High Speed Linear Actuator - 12-Gauge Shotgun?

I would try a custom gun shop....Like Red Jacket Firearms...

I bet this will require a bigger cannon than a 12-gauge shotgun.

[Note: 10 lb ≈ 4.5 kg; not 22 kg.]

Well there are 10 Gauge shotguns?

I'm surprised you haven't considered spring actuated piston. Something on the order of an automotive coil spring that could be compressed by hydraulic cylinder, and released when the required kinetic energy is stored in the spring. Sorry no practical experience.

Tornado is right, there are 2.2 pounds per kilo not the other way round. Or, did you mean 10Kg (22 lb)

Agreed he'll need some kind of truck suspension spring 8700 lbf for the acceleration plus 120 lbf for the friction.

Don't forget to add the extra mass of the spring and other movable parts though.

"...to move about 10 lbs (22 kg.) mass..." Never mind, Tornado has it covered.

Cycles per minute/hour/day?

Things like this exist, but I don't know of any DYI plans.

http://www.specialdevices.com/industrial.htm

I'm hesitant to say this since you want no speculation, but I'd look into the charges that are used to deploy automotive airbags.

You are trying to impart a specific amount of energy into a package, over a given distance.

You can develop the same forces by stopping the package in 6 inches.

This isn't speculation.

We fired six inch diameter aluminum cylinders filled with electronics into 12x12x12 inch blocks of plywood to simulate setback forces of artillery shell fuses. We fired these down a long tube that had a hard vacuum pulled on on one end and compressed air behind it.

I'm speculating (I'm a rebel), but I think this might be the best answer. Hard to know exactly what he is trying to accomplish, but a good guess would be that it has to do with forces tolerated.

It worked very well to simulate the setback forces of a 105 MM artillery shell leaving the barrel.

The shock start spin tester was pretty wicked, too. Couldn't do both at once.

A warning or two and an advice.

All shells, no matter what cannon or gun uses them, rely on specified high chamber pressure to burn properly, otherwise they fizz out unreliably. The chamber pressure is generated by the tightly fit bullet. Tightly against the powder, and tightly against the rifling grooves, where it will be swaged into the grooves before moving.

The primers are normally mechanically initiated, with very many millisecond spread. I do not know how many, but plenty. An aussie outfit built guns with electrically triggered primers. Demo was impressive.

I would pursue a sort of mechanical inversion of a racing Wankel engine, with a few twists. Advantage: racing engine shops know all there is to know about them, their tunig, etc. Multiple fuel iniectors, stock. Multiple ignitions, stock. Cylinder wall porting, stock for intake and exhaust. You need boost? Use nitro or pure oxigen for an 4 - 5 times power boost.

Timing? Those racing engines routinely run over 12thousand rpm. That is 200 rev/sec. That is 5millisec/rev. I am rudely simplifying, but it is for the scale of things only. If the ignition has to be correct to 5%, that is 0,25 millisec only. Electronic control is tighter by a magnitude, than that.

If you think, plain air is not forceful enough, go for oxigen for a 4-5times improvement. If you are brave enough, another 10 times can be gained by compression like in a Wankel.

I am willing to bet a box of good cigar, that the extra compression will not be needed, for a "relaxed" charge and ignite function doing all you need in a relatively simple cylinder / piston arrangement.

And no flying srapnel anywhere.

There is no merit in designing new cylinder head, piston with rings, pins with connecting arms, etc. Those are already done for you. Airplane engines are bolted together from individual components. All have double ignition, bigger ones have direct fuel iniection. Components from a runout engine will do fine.

Go to Youtube for Continental or Lycoming engine rebuilding for visuals, and visit a friendly airplane mechanic at a nearby airport.

If you have to use some sort of explosive device would the charges used in air bags or seat belt tensioners be more controlled?

I guess a mechanical solution would be to use stored energy. Springs have been suggested, another way might be to use a flywheel.

Personally I like the suggestion of accelerating the unit to 168fps then stopping it suddenly.

Shot shells might work. There are many ballistic experts who can build such a device, or you could start with a signal cannon. Make sure you use smokeless powder shells as black powder burns too slowly. If this was my project, I would consult with the people who build the explosive actuators to launch air bags or ejection seats. The explosives they use burn cleaner than any gun powder and they are triggered electrically.

Incidentally, these actuators utilize a rupture disk that fractures at a predefined pressure to release the stored energy in a millisecond or less. It's faster and more reliable than counting on the pressure pulse of the explosion.

What's wrong with a hammer swung on a pendulum? Crank it up to the desired potential energy, and release. The full force of the hammer impacts the target and bang! you have the exact amount of instant acceleration desired.

Set the jig up with a shot filled impact head in rubber or leather and have it hit a plate and pin so you only have to replace the pin. Then you can reduce the force per square inch down to a small area and drive your test peice with that. Think of it like having a captured nail for your hammer to hit.

With everything controlled and connected through simple parts and framework you will have a safe rig with all the adjustability you need.

