How many pump strokes for Asso/Hunter 90?

[Diving Gecko]

Just got a Seac-sub Hunter 90 (same as Asso except handle and a different material spear, I reckon). I am thrilled and will start using it tomorrow. But the manual is awful and doesn't list a table of approximate pump strokes and resulting pressure. I don't have a gauge and gun is emptied for flight. Can someone tell me how many pump strokes to get it started?
Also, power reducer in forward position is the reduced mode, right?

 

[popgun pete]

Just got a Seac-sub Hunter 90 (same as Asso except handle and a different material spear, I reckon). I am thrilled and will start using it tomorrow. But the manual is awful and doesn't list a table of approximate pump strokes and resulting pressure. I don't have a gauge and gun is emptied for flight. Can someone tell me how many pump strokes to get it started?
Also, power reducer in forward position is the reduced mode, right?

20 bar 300 strokes, 15 bar 250 strokes, 10 bar 200 strokes for the "Asso" 90 cm, so that is not for the "Hunter", but may be close enough. Forward position of the regulator is low power, rearward is high power. The gun should already be pressurized, so I suggest you try it out as is before changing anything.

 

[Diving Gecko]

Pete, thanks SO much. You do know everything. I will start at 222 strokes and trim from there, hehe.
Gun came depressurized which was kinda good to know as I guess it has to for air cargo (that's how the shop said they get them). And I'll be on a domestic flight down south tonite and checked that indeed there was no air at all in it.

Now, I am just wondering how many loops of shooting line to rig it with? There is line enough for 6 lengths of the gun (I guess 3 full loops), but is 4 lengths the way to go?

Best and thanks again,
David

 

[popgun pete]

Pete, thanks SO much. You do know everything. I will start at 222 strokes and trim from there, hehe.
Gun came depressurized which was kinda good to know as I guess it has to for air cargo (that's how the shop said they get them). And I'll be on a domestic flight down south tonite and checked that indeed there was no air at all in it.

Now, I am just wondering how many loops of shooting line to rig it with? There is line enough for 6 lengths of the gun (I guess 3 full loops), but is 4 lengths the way to go?

Best and thanks again,
David

Well I don't know everything, but I can contribute what experience has told me and I have found out for myself by checking out various guns over the years. Pneumatic guns of that size usually shoot two line wraps or four lengths of the barrel, but you can use three wraps, just don't expect the spear to fly in a straight line over that distance. I used three wraps on my old "Sten 90" for a period with the gun pumped to the maximum that I could just load against in the water, but then opted for an easier reload by dropping the pressure back and I shortened the line to two wraps. Too much line in the water can be a problem in terms of it tangling around things when it is deployed and you have grabbed onto the fish and thus have the spear close to you, but three wraps are not going to be unmanageable. Try it out and see for yourself, if you shorten the line you will be cutting it off to the two wraps, so while it is all still in one piece you might as well use it as is. A bowline knot works best and is simple to tie, the manufacturers usually depict that knot on the instruction diagram for the gun.

 

[Diving Gecko]

I think I ended up with app. 450 pump strokes and I could still load it without too much brute force. But there was def one time when it leaked from somewhere inside the handle and not while adding pressure to it. This was on land while rinsing it. I think maybe it lost all the air in one chamber because when I inserted the spear to check it, I could insert it with no resistance but that of the piston. But then when I jiggled the power reducer around, the spear was hard to insert again (I did not fully load it since I was out of the water). Of course this should not at all happen to a brand new gun. But I am not too worried as I love taking things apart and knowing how to service them myself, so I will do that at some point in the future before my next trip with it.
I did keep the three wraps of shooting line and it was not too much of a hassle, but I did not spear big fish that were hard to control at all.
Though it is my first gun and I don't have anything to measure it against, I like it a lot so far. It's trigger is nice and soft enough not to interfere with aiming but I do think it is a bit hard to track fast with but I guess that just comes with the size of the barrel.
Also, in the 90cm size, it fits pretty perfectly in my fin bag which is great when you have to lug it around airports, taxis and cars.
Now, I guess I just have to start thinking about dry-barrelling it...;-)

 

[popgun pete]

I would be a little concerned about that air leak as from your description it emptied the inner barrel and pre-chamber, but not the main pressure reservoir that occupies most of the gun from just forwards of the rear handle molding. The reason the whole lot did not escape is you still had the gun on "low power" which seals off the partitioning bulkhead inside the gun. That bulkhead separates the two air chambers inside the gun; the inner barrel and pre-chamber, which are always connected, represent a much smaller combined volume than the main pressure reservoir or tank which is sealed off for low power shots by a plug operated by the power regulator switch or knob. Now after a low power shot the pressure in the inner barrel and pre-chamber is much less, that is the only air volume that expanded for the shot, so there is less force on the seals and that is why one leaked somewhere where the pressure seal is not perfect. When hit again with near to full pressure by moving the power regulator to "full power" the leak stops sufficiently not to be noticeable in the short term, although the pressure will be down from what you had pumped the gun up to as you lost the volume of compressed air contained in the inner barrel and pre-chamber. The fact that you pumped the gun for 450 pump strokes indicates that there was a slow leak, but as the pressure rose in the gun the leak slowed or stopped, so the effective pump strokes that actually remained in the gun was less than what you had supplied, but you lost less air as the increasing internal air pressure caused all the seals to take up.

