Mainspring at rest below lock mortice/plate. rectify?

[ddoyle]

Playing with my new toy. Hate to actually ever finish a project so like to have too many on the go . To be clear this is not a complaining post. I was happy to get this lock and fully expected to put a bushing in the plate and do a half dozen other things to it. (much thanks to ALR for the posts I have been studying)

The task that I am not sure the best way to proceed with is how best to make it so the mainspring does not rest below the bottom of the plate.  (if/when something breaks)

Any opinions/thoughts about what combination of removing material (option #1)    and/or softening- bending- re tempering (option #2) would be the smartest way to address it? There is room against the barrel to move the upper arm upwards (maybe need to thin that arm just a bit). My gut says I'd rather try the easier way first. I'd also like to keep the ordering of replacement springs to a minimum  .



Here is how it sits now:





I think I would prefer that it looked like this:









Here you can see a faint pencil line indicating how much I figure the spring needs to move. (i.e the spot I would grind)

[FALout]

Go for it, go ahead and grind it down.  But you might want to order another main spring since your lock will now be no functioning.  At first I thought you were saying that your main spring was below the lock plate when installed, if it is you didn't post a pic of that.  So, I'm assuming your concerned solely if something breaks?  Murphy's law can apply here, but it's not likely in normal operation.  Most modern locks (I'd have to see which l&r lock your using) have the cock hit the lock plate to prevent too much rotation forward.  Some locks also have a contact point for the tumbler to stop on the bridle.  You are worrying about nothing.  With most quality made modern locks, the two main weak spots are the main spring itself and the tip of the sear.  The only time I've seen a main spring break is when someone tries to remove/install by putting too much pressure on it.

[Bob Roller]

 You're borrowing trouble. I heard of this happening ONCE and that was a lock with a linked mainspring in the early 1980's. If that L&R lock has a later forged spring and it breaks it will more than likely partially fail (crack) at the bend.I can't comment from experience on the cast spring types.

Bob Roller

[rich pierce]

This is normal.

[bob in the woods]

Everything looks fine to me. I'd leave well enough alone.

[Pete G.]

You are overthinking this. The mainspring needs to be above the bottom of the plate when the foot is resting on the tumbler. Then the bridle and the stop on the cock both keep it from going further. If you start weakening the mainspring you will end up with a non functioning lock.

[smylee grouch]

If the portion of the tumbler that the main spring rides on breaks then you could have a problem but that is what you are asking about I think. I have had one of L&R s tumblers break but it was on the square where the hammer went. I have never had any other problems of that sort with L&R or any of the other better quality locks out there.

[retired fella]

If  you hone down your mainspring I would think you won't have enough force to make the lock spark properly.  I would leave it as it is.

[flinchrocket]

all you need to do is take your mainspring vise and compress the mainspring just enough to install it in the lock.

[L. Akers]

I concur with previous posts--you are contemplating creating a problem where none exists.  The only way for the spring to blow out the bottom of the mortise is for the tumbler cam to break or wear completely out (not likely in your lifetime) and I am sure you would notice that in time to replace the tumbler.  Linked tumblers are a different animal but said tumblers are designed to catch the spring if the link should break.

[bob in the woods]

I check 3 of my locks, 2 Chambers and 1 Davis.  [ I was curious ]    The main springs all extend past the lock plate to some degree or other when not compressed.  Seems like a normal state of affairs.

[jerrywh]

 There is nothing wrong with the way that spring is positioned. That is the way it should be when not engaged with the tumbler. I usually figure it should be from 1/4" to 5/16" below the tumbler hook when the hammer is on the stop.

[M. E. Pering]

In every lock I have ever worked on, when the spring is at rest, it is NORMAL for the hook to be below the bottom of the lock plate.  In fact, I have an L &R lock sitting before me right now, which is totally assembled.  The bottom of the hook as it sits in the tumbler cam is only 3/32nds" above the bottom of the lock plate.  At  rest, the hook is about 1/2" below the bottom of the lock plate.  If it didn't do this, the spring would not have enough tension to deliver enough energy to make the lock function properly.
Sure... If the tumbler cam breaks in just the right way, there is the potential for the spring to break through the bottom of the stock, but I have never heard of this happening.  Springs usually break at the bend from what I have heard, so that shouldn't be a concern.  So unless the spring is overly strong, I wouldn't try bending or weakening it, and just leave it as it is.

