Hand pumps for the ancient big bores: Part 2

by Tom Gaylord
Writing as B.B. Pelletier

A history of airguns

Part 1

This report covers:

  • Air intake and outlet valves
  • The key to the test
  • That’s not all
  • I tested one, too
  • More questions answered
  • Maintaining consistency
  • Three-stage hand pumps
  • Summary

Today I will hopefully answer all your questions about the hand pump test that Dennis Quackenbush and I did many years ago. Remember — we were trying to determine how powerful the old big bore airguns had been. One part of that was knowing what kind of air pressure they used, and that is all we are looking at in this report.

Air intake and outlet valves

First I want to address a question from reader GunFun1. He asked about the pump’s air inlet valve. I told him there was no inlet valve. There is an air hole located at the top of the pump cylinder, and when the pump piston head rises past it, air is sucked into the cylinder — exactly the same as a conventional piston port 2-stroke engine. No valve is required. When the piston head drops below the air hole, the cylinder is sealed again and the piston is able to compress the air that’s now trapped inside.

But get this — there is also no outlet valve! The single stage hand pumps of antiquity have no valves of any kind. They rely on the firing valve in the airgun’s reservoir to serve as an inlet valve, which also doubles as their outlet valve. Once the air is forced inside the reservoir, that valve traps it.

Since the hand pump is tightly connected to the reservoir, this works well and is very simple to build. The airgun valve in the reservoir is the only valve in the entire system, and the air pressures are so (relatively) low that it doesn’t have to be high-tech. In its day, though, I’m sure it was regarded as magic.

The key to the test

What we are testing is how much pressure a single-stage hand pump can generate. Remember your math teacher I talked about in Part 1? Well, he taught you that the surface area of a cylinder/piston (circle) grows rapidly as the diameter increases.The formula is A(area) = π r². Dennis made 2 pumps to test. One had a piston diameter of 5/8-inch. The other had a piston diameter of 3/4-inch. Dennis weighed about 220 lbs. at the time the test was conducted. Here is the math.

The first chart is a record of Dennis pumping the test reservoir with both hand pumps. Notice that he also filled the reservoir with a modern three-stage Axxor hand pump.

pump chart 1

pump chart 2

What Dennis’ math shows is how much pressure can be generated by a piston of a given size, when the force (his weight) is constant.

replica hand pumps
These are two of the hand pumps Dennis Quackenbush built for this test. Both pumps have a synthetic piston seal. They are different sizes to fit cased airguns better. The larger pump has a 3/4-inch diameter piston and is sized for a long air gun or air rifle. The smaller pump has a 5/8-inch piston and is made for an air cane.

Dennis worked out the math for you, and you can see that the results fall in line with the predictions. And bear in mind that the small gauge Dennis used on the reservoir isn’t entirely accurate. So, his findings are ballpark — not exact. I would say we have good correlation with what the math predicts, the weight of the pumper and the end results.

That’s not all

Dennis used synthetic piston seals in both his hand pumps because he always makes his pumps that way. He and I both believed they would seal better than just a close-fitted piston that was oiled. I mentioned that in Part 1. In the interest of knowing the truth, however, Dennis also made another hand pump with a close-fitted 5/8-inch piston that had no seal other than the oil he used with it. To his surprise, that pump achieved almost exactly the same pressure as the pump of the same size with the synthetic piston seal. And the number of pump strokes was about the same.

He also tried “rapping” the 5/8-inch pump. Rapping means jumping on the pump handle to force in more air. He reported that he was able to get the pressure up to 810 psi that way — a 90 psi increase over normal pumping, but the cost was great. Rapping injured his wrists and hands to such an extent that he doesn’t recommend it to anyone.

I tested one, too

Dennis shipped me the 5/8-inch hand pump with the synthetic seal so I could test it. He had not told me any of his results before sending it, to keep the bias under control. I did two things. First I pumped it as high as I could. I got exactly 840 psi. I actually did “rap” in some air at the end. I weighed 240 lbs. at the time I tested the pump. I lost track of the pump strokes because the rapping was so painful. I know the count was something over 200 strokes.

Then I emptied the reservoir and pumped it back up to 500 psi. I left it at that pressure for 4 months, just to see how long the reservoir would hold. Four months later, no pressure had been lost!

pump gauges
I was able to pump to 840 psi with the 5/8-inch pump (right). Then I left the reservoir charged to 500 psi for 4 months and it held perfectly (left).

