Every now and then, we here at the Autopian take a moment to consider the Big Questions: Who are we? Why are we here? Why do we love all these miserable cars so much? Why does it still burn when I pee? This happened today, as David and I had a conversation this morning that veered into the essence of vehicles. I started thinking about vehicles like cable cars and elevators and their status as self-propelled vehicles, a category that all automobiles fit into. And then I started thinking about sailboats. And hot-air balloons. And then I confused myself. So, help.
Okay, let’s back up: a self-propelled vehicle is pretty much any sort of conveyance that, you know, can make itself move. This includes everything from wind-up cars to Japanese Shinkansen trains to rockets to a hovercraft to your friend’s dad’s old Fiat 128 to that moped you always wanted as a kid and never got. Now, let’s think a little more about self-propelled vehicles. Let’s consider old cable cars.
The famous San Francisco cable cars worked like this: in between their tracks was a channel with a moving braided cable. Here’s how the Cable Car Museum describes the system:
The cable car is pulled on rails by latching onto a moving cable inside a channel beneath the street. The cable is guided by an intricate system of pulleys and sheaves (large pulleys). At the powerhouse, huge winding wheels driven by 510 horsepower electric motors pull cable loops at a constant speed of 9.5 miles per hour.
Through a slot in the street the car grabs the cable with a big vice-like lever mechanism called a grip. To start the car, the gripman pulls back on the lever which closes the grip around the cable. To stop the car, the gripman releases the grip and applies the brakes.
Were you to look at these famous cable cars in operation, they sure would look like self-propelled vehicles, as this 1984 video shows, as it explains it all to you, too. They’ve been around since 1873! Look:
Did you just lose about 16 minutes on that like I did? If so, sorry. But, you get my point: these behave like self-propelled vehicles, though the motive force, a number of 510 horsepower electric motors turning huge winding wheels that actually pull those cables, is not aboard the cable cars themselves. The cable car itself has a clamp to “harness” the energy of the moving cable. So, does that mean they’re not self-propelled vehicles? Or is the clamp system enough of a mechanism to consider it to be simply using the energy from the motion of the cable for propulsion?
Something like an elevator, which I do think is a vehicle, much like a short-distance vertical railroad, works in a similar manner. Now, stay with me here: If we don’t think that a cable car qualifies as a self-propelled vehicle, what about electric buses and trolleys that have motors on-board but get their electricity from overhead wires? You know, trolleybuses like these:
Really, these aren’t any different than other electric-powered vehicles like subways or trolleys with an electrified rail or a slot car track, even. Like the cable car, these machines get their power from conveyers of that power on a network. In the case of trolleybuses, that power is in the form of electricity, through wires. In the case of cable cars, the power is the motion of the cable. Is it that different? Both need outside energy sources to work; one gets that energy and then converts it to rotational, and then forward motion. The other gets the energy in the form of motion from the get-go.
Now, if we keep thinking along these lines, we get to sailboats. Are sailboats self-propelled in the same way that a cable car or subway or trolleybus is? In all cases, we have a vehicle that gets its energy from some outside network: the trolleybus from the overhead wires, connected to the power grid and then fed to the on-board electric motors to convert to motion; the cable car from the moving cable under the road, the clamp system transferring the motion from the cable to the whole car; and in the case of a sailboat, the power comes from the wind, air moving in the atmosphere of the Earth, which is harnessed by the boat’s sails and the motion of the wind is transferred into motion of the whole boat.
A sail is a mechanism for capturing energy and turning it into motion, like an electric motor can turn electromagnetic energy into physical motion, just in a very different way. The motive network of a sailboat is the whole atmosphere wherever the boat may be, and as such is quite vast and expansive.
So, back to my original question: do any of these count as self-propelled? Is a requirement for being self-propelled that the energy source must be able to be stored aboard the vehicle? The fuel in your car’s tank is really part of an energy network as well, one that started with dinosaurs keeling over, and then lots and lots of time and heat and pressure and microorganisms and probably a bit of magic, then continues with oil companies pumping and refining and trucking and storage and so many steps before it gets to a pump to squirt into the tank of your car.
Is that any different than grabbing a moving cable or capturing wind? Or is it essentially the same idea, just instead of drinking continuously from the spring of energy to move, you’re taking mouthfuls away, moving around, and coming back for more? A battery EV, too, is the same: just like a wire-powered trolleybus, but taking some amount of electricity on-board, replenishing as needed.