Matt

[smylee grouch]

I don't think the spring breaking is as much of a concern as say the tumbler cam breaking thus causing the loaded spring to decompress and damage the bottom of the lock mortice. I think that is the concern of the original poster. But as most have said so far, that happening is quite remote but not unheard of. Did I read that right  ddoyle?

[ddoyle]

yes that was my thought. spring erupting thru the bottom of the mortise. Mostly though it is just a pride of ownership/want to learn thing and would like to make it as right as possible.

So this is normal but is it the way it should be (given time/money would locks be like this? i.e would some french kings double have springs that unconfined would rest below the lock plate)? Would a 'perfect' lock be set up this way or would it better to have the mechanisms potential path of travel inside the plate footprint?

If it would be desirable to have the springs travel confined to the mortise space, what design considerations preclude building them as such? i.e is it the need to keep the plate narrow? Impossible to make a spring function properly with reduced arc of travel at the tip?  

One does not get a chance to see many fine locks with thier spring not compressed by the tumbler. So I largely appreciate the input.

Funny that a Chambers tumbler never started me thinking about this........dam smug right handers and your utopia of out of the box locks........

[bob in the woods]

Actually, regarding your comment about viewing fine locks;  I get to see every lock I use in a disassembled state.
Polishing, alone requires it.  I guess I never viewed what I saw as a problem, and it's now confirmed that all is well 

[ddoyle]

Bob,

I think there might often be a difference between what is well and good enough and what is the best. All my locks are like yours but I also live in a wood frame structure, work for a living and pay income tax so I am not fooled into thinking my experience is the last word on anything.   Am not trying to say there is anything wrong with anyone's lock.

Been bending wire and comparing with other mainsprings and I think the answer to my questions is to order another main spring and reform it to experiment with. Cheap fun.

Just an observation on potential for tumbler failure this particular lock does not (currently) stop from the cock hitting the plate . There was only a pin head size piece of material stopping it, once that peened itself flat (4-5 hammer falls) the lock started relying on the tumbler/bridle and the 3 threads in a wonky hole . Never say never.  

[frogwalking]

I certainly have not handled and inspected many old rifles compared to most of you guys, but I have seen a number where the mainspring has bashed a dip out of the bottom of the stock's lock mortis.  When, how or why, I don't know.  I guess I assumed someone had dry fired  the gun to the point that it either damaged the internal stop as well as the hammer or plate, or the tumbler wore to the point it let the spring loose.  On the other hand, if you modify the spring so that it does not extend below the bottom of the lock, when not restrained by the tumbler, you will have reduced the power of the spring unless you also increased the spring rate.  These flinters require a healthy spring to be reliable sparkers.

[ddoyle]

modify the spring so that it does not extend below the bottom of the lock, when not restrained by the tumbler, you will have reduced the power of the spring unless you also increased the spring rate.  These flinters require a healthy spring to be reliable sparkers.

Well this all makes for good, cheap, fun constructive fun. I think you have defined the challenge perfectly. Failing will be cheaper then a trip to macdonalds and a pack of smokes so I 'll give it a whirl.

 No wonder the lock maker and  gun builder (screwertogether in the parlance of the day) were usually two seperate respected trades. So much to learn.  

[Mark Elliott]

Not all opinions are equal.    Bob Roller is one of the best lock makers around.   If Bob Roller tells you that you don't have a problem and shouldn't modify the spring, then you don't have a problem and shouldn't modify the spring.  .   Springs must be compressed, and what you are showing is normal and proper.   That is why you need a proper mainspring vise to install and remove a mainspring safely.   Please don't listen to the people telling you to modify the spring to reduce the amount it is compressed.    

