Speaker 1: Welcome to tex Stuff, a production from my Heart Radio.
Speaker 1: He there, and welcome to tech Stuff. I'm your host,
Speaker 1: Jonathan Strickland, and I'm an executive producer right here at
Speaker 1: the Heart Radio. And how the tech are you. I've
Speaker 1: got an upcoming episode with a special guest that I'm
Speaker 1: really excited about. And in that episode, I'm probably gonna
Speaker 1: talk a little bit about a system that uses cams.
Speaker 1: So I thought today's Tech Stuff Tidbits, I would actually
Speaker 1: talk about cams, what they are, what they do. This
Speaker 1: will be a true tidbits episode. It will not be
Speaker 1: a fifty minute tidbits episode. So we're just gonna look
Speaker 1: at cams and what they do. Now. And now, first
Speaker 1: of all, I am talking about mechanical cams mechanical systems,
Speaker 1: So when I say cams, I am not talking about cameras.
Speaker 1: So this is not about webcams or anything like that.
Speaker 1: That's a totally different thing. Instead, we're talking about components
Speaker 1: used in some mechanical systems for the purposes of generating
Speaker 1: a particular motion at a specific timing. So, to put
Speaker 1: it simply, cams are components in a mechanical system that
Speaker 1: convert ordinary rotational motion into something else typically into a
Speaker 1: reciprocating motion, a linear reciprocating motion, so it and up
Speaker 1: and down or in and out motion, if you want
Speaker 1: to think of it that way. Now, to talk about
Speaker 1: cams and how they work, let's let's really consider mechanical systems,
Speaker 1: and I'm going to really look at, you know, electro
Speaker 1: mechanical systems in particular. So first let's let's think about
Speaker 1: motors and electro magnets. And I know I talk about
Speaker 1: electro magnets a lot on this show, but as it
Speaker 1: turns out, there at the heart of a lot of
Speaker 1: different mechanical and electrical systems. So it comes with the territory, right.
Speaker 1: I'm sure most of us know that if you wrap
Speaker 1: a conductive wire around, say a core of iron, like
Speaker 1: a little iron rod, or the very simple version an
Speaker 1: iron nail. So you get some copper wire and you
Speaker 1: wrap several coils around a copper nail, and then you
Speaker 1: connect that wire to something that generates a current, like
Speaker 1: a battery. Then you get yourself an electro magnet. The
Speaker 1: electro magnet will have its own magnetic field, with its
Speaker 1: own magnetic north and magnetic south pole, and it will
Speaker 1: behave just like a permanent magnet would, which means if
Speaker 1: you bring the north end of your electro magnet near
Speaker 1: the south end of a permanent magnet, the two magnets
Speaker 1: will attract each other. If you bring the north end
Speaker 1: of your electro magnet near the north end of a
Speaker 1: permanent magnet, they will repel each other because opposite magnetic
Speaker 1: charges attract, and like magnetic charges or poles, if you
Speaker 1: prefer repel. Now, let's make things a bit more complicated.
Speaker 1: Let's say that we connect our electromagnet not to a
Speaker 1: battery which supplies direct current, meaning the current always flows
Speaker 1: in the same direction, but to a source of alternating current.
