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Technisub "Drago" pneumatic speargun

Jegwan

Well-Known Member
Oct 1, 2012
353
69
83
Sealand, Denmark
I recently got my hands on a Technisub "Drago" that I now have repaired and restored.

The "Drago" has been a hitch-hiker in other speargun threads on the forum, so it is already described in details on the forum. The "Drago" offers a rather ingenious design, so I thought that it deserved its own thread.

The Technisub "Drago" is a forward latching pneumatic speargun and features a sliding handle which can be locked at various positions along the reservoir tube to provide either a rear handle or mid-handle speargun.

A more detailed description by Popgun Pete can be found here:
http://forums.deeperblue.com/threads/inalex-alpha-c1-pneumatic-speargun.88246/

The "Drago" was introduced in February 1971 together with the "Pulce" [Gizzo]. The first model had a silver barrel and grey handle. Later this was changed to an all black model. The "Drago came in two lengths - a 80cmm and a 100cm; both supplied with a 9mm threaded shaft.

The patent for the "Drago" is dated 1970 [Popgun Pete]. The inventors were Luigi Ferraro and Gianni Beltrami [Gizzo].
The early technical drawing can be found here:
http://forums.deeperblue.com/threads/technisub-grinta-pneumatic-speargun.100365/#post-927513

Here's some studio photos of the result of my restoration. It's the later black version in 80cm.
The Pump is from a newer Technisub "Ranger".


Studio Session-Technisub Drago Corto_medium.jpg

Studio Session- Technisub Drago Corto_Open_Medium.jpg


Jégwan
 
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Jegwan

Jegwan

Well-Known Member
Oct 1, 2012
353
69
83
Sealand, Denmark
So here's a photo of the latching system with the 3 balls in the front muzzle:

Drago front muzzle.JPG


And here's a photo of the rear with the throttle system:

Drago inside back.png



Any questions or comments to the "Drago" are welcome.

Jégwan
 
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popgun pete

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Jul 30, 2008
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Here are the diagrams to keep all the info together on this thread. The gun as operated with the sliding handle, the muzzle and how the ball system works and the power regulator throttle device in the rear end. Note the different form of the inlet valve seen here and in the photos, very different to the usual inlet valve design.
Technisub Drago.jpg
Technisub Drago muzzle R.gif
Technisub Drago muzzle operation R.gif
Technisub Drago power regulator VRX.jpg
 
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popgun pete

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Jul 30, 2008
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Why the "Drago" floats after spear discharge is the extensive use of plastic in the design, including the pressure bulkheads and the grip parts and the handle lock system. The ingenious, but temperamental, ball system in the muzzle is probably what killed the gun off, plus the price to buy it and ultimately the cost to produce it, including assembly time on the production line.
 

popgun pete

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Jul 30, 2008
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Australia
You can see in the dismantled gun photos that Technisub used a different inlet valve in the actual production gun, in fact it is similar to the one found in the "Grinta". I expect the "Grinta" uses the "Drago" inlet valve rather than the other way around. The actual valve seal is a flat rubber washer with curved inner and outer edges which sits on a washer with a similarly curved groove on its periphery to hold it. The original inlet valve design is highly unusual, I was surprised to see it at first and had no idea how it worked, but if you consider each part in turn it soon becomes obvious. Right out of left field in design terms!
 
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Jegwan

Jegwan

Well-Known Member
Oct 1, 2012
353
69
83
Sealand, Denmark
Many thanks for the diagrams.

Yes, I noticed that when I saw your photos of the inside of the "Grinta". I had to Google "out of left field" - and yes - absolutely! :LOL:

It's pretty hard to evacuate the air if the gun is pumped up to a high pressure. I needed to press the back of a screwdriver handle against it to release it..

Speaking about odd O-ring seals makes me remember the simple and clever seal solution between the "muzzle" and the inner barrel on the Aquatech guns.

Jégwan
 

popgun pete

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Jul 30, 2008
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Are you referring to the rubber annular ring inlet valve in the "Aquatech" muzzle? Yes, it is another type of valve format, also used in the "RPS-3" as well, but it is easy to damage it in an "Aquatech" when you release the compressed air from the tank by pressing a blunt pin into it. At least in the "RPS-3" you have a separate air release screw, just as was envisaged for the "Drago" in the original design. Not all "Aquatech" guns have a separate air release screw, the inlet valve is item 2 on the following schematic.
aqua9.gif
 
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Jegwan

Jegwan

Well-Known Member
Oct 1, 2012
353
69
83
Sealand, Denmark
No, I was actually thinking of the one sealing between the aluminium muzzle and the SS inner barrel located at 1. Not the 2.
Jégwan
 

popgun pete

Well-Known Member
Jul 30, 2008
3,565
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Australia
What do you think is clever about it? I have never pulled that section of the gun apart to check it out. Note that the "one-way" valve in the "Drago", i.e. the rubber cone seal facing away from the piston tail, is to stop air for the shot flowing through any air pathway other than the circular ports in the inner barrel tube and the ports in the sliding collar. That "one-way" valve is still there in the later design, only the rear end of the rod that it sits on now holds the coil spring that biases the more familiar type of inlet valve. In your photo it was positioned the wrong way around, but I see you have now switched it to the correct orientation.
 
