Inalex Alpha C1 Pneumatic Speargun

[popgun pete]

It looks like I misinterpreted the comment concerning the maximum pressure achievable in the "Alpha C1" gun as being 30 Bar (refer post#28). For that to happen the pump rod stroke length needs to be limited to 30 times the length of the dead space at the far end of the inner barrel, which in the "Alpha C1" serves as the hand pump bore, assuming that the volumes concerned both before and after the pump stroke are simply sections of the same diameter cylinder. However I have since learned that the spear shaft is used as the pump rod, which means that the piston can reach all the way back to the face of the closed off releasing valve. This results in a very small pumping dead space and hence the pressure level attained in the gun can be higher than 30 Bar. Bear in mind that a 14 mm diameter inner barrel represents a 16% increase in cross-sectional area over a 13 mm diameter inner barrel and a 62% increase in cross-sectional area over an 11 mm diameter inner barrel, hence the force required will be that much higher to push the pump handle down at the very end of the pumping stroke as the air transfers across into the outer tank. To reach 30 Bar that effort would be about 46 kg or 100 pounds on the pump handle, which indicates that 20 to 25 Bar is probably enough chamber pressure! Conversely the big bore inner barrel also means that less chamber pressure is required to shoot the spear with the same level of propulsive force, assuming that the extra water volume in the inner barrel can exit the muzzle without causing any offsetting loss of performance. The large muzzle relief ports are positioned close to the tip of the muzzle as the shock absorber is mounted on the front of the piston rather than mounted inside the muzzle body where the relief ports would have to be behind the "anvil" or "stopper" face.

 

[tromic]

 

[popgun pete]

One of these guns has recently arrived in the USA, an order was placed via the company's web-site.

 

[Anastasios Hondros]

Hello Pete.
I bought the Alpha C1 127 a month ago!
I'm very pleased with the gun and i'm using it for deep hunting. ( 30+ meters)
The preasure is at 30bar , ( at least for now )!
It is very powerfull !!
Im in touch with Alex for any development!
I would be happy to contribut to your conversation and help any friend that has questions.

 

[popgun pete]

There is now the possibility of a pneumo-vacuum version as there is a patent for a vacuum muzzle for this gun. The diagram from the patent is attached here. "GR20120100237A" is the patent number

 

[Diving Gecko]

Hello Pete.
I bought the Alpha C1 127 a month ago!
I'm very pleased with the gun and i'm using it for deep hunting. ( 30+ meters)
The preasure is at 30bar , ( at least for now )!
It is very powerfull !!
Im in touch with Alex for any development!
I would be happy to contribut to your conversation and help any friend that has questions.
View attachment 40905 View attachment 40906 View attachment 40907 View attachment 40908 View attachment 40909 View attachment 40910 View attachment 40911

Just curious - how do you manage to load a 14mm gun at 30 bar?
I have trouble loading my 13mm gun at more than 20bar (with a 6.75mm spear).

 

[popgun pete]

It is not easy, but releasing valve trigger operation makes step-wise loading possible, similar to loading the 14 mm bore GSD "Katiuscia" and "Dynamic" guns which also use a releasing valve. I did use both those GSD pneumatic guns, but the trigger valve piston's "O" ring sealing valve seat had problems, in fact my smallest "Dynamic" never fired a shot in anger. I rebuilt a multi-power switch "Katiuscia", but it took three guns donating parts to do it. When new I could not afford to buy one as they were much more expensive than a "Sten" and were full of tiny intricate parts. At that time the Mares "Cyrano" did not even exist.

 

[Diving Gecko]

[...]

Maximum Operating Pressure: 30 Bar
Usual Operating Pressure: 18 - 20 Bar
Loading Effort: 22 - 25 kgf for the above air pressures

[...]

I don't understand these numbers, but I might be missing something;-)
A 14mm piston has a surface area of 1.54cm2, correct?
So, at the muzzle, the loading effort at 20bar shouldn't that be (1.54cm2 x 20kg/cm2 x 1.019) = 31.4kgf?

Where is the magic happening in this gun?

Also, about the step-wise loading. I can't get my head around how that, in practical terms, should make things that much better. When I load my gun, it is easiest in the beginning as the pressure acting on the piston is lower. Then just before latching, pressure is much higher but at least the spear is better supported so I can put more force on it. So, I pressurize my guns to what I can load against at max @ the trigger latching point.
Does that change with step-wise loading? The max force needed is still the same and still at the end the pump stroke, right?
You can take a few breaks through the loading process but does that really help that much? Maybe it does.

