The Separation of Components Principle

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The concepts discussed in this document are dealt with tentatively in the latest spreadsheet on a tab called Torque and a tab called Torque and Power. The URL for the new spreadsheet is:

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This is not a revolutionary scientific principle, it is a design trick that air car inventor Bill Truitt tried to teach me in 1986 when I asked him how he got around the laws of physics. It isn’t really a way around the law, there isn’t one. It is a way over the hurdles presented by being constrained by the various laws of nature. For example, a perfectly capable air powered piston can have many times more power than it needs to do the job, but it might not have enough force to move one millimeter. The sort of constraint that is a real stumbling block when the math works fine on the generalities, but the nuts and bolts is still impossible without a complete re-thinking. The math doesn’t lie, but it takes a lot of experience to know when it is wrong, incomplete, or suggesting something misleading.

The math for the downhill equalizer seems to work fine but I still have to look at the details. The operation of two compressors has been isolated from the characteristics specific to the tank so that the tank’s pressure and other characteristics will not impose unnecessary limitations on what the two compressors are capable of actually doing. The math isn’t the problem, I mean the amount of work they have to do is puny compared to the work done by the compressor you can buy at Home Depot, the one that’s deeply appreciated by your local Power Company. But so many of my hot ideas have failed to get past the hard look dept. that I have finally caved in and said OK to electricity. I didn’t want to mix media, I wanted purely pneumatic, but just for the sake of learning a new trick, let’s try to look at what could be gained by using electricity to operate the two compressors instead of beating my head against Rube Goldberg’s sacred wall of configurationalism.

The piston in the tank idea keeps popping up and keeps getting rejected for the same reason. The booster piston in the current Downhill Equalizer configuration looks like it’s in the tank, but it is only in the equalizer. That is why the intake pipe goes all the way through the tank to the other end. So there is no back pressure except atmospheric air on the back side of the booster piston. The equalizer is smooth and polished to a close tolerance like any compressor cylinder, and the booster piston reciprocates in it. It is a one-way actuator, with only the compression stroke doing anything of importance. On the return stroke it might look like it’s drawing in atmosphere, but it’s just getting out of the way; the atmosphere is pumped in positively by a separate compressor. Since these two compressors don’t limit each other, it helps insure that the dang thing should work. An exotic variation would be to try to use the booster compressor as the intake compressor on its return stroke. It might work, but the entanglement might get one device over-involved in the business of the other if you try to combine them. I haven’t thought it out yet.

Knowing that the pre-filled tank has plenty of energy to compress a little atmosphere to 4 psi higher in pressure than it started out, and being able to prove it with standard compressed air calculations, it is not a question of the work. Work and energy are two sides of the same coin and measured by the same units—I use foot-pounds since I’m over 50 and undereducated. Feet and meters, it’s all the same. But once you get TIME into the equation, you have a potentially real machine to deal with, preferably on paper, before you go out and buy the parts to prove that your real machine only works as an oversized paper weight.

Power is work done per unit time. It can be broken down in different ways, including those in the table (DOWNLOAD MS DOC FOR CORRECT FORMAT, SEE URL ABOVE):

power = work / time
power = force x distance / time
power = pressure x area x distance / time
power = pressure x volume / time
power = force x speed
power = mass x acceleration x speed
power = linear force x linear speed
power = force x radius x angular speed
power = torque x angular speed
power in ft-lbs/min = torque in lb-ft x 2π * rpm

Regarding the bottom rows of the table, the term “speed = distance per time”, when applied to circular efforts of devices such as engine shafts and wheels, is technically rendered “angular speed”, and examination of the table should lead us to expect that torque is a circular force that can be measured in pounds. This is approximately correct so in order to understand why a rotating motor outside the air tank can do things that a piston inside the air tank can’t do with the same amount of energy, a review of TORQUE and ANGULAR SPEED is needed. I will keep it short and you can refer to the spreadsheet for the math and to my book Compressed Air Power Secrets for a detailed discussion of torque. Here’s the crux of it:

Power = force * distance / time = force * speed
Power = linear force * linear speed
Torque = force * wheel radius, crank radius, gear radius, etc.
Linear speed / radius = angular speed
Power = torque * angular speed

The point is to see what these values are, so they don’t have to be accepted as abstractions that only geniuses can apprehend. And to show that trying to use linear piston-on-piston concepts is rigid and constrained compared to using a rotating shaft. The motor adds abilities to the system and flexibility to the design by adding factors within the power available that are easily juggled till force, torque, work, and power are all adequate to perform the task.

