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[erikp]

http://forum.m1911.org/showthread.php?t=19938&highlight=spring+tester

Lemmesee.... nice design, doable for a 12 thumbs guy!

But I understand that one should pull exactly one inch compression, and read the scale at that point like 18lbs/ per inch?

Isn't that the measurement the industry uses, if one does not pull back the same every time, the radings will be all over the scale, won't it?

I'll have a look see to see if I still have a few pieces of channel here... nice project at the onset of a cold autumn.

[niemi24s]

Recoil springs are designated by the force (in pounds) required to compress them to their length at full recoil, which is about 1.60 inch (41mm) for a full-size M1911A1.

You were referring to the pounds to compress 1 inch, which is the springs rate (lbs/in).
The rate for a U.S.G.I. recoil spring is 2.88 lbs/inch, but this figure is not used much.

An "18lb" recoil spring will take 18 pounds to compress to 1.6in (41mm). Cheers

[erikp]

Thank you for the heads up!

I live in europe, like John, and it's already hard enough to deal with pounds and imagine I have 12 fingers!

Cheers mate!

[niemi24s]

You are most welcome, Erikp.

Had I been thorough, I should have converted the pounds to kilograms. Should have also converted the rate in pounds per inch to newtons per meter, but would probably have got it wrong - with my 12 thumbs poking at the calculator!

Or is it Pascals per meter?....... :confused: Cheers

[Hawkmoon]

Niemi is correct -- don't confuse the spring rate with the total force needed to achieve compression at the designated (design) dimension. It doesn't show in the photo, but I have three tick marks on the masking tape: one for Government models, one for Commanders, and one for Officers. I suppose I should consider adding a fourth for pistols with a 3" barrel, but all those I've seen have those encapsulated dual spring recoil assemblies and those won't work in my tester anyway.

Conversions to metric aren't hard. We're not talking torque, so you don't have to convert into Newton-Meters or kilo-Pascals. 1 inch = 25.4 mm. 1 kilogram = 2.2 pounds. That's all you need to know. (Plus, of course, the compressed lengths for the three sizes of pistol.)

For those without the full issue of 12 thumbs, I should point out that the end plate, through which the pull rod runs and which serves as the stop for the spring, was intentionally made about an inch (25mm) deeper than the unistrut channel. That leaves a nice flange that allows the tester to be clamped into a vise, eliminating the need for several of those thumbs.

[erikp]

You are most welcome, Erikp.

Had I been thorough, I should have converted the pounds to kilograms. Should have also converted the rate in pounds per inch to newtons per meter, but would probably have got it wrong - with my 12 thumbs poking at the calculator!

Or is it Pascals per meter?....... :confused: Cheers

Not to worry, the metrics guys get confused too, one over here did some impressive math and told us his 357 magnum "generated 1856 hp" every time he fired his gun.

I told him to come install that remarkable heat engine in my home, saving me 1000's in heating every winter!
:-)

[erikp]

Hawkmoon! Thank you very much, I've learned a trick or two, and find I can manage with my two missing digits!!
:-)

[Hawkmoon]

Not to worry, the metrics guys get confused too, one over here did some impressive math and told us his 357 magnum "generated 1856 hp" every time he fired his gun.

I told him to come install that remarkable heat engine in my home, saving me 1000's in heating every winter!
:-)
Never mind the heat -- I want one of those in my Jeep!

[erikp]

Never mind the heat -- I want one of those in my Jeep!
Fire a cylinder-full and Branson from Virgin Air will approach you for a better mousetrap in his space tourism venture! LOL!