Force required to snap open the frizzen.

[Ironoxide]

Hi,

I've been shooting cap locks for quite a while and I recently managed to get for a fair price a Kentucky flintlock pistol clone (mady in the 70-ties by Armi Jager company). It is immensely enjoyable to shoot. It ignites pretty much every time if used with a sharp flint, but the flints don't last as long as I think they should based on what I read. The original edge on an english black flint lasts maybe 3-5 shots, then the flint is getting shorter with almost every shot until after 10-15 shots(total) it is pretty much done for. Sometimes I can knapp it in place using an often described technique to get up to 5 more shots from it, but that's it. I also often get flints shattering, breaking in half lengthwise etc.

The lock is made for 5/8ths flints, but those last only few shots before they break completely. The numbers I mention above are achieved with half inch flints. They are a bit too small, but they seem to be a lot more resilient.

I recently started thinking that the force that keeps the pan closed is a bit too much. I haven't measured it, but it feels close to 8-9 pounds all the way. Also, the frizzen snaps open maybe a third of the times it is fired. Most of the time after ignition it ends up on top of the hammer and I have to open it by hand before I reload.

Unfortunately I haven't got another flintlock to compare it with. Can anyone suggest a book, or a website that explains how to tune the lock with the right force? I could file and polish the part of the frizzen that engages the spring and the spring itself, but I need some method to determine how much force is the right amount.

I would really like to get 40-50 shots out of a flint like some people report.

 

[BruceHH]

If I am understanding correctly, your problem is not the amount of force that is required to open the frizzen. The problem is your frizzen is rebounding back and hitting your cock/flint. That is what is breaking your flint. If so, the fix is changing some angles at the toe of the frizzen where it contacts the spring - at the time it cams over - causing it to stay open. Not something that you (or I) should be attempting w/o a lot of experience. A good/qualified/experienced lock expert is the one you should seek out. Meanwhile, a sometimes successful quick fix is to use a larger size piece of leather jaw pad. Let it extend out to almost the tip of your flint on top - thereby absorbing the rebound impact of the frizzen.

 

[Ironoxide]

If I am understanding correctly, your problem is not the amount of force that is required to open the frizzen. The problem is your frizzen is rebounding back and hitting your cock/flint. That is what is breaking your flint. If so, the fix is changing some angles at the toe of the frizzen where it contacts the spring - at the time it cams over - causing it to stay open. Not something that you (or I) should be attempting w/o a lot of experience. A good/qualified/experienced lock expert is the one you should seek out. Meanwhile, a sometimes successful quick fix is to use a larger size piece of leather jaw pad. Let it extend out to almost the tip of your flint on top - thereby absorbing the rebound impact of the frizzen.

Hi, no, that's not it. I looked at it when firing with no powder. The frizzen is definitely not rebounding. It is the force to open the frizzen in the first place. When the hammer hits, the flint slides down the frizzen and most of the time it doesn't transfer enough momentum to the frizzen to open it fully so the frizzen stays on top of the cock/flint.

Edit: Just to add something to picture the magnitude of the force required to open the frizzen better. Imagine you're trying to lift a 8-9 pound (4.5kg) weights from the floor with your first finger. That's the amount of force required to open the frizzen. Perhaps 80% of the force required to cock the lock.

 

[Britsmoothy]

I have suffered from this too.
I lightened frizzen springs on two of my guns and now get good flint life and sparks.
Sometimes the part that sits on the spring is completely the wrong shape. Despite that, many a production flint lock has way to heavy a frizzen spring.

