by Tom Gaylord
Writing as B.B. Pelletier
This report covers:
- First air compressor
- Condensing chamber/reservoir
- Controlling force
- Sealing against air loss
- The first air valve
- The rest of the gun was easy
- When did it happen?
I just finished reading about the Wright brothers quest to fly, and I learned some things. For starters, I never thought about their first flight — how did they know what to do? There was nobody to teach them because mankind hadn’t flown a powered airplane yet. So how did the Wright brothers learn to fly?
Don’t answer that. That was a large part of what the book was about. But do you see a parallel between the Wrights and the person who built the first pneumatic airgun? He had no one to copy, either. He had to do everything himself, because pneumatic guns didn’t exist yet.
First air compressor
The inventor of the first pneumatic gun was probably aware of certain pneumatic experiments that came before his time. The condensing syringe was known to the Greeks of Alexandria 200 years before the birth of Christ. We call them air pumps today, but they do their work today the same as they did back then. This is the first air compressor. With it, the pneumatic airgun becomes possible.
Compressed air can be used immediately upon compression to do things like power a siren or a whistle. The sound tells you that the air was compressed and it also tells you when the compressed air is completely exhausted. However, if you could store the compressed air and then call upon it at any time, it would be a source of energy that might have a lot more uses.
I don’t know when the first condensing chamber (reservoir) was invented, because its history is pretty vague. But it is the key to the first airgun. We know that airguns with bellows have been around since the 1500s, but the bellows gun is a spring gun that compresses air and uses it immediately. The gun we are interested in is the one that holds compressed air as long as desired and releases it suddenly on command. To be able to do that you first need a way to store the compressed air, and that’s where the condensing chamber (reservoir) comes in.
A reservoir (I will use that term from now on) needs a way to accept compressed air, and we call that an inlet valve. If there were no inlet valve but only a straight hole into the reservoir, the air would enter, but the moment the incoming pressure was relaxed it would come back out again. The valve acts as a door that only opens one way.
Once the air is safely stored inside the reservoir, there needs to be a way to release it on command, as well. That’s another valve. It could be the same valve as the inlet valve, but it has to work in the opposite direction — to only release air from the reservoir. The same valve can be made to do both tasks, but the mechanism needed to do both things with a single valve is complicated. It’s easier to just use a second valve that’s located at a different place on the reservoir.
This valve has to work one way also, but its function is exactly opposite that of the inlet valve — to only release air from the reservoir. You have probably experimented with something like this already if you ever shook a bottle of soda pop and held your thumb over the opening. Your thumb acts as the valve and with it you can control where the soda spray goes. The gas pressure of the soda is low enough that you can control it.
We are just getting started designing the first pneumatic gun, but building the reservoir is the key. Barrels, triggers and locks are simple compared to pneumatic valves. At the time the first pneumatic gun was created, mankind was used to valves that controlled water. The pneumatic valve had to control air — something much more ephemeral. What could do it? Not your thumb — that’s for sure!
One key to making a valve was controlling a powerful force. A clockmaker, for example, knew that a small lever could be used to control a very powerful force if the lever’s fulcrum were in the right location. The air valve had to be like that — able to control a large force with just a little effort.
Something better than a thumb was needed. The valve had to be strong enough to hold back the air, yet it had to be able to open at the right time. Before you start wondering how this was ever conceived, remember that at this time in history (a time we don’t exactly know) men already knew a lot about designing gun locks, door locks and mechanisms like clocks. These were the same men who had the knowledge to design the first pneumatic gun.
Another key was controlling the amount of the force, itself. Mill operators knew that opening the millrace allowed more water to flow through and hit the wheel, generating greater force. The way to control the mill was to control the flow of water through the race. The same idea could be applied to compressed air, though in far smaller scale because of the thinness of air.
Sealing against air loss
This is the big one. The other problems have solutions in other areas that can be studied and modified, but no one had ever tried to contain compressed air before. However, they weren’t without ideas. One was obvious, although I don’t suppose it struck them that way until they tried it and found that it worked. Make the seal from leather! Make a leather valve face contact a metal valve seat, sealing all airflow through the valve. As long as the leather remained pliable, it would seal against air loss pretty well. No one knew this until they built several valves and tried them for the first time, of course, but it did work.
This seal worked for both inlet valves and exhaust valves. Once a valve was finally built, the builders discovered that the pressure of air compressed by a condensing syringe (hand pump) was sufficient to open the valve to admit more compressed air into the reservoir. When the incoming air pressure dropped (at the end of the pump stroke), the valve spring inside the inlet valve forced the valve shut again. Once that happened, the air pressure inside the reservoir held the valve shut, along with the tension of the valve spring.
The first air valve
Controlling the amount of force that came from the reservoir was solved by making the air passage through the valve body very small. It was just like the millrace only far smaller. They couldn’t control the power in the same way as the race, because once the air valve opened things happened too fast. So they found themselves in our world of valve dwell time. The size of the air passage leading out of the valve combined with the strength of the spring holding the valve shut determined how much air escaped when the valve was hammered open.
Sounds cool, no? Well, at the time it was among the most advanced technology mankind had ever seen. Still, leather is somewhat porous and also prone to dry out, so the compressed air didn’t stay inside the reservoir for long. At best it might hold for several days. But eventually it leaked out and you had to fill the reservoir again.
The rest of the gun was easy
Once he had his air reservoir holding air that could be released at will, the first airgun designer found the rest of his task easy. As I said before, designing a lock to hammer the exhaust valve open was child’s play. And the remainder of the gun came together rapidly.
It was a successful condensing syringe (hand pump) and a working valve inside a working air reservoir that challenged that first airgun designer.
Once all these things came together, a first shot was fired. Maybe the projectile (a ball?) came out of the barrel at 200 f.p.s. — fast enough to dent the wooden walls of his shop. Within a week he was denting the wood deeply and on one fine day that first ball passed completely through the wooden plank and left the building. That shot wouldn’t impress any of us today, but to the man doing the work back then it must have looked like he had just invented anti-gravity or invisibility!
When did it happen?
No one knows when that first pneumatic airgun was invented. We suspect it might have been in the mid-1500s, though there are sources that claim it happened as early as the mid-1400s. We do know it wasn’t much earlier than that because no trace of airguns or writing about them dates that early. We also know of dated airgun parts from around the year 1600. Their designs are advanced far enough to suggest that there must have been something that came before. So the time of the first pneumatic airgun is pretty much fixed to between 1450 and 1600 AD.
That puts the first airguns at 100 to 200 years after the invention of firearms. But firearms advanced rapidly after they were invented, because their technology was relatively simple. Airguns, though, would remain the stuff of rumors and legend for several hundred more years.