Speaker 1: So now the direction of current switches from one direction
Speaker 1: to the other, often at very high frequencies, and each
Speaker 1: time it switches, the magnetic field switches as well. So
Speaker 1: when the current flows in one direction, the north poles
Speaker 1: on one side of the electromagnet the south poles on
Speaker 1: the other, current switches directions those poles flip. So what
Speaker 1: was the north pole of the electromagnet is now the
Speaker 1: south pole, and vice versa. Now, if you brought this
Speaker 1: kind of electro magnet near a permanent magnets, poll doesn't
Speaker 1: matter which of the poles we're talking about. Your electro
Speaker 1: magnet would alternately attract and repel the permanent magnet because
Speaker 1: the poll would be flipping on your electromagnet. So some
Speaker 1: times it would be north to north and sometimes it
Speaker 1: would be north to south. All right, Now, let's imagine
Speaker 1: that we've got a permanent magnet. Let's say it's in
Speaker 1: the shape of a U. Okay, and the north pole
Speaker 1: is on the left tip of the U from our perspective,
Speaker 1: and the south pole is on the right tip of
Speaker 1: the U. This magnet does not move. It's in a
Speaker 1: fixed position. We call it a statter. It is stationary,
Speaker 1: so statters s T A T O R. In between
Speaker 1: these poles. In the center between the two we mount
Speaker 1: our electro magnet, which has no magnetic field. If we're
Speaker 1: not running a current through those coils, right, and our
Speaker 1: electro magnet is on an axle that can rotate, so
Speaker 1: the electromagnet can spin freely between the two poles of
Speaker 1: the permanent magnet. Now, if we run alternating current through
Speaker 1: our electro magnet at the right frequency, we can cause
Speaker 1: this electro magnet to rotate and keep rotating by flipping
Speaker 1: the direction of the current and thus the electro magnets
Speaker 1: magnetic field, and it will consistently push against the permanent
Speaker 1: magnets magnetic field on either side, because that field is
Speaker 1: not going to move right. The permanent magnets field is fixed.
Speaker 1: It's a statu our rotor the electro magnet. It's poles
Speaker 1: keep flipping so that it's consistently pushing against these magnetic fields,
Speaker 1: causing the electro magnet to rotate. So if you just
Speaker 1: time this perfectly, you can create this source of rotational force. Now,
Speaker 1: if we want to use a direct current, we could.
Speaker 1: You know, the problem with the direct current is unless
Speaker 1: you have a way of flipping the poles of your
Speaker 1: electro magnet, your electro magnet is just going to orient
Speaker 1: itself so that the opposite poles are attracted to the
Speaker 1: permanent magnet. Right, it'll move in a horizontal plane relative
Speaker 1: to our our permanent magnet's polls, and it won't go
Speaker 1: any further than that because it will be held in
Speaker 1: place by magnetic force. But if we use a structure
Speaker 1: called a commutator, which effectively flips the polarity of the
Speaker 1: electro magnets magnetic field, by changing how the electromagnet connects
Speaker 1: to the circuit that's providing the current as the electromagnet rotates,
Speaker 1: then you have essentially the same effect as if you
Speaker 1: had connected the electro magnet to an alternating current. There's
Speaker 1: more to it than that, but we've already spent enough
Speaker 1: time here, and I've done other episodes where I've talked
Speaker 1: about commutators and how they work. Now, the point is
Speaker 1: that these motors, these electric motors, generate rotational force. But
Speaker 1: that's all they do, right. They can't they can't generate
Speaker 1: a different kind of force there. The way that they
Speaker 1: are designed mechanically means that they make things spin. They
Speaker 1: don't make things go up and down or anything like that.
Speaker 1: But rotational force can be useful for a lot of stuff.
Speaker 1: Like you know, a relatively simple use would be to
Speaker 1: drive an electric drill. The rotational force from the motor
Speaker 1: provides the drilling action you need. It's providing the rotational
Speaker 1: force to your drill. Bit. So there are legit uses,
Speaker 1: simple uses for the electric motor, but a lot of
Speaker 1: mechanical systems often require other types of motion, not just rotational.
Speaker 1: So to accomplish that we have to get a little creative.