 

[dave_person]

Hi,
This is very hard to diagnose without seeing the lock. A photo of it would help. Many mass produced reproduction locks have terrible geometry. I do not doubt your assessment that the frizzen is not opening but keep in mind you cannot see rebound. It happens too fast for the human eye to detect. The only way to tell is to place a piece of masking tape on the frizzen spring where the frizzen toe hits it and fire the lock. If you see a dimple on the tape, you have rebound. When I tune a lock, I start by polishing all the bearing surfaces. Then I use a small portable luggage scale or small spring scale, hook it to the middle of the frizzen face and pull until it opens. This would typically be about 3-5 pounds. Next, I hook the scale on the flintcock top jaw screw and pull it back to full cock measuring the peak force needed. I want that to be about 3 times greater than the force to open the frizzen. That is where I begin but on some locks I need to increase one force relative to the other depending on geometry and it takes experience to know when to do that. There are also other variables. At what angle does the flint hit the frizzen? If straight on, flints can get smashed. Does the flint cock overhang the pan sufficient to assure the flint kicks the frizzen over and sparks drop into the pan not behind it or in front? Again, it is hard to diagnose this from a written description.

dave

 

[Ironoxide]

Dave, this is very interesting. The forces you mention are going to be specially useful. I'll do the tape test you suggest, but I'm 99% sure it is not rebounding.

Regarding pictures, sorry the lock is not properly cleaned yet.

The lock looks like this:

This is the point beyond which the frizzen will snap open:

 

[BruceHH]

I was just accessing what could/would normally be the situation - given the information available.

The rounded heel on the bottom of the frizzen face is not going to be a big help in kicking the frizzen over. More pictures showing contact with the flint and the frizzen face at it's lowest contact point will help.

Dave knows more about this than I could, so I am backing out to let him guide you. In the mean time, try turning your flint over for bevel down and see if that helps.

 

[Ironoxide]

I was just accessing what could/would normally be the situation - given the information available.

The rounded heel on the bottom of the frizzen face is not going to be a big help in kicking the frizzen over. More pictures showing contact with the flint and the frizzen face at it's lowest contact point will help.

Dave knows more about this than I could, so I am backing out to let him guide you. In the mean time, try turning your flint over for bevel down and see if that helps.

BruceHH, I didn't mean my reply to sound uncourteous. Your help is appreciated.

Please see the picture below. This is the lowest flint contact point between the flint and the frizzen:

This is how the lock ends up after the majority of shots (note that the frizzen rests on the top jaw of the cock rather than flint):

And this is the frizzen's face:

Based on working the lock slowly I think there are two issues. One is the force to open I mentioned, the other, is that because the frizzen doesn't snap open it ends up briefly resting/hitting the top of the flint before the top jaw of the cock pushes it away. I think this is slightly different from rebound as rebound suggests frizzen moves away and then back, while here it is held by spring tension in the closing direction all the time.

To be fair, considering the tension of that spring I'm not sure how it can end up open even a third of the times. I suspect that perhaps the gasses from the barrel escaping through the flash hole located towards the bottom of the pan are diverted by the end of the pan upwards and propel it to be opened if I load the pistol hot enough. This is just a hypothesis.

Edit: I forgot to mention I did try turning the flint around for the bevel to face down, but it wouldn't spark reliably. I think the angle of contact was wrong.

 

[Blogman]

Ok I'm a noobie so don't smack me too hard if I'm not reading this right. Would the frizzen be "jumping" or slowing the movement because the spring has those ridges or washboard effect or am I seeing the pic wrong?

 

[EC121]

At that point in your picture the frizzen should be snapped open. The geometry is way off on the spring and frizzen toe. Too much hump in the spring and wrong shape in the toe. You might try stoning an angled flat right where the right side of the red circle crosses the toe of the frizzen, but that won't reduce the initial opening force. It will help the snap. The face of the frizzen also has rounded heel that just doesn't look right.

 

[Zonie]

The frizzen spring has two jobs to do. It needs to keep the pan cover against the pan to keep the priming powder from falling out and it needs to keep the frizzen from bouncing back to land on the top of the cock.
The lock will spark and fire the gun just fine even if the frizzen spring is not on the lock. Just the inertia or mass of the frizzen should be enough to generate sparks all by itself when the flint strikes it. Of course, if the spring isn't there, the cover will bounce back and end up on top of the cock jaw. This in itself isn't harmful to the lock but it does look rather strange to anyone looking at the lock after it has just been fired.