Why dont you try using a servomotor (1.5 Kw would do) and a ballscrew with long lead, normally a servomotor has 3000 rpm and if you use a ballscrew with a lead of 40 mm 3000/60=50 rev/sec 1 rev=40mm, 4 rev=160 mm 0.2 milisec aproximately,

??

50 rev/sec = .020 (20 milliseconds) per rev. 4 revs = 80 ms

Getting the motor up to 3000 rpm in a few milliseconds would be a challenge.

Wouldn't you get the motor running first, possibly with a flywheel to give it some inertia, then 'dump the clutch' to engage the actuator?

Wouldn't you get the motor running first, possibly with a flywheel to give it some inertia, then 'dump the clutch' to engage the actuator?

Then there would be no need for a servo motor. Also, STL has ruled out using a clutch according to his original post:Originally we had thought to drive it with a slider crank mechanism powered by a motor/flywheel combination running at 3600 RPM, but that became infeasible when we could not find a clutch/brake that would engage quickly enough (3-4 milliseconds).

Maybe a very large dog clutch could be used, perhaps with malleable engagement faces that could be replaced as required.

This is a simple physics problem. I've used the 10kg mass (in dispute) as an example. I've also assumed that 6 ms is an acceptable acceleration time. Based on these numbers, it should be clear that meeting the OP specs will NOT be as easy as some expect. The energy, power, and force involved are pretty extreme.

10.00 (kg) mass
50.00 (m/s) velocity
0.15 (m) distance
8333 (m/s^2) acceleration
12500 (J) energy
83333 (N) force
0.006 (s) time
2.08E+06 (W) power required

Chemical energy will work. I've sequentially electrically fired multiple primers (in 357 magnum shells) with millisecond accuracy, but it was a significant effort.

EM energy will also work. I've designed and tested electromagnetic launchers which would meet your specs for a 1/2 kg mass. One could be designed to perform the function you described. The type of EM launchers I'm referring to are NOT the classic rail-gun or coil-gun type, but they are fast (sub-millisecond), repeatable, and require minimal maintenance. Without knowing your project time and cost constraints, I'd guess the EM launcher approach will be too costly.

Best wishes finding an off-the-shelf mechanism for your application.

I suppose you would need to first decide upon a mass (did you mean 10 Kg?) and then calculate the muzzle energy. It seems that a 12 gauge shell would be a small part of the energy required, in any case.

I must question the LINEAR actuator in the otherwise well written up piece. The only really linear I could come up with is the Hypersonic Wind Tunnel (Nasa, Wikipedia). I am sure, that is a bit over the top for you. The next is the steam catapult on an aircraft carrier. Fairly linear, moves 30 tons+, easily reaches over the required speed. Getting a ship for it? Still over the top. The next down is an Eathquake Shaking Table and Shaking Table used by outfits like Nasa, to shake payloads thru various frequencies. Complex and verry expensive. Still over the top.

The post driver you mentioned is a hammer. It does not actuate, it imparts impulse. The piston pushes the ram, that compresses, and impart a short stroke / large force (40/700 times shorter, at least) to hammer something. Highly nonlinear, very short stroke.

A hovitzer has muzzle velocity over 3000fps. A slowdown device attached to the muzzle. Ammunition piled up on the side. Wow! I would like to witness the permitting process for that!!

Nah, your best chances come from the good old piston engines. Picking the right cylinder /piston combination will give you the stroke you want, and the force you desire. No explosion (knocking) in the cylinder, but controlled burning. More or less linear movement. Components off-the shelf. Even the propane conversion is too, if you so desire. Or direct iniection. All needed knowledge and diagnostic tools available. Including boosting with nitro and oxygen.

Maybe have a look at a captive bolt stun gun for ideas.

Nah, your best chances come from the good old piston engines. Picking the right cylinder /piston combination will give you the stroke you want, and the force you desire.

It sounds like you are thinking of one cylinder to do the expansion, and another to do the launching? A 12 inch stroke engine would be required, because only the the first 90 degrees of the stroke would be accelerating the payload. That's a pretty huge engine, and it would be difficult to get the required acceleration, given any conventional fuels and cylinder pressures.

I wonder if a partial stick of dynamite (or some water gell explosive) in a 8" bore hydraulic cylinder might work. Fast acting blasting caps ignite quickly enough for the application. If the rod side of the cylinder were air filled, and closed with a valve, then the stroke of the rod could be cushioned. The first 6" of stroke would be used to launch the payload, and the remaining 3 feet (or so) of stroke would be used for deceleration of the piston and rod.

There are cordless and hose less nail guns available. They rely on a predetermined propane gas charge to be ignited by a spark in turn provided by an onboard battery. The manufacturer is Pace I think. Available at the big orange home improvement stores.

I am pleased, that you put thought into the discussion.

What I proposed, is a single cylinder head, a single piston+rings, a single connecting arm, and no crankshaft. Instead, it pushes the actuator arm straight. The reason I proposed it that way, that the loosely fit piston does wobble. An engine handles that fine, there is no need to control it any better.

If you take a close look to the propane hammer, many ancillaries are dealt with, including a relatively weak return spring. The return of the test mass to zero is the designer's business, not mine.