More questions answered

What the data shows is that it’s possible to calculate the maximum pressure for any single-stage air pump by simply dividing the weight of the pump operator by the area of the piston head. There should be some loss of efficiency due to friction in the pump, but this is most probably offset by some imprecision in determining the person’s body weight, the gauge error and also from small differences in effort each time the pump is used (i.e. not every person applies the same force, even when they may weigh the same).

220 lbs. divided by .3068 = 717.08 psi

This allows us to test a “theoretical pump” that can generate whatever pressure we desire within the limits of physical laws. For example:

250-lb. operator using a pump with a 1/2″ piston
250 lbs. divided by .19635 = 1,273.24 psi

150-lb. operator using a pump with a 1/2″ piston
150 lbs. divided by .19635 = 763.94 psi

Notice that the length of the piston stroke does not enter into this calculation. That’s because the length of the stroke determines only how much air is being compressed. It doesn’t affect the highest pressure that can be achieved by that piston. A longer stroke will compress a greater volume of air; a small-diameter piston will allow it to build to higher pressure.

Maintaining consistency

Reader Bruce, whose handle is BBB, asked how the airgunners of old were able to fill their guns to the same consistent pressure when they lacked gauges of any kind. Well, Bruce, I bet you have guessed the answer by this time.

Airgunners of old regulated their fill pressure in the same way Harley Davidson cycle owners of the 1930s controlled the torque they put on the various nuts and bolts on their motorcycles — they tightened/pumped as much as they could every time. Does this mean that a heavy owner could compress air more than a light owner? It sure does! Just as a strong motorcycle owner can apply more torque than a weaker one when both use the same wrench.

Consider the level of technology we are discussing. These old big bores are not that sophisticated. “About” and “close enough” are all they need. As long as you try to fill an old big bore with a hand pump of the period you won’t get into too much trouble — [Note: That statement only applies when everything is new. An airgun that is old has to be examined before anything else is done to it, because metal fatigues over time. The same thing is true for the old Harley.]

Three-stage hand pumps

Now that you understand the physics of hand pumps, it’s time to dream. If a small piston head allows you to compress air to high levels, what would a REALLY SMALL HEAD DO? What if the piston head were only 1/8-inch in diameter? Wow! You could get a lot more pressure with that! Let’s use Quackenbush’s formula and see. That would be the radius of a 0.125-inch circle (0.0625-inches) times pi (3.14159) and square the result. I get 0.03855 square inches as the area of a 1./8-inch circle.

250 divided by 0.03855 = 6484.57 psi

But you would have to pump all day! It would take many thousands of pump strokes to fill a 9 cubic inch reservoir with a 1/8-inch piston. Wait a moment — what about increasing the length of the stroke to get a greater volume of air in each stroke? Brilliant!

And that, dear readers, is how you get a three-stage hand pump. Instead of an 8-foot long pump cylinder, someone (namely Fredrik Axelsson of FX Airguns) folded it into three sections. The first section compresses a lot of air to a relatively low pressure. On the next stroke, the air that was compressed in stage one flows into a second section that takes it from low pressure to a moderately high pressure. On the third stroke the air in the second stage flows into the final stage where the very small piston compresses it the rest of the way — to anywhere from 3,000 all the way up to nearly 4,500 psi! Of course as the air flows from section/stage to section/stage, all stages are at work. So the process of air compression is continuous.

But the formula says we can go up to almost 6500 psi, doesn’t it? Yes, but the formula is looking at a single stage pump — it doesn’t take into account the effort required to compress air for stages one and two. That effort has to be added in, and that is what determines the top pressure that can be achieved by a 3-stage hand pump.

Summary

That’s it, kids. That’s how the hand pumps of antiquity work, and now you know where the three-stage hand pump comes from.

Someone jokingly asked if a 4-stage hand pump was possible. Of course it is, but as more stages are added, the pump cylinder gets fatter, and the interior volume may be reduced — in an effort to keep the pump cylinder thin. I think we have it pretty good with what exists today. The only thing I would add is the butterfly pump linkage that reduces the pump effort.

74 thoughts on “Hand pumps for the ancient big bores: Part 2


  1. BB
    What about this.
    “But the formula says we can go up to almost 6500 psi, doesn’t it? Yes, but the formula is looking at a single stage pump — it doesn’t take into account the effort required to compress air for stages one and two. That effort has to be added in, and that is what determines the top pressure that can be achieved by a 3-stage hand pump.”