Speaker 1: We have to think of ways to convert rotational force
Speaker 1: generated by the electric motor into something else, and that's
Speaker 1: kind of where cams can come in. So a cam
Speaker 1: rotates on the axis of a shaft that could be
Speaker 1: driven by something like an electric motor, So it's getting
Speaker 1: rotational force from some part of the mechanical system. And
Speaker 1: a cam on a shaft is frequently and a regularly
Speaker 1: shaped object. It can be sort of like an eccentric
Speaker 1: wheel is a very frequent example. So imagine you have
Speaker 1: a wheel. Let's start with a perfect circle. Just imagine
Speaker 1: a perfect circle on your mind. Now imagine deforming this
Speaker 1: perfect circle a bit. Maybe parts along the circumference bulge out,
Speaker 1: making it a little more oblong, or maybe they dip
Speaker 1: inward a bit, so that you have still generally a
Speaker 1: circular shape, but it's not perfect anymore. There are parts
Speaker 1: of the circumference where it's a different shape. So by
Speaker 1: positioning cams at specific points along a shaft where they
Speaker 1: will make contact with other mechanical elements such as levers,
Speaker 1: you can translate rotational motion into something else, like reciprocating
Speaker 1: linear motion. So let me give you an example imagine
Speaker 1: you have a horizontal shaft that can rotate in a
Speaker 1: particular way. And this shaft, and in this example, we'll
Speaker 1: say it connects to an electric motor. So the electric
Speaker 1: motor is providing the rotational force turning the shaft, and
Speaker 1: you know, let's say it's a clockwise direction from our perspective.
Speaker 1: And then let's say that we have a cam positioned
Speaker 1: midway down the length of this shaft. It is permanently
Speaker 1: attached to the shaft. It will rotate along with the shaft.
Speaker 1: It is as as far as we're concerned, part of
Speaker 1: that shaft. This cam, let's say his egg shaped, so
Speaker 1: one side of the cam bulges outward compared to the
Speaker 1: rest of it. And positioned above this cam is a
Speaker 1: type of lever that will call a cam follower. So
Speaker 1: this follower is actually making contact with the surface of
Speaker 1: the cam itself. So if you're thinking about let's say
Speaker 1: a vinyl record or a wheel, it's making contact with
Speaker 1: the the outer surface of this wheel, like the edge
Speaker 1: of it. In other words, and the lever is attached
Speaker 1: to something else in this mechanical system. So let's say
Speaker 1: in our example, this lever which can move up and
Speaker 1: down is connected to a little mechanical gopher, and this
Speaker 1: gopher will pop out of a hole that's in some
Speaker 1: rundown and yet still vaguely charming theme park attraction at
Speaker 1: your local amusement park. So as the shaft rotates, the
Speaker 1: cam rotates too, because it's attached to the shaft, it's
Speaker 1: part of the shaft, and the bulging bit of this
Speaker 1: oblong cam's surface rises up to meet the lever, which
Speaker 1: means it pushes against the lever, pushing it upward. So
Speaker 1: the lever goes up, which in turn pushes our little
Speaker 1: mechanical gopher up out of the hole. The cam continues
Speaker 1: to rotate with the shaft, and so the bulging bit
Speaker 1: of this part of the cam is now sloping away
Speaker 1: from the lever, so the lever can actually start to
Speaker 1: come back down again. It's sliding along the surface of
Speaker 1: the cam as the cam rotates away, and you know,
Speaker 1: gravity just pulls our little gopher back down the hole.
Speaker 1: The full distance that the lever is able to travel
Speaker 1: due to how it connects to this cam is called
Speaker 1: the throw. That is the throw of our cam follower.