It is a good idea to store the gun with the power regulator set to "high power", but to verify a leak leave it on "low power" and see if the inner barrel depressurizes again. In the event that happens I would return the gun for repair or ask for a new replacement as the gun will be under warranty. A possible cause is something small is stuck in the inlet valve, but the only way to pin point a leak is to put the gun with the rear inlet valve cap removed in a tub of water with a little bit of detergent added and look for foam forming on the surface as bubbles accumulate above the location of the leak, which may be very slow. Bubbles around the trigger indicate a trigger transmission pin seal leak, so work the trigger back and forth and see if any bubbles emerge with the rear of the gun submerged in the tub. The rearmost tank body seal can also cause the pre-chamber and inner barrel to lose air, but you should be able to see leaks there as an oily bloom will form on the gun in that location around the position of the leak.

Although they should be pressure tight from new, the piston seals may be needing to bed in, so try reloading the gun by pumping the spear in the inner barrel up and down without actually cocking the gun and see if it leaks air. Wet the gun for lubrication first as it helps the leading outside edge of the piston seal and the front of the piston body as they move back up the inner barrel. One thing you do know is the power regulator shaft seal and the plug seal for the bulkhead are working OK as the main tank retained its air pressure.

 

[Diving Gecko]

Coincidentally, this morning I recorded the leak on video. Will try to upload later. But off to Myanmar for a week of work so might not have time.
Seeing the leak (big bubbles, easy to spot) in the sink also made me more serious about it than I was initially. This is a brand new gun. It shouldn't happen. But could be that it has been stored for too long or seals have not set. It does seem to leak less with more pressure.
More later.

 

[Diving Gecko]

Here is the video of the leak.

https://vimeo.com/48305095
(Unfortunately, I dunno how to embed it on deeperblue)

It seems I can only get it to leak if the gun is not cocked. Also, there was not much pressure in the gun at all. Maybe 20-30 strokes.
It looked very much like the leak came from the trigger where it goes into the trigger housing. Not sure what that means.
Sending the gun back to Italy would be a huge hassle from Thailand. And the return even worse as even repaired items often get taxed on their way back through Thai customs. I might see what the local shop has to say. Not much hope for a replacement as the other 90 I saw there was covered in oil. Perhaps just a messy job from taking the pressure out of it or perhaps a leak.
Not entirely sure what to do now. Would taking the handle off and checking the o-rings be easy enough?

Best,
David

 

[popgun pete]

Here is the video of the leak.

https://vimeo.com/48305095
(Unfortunately, I dunno how to embed it on deeperblue)

It seems I can only get it to leak if the gun is not cocked. Also, there was not much pressure in the gun at all. Maybe 20-30 strokes.
It looked very much like the leak came from the trigger where it goes into the trigger housing. Not sure what that means.
Sending the gun back to Italy would be a huge hassle from Thailand. And the return even worse as even repaired items often get taxed on their way back through Thai customs. I might see what the local shop has to say. Not much hope for a replacement as the other 90 I saw there was covered in oil. Perhaps just a messy job from taking the pressure out of it or perhaps a leak.
Not entirely sure what to do now. Would taking the handle off and checking the o-rings be easy enough?

Best,
David

Once you dismantle the gun the warranty no longer applies. You say the other 90 cm gun in the store was covered in oil! That sounds like an assembly problem at the factory, only your gun is less affected. Fixing it yourself is an option, but you may find further problems if other "O" rings have been marked, but are currently twisted away from causing a problem.

The "Hunter" is a newer gun for the factory workers to assemble, although pneumatic guns are very similar in the detail of seals and seating positions. Personally although it is a hassle I would be looking for another gun from the company. Send an e-mail to their customer service and mention your video of the problem. Also attach an image of your purchase receipt.

 

[popgun pete]

If it is only the trigger seal then you can change it without pulling the gun apart. With the gun fully depressurized (power regulator is set to "full power") use a small diameter rod and hammer to push the trigger pivot pin out one side of the gun. The trigger will now be free, but you will need to wiggle it out after pushing the safety slide out of the way. Once the trigger is out the safety slide can be pushed out as well, it goes in only one way and the trigger stops it coming out with everything assembled. Under where the trigger was there should be a slotted metal disc with a central hole which the trigger transmission pin pokes out of. Using some needle nose pliers grab the pin and pull it up out of the gun. Note the end of the pin which goes into the gun and makes sure you put that end back in the gun, it is usually rounded while the outer end is flat. Then with a screwdriver that fits the slot exactly undo the disc which is actually a threaded cylinder and remove it. Underneath that threaded cylinder is an "O" ring which you need to replace with one that is exactly the same size. Reassembly is the reverse of removal, but you put the pin in the disc/cylinder and do it up just enough to trap the "O" ring in the correct alignment (the pin is used as dowel to centralize the "O" ring), then remove the pin and tighten the disc up. Some special screwdrivers have a slot in the blade tip, so you can do the disc/cylinder up with the pin in place. Don't over tighten it or you will strip the screw threads in the gun. Push the pin back in the gun with some grease to lubricate it or a coating of oil, it will be a slightly tight fit. That is why it has a rounded tip to help it through the "O" ring.