    But it all depends on how much energy or force is exerted. Add mechanical leverage into the equation and the 6500 psi could be achieved.

    Sure wish Benjamin could of got things worked out by their suppliers for the butterfly pump.

    Maybe 6500 psi could of been acheived by a person hand pumping. Still could be tuff. Or maybe we should look at it like that person could achieve about half that psi in a faster amount of time.

    That would then be a big bennifit then with a hand pump. I still have a hand pump as a backup for my Shoebox compressor. Maybe I wouldn’t need the Shoebox if I had a butterfly hand pump.


    • Theoretically a person can achieve any pressure given small enough piston or long enough lever for mechanical advantage. Practical limits are set by things like how many strokes are too many to fill a big enough reservoir, can the pump arm withstand the force without bending and is the lever arm actually heavier to lift than the pump is to pump? Many other problems will come up as one tries to maximise the attainable pressure, and like BB I believe most if not all that can be practically solved have been solved in the 3 stage pump.


      • Monoph
        What I was getting at is the 3 stage pump would be able to achieve 3000 psi easier with leverage. Like the Crosman butterfly pump. To bad the suppliers didn’t pan out in that case.

        Don’t know if there is any pcp air guns that use 6000 psi. But alot use 3000 psi. I would much rather pump a gun up to 3000 psi with a 3 stage pump that used leverage than one that didn’t.


        • GF1,

          Just when I got used to pumping to 3000 PSI, they start coming out with air rifles with operating pressures of 4500 PSI. I don’t think I squeeze that much more out.



            • Using the G6 pump to pressurize a Benjamin Discovery to 2000 psi, how many pump strokes would be required?

              Using the G6 pump to pressurize a Benjamin Marauder to 3000 psi, how many pump strokes would be required?


          • RR
            Don’t know about your Edge but my Talon SS is happy at 2600 psi. Now on the other hand my .25 Marauder is liking 3300 psi now. Of course it’s modded.

            But depending on how much a person shoots a Shoebox compressor is a nice option.

            Oh and it takes longer to fill the Talon SS from 1800 psi to 2600 psi than the Marauder from 2500 psi to 3300 psi. More resivoir volume with the Talon SS.

            So that’s something to think about too when you get a pcp gun.

            The Discovery’s have about the best balance I believe of the low 2000 psi fill pressure and resivoir volume to shot count you get. That is a gun that I can hand pump all day.


            • GF1,

              My Edge is regulated. The tank is filled to 3000 PSI and the operating pressure is 1000 PSI. My Talon SS was operating at 1800 PSI. I am about to rebuild the valve, so we will see how it does then.

              I have been giving serious consideration to a .22 Marauder. If I end up with one I will likely tune it to 2000 PSI and add a reservoir extension. I do not see me getting a compressor and/or a tank unless I go big bore. The Rogue taught me that a hand pump and a lot of shooting with a big bore is no fun.

              I like the Compact Swat on the 46E. I was shooting some pretty nice groups the other day at 25 yards with it. I had to take off the drooper mount though. It throws the scope too high for my rings. We will see how things go.



                • At the moment all I have are some Wally World Benjamin hollow points and H&N Baracudas. It seems to do quite well with the Baracudas.

                  Once my wallet finishes recovering from Christmas I will try some JSBs, Field Target Trophies and RWS Superdomes. I strongly suspect the JSBs will be the way to go, but I have had the others do real well in .177 in other air rifles I have used them in. My 1906 BSA seems to prefer the Superdomes and the CFX I had loved the FTTs in 4.52mm.


                • Speaking of Wally World, have you seen the new Crosman Piranha pellets in .22? I was almost tempted to pick up a tin and try them out. Then I remembered that they are just a fancy fishing lure.



  2. BB
    You have, again, come thru as you had promised! This stuff makes my mind go in all different directions! You mentioned that a man named Axelsson was responsible for the design of the three stage airpump and I am wondering when that happened. That thought led me to then question the development of pcp’s in England and Europe during the years after WW 1 up into the 1960’s and 70’s. Was there much done to advance the technology of pcp’s during that time frame? I am assuming that the 3 stage pump came out maybe in the 60’s or 70’s.
    Bruce


  3. Very interesting article that answered some questions and brought up others. I am going to have to re-read this several times. Now, would it be possible to add a air tank to a Crosman 1377 and use the existing pump and get more shots? If I can get one shot at 500 fps with 8 pumps, why couldn’t I get 10 shots with 80 pumps. Has that feature every been used ? I guess we could call it a self contained pcp air gun. Good reading and thanks.
    Harvey


  4. BB,

    This pertains to the filling of the Giradoni reservoirs.

