Frizzen rebound

[Pete G.]

Last several times I've been to the range I noticed a thin black line forming atop the flint about 5/16" back from the front edge. On close examination it proved to be where the heel of the frizzen falls if I push it back against the spring until it touches the flint. I don't see where it could be anything but the frizzen rebounding, but I am having a hard time grasping just how quickly this must happen. I can trip the lock while watching closely and see a small amount of rebound if I watch very closely, but the gap with the cock at rest is a little more than 3/8", which seems like an awful long way to bounce back. Could there be something going on while firing that I am not seeing while just tripping the lock? I am getting long flint life and reliable performance, so is this something I really even need to be thinking about?

Incidentally it is a Chambers Late Ketland with a roller if that means anything.

Comments???

[rich pierce]

Pletch's super fast movies of locks show they all rebound.  It's too fast for us to see.  I think some rebound with a lot more force than others.

[Larry Pletcher]

Rich has it right.  They all rebound -- some more than once.  The only way to see what is happening is to watch in in slow motion.  These clips are filmed at 5000fps and are played back at 30.  See the link below:

http://www.blackpowdermag.com/featured-articles/new-high-speed-video-from-friendship-09.php

Regards,
Pletch

[smylee grouch]

Thanks for posting those vidieos Larry, they are a real eye opener and give everyone more perspective as to what realy happens when we pull the trigger.  Gary

[Pete G.]

Thanks again, Larry for your work in this field. It has helped to dispel a lot of the old "truths" about these locks. I had watched your videos previously, but more from the aspect of ignition. I went back this time with the specific idea of rebound. It is suprising how much some of these things do come back, but still I didn't see any that came back enough to actually strike the flint. I'm thinking that my lock does so because the wheel has reduced friction enough to let this happen. Perhaps advancements are always so, eh ? Now I've got one more thing to try and ignore while shooting. Maybe this is one of the reasons I haven't been able to shoot this rifle offhand quite as well as some of my others. Well, that, and the double set trigger that feels a little different, and the weight of the rifle, and the different sights, and the phase of the moon, and.............you name i t. One more good reason to keep burning powder.

[plastikosmd]

Something wrong w me, watched every one

[Daryl]

I watched them all too - cool show!

I've been wondering, Larry, when timing, or setting a time for a particular lock or priming compound, when, ie: at what point in the ignition cycle is the 'time' recorded' as being the time for ignition of that lock or powder grade?  Is the time set when the flame propogates to the top surface of the lock pan - ie: table?, when ignition is first seen of the priming charge, or some other height of flame front?

I also noticed that lock geometry is reponsible for the height or resting position of the rebounding frizzen - ie: angles of wheels, stirrups, etc.  Due the roller bearings on the frizzen running off arches or raised portions on the spring's surface, the main level of the spring where the wheel comes to rest is much lower in relation to the level at 'cocked' postion.  Once 'fired', this alone allows the frizzen to rebound further back against the flint and actually hit it.  This was evident in several of the locks, ie; Mantons as used on many Hawken or English-type rifles.

[Larry Pletcher]

I watched them all too - cool show!

I've been wondering, Larry, when timing, or setting a time for a particular lock or priming compound, when, ie: at what point in the ignition cycle is the 'time' recorded' as being the time for ignition of that lock or powder grade?  Is the time set when the flame propogates to the top surface of the lock pan - ie: table?, when ignition is first seen of the priming charge, or some other height of flame front?
.... snipped

Hi Daryl,
There are actually 2 possibilities.  The only one I depend on is when using the computer. In this case the time stops when the photo cell "triggers, floods, trips, fires, etc".  (The term "trigger" may be the best .)  The photo cell should change the "zero" to a "one" at the same point every time.  I don't know how much light it takes to trigger it.  I guess it doesn't make much difference since it requires the same amount of light to trigger it each time.

If I have to judge time by looking at a slow motion video human judgement enters the picture.  If determining mechanical time I'm comfortable.  I can run the video frame by frame and tell exactly when the flint edge stops.  In fact, it was doing this that I could see the top of the cock flex downward after the rotation stopped.  This would often take 2 frames; then the top of the cock would return to normal.  So, using this method we're good to the nearest frame: 1/5000 second.

But - dealing with ignition is another story.  Using video, one has to decide how much light constitutes ignition.  This is obviously arbitrary, and that's why I am not fond of quoting ignition times from video.   My method was to decide that a ball of flame the size of a nickel would be my ignition point.  I tried to visualize a nickel over the pan and stop the frame by frame when the flame reached that size.  I'd note the frame number at that point. You can quickly see why I don't like the video method for pan ignition.

Actually there are 2 reasons for not using slo-mo for times.  One is that with the computer I can time the lock for 20 tries and find the average.  That's much better than one video trial.  Add to that the arbitrary decision-making done with video and the computer wins hands down.

The videos strength lies in the ability to actually see what is happening with the flint, spark development, frizzen movement, etc.  We've seen stuff that we never dreamed was happening.  Anyway - cool stuff.  I wish I could afford to own one of these cameras.  We're just scratching the surface.

Regards,
Pletch

 

[Daryl]

TKS for the explanation Larry.  It is a complicated process.