(BTW, apologize for the strong response to you on the other forum;-))

 

[tromic]

You can think about step-wise loading to be like using a hammer. Insted of pushing a nail in a board you use momentum of the hammer.

 

[Diving Gecko]

You can think about step-wise loading to be like using a hammer. Insted of pushing a nail in a board you use momentum of the hammer.

Thanks Tomi,
Hopefully, some day I can try a gun with this feature. Until then, I will just have to wait until someone who has one can try to load his and then try to load a regular oleo to see how much it helps in real life.

BTW, I am allegedly too stupid to figure the following out, can you help? But how come a gun with a 14mm piston only needs 25kgf loading force at 20bar?

 

[popgun pete]

My experience is real life, the theoretical stuff is to help explain the real world to guys like you. That loading force range is from the manufacturer's figures, but they are for the low end of charge pressures used in the Alpha C1 gun and are not representative of the force required to use the gun at the max pressure of 30 Bar. It is common practice in speargun manuals to quote figures that will not turn potential buyers off, so the loading effort is usually under quoted. Plus guns supplied from the factory are often only at 15 to 20 Bar for many pneumatic guns. In a sense the manufacturers want to start the user off at the shallow end of the pool rather than throw them in the deep end from the beginning. Also loading figures should really be in energy terms, such as Newton-metre or Foot-pounds as it is the force, which varies, over a loading distance X which is the working course of the piston.

 

[popgun pete]

In Russia, where the firing squad probably underpinned the need to be honest in providing gun specifications for Soviet State owned factory production underwater weapons you received this level of information in the "handbook for operating".

Note the significant difference between the ranges "flying harpoon" and "striking target"!

 

[popgun pete]

The "Prizm", or RPB-1M, has a 14 mm diameter inner barrel and a compression ratio near 2.0, so too much initial pressure and you cannot cock it. Mainly because the spear has a necked down notch for the forward latching sear tooth to engage and too much loading effort can bend the spear at that weak point, even though the shaft body is of 9 mm diameter. The "Prizm" tank is 30 mm OD and with plastic only used in the handgrip's scales and the "safety tube", screw action gadget, the gun sinks like a stone.

In the Inalex "Alpha C1" the outer tank is much larger in diameter in order to bring the compression ratio down to more realistic levels. Another feature is that the "Alpha C1" gun uses its inner barrel as an air pump when you initially charge the gun at the start of the season. Thus if you can push the piston down the inner barrel on the last stroke to pressurize the gun then you should be able to load it when the gun is set to shooting mode. However some users may prefer to leave that big effort to actually cocking the gun and choose instead to pressurize the gun with a scuba tank, as is seen in the above photos. That is why the scuba tank is connected via the gun's muzzle as the releasing valve trigger system blocks off any access to the tank at the rear end of the "Alpha C1" pneumatic speargun.

 

[tromic]

Thanks Tomi,
Hopefully, some day I can try a gun with this feature. Until then, I will just have to wait until someone who has one can try to load his and then try to load a regular oleo to see how much it helps in real life.

BTW, I am allegedly too stupid to figure the following out, can you help? But how come a gun with a 14mm piston only needs 25kgf loading force at 20bar?

Force on 14 mm piston under 20 bar pressure is 31.38 kgf!

 

[popgun pete]

A new video is shown here comparing two guns, "Alpha C1" and a band gun with carbon barrel: http://www.google.com/url?q=http://vk.com/video224496305_171564282?fb_ref=Default&sa=D&sntz=1&usg=AFQjCNHy9L-BuGm7Gez70mbXYusm6RU3gQ

 

[Diving Gecko]

Force on 14 mm piston under 20 bar pressure is 31.38 kgf!

Thanks for clearing that up. So, it seems like there is an error in the data posted here and elsewhere, or at least it is unfortunately worded when it mentions a specific pressure range and then in the next sentence, just underneath, it lists the loading effort for "the above pressures".

Sadly enough I got insulted for asking the same question on another forum so thanks so much for helping me out. I guess I was naive in thinking that Pete and Aleks couldn't make honest mistakes like these. I just looked at the numbers and didn't understand if there was any secret sauce or Mirage'ish tricks in the gun.

 

[popgun pete]

Translation 2014/11/04

 

[popgun pete]

I will now discuss what the numbers mean in that specification table for the "Prizm" or the RPB-1M. The calculations are easy because the Soviets included numbers in the corresponding size units. The force on a piston is obtained by multiplying the pressure in the gun by the cross-sectional area of the piston. (Note that a square centimetre is 0.0001 square metre or 1 x 10^-4).