Speaker 1: Now the cam followers don't have to rely purely on
Speaker 1: gravity to move back down. In fact, that would be
Speaker 1: a very bad design because over time the leaver could
Speaker 1: start to stick in the up position. Our gopher might
Speaker 1: not ever go back down into its hole. It just
Speaker 1: stays up there, which is just another reminder of how
Speaker 1: this park isn't the same as it was when you
Speaker 1: were a kid. No, I made myself sad. We'll tell
Speaker 1: you what. We're gonna take a quick break. When it
Speaker 1: come back, we'll get happy again. Okay, let's get back
Speaker 1: to our discussion about cams and and the example we
Speaker 1: were thinking about with the little gopher that can pop
Speaker 1: up and down based upon the rotation of this cam
Speaker 1: pushing against a lever. Again, you probably wouldn't just rely
Speaker 1: on gravity on these systems. You would probably have some
Speaker 1: other form of device that would ensure that the lever
Speaker 1: would return to uh it's full down position in this case,
Speaker 1: so we would probably have something like maybe a spring
Speaker 1: connected to this lever, so that when the cam is
Speaker 1: pushing against the lever, pushing it up, you know, moving
Speaker 1: the gopher up out of the whole. In the process,
Speaker 1: the lever is also compressing a spring, and as the
Speaker 1: cam's edge slopes away from the lever, allowing it to
Speaker 1: move back down again. The spring actually forces the lever
Speaker 1: to move back down towards the cams surface, so that
Speaker 1: you don't just have a gopher stuck out of its hole.
Speaker 1: Internal combustion engine cars use cams. In fact, they have
Speaker 1: a special shaft called the cam shaft that uses these
Speaker 1: to govern the intake and exhaust valves in the combustion engine.
Speaker 1: That's why I specifically say internal combustion engine cars. The
Speaker 1: cams in this case are used to to govern, or
Speaker 1: to control when an intake valve is open and when
Speaker 1: it's closed, and when the exhaust valve is open and
Speaker 1: when it's closed. You don't need those in an electric
Speaker 1: vehicle because you don't have the combustion uh cylinders. So
Speaker 1: let's talk about internal combustion engines and cams in those
Speaker 1: really quickly to kind of understand how cams are used
Speaker 1: in modern mechanical systems. So, an internal combustion engine burns
Speaker 1: a mixture of fuel and air inside fix cylinders. The
Speaker 1: energy generated from this combustion it's really an explosion, is
Speaker 1: used to push a piston outward. The piston, in turn
Speaker 1: provides power to the car's power train. Via a crankshaft
Speaker 1: and then in turn provides power to the wheels. The
Speaker 1: crankscheft also, by the way, provides rotational power for the
Speaker 1: actual camshaft. That's part of this system too. Will get
Speaker 1: to that. And all of this means that you can
Speaker 1: have your car go without having to do the flintstones
Speaker 1: thing and just use your feets. So the pistons connect
Speaker 1: to a crank cheft via piston rods. It's that connection
Speaker 1: that allows the reciprocating motion of the pistons, the in
Speaker 1: and out motion of the pistons as they move relative
Speaker 1: to the cylinders, into rotational motion for the shaft itself.
Speaker 1: These are really tricky things to talk about without the
Speaker 1: use of visual aids, but you know, just think that
Speaker 1: the up and down motion of the piston is connected
Speaker 1: via this rod to a shaft that can then rotate
Speaker 1: due to the up and down motion of the piston.
Speaker 1: All right, Now, let's talk about a four stroke engine
Speaker 1: because that will illustrate how this is all working and
Speaker 1: where the cams come involved. So when we say stroke,
Speaker 1: what we mean is one full travel of a piston,
Speaker 1: either inward into the cylinder or outward relative to the cylinder.
Speaker 1: So in is one stroke, out is another stroke, and
Speaker 1: internal combustion engines traditionally use four strokes, so those four
Speaker 1: strokes are intake. This is where a cylinder pulls in air,
Speaker 1: and it does this by opening the intake valve. As
Speaker 1: the piston is traveling outward from the cylinder, This draws
Speaker 1: air into the cylinder, kind of like if you were
Speaker 1: pulling the plunger back on a syringe. At the end
Speaker 1: of the stroke, the intake valve closes, which is absolutely critical.
