Home Forums Hunting & Shooting Hunter's Campfire Simple Metalworking Question

delete, need to look up a formula when I am awake.

I think you should look at using Micarta. It can be bought in 1/8" thick slabs or sheets.

Titanium is very springy and is available in many thicknesses. Admiral Steel Supply is one, plus it is available from many knifemaker suppliers.

Or, if you could find an industrial hack saw blade about an inch wide at either a hardware store or industrial supply house.

Or a shop that does metal working might have some broken ones lying around that they would give you. A 1/16" hacksaw blade would be plenty rigid enough, plus have some spring back.

If you want to make it your self, spring steel is usually tempered to about Rc 55.

nighthawk, that's very helpful information. It's the first time I've seen force measured in recoil, and it does give me a ballpark to start with.

I had previously figured out the acceleration of the rifle, which peaks at around 560 g, which is surprisingly large. But building a model of a shoulder restraining the rifle is more than I could do to get to force.

Found a textbook, A36 has a yield strength of about 36 ksi, that's yield, not ultimate yield. Hardware store steel is A36, 1018, or something along that line. So if you stay 15% or so below yield you should stay in the linear region and below the proportional limit. Modulus of elasticity given as 28,000 to 30,000 ksi.

Tell you what ya might try.

That steel strapping that's used to bind stuff with is typically 1/32nd of an inch thick and about an inch to an inch and a quarter wide when it's being used for heavy duty applications.

The place I used to work used big rolls of steel that came bound with that kind of strapping and it was cut from the rolls and stuffed in the scrap hopper.

It's used to bind all kinds of things, 3 or 4 thicknesses of it may be just what you need,..and you can probably find it in the dumpsters of lumber yards or anywhere else that buys stuff that has to be strapped down to a pallet.

,..just a thought,...

This stuff.

Scrap hoppers all over the world are crammed with it.

http://www.tradekey.com/product_view/id/45721.htm

Assuming the leaf spring has a linear rate, the value for energy stored/absorbed by a spring is:

.5 x k x (f^2) where k is the spring rate in pounds per foot, and f is the deflection in feet.

We know that the recoil energy of a .30-06 is 20 ft-lbs. Plug the numbers in, and it will tell you that you need a really high spring rate, to limit deflection to only .005".

Leaf spring rates can vary a little depending on how they are mounted, but still I think your leaf needs to be a good deal thicker, if you only want it to deflect .005" max, under recoil.

naught, naught,..then carry the naught,..

By golly!,...you're right!

Spent the afternoon trying to become a Mech E. Ugh. Not pretty.

Anyway, you are right that thicker material is in order if the peak force is 1,000 pounds.

At .062" thick, the deflection in the middle of a 2" span is .372" and the elongation of the surface (the one facing forward) is 2.1%. That's got to be into yield. Going up to .125" thick brings it down to a deflection of .045" with .57% elongation at the surface. That seems like a lot, because maximum allowed percent stretch in barrel steel is around 1/10 that much.

Bristoe has got me thinking about changing the design and putting a piece of that strapping steel taut like a bowstring between two strong supports. It would be a LOT lighter weight, and I'm sure it would be strong enough. Up until now, I've been just thinking in terms of a simple flexing beam, but that may not be the easy way.

Plan B ?

why not use a rigid "Shoulder Pad" and spring the thing on simple Belleville Washers, or play with cruder coil springs ?

just set the thing up on bushings / gliders, and buffer with the right rate of spring tension.

Bellevilles can give you the same rate as a coil in about 1/4 to 1/5th the distance required by a coil.

Lemme find a link to Smalley,....they do that well.

GTC

Here ya' be.

God, I wish we could put up sketches on a bar napkin.

Link: http://www.smalley.com/wave_springs/about_springs.asp

If we go with that value for the force and plug it into simple beam equations, it says you need a leaf .522" thick (x .75 wide, x 4" effective length) to limit deflection to .005".

.558 thick is a stocking size for us, we may have some 5160H scrap I could send you. That should be a little stiffer than you need.

And yes I design springs for a living.