TargetTalk

A Hill 4th Gen. Hand Pump arrived today. It is the first hand pump of any kind that I have owned or used. There is no mention of when to use the bleeder screw in the instructions. I put 200 bar into a cylinder, opened the bleeder screw and all the air came out of the cylinder. I would like to avoid doing that again. Help!
Thanks.

What model cylinder? You should only open the bleeder very briefly.

haha, pumping it up back to 200 is no fun :D

the Answer: it depends on the model of your air pistol.

Steyr: Pump to 205 bar and quickly open the valve for a fraction of a second to let the water out OR turn open the cylinder exactly ONE turn and then open the valve screw.

Look in the manual of your air pistol/rifle (the manuals can also be found online)

Also, use your weight to pump not your hands, bend your knees and ride it down each time

Thanks for the replies. I found a manual online and downloaded it, which I should have done in the first place. All is well.

It's quite simple.

Pump the cylinder to 200 bar, unscrew the cylinder ONE turn, open the bleed valve, only then do you unscrew the cylinder off.

Hope this helps

Okay now that I have some time to actually post my full thoughts, let me explain the process and what's happening. I wish I had this information when I started out with a Hill pump. It would have been helpful.

When filling a PCP cylinder, there are two pressurized chambers involved. One is the cylinder that you want to fill, the other is the delivery mechanism, whether it's a pump or a diving cylinder. The connection between the two allows the pressure to equalize, thus "filling" the PCP cylinder.

Diving cylinders are fairly self explanatory and user friendly. High pressure hand pumps are not. The pumping action fills up a small, pressurized chamber in the hand pump. It is very small; much smaller than a diving cylinder. The seals around this chamber are easy to break through improper technique because the air takes time to equalize between the pump chamber and the steyr cylinder. Always use slow, deliberate strokes, stopping for a few seconds at the top and bottom of each stroke to give that pressure chamber time to take in the air and equalize with the cylinder. Otherwise you're going to have ruptured seals as you are placing that smaller chamber under far more stress than it was designed for.

When you pull the bleed valve on a steyr cylinder (can't speak for morini and so on), due to the design of the cylinder, you are opening BOTH the pressurized part of the hand pump and the steyr cylinder, not just hand pump. To prevent this from occuring, you have to ensure that the cylinder's gateway to the hand pump is closed when you cylinder you are attempting to fill is shut off from the rest of the hand pump when you turn the bleed valve. To do this, you turn the Steyr cylinder ONE FULL TURN. No more, and definitely not less. Error slightly on the side of overturning if you're confused, but my steyr cylinders have a small dot on them that makes alignment and turns easy to keep track of. Once this has been done, the steyr cylinder is disconnected from the pump, and you can apply the bleed screw. Open it very slightly to remove humidity ONLY. You are not trying to clear the chamber entirely. That happens in the next step, when you fully remove the steyr cylinder from the hand pump. You will hear a hissing sound indicating that the chamber is depressurized.

So, in sum:
1. Attach steyr cylinder using adapter to the pump
2. Ensure bleeding screw is tightly closed.
3. Begin pumping using slow, deliberate strokes. Always use slow, deliberate strokes, stopping for a few seconds at the top and bottom of each stroke to give that pressure chamber time to take in the air and equalize with the cylinder.
3a. It will become progressively harder to pump as you approach 200 bar. As one of the previous posters said, use your body weight, NOT your hands to enable this to happen. This is for two reasons. One, it doesn't hurt as much. Two, the chamber in the hand pump is nearing its maximum. You want to slowly add air at that point, not quickly. Using your body weight naturally slows the process down.
4. When you are satisfied with the valve readings, turn the steyr cylinder one full turn. Do not completely remove it unless you want a bottle rocket.
5. Quickly open and shut the bleeding screw. You will hear a sharp hiss that gets cut off.
6. Grasp the cylinder and swiftly unscrew it completely from the pump. You will hear air hissing and escaping, keep going. That's just the air from the chamber in the hand pump being released.
7. You should now have a filled steyr cylinder.

If I haven't covered something or if anyone thinks something I have said is in error, please let me know. I'm not an engineer. I recognize that 5 and 6 are probably redundant, but I figure better safe than sorry.

