Tufnol and leaf springs

[ivanj]

Does anyone know where to get 1/32 thick tufnol for making leaf springs and also where to come by spring steel of the right sort.

Any tips on leaf spring manufacture would be helpful too.

Thanks

Ivanj

[chris vine]

Hi IvanJ

I am not too sure about tufnol, I think Reeves used to sell it??

Reeves certainly sell spring steel strip for making into leaf springs although another source might be the spring steel strapping, used to hold loads onto pallets. There is usually a skip full of it somewhere round an industrial estate.

For making the springs there are two main stages, 1, bending the leaves to the right radius and 2, (usuall) putting a hole(s) in them.

1. I find that with a former and some sort of press (EG pillar drill) they can be bent to a tighter radius and allowed to spring back. A bit of experimenting and playing around with the bend spring will soon find the right radius to press them to.

2. Putting holes in the leaves. I find the best way is to punch them in, especially as I was given, years ago, an old toggle press by a rally motor mechanic. 1/8" holes in 16G springs come out like bullets and ricochet around the workshop!! Another method would be to drill them with a carbide drill from J and L or similar.

I notice a lot of people seem to advise softing the spring first and then re-hardening and tempering after bending and drilling. This all sounds like a recipe for hard work and to be avoided at all costs!!!!

Cheers
Chris.

[baggo]

Hi Ivan,

Yes, Reeves do list 1/32" Tufnol in 48" lengths. The width is 3/8" so you may have to trim it.

For punching holes in spring steel LBSC recommended making a little punch out of hardened silver steel and using that on a lead block. Pretty much as Chris suggests.

I've had a look through my ME index for articles on making leaf springs but could only find an old article about making 'scale' springs with spring steel only. There's quite a few letters about them appeared in Postbag but no real articles dedicated to them. I think quite a few of the loco construction articles contain details of how to make them if applicable to the design. I seem to recall that the Tufnol has to hardened (?) by heating it until the surface blisters!

John

[Peter W.]

Doug Hewson sells spring steel strip in annealed state.
Easy to shape & drill, then harden & temper.

www.the-hewsons.co.uk

Unfortunately, steel only springs are far too strong, so you
need something to pad out. Many folks have used
tufnol for that, but strangely enough I've just been asking
around for opinions of alternatives when your post appeared.

[ivanj]

The next question is how does one determine the rate for the spring or is it a question of trial and error?

[baggo]

Hi Ivan,

I've done a bit more searching and come across a couple of articles by Keith Wilson on designing leaf springs. They are in ME vol 167 issues 3911 and 3913. He does give calculations etc for working out the strength required etc. which may be of some help to you. If you don't have access to copies I can scan them for you. Tubal Cain also did several articles in his workshop series which went into greater detail although he seems to deal more with full size springs. Apparently he wrote a book, 'Spring Design and Manufacture' which was published by Argus as No. 19 in the Workshop Practice series.

John

[Shawki Shlemon]

Hi
As for shaping spring strips I put a bar in the vice and pull the strip to roll it slightly more than I need ,it spring back a little bit later then cut it to required lengths. For drilling holes I drill them with ordinary good quality drill bits at very low speed ,and resharpen the drill every 6 holes or so .I put weight on formed spring and find out what it support,then work out what I need approximately . This method works for me .

[ivanj]

Thanks Baggo, I don't have access to MEs so I would really appreciate it if you would send me a scan.

[baggo]

Hi Ivan,

will do.

John

[waggy]

See "Leaf springs" on page 8 of this forum.

Waggy.

[Laurie_B]

Having read the interesting replies above,I was wondering if anyone had tried using phosphor bronze strip in their leaf springs?In strip form it isn't a material I've seen advertised by our regular suppliers.

[Jo]

My Royal Scot has phosphor bronze strip leaf springs for the bogie. No complaints, much easier to get it to do what I wanted than tufnol and no rust! All cut individually from a sheet of PB that I acquired somewhere.

Jo