Speaker 1: It has to close, and that seals the cylinder. You
Speaker 1: also get a mix of fuel that enters into the
Speaker 1: cylinder at this point, so in older cars that would
Speaker 1: come from a carburetor, in modern vehicles from the fuel
Speaker 1: injection system. The next stroke, the piston is moving back
Speaker 1: inward relative to the cylinder, and this stroke is called
Speaker 1: compression because the piston, which is you know, snugly set
Speaker 1: in the cylinder so nothing can escape along the sides
Speaker 1: of the piston. As it moves back into the cylinder,
Speaker 1: the piston compresses this mixture of air and fuel that
Speaker 1: has entered into the cylinder. At the end of this stroke,
Speaker 1: the piston is as far into the cylinder as it goes,
Speaker 1: and both intake and exhaust valves have to be closed, right,
Speaker 1: because if either valve were open, then that would mean
Speaker 1: that you couldn't compress the mixture. The mixture would be
Speaker 1: forced out of the cylinder because one of the valves
Speaker 1: had opened, So these valves have to be shut. The
Speaker 1: next stroke is combustion. This is when the spark plug sparks,
Speaker 1: which ignites the mix of air and fuel. It causes
Speaker 1: the explosion that forces the piston outward again, so the
Speaker 1: piston moves down the length of the cylinder. It's this
Speaker 1: force that provides the rotational force to the crank shaft
Speaker 1: that ultimately makes the car go. As the crank shaft turns,
Speaker 1: it pushes the piston rod as it rotates a one
Speaker 1: full rotation around that therefore makes the piston go back
Speaker 1: into the cylinder. For the fourth and final stroke of
Speaker 1: this process, this is the exhaust stroke. So this is
Speaker 1: when the exhaust valve opens and it allows the spent
Speaker 1: air fuel mixture to escape the cylinder. At the end
Speaker 1: of the stroke, the piston is as far into the
Speaker 1: cylinder as it can be. The whole process is set
Speaker 1: to repeat with the next intake stroke. And we do
Speaker 1: it all again. So let's finally get to the cams,
Speaker 1: because it's the cams that control the opening and closing
Speaker 1: of those intake and exhaust valves. The cams are on
Speaker 1: a cam shaft that ultimately receives its rotational power from
Speaker 1: the crank shaft. As the cams rotate, their surface forces
Speaker 1: their respective valves to open at just the right spot
Speaker 1: during that rotation, and then the valves will close again
Speaker 1: as the cams slopes away from the lever that is
Speaker 1: attached to the valves. The cams are positioned in such
Speaker 1: a way that they will always cause the valves to
Speaker 1: open at just the right part in the stroke process
Speaker 1: as the pistons are moving in and all of the cylinders,
Speaker 1: and then they will remain closed for the other three
Speaker 1: strokes of the four stroke process. Now, cams are used
Speaker 1: in all sorts of mechanical systems, not just cars, And
Speaker 1: the reason I even wanted to touch on these today
Speaker 1: is because again, next week, I should have a new
Speaker 1: episode up in which I'll talk about a theme park
Speaker 1: that used cams in its attractions. Very some alert to
Speaker 1: the gopher example I gave out, but far more complicated,
Speaker 1: and I think it's good to occasionally reflect on mechanical
Speaker 1: systems and get an understanding and appreciation for how humans
Speaker 1: were able to create one and and and create devices
Speaker 1: that could generate forces and also figure out ways to
Speaker 1: harness that force to do work, even if it meant
Speaker 1: having to convert one form of motion into another. It's
Speaker 1: really clever stuff. And with cams, it's also old stuff.
Speaker 1: There are illustrations of Chinese mechanical systems that used cams
Speaker 1: to convert rotational motion like that provided by a water
Speaker 1: wheel into reciprocating motion, so they've been around for a
Speaker 1: really long time. Anyway, I hope you found that interesting
Speaker 1: in this Tech Stuff Tidbits episode, and you know I'm
Speaker 1: looking forward to that episode for next week. Keep an
Speaker 1: ear out for it should be pretty fun and I'll
Speaker 1: talk to you again really soon. Text Stuff is an
Speaker 1: I Heart Radio production. For more podcasts from I Heart Radio,
Speaker 1: visit the i Heart Radio app, Apple Podcasts, or wherever
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