Thus for charge pressure P at 147 x 10^4 N/m^2 and a piston cross section A of 1.5 cm^2 or 0.00015 m^2 we get a force value F = P x A = 147 x 1.5 = 220.5 N, (note that N is the force expressed in Newton as the measurement unit). The 10^4 cancels out with the 0.0001 or 10^-4. The table gives a range of force values between 98.1 and 225.63 Newtons which is equivalent to a range of 10 to 22.3 kgf, so the numbers agree with the P x A calculation.

What was not revealed in the table was what level of initial chamber pressure was used, i.e. what pressure had the gun been pumped up to in the first place. Now I calculated the compression ratio of the RPB-1M gun at 2.0, which is pretty high for a pneumatic speargun. Hence that means initial charge pressure must be 147/2 or 73.5 x 10^4 N/m^2 or 15/2 or 7.5 kg/cm^2 which is relatively low, about 7.5 Bar. To obtain initial charge pressure we have divided the final, or cocked pressure, by the compression ratio.

So what if we had ignored the RPB-1M instruction book and using the handpump then squeezed 147 x 10^4 N/m^2 or about 15 kg/cm^2 into the gun as the initial pressure. That would mean that charged to shoot pressure would be 30 kg/cm^2 and final force application to obtain latch would then be 441 Newtons!! A Newton is a kgf x 9.8 as it is an absolute force unit in the SI system, therefore 441 Newton is 45 kgf. or close to 100 pounds of force. The table lists a caution with maximum permissible chamber pressure being 196 x 10^4 N/m^2 which limits the force to 196 x 1.5 or 294 N which is about 30 kgf or 66 pounds of force. Any more pressure and there is a real prospect of bending the spear which is necked down to provide a catch position for the sear tooth to engage which effectively weakens the 9 mm diameter RPB-1M's shaft.

 

[popgun pete]

The reason I have added the "Prizm" or RPB-1M to this discussion is that it has the same diameter bore as the "Alpha C1" and the calculations will therefore be the same. The difference is the "Alpha C1" has a big air tank of a large OD and a much lower compression ratio than the "Prizm" and it also has a much stronger spear because there are no weakening grooves in its spear. To muzzle load any pneumatic gun the effort is not always revealed in the figures as you can have "stiction" added to the force being provided by the gun's internal pressure. At the start of a hunting session I have seen the spear bow on my "Sten" as I apply the first muzzle loading effort of the day, the piston apparently jammed tight into the muzzle, then it suddenly moves down the barrel. On subsequent shots this "refuses to budge" opposition by the piston has completely disappeared, but unfortunately the final latch effort stays the same. As to what is the loading effort and how to describe it, well you never get an answer unless it is the "latching effort to cock the gun" at final shooting pressure. Gun manufacturers could make it easy to calculate if they gave you their gun's compression ratio, but they rarely do.

The advantage of a 14 mm diameter inner barrel gun is only 16% compared to a 13 mm diameter inner barrel gun as 14^2/13^2 equals 196/169 which is 1.16. In the sixties and seventies the majority of pneumatic speargun were 13 mm or 0.5" as that was the "standard", but more expensive guns such as the GSD models had 14 mm diameter inner barrels using their increased power as a selling point. A similar calculation for 13 mm and 11 mm inner barrels gives the answer as 13^2/11^2 equals 169/121 which is 1.40 or 40% improvement. Not surprisingly divers find those 11 mm diameter inner barrel guns easy to load, especially if they are stepping down from 13 mm guns.

 

[popgun pete]

Here is an example where rather than the compression ratio the "initial" and "cocked to shoot" pressures have been supplied in the owner's manual or "handbook for operating" as part of the pumping table for the gun. This table is from the "Seabear" MAK handbook for the Russian manufactured "Pyrometer", but it is the USA version. I have placed a red box around the top end of the table as the original Russian manual forbid going over about 17o pump strokes! As I have written elsewhere it was a very big job putting 200 pump strokes into the gun and I had to add a large "Tee" handle onto the hand pump rod and use all my strength to squeeze in 400 strokes. Then the hand pump bore being the diameter of the gun's inner barrel the same effort was required to latch it! At that pressure I could not pull the trigger until I used both hands on the gun's handgrip and used two fingers combined to pull the trigger back. The spear left the muzzle like a beam of light had just been switched on, but reloading in the water was impossible, so I had to bleed the gun down. Fortunately the suppliers had replaced the "Pyrometer" shaft with a JBL spring stainless steel version or I would have bent the shaft during loading. Being a very heavy gun to tote around underwater the "Seabear MAK 103" soon went into long term storage!