My problem with separate systems is that like other wanna-be inventors I have never worked with them; I’m too impractical, always wanting to kill a herd of flying pink elephants with a single pebble. But face it: an air tank can’t dictate or constrain what speed to run your electric motor at. But if you put a piston in the tank to do the same job, the tank pressure and the size of the piston will dictate to you a relatively inflexible set of options.

Ultimately I want to answer the question, Can an air motor do it instead of an electric one? Separate still, depending on gear ratios like the electric motor to get desired characteristics, but without the annoyance and loss of transforming to electricity and trying to store that stuff in a “battery”, whatever that is. It’s bad enough that air and heat are invisible, do I have to get into electricity too? At an extra cost in losses?

The reason a piston producing force directly off an air tank—as simple as it sounds—is inflexible to the point of being doomed in certain applications is known to us: piston balancing forces. When the force is equal pushing both ways on the piston, the piston won’t move. And this is what happens since the piston is the same size on both sides. But what about the other side of the coin: why is it that a rotating shaft introduces flexibility?

It’s because torque is leverage is mechanical advantage. Force is a straight push, and torque is a straight push around a fulcrum. Torque is a straight push: straight around a circle. Like the force used to push a lever, the force applied to produce torque is going to be differently capable depending on the lever length. Torque = force x radius.

So the answer: what is the advantage of running part of an air system off a shaft, a torquer, instead of running everything directly off the same air tank?—is leverage or analogical to leverage. Mechanical advantage and torque are easy to manipulate in design work. In the example of the piston in a tank that won’t move because the tank air feeding it is the same pressure as the tank air resisting it, and the pushing side of the piston is the same area as the resisting side of the piston: making the piston bigger means using more air but it doesn’t solve the problem; pressure is still the same on both sides of the piston. But changing the pushing hardware—from a straight force to a rotating effort—introduces leverage and the flexibility offered by unlimited varieties of lever lengths, gear ratios, etc. Running the motor slower tends to increase its torque. The numbers in my spreadsheet need to be supplemented by real torque vs power data which can be obtained from websites of motor manufacturers.

So that’s my best guess on why Bill Truitt said he had to keep his systems separate. But why bother with electric motors when the air is already available? Air motors have more torque than electric motors, don’t they?

For one thing, an efficient air engine is very large. And once you put valves on something, then you have to find a way to operate the valves. I could carve an engine block with a chisel and pocketknife, but I would need brains to make a valve open and close at the same time. In an overunity air power system, once you have your extra air to use, you can waste it any way you want, but if you don’t first use your stored air frugally or at least carefully and consciously to get the extra air made, then the overunity condition won’t be reachable. So running compressors with electric motors is partly more practical and partly just more convenient. You can go buy an electric motor of any size and speed without worrying about the mode of using the electricity in the motor, but an efficient air engine is not going to be found on the shelf anywhere in the world. Except at your local “piston expander” dept. at Steam Engines R Us. Let me know if you find that place.

The question now seems settled, Why not an air motor to develop the needed torque on a turning shaft? The answer: convenient, efficient, small air motors don’t exist. If they did, we would have been driving air cars a long time ago. Efficient air engines need a big flywheel. Spacewise and convenience-wise and availability-wise, electric motors beat air motors easily, and let me know if I’m wrong. Me and electricity don’t get along but I have to concede. So far I haven’t studied the losses involved in transforming part of the air tank’s pressure to electricity and storing it in a battery. So I’m assuming they are considerable, but worth it, if it works. If the cost in wasted energy is not too much. Then you have your overunity air production unit, and you can make extra air that you can waste any way you want.

Luther