    I saw photos recently of what was purportedly an original “kit” for the Giradoni air rifles. It was a leather shoulder bag that had pockets for a hand pump, two spare air reservoirs, several tubes for balls and a few basic tools. The pump would allow each soldier to fill and/or top off his reservoirs. In battle he could quickly change reservoirs and the tubes allowed him to rapidly reload the magazine. Quite impressive an arrangement really.


  5. BB,
    Was doing so research about the 4 stage hand pump. FX made a 4 stage that shifted gears in a way. Could pump a lot of high volume low pressure air (300cc) then shift to high pressure (200cc) .




    • B.B. Looking very forward to hearing about that one! I wonder if they “discovered” a secret with it being .30 cal. Seems like .25 cal. isn’t that great in a break barrel. It’s much better in a PCP from what I’ve read on here. So if they have found a secret, could my hopes of a break barrel shotgun still be possible? Only time with tell.

      Doc



    • BB
      I hope you get to shoot it at least once. I want to know how hard it is to cock and what the shot cycle is like.

      Maybe it will even feel like a .30 caliber firearm when it shoots. And heck throw a light weight pellet down the barrel and it might even sound like a firearm.

      Of course I’m just joking around. If it turns out nice that’s great.

      And could Hatsan maybe of messed up the notification. I thought they already call their .30 caliber pcp a Carnivore.


      • GF1,

        Unfortunately Hatsan did not opt to attend Media Day at the Range, so there isn’t going to be any way to shoot this gun at the show. Companies usually do that when the product is not completely developed. They will display a non-functional shell, but the insides are still under development.

        When Pyramyd Air gets them I will be sure to test one.

        B.B.


        • BB
          Now that you say that I remember you mentioning that in the past about products at the show.

          It will be a interesting gun that’s for sure. I still keep dreaming of a nice big caliber (.25 and up) springer. Maybe one built like the Diana 54 air king with its sliding action.

          They could put a longer cocking arm on it to help with the cocking effort from the heavy spring and the anti recoil slide system could take away the harsh shot cycle. Maybe Diana did make one in .25 caliber at one time. Or maybe it’s the Diana 56 hunter. Can’t remember right now without looking.

          But I think that would be a good platform for a big bore springer.




  6. B.B.,

    The serious engineering of the past always interests me. Here we see the capabilities of antique hand pumps that could produce serious psi, and that leads me to thinking about the pyramids, Stonehenge, Easter Island, and all sorts of remarkable feats, some of which would be a serious undertaking even today.

    Thanks for these reports, as well as the air cane info.

    Michael


  7. B.B,

    Wow! Since I only weigh 180 lbs at age 74, I think I will stick with my Air Tanks. This tires me out just thinking about it. It’s amazing how much man could accomplish in the past with so little. The future looks great.

    Boomer


  8. Interesting discussion on pumps.

    I have a Hill pump that I use for backup.

    Got to thinking (while pumping) that I need to increase the leverage… maybe add something like the handle you used to see on those old well-pumps or a flywheel and slide like on a steam locomotive… could motorize that. 🙂



    • Vans2

      I have read of folks adding leverage to their pumps just as you suggest similar to the old water pump design. A simple lever to double the stroke will half the effort, giving a 100 lb person the same pressure as a 200 lb person.

      I plan on making a large crank shaft run by a small electric motor to operate my hand pump. It should be less stress on the pump than a person. With the crankshaft at about 15 rpm that would be 4 seconds per stroke it will fill my maurader in about 5 minutes.

      With lower rpm a hand pump might even fill a tank without getting too hot.

      The problem with these simple machines commercially is in using new expensive parts and shipping large levers and crankshaft.

      This discussion has renewed my interest in automating my hand pump.

      My initial idea was to use a hydraulic ram like a miniature log splitter to operate the hand pump. I think the crankshaft will be lower tech and cost less.

      Great discussion.

      Don


      • Don

        Motorizing would be interesting with lots of options available. Think that you would have to watch the pump closely – my main concern would be that the pump could seize if it overheated and a lot of things could get seriously bent.

