Recoil testing of large caliber muzzle breaks

[choppero]

You have made my day again. Now I need to buffer the return in order to be able to test rifle with scopes attached. As It stands now, the sled rest against a solid stop. And I would assume the return force is equal to the recoil force. Not good to drop a scope from such a great height. I may be able to make the stop like a recoil pad or design a spring stop. The pad idea seems a lot less labor intensive.

[JAlberts]

I'm glad to hear you are making progress with your test assembly and I have really enjoyed be able to participate.

You should definitely pursue the recoil pad solution.

Using spring would only create another problem rather than solving the current one. A return damper needs to be something (like a recoil pad) that absorbs energy; and, springs store and return energy rather than absorbing it.

If a spring were to be installed, it will be compressed by the returning slide resulting in a recoil force of its own that will then partially compress your original recoil spring which will then react and start a period of undamped oscillation between the two springs that will shake the complete test assembly.

[dalecyr]

Hey Joe:

I've been thinking about making this sort of thing myself.
This has been a good discussion to follow.

Would the concept shown in the attached drawing mitigate the issues around a coil spring?

(this drawing does not show the sled, but something like that would be necessary.)

dale

[JAlberts]

I'm not Joe but I will weigh in a bit on this arrangement because it looks like it could be a very viable solution provided you can get a cantilever leaf spring design long and/or flexible enough to allow the amount of recoil travel suitable for providing good measurements in a reasonably compact design.

Just a couple of comments on details about the concept: One of the advantages of thios arrangement is that by placing the top leaf connection point on the rear cup a bit higher directly in line with the gun barrel bore you will be able to totally eliminate any vertical reactions that would create any friction on a guide assembly. Also, the best arrangement as far as a "sled" is concerned might be to simply place a compact guide and measuring assembly directly at the top of your current barrel support post with a moving guide that clamps directly on to the gun barrel.

At the same time, you are still going to have to deal with the same post firing return stroke damping as choppero is now working on so the front guide mounting and post would need to be reinforced to handle this loading.

As far as the back assembly, for safety the complete rear mounting assembly, spring, etc could be enclosed in an open front box cover.

[JAlberts]

After thinking about my above response, I think I need to clarify/********** a couple of items.

First, my response about only needing a front mount guide is predicated on the assumption that the top end of the cantilever spring will attached to the gun butt receiver with hinge pin assembly.

Second, although the simple arrangement does not require a "sled" assembly, it might be a good idea to connect the gun butt receiver to the front guide assembly, possibly with a couple of side plates that would allow adding some additional weight(s) to the moving assembly. My reason for mentioning this is that in choppero's design, his sled assembly adds weight that acts as an inertial damper to slow the acceleration and velocity of the gun assembly under recoil (and rebound) much in the way that a heavier gun can reduce the shock and recoil speed on a high caliber weapon.

[dalecyr]

I'm not Joe ....

Ah, yes. Sorry about that.
I was thinking of Mr. Boggs.


Anyway, another idea, not very well thought out.

Instead of using a spring of any kind, with its attendant problems,
what do you think of the concept of using weights on an incline ramp
to measure real world recoil?


I haven't drawn up such a contraption,
but it seems more reliable than springs,
with the benefit of being able to calculate actual psi of recoil.


Thoughts?

[dalecyr]

The concept is not unlike the High Striker at a county fair.
The more force applied to the striker plate, the higher the hammer goes.

[JAlberts]

Dale,
First, as far as the benefits of other methods of measuring force vs a well designed and installed spring, the spring wins by miles. It is for this reason that every one of the 100,000's of safety and pressure relief valves used as the "last line of defense" in pressure systems in power generating, chemical and petrochemical plants all over the world ultimately depend on a spring as their primary operating element. While many parts in these valves that have rubbing contact or sealing functions are periodically replaced, the one part that is essentially never included in a valve service kit is the spring. Functionally, springs have the benefit of operating totally without friction and particularing in very dynamic operating condtions with very little weight and reciprocating inertia.