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popgun pete

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Jul 30, 2008
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Australia
I have taken the liberty of annotating your excellent photos of the inner works. If anything is wrong then please let me know and I will change it. Really only the grip handle and the two locking mechanisms left to examine, i.e. the trigger pull rod gripper plates and the handle lock/trigger interlock.
Drago front muzzle annotated RR.jpg
Drago inside back annotated R.jpg
 
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popgun pete

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Jul 30, 2008
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Australia
Here is the "Drago" handle shown in the patent. There were a number of alternative constructions shown in the patent which were not used, so I have edited them out, such as a longitudinal split on one side of the sleeve section above the handgrip with screw or "over-the-centre-action" toggle clamps located at either end to tighten the fore-aft sliding handle onto the elliptical tank. The lever locking clamp on top of the sliding handle was listed and that is shown, but may be different to the actual clamp on your gun. Maybe you can do some annotated photos, especially as there seem to have been a number of changes between what was proposed and what was actually used.
Technisub Drago handle R.gif
 
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Jegwan

Jegwan

Well-Known Member
Oct 1, 2012
353
69
83
Sealand, Denmark
What do you think is clever about it? I have never pulled that section of the gun apart to check it out. Note that the "one-way" valve in the "Drago", i.e. the rubber cone seal facing away from the piston tail, is to stop air for the shot flowing through any air pathway other than the circular ports in the inner barrel tube and the ports in the sliding collar. That "one-way" valve is still there in the later design, only the rear end of the rod that it sits on now holds the coil spring that biases the more familiar type of inlet valve. In your photo it was positioned the wrong way around, but I see you have now switched it to the correct orientation.
It surprised me to see how simple it was made (an O-ring on a trumpet shaped end of the inner barrel) and that it actually keeps the front cone/muzzle and the inner barrel tight together with help from the pressure in the gun. I have posted a new thread with the "Dnepr" - have a look here:

http://forums.deeperblue.com/threads/aquatech-dnepr-hydropneumatic-speargun.100512/

Jégwan
 
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Jegwan

Jegwan

Well-Known Member
Oct 1, 2012
353
69
83
Sealand, Denmark
I have taken the liberty of annotating your excellent photos of the inner works. If anything is wrong then please let me know and I will change it. Really only the grip handle and the two locking mechanisms left to examine, i.e. the trigger pull rod gripper plates and the handle lock/trigger interlock.
That's great. Everything looks right. Many thanks.

The "sliding collar" is the cage holding the three SS balls.

I can take the handle apart later - the gun is now pressurized - so I'll wait until I have used it a couple of times and hopefully shot a nice dinner fish.

Jégwan
 
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Jegwan

Jegwan

Well-Known Member
Oct 1, 2012
353
69
83
Sealand, Denmark
Frederico (who sold me the gun) was kind to send me the attached Scan of the Drago Parts diagram. It was disappeared after he moved resident, but now it's found.

The final version of the inside of the handle is shown on the diagram.

Jégwan
 

Attachments

popgun pete

Well-Known Member
Jul 30, 2008
3,565
831
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Australia
Thanks for the schematic and parts listing as now we can see the changes made to the production gun. The gripper plates that clamp the trigger pull rod are now replaced by a tilting friction washer component, although it looks a bit different to a "washer", being a rectangular shape instead (part 41). The safety is a pivoting lever (part 44) located behind the separate block (part 50) that contains the "washer" instead of a transverse blocking slide with the usual cutout. Hence to unclamp and then clamp the trigger pull rod when moving the handle position on the outer tank there is no need to turn a screw in the side of the forward section of the handle frame as had been indicated before. Also the handle clamp control lever was shown as being at the rear before, but is now at the front of the handgrip section.

The spring on the spear tail butt is a shock spring for the spear tail stop diameter which can move backwards on the shaft slightly as the spring holds it away from the fixed butt end which is screwed on the rear end of the shaft (I just checked which part was free to move on the parts list as I previously thought the reverse was the case). Usually the shock spring is placed on the shaft just behind the line slide, but here it is different as there is a second sliding ring on the shaft.

With many small parts to manufacture and then assemble on the production line, this shows why the "Drago" pneumatic was an expensive speargun to buy. It is a very ingenious and well executed design, but let down by the exposed ball front latching system which is susceptible to corrosion and contaminants such as sand particles.
Drago schematic annotated R.jpg
 
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popgun pete

Well-Known Member
Jul 30, 2008
3,565
831
153
Australia
I also transposed the parts list descriptions onto the diagram itself, but at full size the file was too big, so I reduced it to 40%. I note that the diagram seems to indicate that at one time the mechanism outer cover or shroud, part 2, was transparent, as is part 3 in your photo.

Sand particles have the potential to get between the moving parts of any spearguns that have large diameter sliding outer collars and will scratch the surface of anodized cylinders as the sand particles can embed in the plastic item moving over the top of them. Any sign of such scratches in the "Drago" elliptical tank? One way to avoid it happening would be to never operate the sliding handle system during a dive in anything but clean water, or on the beach where wind blown sand can get in where you do not want it to go. I have had it happen and a fine silvery track traced every movement in the anodized coating as I wiggled the outer plastic cover to release the unseen particle, although I could certainly feel the gritty resistance it offered to cover movement. I soon removed the plastic cover!
 
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