        Seems that my Hill pump needs a 2-3 second hesitation at the top of the stroke to allow the cylinder to fill completely and a 2-3 hesitation at the bottom of the stroke to pass the compressed air into the micro-bore hose. The hesitations would be pretty difficult to build into a motorized system with a simple linkage. Might be able to do it with special shaped cams, the design of witch would be an interesting project in itsself.

        Since I am not concerned with portability (my shooting range is in the back yard) I think I could attach a hinged base to the floor to mount the pump on and the lever to the wall at the appropriate height.

        I would make a double lever (spaced about a foot apart) for rigidity with a single handle across to help keep things aligned.

        Another option would be with cables and weights. I was looking at some exercise machines and thinking that I could kill two birds with one stone – get a work-out and charge the reservoir. Mind you that it might be difficult to shoot accurately after working-out.

        Your log-splitter idea has a lot of potential. I have a 6-ton electric splitter. Think it has about a 24″ stroke. Wouldn’t take much to make that work because the linear motion is already there, it would depend on if the pump stroke matched. Might be an economical idea as well, seen the 4-ton units as cheap as $200 on sale.

        Rather that fitting an expensive hand-pump to a log-splitter It may be a lot more practical to make a piston/cylinder (we have a huge amount of force available – equivalent to a 8,000 pound man) to compress the air. Thinking that a couple of truck shock-absorbers could be used as pumps.

        So now I am totally distracted! 🙂 Have a great day!

        Hank



  9. BB
    Speaking of pumps, I was looking at the onboard pump for the big bore multi-pump that Bob Chilco had. it looked like it had an narrow piston tube and a long throw. Did you ever get to handle or shoot that gun or know what the ballistics were for it?
    Brent


  10. The red editor’s note caught my attention. Does metal fatigue through prolonged use or by just sitting around as my Mosin sniper rifle did in the Ukraine for some decades?

    Ancient hand pumps make me shudder since you don’t have the convenience of a scuba tank. The pump linkage was suggested by blog reader and master engineer Jane Hansen and is a good idea. But I think the older hand pumps have another advantage. Given the different ethics of earlier times and the abundance of cheap labor you can imagine a scene like what I saw from the film 300 Rise of an Empire where people are flourishing whips among the rowers on the Persian ships. You can even add a sign like: “The pumping will continue until morale improves.”

    Matt61


  11. Oh and forgot. I ordered your book today with my pellet order. Kind of excited to get it. Been a long while since I actually bought a book or even magazine to read for that fact. Pretty much all internet reading for me for a long time now. And told my daughters I got the book coming so they said they want to read it. They are all the he time reading stuff.

    And while I’m at it. Got me some more of the JSB .177 caliber 10.34’s and some JSB .22 caliber 15.89’s. The description said there was only 2 tins of the 500 count JSB 15.89’s left after my order. Man everybody must be buying them up. They just got back in stock a few days ago.

    I guess everybody is ordering sausages now days.




        • GF1,

          I got the heavy snipers as well. 250. HN 18.0g. in .22. Will give ’em a go in the spring. The 18.13 JSB did well this summer so I thought that I would give them a go. That’s about as high as I can go with the TX and LGU.



            • GF1,

              Not as much as I should be. 41′ just is not the same as 75’~150′. The 92FS and the 499 does see their fair share though. The 499 peepers does help keep the scope skills up on a minimal level. Peep/globe sights are fun.

              At 41′, everything will look good, now. Last Winter would have been a different story. I did leave the shooting table set up outside though in case I get some nice 50-60 degree days.

              But yes, I will get some scope time and trigger time on the good ones so I do not loose the “feel”.


  12. BB
    I was quite surprised that reproductions of the 300 year old equipment would:
    1- Reservoir would hold same pressure for 4 months.
    2- Oil and close fit worked as well as seals.
    Decksniper


    • Decksniper,

      Well, Quackenbush did use modern seals in that reservoir — o-rings and Teflon tape.

      The oil and close fit was a surprise to us, as well. I guess it shows how much can be done with simple technology and attention to detail.

      B.B.



  13. Everyone,

    I cleaned out my homemade pellet box this weekend. I got over 13# of lead, steel BBs, copper coated pellets, and non-lead pellets out of it. I called a friend who reloads and casts his own lead balls to see if he wanted it. He passed because of the non-lead items – he didn’t want to take time to sort out the BBs and was not sure of the copper coated and non-lead pellets. Anyone interested? I hate to throw it away.

    Jim


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