Refinements, as mixture control and such, to dial in the precise power to push, is a different story, for a different time.

I have some doubt that the flame fronts of conventional fuels would be fast enough for this operation. Just a guess, though.

Do you think C4 would burn fast enough?

I'm not familiar with it, but this task would probably require a fast explosive.

PMSL!! I read that as:

"Do you think CR4 would burn fast enough?"

I think we probably produce enough hot air without actually combusting / exploding

Power waiting to be harnessed....

I too had to look at what i wrote twice.

I love youguys dearly, but brainfog did set in, really.

C4 explodes. Fuel in a cylinder verry much preferably to burn, fast, with steady flame front. Explosion (low or high grade) in cylinders is called Knocking. Destructive.

I started out with the rotary Wankel engines successfully used in racing trucks. Those guys regularly turn over 12 thousand rpms. Slow flame front? I rather think not!! Quite appropriate to the application.

As mjb wrote it is a simple problem of physics:

let us assume that you accelerate the mass with a constant net force so that acceleration is constant, then the equations are w=a*t and s= (a*t^2)/2.

S/W= t/2 = 0.15 [m]/ 50[m/s] = 3e-3 [s] this would be the time to reach the 5 m/s over 0.15m of stroke.. The acceleration would be a= W/t= 50/0.003=1.67 E4 m/s². The force required to obtain such an acceleration would be F= M*a+Ffriction= 10*1.67E4+ 535= 1.6754E5 N ≈3.766E4 lbs! Involved energy would be E= 1.25E4 J only for acceleration.

I very much doubt that this can be done even with a pyrotechnical device.

It could be better to analyse the effect one wants to obtain and look at an other approach or change the parameters values.

I had difficulty following the math. While it seems correct, - and I left it intentionally to OP himself - it is not nearly the answer in mechanical engineering design.

For example, the piston does not have to start at the same moment as the mass.

But, what bothers me most:

WHERE IS THE OP?!? HE CAN TERMINATE< CONTROL OR REORIENT THE DEBATE>.

IS HE MIA?!?

He has reinvented himself as another entitity.

The OP has not commented since the OP.

Perhaps due largely in part to this statement in the OP:

No speculation please! Does anyone have knowledge of, or experience with such a system or components and/or plans commercially available?

There was an error I forgot a factor of 2! At this opportunity (the second look) I estimated the feasibility. In order to obtain bigger piston diameters I made 2 assumptions 1) the mass is of a light alloy with 2800 kg/m^3 and the length and diameter are equal. This leads to a diameter d= (4*M/(pi*ρ))^1/3 = 0.1657m.

The pressure to bring the necessary force will be p= (4/pi)^1/3*M^1/3*ρ^2/3*a

with M=10kg, ρ=2800kg/m^3 and a= 8.35E3m/s² the pressure is 3.874 N/mm² or about 560 psi. Now the problem is how to generate this pressure without the decreasing curve of a pyrotechnic device. Assuming an adiabatic expansion of air the final air pressure will be p2/p1= (1+ΔV/V1)^-k. If we assume for instance a pressure drop of 5% the ratio p2/p1=0.95 and the air volume has to be V= pi*d²*stroke/0.07445 = 4.32e-2 m^3 ≈ 10 gallon. It seems that it could be done with quite simple equipment.

Thank you Nick #38. That is much closer to my 5 - 10 inches piston diameter, back of the envelope starter of mine. I have a low msec flame front propagation estimate, based on racing Wankels. A large diameter, large throw piston's flame propagation must be even slower from start to end. How much slower? I do strongly doubt, anybody knows. Hence, experimentation is called for. And that is straightforward. The resulting family of curves is sufficient to set experimental parameters.

The piston setup proposed is an atmospheric pressure arrangement, definitely not the 8x - 12x compression engine piston's. But, it is a slow wavefront piston pushing arrangement. You like it, adopt and improve it. You do not like it, abandon it. Any way, it will cost you. As further engineering is not free anymore.

A large diameter, large throw piston's flame propagation must be even slower from start to end.
With low pressures, low temperature, and not much turbulence, 50 cm/sec.
In a V8 with 4" (100mm) bore and 4" stroke, about 40 degrees of spark advance are required to cause the very turbulent, relatively high pressure and high temperature burn to finish by BDC. At 6000 rpm, this (220/360 of a revolution) would require 6 ms. 0.1 m/.006sec = 16.6 m/s

From what I understand, you bracketed that particular quantity nicely. I agree, that it may not be possible to do it much better, without experimentation.

Lots of informed suggestions and some math. The physics is not quite as simple as stated because the acceleration caused by a propellant is not uniform. See http://en.wikipedia.org/wiki/Internal_ballistics. I suggest the best design to solve this problem depends on the conditions under which OP must operate. If a large apparatus can be used in a laboratory, the design will be different than if it is be used on a battlefield. Shot shells were formerly used to start large aircraft engines (cartridge starter). This is due,in part, to the weight and complexity of electric starters and their need for energy storage (batteries). It's more compact to store the required energy chemically.