With the lock in question, I'm not sure if the spring is keeping the frizzen from opening all the way before it closes the frizzen/pan cover back down on the top of the cock but I suspect with its heavy force, that is what is happening. It is obvious based on the picture of the frizzen resting on top of the cock jaw that the cover is being opened far enough to allow the flint and cock to travel below it.

That said, I see no harm in reducing the force of the spring by making it narrower in front area where the bend is made.
Removing the roughness on the top of the spring is a good idea.
Removing some of the height of the cam on the underside of the frizzen is another way of lowering the force needed to open the pan. Because the frizzen is hardened, a grinder is probably needed if the cam is going to be changed.

 

[BruceHH]

With the additional pictures, I do have some more input. I kinda doubt the frizzen ever fully cams over under the current situation. First, with that length flint and the rounded heel on the face - it is doing exactly what it can do - not opening properly. As the others have stated, you can polish, reduce spring weight etc.. but that design is not going to work properly with the current components.

You probably need to do everything suggested and then some. However, unless you get the frizzen to start caming over sooner, you will always have a problem. The rounded heel on the frizzen face, the angle of the toe on the frizzen and the spring are all wrong to work with each other properly.

I suggest you let a well qualified lock smith have a try at it. There are some other options though. See if one of the L&R RPL locks will replace it (I don't think so) or get a builders lock from Chambers and replace it.

If those options don't work for you - before you start reducing or altering the frizzen toe or frizzen spring (probably non replaceable), see about trying a longer flint or put something behind the flint to make it stick further out. Try putting something behind the flint to get it where it almost touches the frizzen face at halfcock. If that does not work to properly open the frizzen - I would be replacing the lock.

I should also note that the bottom jaw of the cock is hitting the frizzen pan fence. That is a problem also.

 

[smo]

I would try going back too a 5/8” flint that you stated the lock called for, flip it bevel down and give it a try.

One of the pics appears too show scrape marks above where your flints are striking the Frizzen face.....

I would give it a try before removing any metal from any springs.

But that’s just me.....

 

[Ironoxide]

Thank you for all suggestions.

I would like to say first the roughness on top of the spring visible on one of the photos is actually burned powder residue. I haven't cleaned the lock properly before taking photos (I used it before).

I've previously tried both 5/8 and 1/2 flint upside down (with the bevel down), but the flints wouldn't spark, would provide minimal sparks and would shatter quickly. I'm currently using the 1/2 flint because I noticed it lasts much longer. 5/8ths flint only lasts few shots. After it is installed it almost touches the frizzen and unfortunately shatters quickly. A new half inch flint leaves a small gap and that is enough for it to strike the frizzen a bit lower which means I do get those 10-15 shots out of it.

After reading your replies above I took a very thick piece of leather (4mm or a bit over an eight of an inch) and I put it between the bottom of the pan and the frizzen spring so the spring was compressed such that there was about 2mm (80 thou) gap between the frizzen heel and the spring. This meant there was no spring pressure on the frizzen when closed and only just before the place where frizzen would snap open it would engage. I found that with this the lock seemed to generate many times more sparks than normally. I also didn't notice any extra damage to the flint after firing the lock multiple times. Unfortunately at this experimental setting the spring doesn't fulfill one of its purposes. Namely there is nothing preventing the pan to open when the pistol is turned around etc.

However, this makes me believe I may get away with making a new weaker spring and I could leave the frizzen as is perhaps.

Those are two pictures of the experimental setup:

And I also created a short slow motion video of how the lock works with the bit of leather depressing the spring. The video is here

So now I just need to find some place that sells annealed spring steel in sheet metal form or go to the junkyard to cut a bit of a leafspring from an old car. Of course I would prefer the former.

