Help Me Design a Spring

Johnm1

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Feb 24, 2008
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Mesa, AZ
The pistol is a Hopkins and Allen 22 short revolver. It is an older model for a Hopkins and Allen. I have a Later version of the same pistol, that is much more refined. This revolver has a solid frame. The later version does have a side plate. The parts behind the side plate of the later version look remarkably like the ones in this pistol. I bought this revolver on the cheap with a broken cylinder pin and it was reported that it would not index. I have done quite a bit to the revolver but the nut I'm trying to crack right now is the hand spring. Here is the revolver

F17623C1-B345-4E61-8F49-A713CDD32833.jpeg


The handspring that was installed in the revolver when I received it was actually made of brass. Although I didn't know that initially. It never did function properly and I understand why. I have tried to make several versions of the original spring from music wire. I have done it a couple of different ways. I have tried to anneal the music wire and shape it and then reharden it. I have also tried to shape it in it's hardened form. In actuality it is just about as easy to shape the hardened music wire as it is to shape the annealed music wire. But in either case I have not been successful.

Here is a general picture from the side with the cylinder and Hammer removed.

20211027_210116.jpg

Here's a photograph of the action parts. The hammer, the hand attached to the Hammer, and a replica of the spring that was originally in the revolver. Seems I can't find the original spring that came with the revolver on my bench. It is quite small, made of brass, and no longer has any spring left in it. So I'm not very concerned about that loss. Except that spring had a specific shape around the hammer pin that really comes into play. I'll explain later.

20211027_210707.jpg

Noticed that the handspring is retained by the hammer pivot pin. And this is the shape I would like to have shown you on the original spring that came with the revolver. The original spring wrapped tightly around the hammer pivot pin and could not slip off. I'm having difficulty replicating that shape either in the annealed form or in the hardened form. Notice that the handspring is only retained by the small ledge formed into the side of the hammer.


Here's a photograph looking from behind the revolver into the hammer slot. You can see the slot for the hand in this photograph.

20211027_210234.jpg

Believe it or not, the clearance between the side of the hammer in the inside of the frame is close enough to retain the handspring in place. The hand is only 0.038 in thick and the original spring was slightly slightly thicker. Because the thicknesses are so small I believe the handspring must protrude into a hand slot in The Recoil shield in order to maintain its location on the hand. Because this clearance between the hammer and the inside of the frame is so small, the original hand spring did not wrap around the hammer pivot pin even once. I am convinced, though willing to be corrected, that the brass handspring that was in the revolver when I received it was some kind of homemade replacement. But, there is very little room to wrap a spring around the hammer pivot pin. Possibly, with a much smaller music wire I can accomplish at least one wrap around the hammer pivot pin.

So far, I have tried 0.47 in music wire which is approximately the same thickness as the original spring. The hobby shop near my home carries much smaller music wire and my thoughts are that I will need to go to a smaller diameter music wire and form at least one entire rap of the hammer pivot pin.

The problem has been that in all my attempts at making a spring that wraps around the Hammer pivot pin, I cannot get the correct amount of force on the hand. It is always too little Force. It is possible that because I cannot form the new spring with the correct shape around the hammer pivot pin that the hammer spring is pushed backwards and not allowing the spring to be loaded by the movement of the hand. And I'm just not sure how I need to shape the replacement spring in order to put force onto the hand.

In my mind, however dangerous that may be, I have thought that the Spring May well have been a coil spring that looks like the mainspring on a watch or clock. That would, in my mind, work differently than the original spring or what I have tried to form so far.

I would like some opinions on what you think the shape should be and how I should go about accomplishing it. I do have the ability to anneal Steel and to re Harden it as well as temper it if need be.
 
Keeping in mind that this revolver was made to a price point (a very low one), the original spring would have been the simplest-to-make as possible. It's not clear from your description that you've identified the two places the spring must anchor: one on the back of the hand and the other somewhere on the hammer, probably. The pics aren't clear enough to see from here.

First thing I would do is visit gunpartscorp.com and see if they have a drawing of that gun, or an exploded diagram.
 
What is the diameter of the hammer pivot pin. You might be able to find a spring of the same or slightly smaller diameter and mod it. Mcmaster is a great place to look.
 
Keeping in mind that this revolver was made to a price point (a very low one), the original spring would have been the simplest-to-make as possible. It's not clear from your description that you've identified the two places the spring must anchor: one on the back of the hand and the other somewhere on the hammer, probably. The pics aren't clear enough to see from here.

First thing I would do is visit gunpartscorp.com and see if they have a drawing of that gun, or an exploded diagram.

In picture #3 one side of the spring presses on the back of the hand and the other is presses against a tiny 'ledge' formed in the hammer. The clearance between the hammer and the inside of the frame is small enough to retain the spring in place. Good thought on Gunpartscorp. I've searched the internet but not there.

What is the diameter of the hammer pivot pin. You might be able to find a spring of the same or slightly smaller diameter and mod it. Mcmaster is a great place to look.

Diameter is 0.150" So far I've looked at both McMaster and Grainger as well as Wolf Springs. Ill need to call to get better descriptions. I have considered contacting a watchmaker. Believe it or not there still are watchmakers.
 
You might be able to use one side of McMaster part number 1330k29 the inside diameter of the hook is .156
With a little bending
 

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I'd fart around with safety pins with a smaller diameter. (because of the extra loop) I've used them for several applications where springs like your were needed.

Buy a bag of assorted ones and start cutting them to length.
 
