS TO UNDERGO A PARTICULAR 'HEATING & COOLING DOWN PROCESS' (WHICH I'M TRYING TO FIND OUT) TO DEVELOP THE ACTUAL 'SPRING TENSION' THAT IS REQUIRED FOR THE PIECE TO ACT CORRECTLY...….I CONSIDER MY ENGINEERING COLLEAGUE TO BE EXTREMELY KNOWLEDGABLE & HAVE NO REASON,AT THIS STAGE OF ENQUIRY,TO DOUBT HIS OPINION/KNOWLEDGE....HENSE MY CONFUSION.....BUT AS HE HAS NOT DONE THIS 'PROCESS' EITHER, I AM RELYING ON 'KNOWLEDGABLE'OTHERS TO POINT ME IN THE RIGHT DIRECTION TO A SUCCESSFUL CONCLUSION TO MY 'PROBLEM'...….CHEERS...cOLIN

 

[SwinnyGG]

Easy with the caps lock..

What you're describing is heat treatment and tempering- which hardens the steel and makes it stronger, so that it can do whatever job the spring is designed to do without bending into a permanent deformed shape.

The best course of action would be for you to call a local heat treatment company and tell them what material you have and what you're trying to accomplish.

 

[Colin1190]

Hi jgKRI...apologies for the 'capitals'..when writing out my first reply the print was coming out quite small & tried out with capitals afterwards......anyway....thanks for your advice too & will check out a 'local' h/t firm...hope they accept that the four bits will fit inside 'the palm of one hand',without having a laugh......cheers...Colin

 

[GregLocock]

Basically heat them up to the right temperature and then cool them down rapidly. The details are material dependent, you could use scrap stock to find out. Your local model engineering people may be able to help.

Cheers

Greg Locock


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[ivymike]

sorry, I misunderstood. Maybe these will help?

http://springsteelstock.co.uk/hardening-and-tempering/

https://www.acxesspring.com/how-to-heat-treat-spring-steel.html

It has been a while since I did anything important with spring design, but I didn't think the spring tension was affected by the heat treatment process (assuming the geometry is unchanged), and the important effect was on fatigue strength.

There is also a "spring engineering" forum within this site, it may be more useful.

 

[Colin1190]

To: Greg & Mike...thanks guys for your replies yesterday...and the links as well...I'll check them out.....all advice etc. has been really appreciated ! ...going to have a busy 'on-'line' w/end I guess....in case you are interested this 'little job' facing me is one of the last few minor jobs on fitting up (finally painted a few months back) my '49 Studebaker 1/2 ton pick-up...after spending the last 12 years rebuilding her....thanks again.....cheers...Colin

 

[EdStainless]

Springs are formed in fully heat treated material, you don't HT afterwards.
You will not get the correct properties.
Spring materials (strip and wire) are HT before the final cold work, and then tempered afterwards for the right properties.
If your wire is hard, then it just needs a low temp stress relief (500-550F).
Yes it takes a lot of force to form springs, but this why they work.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[GregLocock]

Thanks Ed, I knew they went into an oven, I hadn't realised it was just to temper them, not harden them

here's a chart

https://www.acxesspring.com/how-to-heat-treat-spring-steel.html

Cheers

Greg Locock


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