With respect to the ramp and block concept, in this arrangement you are totally depending on friction between the block and ramp to dissipate the energy of the muzzle blast and the accuracy of your test assembly; and, friction is one the most unreliable and variable forces due to potential changes due to surface contamination and/or wearing over time.

With regard to the striker, since the weight is traveling vertically up the rod there is really no friction involved (unless the operator does something to create it). So, if you want to make an assembly that directs your muzzle reaction to a vertically rising weight that should potentially work very well.

[Cragyon]

Well, didn't i miss all the fun.

[dalecyr]

I managed to get a little time to think about this today. I can redirect a horizontal force into a vertical force with insignificant loss (insignificant for this application). So I can then use that impulse force to lift a weight of known quantity vertically, with no significant friction. It seems like knowing the weight, and measuring the amount of vertical rise of that known weight before it falls back to the resting state, I should be able to calculate the absolute force to do so in... oh, say... psi or some other useful unit of measure. So I spent some time rummaging around in Newton's laws, force transfer equations, and the like. But for the life of me, I can't seem to find the right combination of Greek letters to figure it out. Lets say the vertical impulse force raises a one pound weight to a height of 1 foot. How do I figure out what the initial force was in psi? (Feel free to modify the units.)

[JAlberts]

Dale,

First, I want to clarify the issue of the units of Force vs Pressure. Force is the total load one object exerts on another and is generally stated in lbs, ounces, etc, or their equivalents in the metric system. Pressure is the measure of how that Force is distributed over the contact area between those two bodies and is generally stated in psi (lbs/sq. inch), psf (lbs/ sq ft), etc or its metric equivalents.

Next, like you, although I am not saying it cannot be done, I have not been able to envision or identify a method to calculate a specific rifle reaction force based upon the resulting height of a weight in the type of device you are proposing.

In a static system (like a block sitting on a table, etc) it is easy to determine the force the block exerts on the table.

With a transient dynamic force such as the firing of a rifle, there are several factors involved in calculating the recoil force delivered to the gun by the acceleration of the bullet and the thrust force generated by the high velocity gas discharge at the muzzle of the rifle barrel. The only way that this kind of force measurement can be easily and accurately determined is with an electronic load cell and an analog plot of the load cell’s output during the recoil event.

On the other hand, I suggest that an absolute force value is not really necessary or appropriate for determining the relative effect of one rifle caliber or muzzle brake design vs. another. I propose that the effects of a rifle recoil between one individual and another are more dependent upon the physical characteristics, i.e. weight, amount of shoulder ****** mass, etc, of each user than on the actual recoil force delivered to the shooter’s shoulder that must be absorbed and dissipated by the resistance and recoil of the shooter’s body.

As a result, what I am proposing is that your device, by its capability to deliver a variable maximum weight height proportional to the recoil of a weapon, will allow you to differentiate the effects of any combination of rifle calibers and/or muzzle brakes and convey this information to a potential user in terms of a percent value of one arrangement vs. another.

Of course, the ultimate test is how the shooter perceives the difference.

[dalecyr]

Well now. There is a wrinkle in the concept.
That is, describe the recoil relative to a commonly known "standard".
Interesting.

I'll still have to figure out how to quantify the force in some reasonable unit of measure.
But rather than lbs (for example), it will be in percent.
Or maybe a scale.
Ruger Model 10/22, standard rifle, full length barrel, yada, yada, yada is = "1".
Winchester Model 12, pump action, 3" magnum, being "10". (for example)
This idea makes it relative to something the shooter might already know.
I like it.

Another idea I had was to calibrate it empirically, via a weight on a pendulum.
Raise the weight to x height, and let it slam into the measuring device's contact point.
It is easy to calculate the engery transfer with this method.

And maybe I can figure out, or develope, the equation to quanitify the force of any particular firearm.
Further thought is required.
(that happens a lot with my ideas )