Bolt Thrust Experiment #3 .22 LR & .44-40

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Bryan Austin
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Re: Bolt Thrust Experiment #3 .22 LR & .44-40

Post by Bryan Austin »

AJMD429 wrote:
Sun Oct 11, 2020 9:45 pm
and my kinetic energy
Yeap, that is certainly there somewhere.

Here is the same load in the test barrel, it did not move at all...and the firing pin, in this case the punch, was free to exit the housing. Energy is being transferred somewhere in there.

VIDEO - https://www.youtube.com/watch?v=a-NZFhkPip0
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Re: Bolt Thrust Experiment #3 .22 LR & .44-40

Post by KWK »

I'm sorry, oh brave Bryan, but the doctor is correct. Time is involved, and we don't have enough information here. We could figure out how much energy was used to move the hammer back (force times distance), but the energy to do that could come from a brief pulse of high force or a longer pulse of lower force. At least I don't see enough information, at first glance.

You know, if you made a straight link forked at each end, to replace the toggle pairs, and then put a strain gauge on it, you'd have a little load cell which could be recorded on a PressureTrace. It would be clumsy in use but should provide The Answer. Actually, a little rod of the correct length with a little strain gauge might do the trick.
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Re: Bolt Thrust Experiment #3 .22 LR & .44-40

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KWK wrote:
Sun Oct 11, 2020 10:15 pm
I'm sorry, oh brave Bryan, but the doctor is correct. Time is involved, and we don't have enough information here. We could figure out how much energy was used to move the hammer back (force times distance), but the energy to do that could come from a brief pulse of high force or a longer pulse of lower force. At least I don't see enough information, at first glance.

You know, if you made a straight link forked at each end, to replace the toggle pairs, and then put a strain gauge on it, you'd have a little load cell which could be recorded on a PressureTrace. It would be clumsy in use but should provide The Answer. Actually, a little rod of the correct length with a little strain gauge might do the trick.
I actually thought of that but my pressuretrace was sent to Larry for the 44 Mag Oehler/Pressuretrace comparison results tests. I was also looking at some industrial strain gauges but I don't see anything that would work at the moment.
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Re: Bolt Thrust Experiment #3 .22 LR & .44-40

Post by KWK »

Finding a suitable strain gauge should be straightforward. While the PressureTrace can record the information, it would take some work to calibrate it for this use, because it's set up for inputs assuming a round steel chamber, etc.

The simplest set up would use an oscilloscope. Excite the strain gauge with some battery, use a couple of resistors to form the bridge, and have at. The little rod set up could be calibrated by pressing it on a bathroom scale to, say, 50 lb.

Do you know anyone there with access to an oscilloscope? A buddy of mine owns one, but no local shooter I know has a '73 (and certainly none who would loan me one for such a test :D ).

It might be possible to put a strain gauge directly to one of the forward toggle links. A couple of assumptions have to be made here, and calibration isn't as easy.

Also, your basement set up could be used after fashioning a new breech, say a tube with a strain gauge on it, or a cantilever plate with the gauge and a firing pin hole.
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Re: Bolt Thrust Experiment #3 .22 LR & .44-40

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KWK wrote:
Mon Oct 12, 2020 11:36 am
Do you know anyone there with access to an oscilloscope?
Bryan, I'll work on this problem further before spring and get back to you with whatever I come up with.

I see the microphone jack of a smartphone can be used as an oscilloscope. It might be capable of recording a strain gauge for a pressure trace or bolt thrust experiment. Last night I loaded 2 free apps onto my iPhone to play with. While I'm an ME, I have several friends who are EE, so I can get a conditioning circuit right for a strain gauge, but I'll need to brush up on strain gauge calculations. edit: I looked at information for the mic input on my iPhone, and I'm not sure what it will take to condition the signal for such.

If nothing else, a cheapie oscilloscope in various forms can be found on Amazon for about $100. Some are stand alone, some use a phone or a laptop for display and recording. These would surely work and could replace a PressureTrace unit, at least for my purposes. I was planning to get a PressureTrace for some .30-40 load development, but this whole thing here has me wanting a more versatile set up for strain gauges. edit: I finally noticed 'scopes aren't sensitive enough to gather the signal directly from a strain gauge bridge circuit, so you'd still need a basic conditioning circuit, which brings me back to feeding a mic input.

Karl
Last edited by KWK on Wed Oct 14, 2020 10:28 am, edited 1 time in total.
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Re: Bolt Thrust Experiment #3 .22 LR & .44-40

Post by Bryan Austin »

Haven't seen one since 1983. I bet new ones are nice with all this technology!!
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Re: Bolt Thrust Experiment #3 .22 LR & .44-40

Post by Bryan Austin »

KWK, I catually do recall Jim talking about making a module out of an iphone but he was trying to keep the cost down as low as he could. I never thought to ask more questions about the iphone mod. I do have a few spare phones if you get a hankering to modify one.
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Re: Bolt Thrust Experiment #3 .22 LR & .44-40

Post by KWK »

Thank you Bryan, but it would not require any modification to a phone. The strain gauge amplifier board would just plug into the mic jack with a short cable. With a EE friend of mine, I'll be playing with this over the winter. If we get it working, I can mail you a duplicate of the amplifier board, and we can try to measure breech thrust with your basement set up.

There are many problems my friend and I can imagine, so I may need to punt and use a cheap pocket LCD oscilloscope instead of my iPhone. I should also note that while inexpensive, the smartphone option is limited in resolution in time. This will not be a replacement for a PressureTrace, but it would be good enough for me and possibly others to develop typical loads by.

To keep this thread from popping up too often, I'll keep in touch with you by PM. Thanks for all your work on this problem. It's interesting, as is your web site on the .44 WCF.

Karl
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Re: Bolt Thrust Experiment #3 .22 LR & .44-40

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KWK wrote:
Thu Oct 15, 2020 1:22 pm
Thank you Bryan, but it would not require any modification to a phone. The strain gauge amplifier board would just plug into the mic jack with a short cable. With a EE friend of mine, I'll be playing with this over the winter. If we get it working, I can mail you a duplicate of the amplifier board, and we can try to measure breech thrust with your basement set up.

There are many problems my friend and I can imagine, so I may need to punt and use a cheap pocket LCD oscilloscope instead of my iPhone. I should also note that while inexpensive, the smartphone option is limited in resolution in time. This will not be a replacement for a PressureTrace, but it would be good enough for me and possibly others to develop typical loads by.

To keep this thread from popping up too often, I'll keep in touch with you by PM. Thanks for all your work on this problem. It's interesting, as is your web site on the .44 WCF.

Karl
Thanks,

I also found a few things....which I am sure there are tons more...

I saw where some think the primer creates 5k to 10k psi just inside the primer pocket (not chamber pressure) and can create 700lbs of forward case thrust.
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Re: Bolt Thrust Experiment #3 .22 LR & .44-40

Post by KWK »

I saw where some think the primer creates 5k to 10k psi just inside the primer pocket (not chamber pressure) and can create 700lbs of forward case thrust.
I hadn't come across that one. I always imagined the primer as more of a blow torch than a pressure chamber. Now, if it's 700 lb forward, it would be 700 rearward as well. However, the primer pocket is only .210" in diameter, and if the primer were a perfect piston, 10 ksi on it would be about 350 lb, so 700 seems rather unlikely. Then you add in the primer's cling to the pocket as the pressure inside it rises...
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Re: Bolt Thrust Experiment #3 .22 LR & .44-40

Post by piller »

Is it any wonder that some people have had catastrophic failures when they use the wrong powder or overload a case?

There really is more physics to this than what it first appears.
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