The downside of doing this work yourself is you will leave slight marks on the screwdriver slot in the disc and the end of the pin where the pliers grabbed onto it, so someone who is an expert will know you have had a go at fixing it. That will void your warranty which should be good for one year.

Note that there are slight detail variations in some guns, so the above is only a general description.

 

[Diving Gecko]

Hi again,
So, the issue has been resolved and Pete was right on. Short version of the story is that the o-ring had to be changed.
Longer version is that I took the trigger mech apart myself to have a go at fixing it.
I cleaned everything out, inspected the o-ring (which looked fine) and put it together again.
A note here: To unscrew the bushing it helps with a slotted tool, as the trigger pin comes out of the center of the bushing and though it depresses, you can't push it in far enough that a normal, large flat screwdriver can reach the bushing. (Makes more sense when you look at it yourself). What I did was to buy a cheap screwdriver thinking the metal would not be of great quality. Then I made a slot in it with a hacksaw and filed it a bit and it worked a charm. (Oh, just re-read Pete's instructions and I could have just pulled out the pin with a pair of pliers and used the screwdriver w.o. the modification...)
But as said, it didn't solve the problem. When I finally made it back to where I had bought the gun, I took it to the shop and they changed the o-ring in a day and it stopped leaking. So, if I had had a replacement o-ring in that size, I could def have done it myself. These things are quite a lot more simple than I initially thought. I would love to have a full set of spare o-rings to travel with and I am pretty sure all repairs could be made DYI.

On a side-note, I even emailed Seac-Sub and they sent instructions on how to take apart the trigger mech and told me it was an easy enough operation. Also, the shop did not give me any issues over having had it taken apart myself.

Thanks again Pete,
David

 

[popgun pete]

Unfortunately "O" rings can look fine and yet still leak because the damage is almost impossible to see with the naked eye. I replaced a power regulator "O" ring on the control shaft of a "Cyrano" and on inspecting it afterwards I thought that it looked perfect. I knew that it was leaking, so I had another look with a jeweller’s loupe and still thought it was OK until I just caught a glimpse of a fleck of metal which was so tiny only the sunlight outside momentarily reflecting off the fleck picked it up as I slowly turned the "O" ring around. The thin metal had cut the inner contact surface of the "O" ring and I was hard pressed to find the spot again once I wiped the fleck away with a wooden toothpick, so the damage was nearly invisible even when looking through the loupe! After checking their size for future reference those damaged rings need to go in the trash as it would be too easy to mix them up with other new rings, particularly once the oil has been wiped off their surface.

As for the fleck of metal, well it was a tiny flake of aluminium from the original machining that had been drifting around in the gun and finally found its way into the gap between control shaft and "O" ring. Years ago you used to find short curly fragments of turnings or "swarf" inside guns from the cutting of the large screw threads, but fortunately things have improved a lot since then. Guns could operate for years without this metal doing any damage, especially if it stayed in the main tank. Smaller pieces being more able to pass through gaps tended to cause more problems than larger pieces.

Glad to hear you got the gun fixed, being brand new the guys at the shop were probably prepared to be more accommodating, especially if they wanted to sell you another gun at some future date.

 

[Diving Gecko]

Hi again Pete,
Thanks for the very important anecdotal reminder on the importance of o-ring "hygiene".
I actually had a small flooding of an old Nikonos from a tiny, tiny spec of gravel. I really hard to look hard for it afterwards and it had escaped me completely when I first inspected it before hitting the water.
Luckily, the "dive" it was not deep (swimming pool) and not saltwater and I found out fast and took it apart fast. In the end, no damage was done.
But it served as a reminder to check even more carefully and with my housing for my DSLR, I have never had even the smallest drop of water on the wrong side of any of the many o-rings.

Best,
D.

 

[Diving Gecko]

An update on the pump strokes needed for my Hunter 90.
Since I now have a pressure gauge, I thought I might as well do my own table and it was quite surprising. But basically, it takes a lot more pumping that the Asso table says. I can't find a table for the Hunter, but I thought they were basically the same gun.
But here it goes, according to my measurements:

100 pumps: 4 bar
200 pumps: 8 bar
300 pumps: 11.5 bar
400 pumps: 15 bar

I will edit this post later, as I put more air in it.