springs

[Captchee]

 i was  rolling something over in my mind last night  and got to thinking . would anyone have any idea of the leaf spring ratting  for say a  siler lock .
. How heavy of a spring does jim  chambers use in his locks ?

 I have an original stutzer lock and I swear that spring  is extremely heavy . I cant compress it  while turning my spring vice by hand .
 I also have a couple davis locks that are that way  but still  not as heavy as on the stutzer

any thoughts ?

[keweenaw]

I don't think any of us use any even remotely scientific method of rating spring stiffness.  Apparent stiffness - and what's most important is how it works in the lock, not how it compresses in the vise - depends not only on the spring but on the geometry of the tumbler.  If you look at an 1800 period English lock from a Manton gun, the springs look very thin compared to modern cast springs but they are stiff in the lock action and Larry Plescher has never found a lock faster than one of the original Manton locks he tested.  How stiff a spring is by itself will depend on what metal it was made from, how it was made (cast vs. forged), its geometry and its heat treating so two springs which look identical to the eye might vary widely in stiffness and two that look very different might be very equivalent.

Tom

[Jim Kibler]

The modulus of elasticity of a material is basically a measure of the force required for a given deflection of material a given size.  In steel this doesn't vary much with composition or heat treatment.  The method of manufacture (casting versus forging) has a very slight but not significant effect if I remember correctly.  So what I'm getting at is that for a steel spring of a given geometry working in the elastic range; material, heat treatment and method of manufacture has little impact in the stiffness of the spring.  This is likely counter intuitive to many, but it's true.  Geometry is the overiding factor.

[Dave Dolliver]

Agree with Mr Kibler.  All the heat treat does is extend the elastic range so that greater deflections can be achieved (with greater load) without having permanent "set". 

Dave Dolliver

[Captchee]

 what got me thinking about this is  that the lock seems alot faster on my stutzer then on my  wifes rifle which has a siler .
the stutzer lock also has a lot lonker fall .
 now granted alot of things could be playing into this  to include the "seems factor "

 but yesterday afternoon while out  in the shop . a friend came over. the guy is a mathmatical  wiz.
 i mentioned this to him and he starts of . I can mathmaticaly tell you , which lock  would be faster , if all things were the same , based soul on the main springs . but i need a spring rating

 really the whole thinmg doesnt really mater . both locks are fast  and work well . i just thought it would be kinda interesting to see what he come up with . without knowing what info went with wich lock lol

[keweenaw]

Jim's problem is that he believes all that stuff he learned in his metallurgy classes where the models are for ideal springs.  He also knows that quenching from different temperatures will influence the internal structure of the steel as will drawing to different temperatures.  I for one never want to get confused by the facts or ideal  for at some point in that heat treating that piece of steel starts or stops being a spring but it doesn't do it instantaneously as there is undoubtedly some sloped transition zone.

One thing we both agree on that is geometry is of critical importance.

Tom

[Jim Kibler]

Sorry to sound so agrumentative Tom   I think examples like this are interesting.  It's neat when things that are often assumed correct are understood to be not so.   For example, the impact of stiffness of a spring based on steel alloy and heat treatment is nil.  Cast versus forged, not significant.  It's progress when we can understand what really is and not just accept assumptions or commonly accepted ideas.

As far as the stiffness of original springs go, in my limited experience, it seems original springs were often stronger than those typically found on commercial locks today.  I would guess that spring strength of modern commercial locks is typically kept at a level to provide low failure rates.  When a spring is pushed for strength, the chance of failure also increases.

[Dphariss]

Preload is a factor as well. Light springs that have significant preload will provide equal "strength" and FASTER response since they are LIGHTER.

I am not a metallurgist. But a good forged spring will beat a cast one every time in my experience. Some very thin forged springs are very strong. They also have a low failure rate. I used to replace all my sidelock Sharps springs with original Spencer springs (same lock internals) probably Civil War production. Strong, fast, reliable.
Cast springs are always too heavy and are not likely to survive if made as light as a forged spring can be. I suspect its partly due to the fact that thinner cast springs are harder to cast reliably and are more likely to fail if this.

Saying there is no difference in cast vs forged may be true but in actual practice there is a difference.

Dan

[Jim Kibler]

Here's the problem with most things of this nature...  How are you measuring whether a forged or a cast spring has differing stiffness?  Judgement with these things is poor.  Often we see what we want to see or what is commonly believed to be true.  Look up elastic modulus (Young's Modulus) for cast steel versus forged steel.  The difference between the two is negligible.  Take two springs, one forged and one cast of exactly the same geometry and in a blind test I'd bet my bottom dollar you wouldn't be able to tell the difference.  I don't buy into the "in practice" arguement.  I'll believe in science any day.  Guess old beliefs are sometimes hard to break. 

Now, I will say this about cast versus forged material.  I would expect the presence of defects to be higher in cast material.  These defects can act as stress risers and result in failure.  With this being the case, the tendency might be to not push a cast spring as far as a forged spring. 

Ok, I've made my point.  Accept it if you wish.  Off to other things.

[Captchee]

 well thanks for your posts fellas .

 my opinion is that there is a way  to rate a leaf spring .
 probably the same way automotive springs are rated . but im guessing .
 normally when i make a spring  i make it to work  LOL . either the lock works properly or it doesn’t . I would also agree with Dan . I to find  cast springs to be lacking  and  I replace them with forged springs when ever I get the time .
 I also find them both to be far superior to  those …sssssssshhhhhhh , coil springs
LOL

 i just thought that  providing a mathematical comparison  with all things being - but the  strength of the spring . might  be interesting