 

[BruceHH]

Can you do a slow motion with the bevel down and the pad in and then out? Right now, you are hitting about half way down the frizzen face. It would be interesting to see what the above does.

 

[Zonie]

Before you try making your own spring, use a flat file to reduce the width of the existing spring so that the area of the bend is about 1/2 as thick as it is now. Taper the reduction starting at the original width as shown in this picture. The end location can be reduced or left about where it started. Be sure to sand the filed edge to remove ALL of the scratches or grooves that the file left.

Reducing the spring width to about half of its original width will reduce the spring pressure about in half.

 

[Darkhorse]

O.P. you asked earlier how to check the amount of force required to open the frizzen and what this value should be. I use a simple trigger gauge and hook it on the top of the frizzen and pull until the frizzen opens. The key is to place the gauge in the same spot each time for a consistant measurement. My Siler locks averaged around 8 pounds. At this weight when used on a rifle with set triggers it would jar the rifle so bad accuracy was out of the question. So after much testing I have set values that work well and please me. On a rifle with a single trigger I want my frizzen to open at 3 pounds. On a rifle with set triggers I want the frizzen to open just under 3 pounds.

Are you sure that frizzen spring is the correct one for your lock? It looks to have to severe a hump. When the frizzen toe rides up that slope it is stopped prematurely. I would like to see a slightly flatter spring that allows the frizzen to actually open. I would try a longer flint. The length your using is too short as it allows for metal to metal contact of the hammer to other parts of the lock.
At this point I think a shooting session with a well versed flint lock shooter who can work with your flint lengths would help a lot.

 

[Ironoxide]

Darkhorse, thank you for talking about your method and numbers. I imagine this will be very useful to anyone tuning their flintlock. I'll definitely use it. I just need to get the gauge first.

Can you do a slow motion with the bevel down and the pad in and then out? Right now, you are hitting about half way down the frizzen face. It would be interesting to see what the above does.

Yes and no ;-) I made a video with the flint bevel down, but only with the spring relieved. I only have few flints left so I didn't want this one to get shattered. It probably would if I tried it bevel down with full force of the spring as it happened before.

Also, regarding flint length. Please note there is only a 1.5mm (60 thou) space between the flint and frizzen on half cock so that's all length variation I have to play with. I didn't notice much difference in varying the length slightly, but I ensured videos in this thread are with the flint positioned almost to touch the frizzen at half cock.

So this is the test with the leathery bit and bevel down:


As you can see despite the flint hitting higher up there is a lot less sparks. Also this flint is pretty dull, but still sparks well installed bevel up which shows the video I recorded next.

This is a sort of baseline. It is recorded with no modifications to the lock. I should've probably started this thread with it, but I just recorded it.


As you can see the frizzen is pretty much held to the flint by the spring. Ignition is still good, but it eats through flints.

Before you try making your own spring, use a flat file to reduce the width of the existing spring so that the area of the bend is about 1/2 as thick as it is now.

Thank you for the suggestion, but I like to preserve original parts as much as possible in case I make things worse than they are. Making a new spring shouldn't be that difficult to me as I have a well equipped hobby machine shop. The only difficulty is finding the right material to purchase (ideally somewhere in EU).

It is interesting how much "wrong stuff" there is with this lock. Perhaps someone did swap the spring and it is not the original one. Or the manufacturer made it like this. The pistol was made in the 70-ties by a now non existing German - Italian company called Armi Jager. I could simply replace the lock, but having this pistol made 40 years ago by a defunct company has some collectors value to me so my first attempt is to keep it original where possible.

 

[BruceHH]

After rereading and watching the videos, the best I can offer is to modify/replace the frizzen spring and have fun.

 

[Britsmoothy]

That spring is very similar to ones used by Pedersoli!
You just gotta do as Zonie suggests and you have demonstrated yourself what a difference a reduced spring weight does.
Your not the first to work on their own locks.