[ddoyle]

Mark,

I have massive respect for Bob's knowledge, yours, Jerry's and a ton of other folks on this board. ( I mean real respect not just for what they have learned from burnt fingers and callouses but for the way they give so much time to sharing).

In fact, it is that respect that is responsible for this post. To be honest I blame it squarely and completely it on Mr Roller . I have a binder on my desk full of his (and other's)posts and one thing that has jumped out at me is that Mr Roller's European Customers are more willing to pay for his skill/experience then are domestic customers. This knowledge makes me very suspicious of ANYTHING that we generally consider good enough. I cannot blindly assume just because it is good enough for here that it is as good as can be.  

That said now I know with certainty that a lock that stops it's self properly, has a properly treated spring and properly treated tumbler cam can be considered as good as can be no matter where the tip of the spring rests.

re the spring vise, I am rich with em. couple Indian ones, jewelers vise ones, Tom's version and sundry homemade affairs. No hammer puller though waiting for mr Rase to figure out a smart easy build and post a pic to copy. Until then it is hockey pucks and brass punches.

Again much thanks.

[Dphariss]

Like Bob said.
And...
You are WAY over thinking this and tying to "fix" a problem that is so rare as to be irrelevant.
Spring looks perfect to me as is.
When you start modifying lock parts you can drastically change FUNCTION. IMO you will make the lock useless by doing what you plan. The spring requires preload in order to put the required pressure on the tumbler.
 
Dan

[frogwalking]

I didn't suggest you change the lock.  On the contrary, increasing the spring rate on a flat mainspring to make up for the power lost by the modification is not something anyone can do.  The guns I saw that were damaged were 150 years old.  In rural Tennessee, with the availability of cartridge guns, many of these muzzle loaders were used as toys, and abused horribly.  Also, they may well have been converted from flint to percussion, (thus removing the hammer/plate stop, and the nipple battered into nonexistence by such abuse.  Bob Roller knows more about locks than any one (else) I know.  As Mark Elliot said, all opinions are not equal. and as I said at the introduction of my previous post, I have not handled a large number of these original rifles.   You can, however do as you wish.

[L. Akers]

Just an observation on potential for tumbler failure this particular lock does not (currently) stop from the cock hitting the plate . There was only a pin head size piece of material stopping it, once that peened itself flat (4-5 hammer falls) the lock started relying on the tumbler/bridle and the 3 threads in a wonky hole . Never say never. 

If this is true you can/should solder a shim to the top of the lockplate so that the stop on the cock functions as it should.  What Mr. Roller does to locks does not change their basic design--which is "as good as it can be", he trues the surfaces and tightens tolerances to make them as function as well as is possible.

[ddoyle]

Akers, Yes I had read on here about using a piece of exacto blade soldered and shaped to make up the space.

The bearing surface on the cock has a very steep angle/wave to it (a .012 shim fits in almost half way from the back  end and a  .015 shim fits in almost halfway from the front . (Larger ones would have fit when that dab of metal was there.) once it is flattened there will be need to add material. The angle on the cosk also acts as a wedge pushing the cock away from the plate.

 That said when the tumbler contacts the bridle stop only one corner touches as the tumbler and bridle have contrary angles. (i.e when the hammer is at rest there is a large v of open space and a small point of contact on one edge) When tumbler stop is pushed against the bridle a .010 shim can fit between the two for 3/4s of their width.   Once those are trued/ made parallel to one another and to the axis of rotation the cock might just rest against the plate.  Easier to add material to the plate then tumbler or bridle stop so I'll start with the cock. And try not to over think while doing it

Nice thing about the unfinished state of parts is that you can really see easily where things are contacting as you get that little bright spot contrasting with the rough grey.

Hopefully the mainspring does not make it to the edge of the plate once the stops are timed or I'll have to beg more help.

EDIT:
Totally off topic from my original query.

not good at macro photos so maybe these wont make my garbled writing any clearer but:





Engage file.