And all of this sounds complex, but once you get used to it, you can fill a totally empty cylinder (which you shouldn't let happen) in ten to fifteen minutes.

The question at hand is whether the adaptor opens the valve on the cylinder or not.

It sounds as if the Steyr cylinder, screwed onto the adaptor, has its valve held open. Pumping pressurizes the pump's chamber and the cylinder at the same time. Opening the bleed valve with the cylinder fully attached will empty residual pressure in the pump and the cylinder. Unscrewing the cylinder one turn allows the cylinder valve to clear whatever opens the valve, keeping the pressure in the cylinder, and allows purging the pump of residual pressure in the pressurizing chamber.

I know from experience the Morini cylinder/adaptor does not have the valve held open. A pump stroke pressurizes the pumps chamber, and the higher pressure on the outside of the cylinder valve opens the valve and allows air to flow into the cylinder; when equalized (or nearly so), the valve closes again. The bleed screw on the pump can be opened at any time without loss of pressure in the cylinder.

Don't know about other manufacturers, but it will be pretty evident if the valve is held open (pressure will escape the cylinder when bleeding the pump if you don't back the cylinder off the adaptor.

jky

Presumably you can determine which type of cylinder you have (valve held open or not) by just attaching the adaptor directly to the cylinder (with some residual pressure before refilling) and screwing it up. If you hear hissing then your cylinder is the valve held open type; if not, it isn't.

Bob

Somewhat related newbie question: I am considering upgrading from my Izzie 46 to a PCP....can I get by with just a Hill pump, or should I really be budgeting a SCUBA tank and fittings?

Ed333 wrote:Somewhat related newbie question: I am considering upgrading from my Izzie 46 to a PCP....can I get by with just a Hill pump, or should I really be budgeting a SCUBA tank and fittings?

That depends on your age, body frame, and fitness. I'm not too fit, 30, and 6'4''. The Hill pump gets me a bit out of breath. But I use it exclusively, and it works fine for me. I've had it for about six months. Fair warning: follow the tutorials on how to use it properly as set forth above. The instruction manual sucks. This isn't a bicycle pump and needs to be operated differently. The #1 cause of issues with hill pumps is user error.

If you are short, out of shape, or older, you may wish to consider the SCUBA tank and fittings. Also, air pumps are a pain to keep on refilling (takes on average about 5 minutes per cylinder for me to take it from 100 bar to 200 bar. Anticipate 15 minutes per empty cylinder.).

One other issue with SCUBA tanks. Each time you fill an air pistol/rifle cylinder you drop the pressure (amount of shots you get) on each fill. As you draw air out of the SCUBA tank its pressure also drops. So if you have a 3000 PSI SCUBA tank you get less than 200 bars (200 bars = 3,000 psi) after the first fill. This is not an issue for practice because even filling to 100psi will give you some amount of shots. However it can become a big deal when you are at a match and need to get ~75 shots (including sighters) out of one cylinder and you carry one of the smaller, easy to transport SCUBA tanks. With a Hill pump you can always fill to capacity. It is work though.

Chip

ChipEck wrote:One other issue with SCUBA tanks. Each time you fill an air pistol/rifle cylinder you drop the pressure (amount of shots you get) on each fill. As you draw air out of the SCUBA tank its pressure also drops. So if you have a 3000 PSI SCUBA tank you get less than 200 bars (200 bars = 3,000 psi) after the first fill. This is not an issue for practice because even filling to 100psi will give you some amount of shots. However it can become a big deal when you are at a match and need to get ~75 shots (including sighters) out of one cylinder and you carry one of the smaller, easy to transport SCUBA tanks. With a Hill pump you can always fill to capacity. It is work though.

Chip

I have a friend who says he uses a SCUBA tank for the majority of a fill, then tops it off with a hand pump.

Me, I am 6'3", 250, 77, with some issues, but lots of spare time. Sounds like my weight could come in handy. :)

Chia wrote:This isn't a bicycle pump and needs to be operated differently. The #1 cause of issues with hill pumps is user error.

To get the most amount of air into your cylinder, remember to pull the handle all the way up and fully compress on the down stroke until you feel the piston head is resting on the bottom of the shaft.