Thursday, August 13, 2020
  • Welcome to the DeeperBlue.com Forums, the largest online community dedicated to Freediving, Scuba Diving and Spearfishing. To gain full access to the DeeperBlue.com Forums you must register for a free account. As a registered member you will be able to:

    • Join over 43,000+ fellow diving enthusiasts from around the world on this forum
    • Participate in and browse from over 510,000+ posts.
    • Communicate privately with other divers from around the world.
    • Post your own photos or view from 7,450+ user submitted images.
    • All this and much more...

    You can gain access to all this absolutely free when you register for an account, so sign up today!

Accelerator - Medium Moderator (Water - Gas)

popgun pete

Well-Known Member
Jul 30, 2008
3,861
970
203
Australia
special tip.jpg

I guess that this tip is pressurized with gas by transferring it from a pressure can through the green body valve. The yellow inner body acts as a switch when it moves rearwards by the front "O" ring moving into the expanded annular ring at the front end of the blue body section. When that happen the front "O" ring loses contact on the blue section and gas can escape forwards. Holes in the rear let water out as the yellow inner core slides back. Possibly hydraulic force as the tip hits the fish is what moves the yellow section back by fluid pushing back through the nose ports, then gas blows forwards through the same nose ports.
shoot.jpg
 
Last edited:
  • Like
Reactions: Zahar
OP
OP
Zahar

Zahar

Well-Known Member
Jun 3, 2014
120
13
58
56
Thanks Pete! The tip is triggered before hitting the fish even during the shot in the barrel of the gun or on the barrel of the crossbow! Hydrodynamic pressure through the injectors moves the yellow bushing. and ejectors help!
Actuation force 2.5 - 3 kg. The tip must be turned on even when the spear moves in the barrel of the gun when firing!
 

popgun pete

Well-Known Member
Jul 30, 2008
3,861
970
203
Australia
If the gas turns on too soon then it will slow the shot, so what is the purpose of this device? To provide a boundary separation gas shield the front nozzles would need to be radial in their disposition.
 
OP
OP
Zahar

Zahar

Well-Known Member
Jun 3, 2014
120
13
58
56
Radial holes do not give a cavitation effect and the flow of water rarefied by gas will only remove the frictional resistance against the harpoon! End holes give a cavitation effect and reduce the drag of the harpoon! In whatever period of time the tip would be triggered during a shot, it cannot slow down the harpoon, but only accelerate it!
shoot - копия (2).jpg
shoot - копия.jpg
 
Last edited:
OP
OP
Zahar

Zahar

Well-Known Member
Jun 3, 2014
120
13
58
56
If there are no injection holes, the drag force will not move the plastic movable sleeve! Will not work!
shoot 2.jpg
 
OP
OP
Zahar

Zahar

Well-Known Member
Jun 3, 2014
120
13
58
56
The jerk of it being fired will probably be enough to operate the sliding switch.
Inertial actuation is excluded! The mass of the sliding plastic sleeve is too small and the frictional retention of the O-rings is sufficient! So designed to prevent accidental triggering when dropped to the ground! Only water pressure or forced displacement by the rod is required! This design can have several purposes depending on the goals! You can make an analogue of the counter shark cartridge if you put a stem - a needle!
 

tromic

Well-Known Member
Aug 13, 2007
1,637
185
153
Croatia
Is there any measurement results regarding speed or energy difference to spear without accelerator?
 
OP
OP
Zahar

Zahar

Well-Known Member
Jun 3, 2014
120
13
58
56
Is there any measurement results regarding speed or energy difference to spear without accelerator?
Unfortunately, not yet! I am very constrained by the life circumstances for the possibility of full-fledged research! There is not even a car for going out on the water! I am waiting for help from colleagues and I am going with them! So sorry! The idea is clear - try it yourself! It seems not difficult!
 

tromic

Well-Known Member
Aug 13, 2007
1,637
185
153
Croatia
Unfortunately, not yet! I am very constrained by the life circumstances for the possibility of full-fledged research! There is not even a car for going out on the water! I am waiting for help from colleagues and I am going with them! So sorry! The idea is clear - try it yourself! It seems not difficult!
Zahar, what is the weight of "Пластиковая втулка" containing the lighter gas? And what is the friction force of two O-rings? I suppose the acceleration of the spear during shoot is about 850 m/s2..?
 
OP
OP
Zahar

Zahar

Well-Known Member
Jun 3, 2014
120
13
58
56
Tomislav! I did not measure the weight of the yellow plastic movable sleeve! Made it out of an old 30mm long caprolon piston! Taking into account the holes and the glued sleeve from the lighter, about 6 grams is possible! The frictional force of the o-rings is 2.5-3kg! This force must be applied to shift the plastic sleeve! Acceleration calculation is not available to me! I will rely on experiment! The physics of the process inside the tip during gas release requires comprehension and confirmation by experience! I believe that the useful work of the gas will begin after the end of the uniformly accelerated movement of the harpoon and its separation from the gun!
 

tromic

Well-Known Member
Aug 13, 2007
1,637
185
153
Croatia
Tomislav! I did not measure the weight of the yellow plastic movable sleeve! Made it out of an old 30mm long caprolon piston! Taking into account the holes and the glued sleeve from the lighter, about 6 grams is possible! The frictional force of the o-rings is 2.5-3kg! This force must be applied to shift the plastic sleeve! Acceleration calculation is not available to me! I will rely on experiment! The physics of the process inside the tip during gas release requires comprehension and confirmation by experience! I believe that the useful work of the gas will begin after the end of the uniformly accelerated movement of the harpoon and its separation from the gun!
OK, thanks Zahar! That friction of two O-rings of 2.5 to 3 kgf submerge in water to me seems to be unbelievable high..? What kind of O-ring are that, NBR, Viton.., they must be very hard on very high compression..?
Here is a link to friction estimation:
It seems that your numbers for friction of 2.5 - 3 kgf for two O-rings together might be realistic..
 
Last edited:
OP
OP
Zahar

Zahar

Well-Known Member
Jun 3, 2014
120
13
58
56
OK, thanks Zahar! That friction of two O-rings of 2.5 to 3 kgf submerge in water to me seems to be unbelievable high..? What kind of O-ring are that, NBR, Viton.., they must be very hard on very high compression..?
Here is a link to friction estimation:
It seems that your numbers for friction of 2.5 - 3 kgf for two O-rings together might be realistic..
The sliding friction on the O-ring PTFE is very small, but the resting friction is great! This is due to the O-ring punching the groove at the point of contact! Fluoroplastic is a very soft material! If you use hard plastic POM S, then the actuation force will probably be less!
 

popgun pete

Well-Known Member
Jul 30, 2008
3,861
970
203
Australia
Recharging gas for next shot will make for lengthy reloading times, unless you just use it that way for one shot and as a standard tip for others.
 
OP
OP
Zahar

Zahar

Well-Known Member
Jun 3, 2014
120
13
58
56
Recharging gas for next shot will make for lengthy reloading times, unless you just use it that way for one shot and as a standard tip for others.
Assumes the presence of several gas-charged tips for spearfishing! Do reloads at home or on the shore or on a boat!
 
DeeperBlue.com - The Worlds Largest Community Dedicated To Freediving, Scuba Diving and Spearfishing

ABOUT US

ISSN 1469-865X | Copyright © 1996 - 2020 deeperblue.net limited.

DeeperBlue.com is the World's Largest Community dedicated to Freediving, Scuba Diving, Spearfishing and Diving Travel.

We've been dedicated to bringing you the freshest news, features and discussions from around the underwater world since 1996.

ADVERT