Own Mamba design

[radlimus]

It appears that this is a dry barrel system, not a vacuum barrel system. You load the gun, the barrel already has water inside it, the spear seal at the front end plugs the end of the muzzle and then you lift the gun clear of the water and allow the water to drain from the inner barrel through the muzzle relief ports which are open. After that you slide the muzzle cover shut to close the muzzle relief ports which keeps the water from going back into the inner barrel. There is probably a bit of water still left inside, but nothing to worry about, in fact you need a small amount of water for lubrication.

That´s right!

 

[radlimus]

Radlimus, although I haven't seen the shaft with the sealing O-ring yet, I would say your dry barrel system is OK. It is next to vacuum barrel tovarich system regarding performance. There is no vacuum inside the barrel but there is also no friction between the shaft and the sealing O-ring.

At the moment I see only 3 drawbacks:
-the shaft is weakened at the groove position of the sealing O-ring,
-creates air bubbles after the shoot - not a big problem,
-takes some time to empty the water and close the muzzle holes - not a big problem.

Regards, tromic

That´s right!
It is difficult to find the right dimension for the O-ring on the spear, the o-ring need a lot of tension, if there is not enough tension the o-ring lost his position and make problems during the loading of the gun.

 

[tromic]

This is from the an earlier thread and could be applied to your gun:

If we had 6,5 mm shaft and 11 mm barrel than cross section of the shaft to cross section of the barrel is
(6.5^2) / (11^2) = 0.35.

For dry barrel gun (this is your case, radlimus) at 40 meters of depth it would be shooting as if it had

20 - 4 * 0.35 = 20 - 1.4 = 18.6 Bar in it.
(For more accurate calculation we should pay attention to the air left in the barrel also, which would diminish the value of 18.6 Bar for some amount - could be not negligible (1-2 Bars avg) Radlimus, you said: "Inside the bush are 2 diameters, the smaller one is a little bit bigger than the diameter of the spear." You have to ensure fast escaping of the air left in the barrel after shooting. It would be maybe better to use rubber tubing over the muzzle.)

For vacuum barrel system like tovarich, one should add an average pressure of about 0.95 *(1 - 0.35) Bar for any depth, so the gun would be shooting as if it had:

20 - 4 * 0.35 + 0.95 * (1 - 0.35) = 19.21 bar for the depth of 40 m.

Because there is also a shaft to O-ring friction (at tovarich system) from this result we could subtract about 0.3 Bar (from my measurement) so the result for tovarich at 40 m depth is: 18.9 Bar.

You could see, radlimus, your system could be next to tavarich, almost same in shooting performance. Tovarich is faster and easier to load and there are no air bubbles but the performance of the spear could be similar to your. I said: could be, because it depends on how fast the air from the barrel could escape from the gun.

Regards, tromic

 

[radlimus]

Here is a photo of the spear with the O-ring.

 

[radlimus]

We are comparing different pneumatic systems here.
We should create a testing standard to compare the systems.

My proposal is:

Pressure: 25 Bars
No line connection between spear and gun
On the top pf the spear a cork of a wine bottle
Measurement from top of the spear to to of the spear

We measure the range of the spear and post it here.

 

[tromic]

Testing:
I have to test my speargun in a swimming pool:waterwork,
the sea is too far away......

I put a wine cork in front of the spear and made 2 shoots in the pool (the pool was empty of course, no people there).
There were no line between the gun and the spear.
First shoot without the mamba and the second shoot with mamba but both shots with the modified spear.
Reach 1 shoot: 4.2 meter
Reach 2 shoot: 5.2 meter

The next thursday i will made a shot with the unmodified spear, the reach will be less than the 4.2 meter.

Radlimus, I had got similar result to your, with my mamba: 26% better performance to the factory Cyrano. Your result was: 24%. I had measured the energy of the spear, you measured the shooting distance. I think your method is simple, but still good for estimation and comparation.

http://forums.deeperblue.com/pneumatic-spearguns/81791-tomba-all-one-barrel-sealing-5.html

 

[tromic]

Here is a photo of the spear with the O-ring.

Radlimus, maybe you could use something like this, right side or left and right side of O-ring. If put it on both side the groove is not necessary.

 

[foxfish]

I like the idea of the test, I will try some of my guns out of interest but I guess you would have be very careful not to offset the cork?

 

[radlimus]

Radlimus, maybe you could use something like this, right side or left and right side of O-ring. If put it on both side the groove is not necessary.

Good idea!

 

[radlimus]

Radlimus, I had got similar result to your, with my mamba: 26% better performance to the factory Cyrano. Your result was: 24%. I had measured the energy of the spear, you measured the shooting distance. I think your method is simple, but still good for estimation and comparation.

http://forums.deeperblue.com/pneumatic-spearguns/81791-tomba-all-one-barrel-sealing-5.html

But i measure the wrong distance:crutch.
My measurement was from the top of the spear to the end, but should be from top to top of the spear. So we have to add the length of the spear to my results.
In the next 2 weeks i will make a new test with 25 bars and the correct measurement.

 

[foxfish]

That will be great, we will look forward to the test.