I'd fart around with safety pins with a smaller diameter. (because of the extra loop) I've used them for several applications where springs like your were needed.

Buy a bag of assorted ones and start cutting them to length.

We are looking at everything including safety pins. My wife handed me a a snap hook from a key last night. The inside diameter is nearly perfect for the hammer pivot pin. And the leg I need to ‘push’ the hand springs in the correct direction. The leg that pushes the hand has to be bent a bit and the thickness needs to be ‘thinned’. It looked like it was going to work last night but it was late and I bent the leg cold and it broke while installing it.

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Are these the parts in question?
View attachment 1034856

Yes Col Harrumph, those are the parts. The upper leg of the spring is held by the small relief in the hammer and the other leg pushes the hand against the back of the cylinder.
The hand is TINY.
 
Try another snap hook and this time get it to size, anneal it at least, and then try it in the gun.

I am going to answer this question this morning. But I wonder if the spring will still 'spring' after it is annealed.
 
They did list a flat annealed spring option, and you're working with flat springs. OTOH they are finished product, might not need it.
 
Sometimes it is beneficial to step back and reevaluate what needs to be done. I have/had the preconceived notion that the hand spring should apply constant pressure on the hand. And I believe that the original properly designed hand spring probably did. Trying to figure out where to bend and how much to bend what I have to achieve that constant pressure was confusing at best. Because the hand and spring are impacted by so many things, I decided to stop and reassemble just so I could reevaluate what needed to be done. As it turns out, the hand spring doesn't have to apply constant pressure to function properly. Once the hand spring pushes the hand against the back of the cylinder the hand reliably remains in contact with the cylinder even after the spring stops applying pressure.

I'll update this post next time I disassemble the unit.

Now on to the next issue. The bolt not reliably locking the cylinder in place.
 
The way I see it, the bolt not locking the cylinder is one of two things (or maybe both ).

1. The bolt does not have enough spring tension to hold the cylinder in place.

2. The revolver's timing has been off for a while, and used that way, to the point that the notches aren't able to lock with the bolt properly.
 
The way I see it, the bolt not locking the cylinder is one of two things (or maybe both ).

1. The bolt does not have enough spring tension to hold the cylinder in place.

2. The revolver's timing has been off for a while, and used that way, to the point that the notches aren't able to lock with the bolt properly.

Bolt spring tension was my first thought but I replaced the bolt spring with one at least 150 years newer and as tall as I could fit and still reassemble. Its better but still not reliable. I'll start another thread on the remaining issues. But until then, I can push up on the bolt and it does lock the cylinder. So your intuition is at least very close. I'm currently thinking the bolt is just a tad short. Same with the hand/pawl.
 
The promised update on the springs.

Keeping in mind that this revolver was made to a price point (a very low one), the original spring would have been the simplest-to-make as possible.

The colonel is spot on regarding the springs. All 3 of the springs found in the revolver were made of brass. So the original hand spring may have been original.

For now I have resolved to use the created spring as is. It provides forward pressure on the hand at the at rest position and for about 1/3 of the upwards travel of the hand. But once the hand is engaged in the backside of the cylinder/ratchet teeth the hand doesn't need pressure to keep it engaged with the cylinder. Here is what i ended up with. 20211102_205905.jpg

And here are some of the trials that didn't work.

20211102_210038.jpg
 
Brass color springs are probably Brellium Copper. I have a sheet of here laying around some where.

I can believe that. After cleaning them they are copper in color, non magnetic and surprisingly lose their 'spring' when you try to temper them (thinking it was spring steel).

I still cant imagine a shape that could provide constant pressure for the entire travel of the hand. Though I suppose if you didn't need to install it loose one could make the shape of the original with more `travel`/greater spring action. But it could never be installed. I can't imagine that a slave pin could be used, but maybe I'm wrong.
 
Ia am mostly convinced that all that I have created is a spacer and not a spring. My replacement duplicated what was in the gun when I received it. But there is no proof it wasn't a repair expedient replacement.

Here isnwhat I created

20211027_210707.jpg

It anchors on the ledge on the sidemof the hammer and the shape pushes the hand into position when the hammer is at rest. But as the hammer moves backwards the anchor pointbdoes as well. At that point the spacer doesn't impact the hand.

Here is a picture of a later version of the same model only the later model has a sideplate that contains the hand spring. The internals are the same except for the hand spring.

20211225_075330.jpg

I found the thread in another forum that indicates the hand spring is a long flat spring that anchors in a notch in the grip frame.

https://www.thefirearmsforum.com/th...and-spring-in-an-antique-spur-trigger.217462/

And here is what that longer spring looks like

download (1).jpeg

And here is the notch that could receive that longer flat spring on the actual gun

20211225_072823.jpg

The post from the other forum suggests that the longer flat spring is installed from the grip frame side. Ive tried to install a thin piano wire and can't seem to do it. It has to travel under thr hammer pivot pin in the space between the hand and the pivot pin, a space approximately 0.0180" and over the top of the hand.

Just rambling.
 
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Here is a picture of the newer model with the sideplate off that shows the path the longer flat spring would have to take from the top of the bottom grip frame, under the hammer pivot, and back up again to the top of the hand.

20211225_083633.jpg
 
Did you manage to restore the flat spring? A suitable flat spring is used in the windshield wiper of many vehicles.
View attachment 1088606

No, i have not restored the flat spring. Consider my original work around still functions reliably. It just isn't correct.

I'll look at windshield wipers to see if i can modify one to work. Thanks for the idea!
 
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