Is this the fundamental differentiator for self-propulsion? On-board energy storage? Or does that actually matter, and it’s just the ability of a vehicle to turn energy into self-motion, via some mechanism that could range in complexity from a cloth sail to the complex electric motor unit in a Tesla.
I asked some smart people I trust if they felt a sailboat was self-propelled. They didn’t think so, but the more I think about it, the less sure I am. I think now that a sailboat is self-propelled, and it does have an on-board mechanism for turning energy into motion, or at least one kind of motion (wind) into another (ship moving).
If you don’t think a sailboat is self-propelled, you at least have to admit that it is remarkably independently mobile for something that isn’t. Sailboats have criss-crossed the globe for centuries, not being pulled by whales or massive clusters of plankton or anything like that. They’re very steerable, in the right hands, and behave effectively like something that is self-propelled. I think it is?
But then I wonder where the line gets drawn; why does a glider not feel like it should count? Or, say, a simple raft, which, really, isn’t any different as it flows down a river than a cable car is as it gets dragged down Mission Street.
Or a hot air balloon, even? Does the burner to make heated air that rises count as a propulsion system? It carries fuel with it for that, but it’s only active on the vertical axis, and relies on outside wind energy for horizontal motion; so does that make a hot air balloon self-propelled on the vertical axis but not on the horizontal axis? Or is it just self-propelled?
I’ve taken a simple idea and confused myself really, really effectively. Help me figure this out!
“Why does it still burn when I pee? This happened today, as David and I had a conversation this morning that veered into the essence of vehicles. ” It all happened at the same time?
And what about Keebler delivery trucks? Are they elf-propelled?
Goddamnit.
I am now picturing elves on the hamster wheel, electric truck clearly, because the engineering required to make it purely mechanical boggles my mind!
To paraphrase Lucius Washington: “Don’t you put that evil on me, Jason Torchinsky? Don’t you put that on us!”
I agree with others that the system needs to be better defined.
Reading a lot of the posts, I also seem to come down on the side of storing energy aboard the vehicle is necessary to be considered self-propelled.
Also, what an awesome thought experiment! Torch and DT kicked us off on a great philosophical discussion that most people wouldn’t think about, but the community has actually taken it somewhat seriously in the comments. I applaud all of you! Even if you’re wrong.
Elevators and cable cars are a clear no. Even if you define the elevator as the entire system, including the electric motors, in that case you no longer have a vehicle, you have a stationary object that moves things around inside itself. A warehouse is not a self-propelled vehicle either.
Sailboats are trickier. Their propulsion comes from sails, which are indisputably part of the boat. However, they do need external energy input to provide propulsion. Does that make them not self-propelled? I don’t believe so. A speedboat also requires energy input in the form of gas. No gas, no go. Same for sailboats. No wind, no go. I don’t think it matters if the energy is stored onboard (which is why electric buses are also self-propelled, the energy is external, but the propulsion is onboard).
Another example I haven’t seen mentioned: A 100% solar-powered car (i.e. no batteries). I don’t know if such a thing even exists, but if it did it would only be able to move if there was sun, yet I think it is inarguably self-propelled. Almost the exact same case as a sailboat.
Of course, as with any good philosophical debate you might choose to draw the line somewhere else and come up with a completely different set of self-propelled vehicles. The fun part is finding an internally consistent argument that you can at least defend in the face of someone who is starting from a different set of assumptions. 🙂
When running from a bull, you’re self-propelled. Having been tossed in the air by said bull, you are no longer self-propelled. No sailboat, no cable car, nor an any elevator i’ve ever ridden generate their own motive force (other than infinitesimal gravitational pull, but i’m not sure i’ve got a handle on gravity).
Sailboats are propelled proportionally to the amount of ‘sailing juice’ consumed by the crew.
Ergo, sailboats are actually alcohol fueled.
You know my dad and his friends?!
Minnesota had (has?) laws that motorboats and sailboats were separated in terms of BUI (boating under the influence). Story was the lawmakers had sailboats so carved out exceptions for themselves. (No, I didn’t take the time to research this, just remembered from my childhood on the lakes, most often on sailboats with no motors.)
I feel like the key point is….
“at will”
Aka, it is self propelled, regardless, if it can be propelled at will. A hot air balloon is propelled at will (and NOT at will). So, it’s both, IMHO.
Soap box racer, self-propelled. I can move it, at will, should I have the energy (gravity) to do so.
I do not believe the “at will” requires motion in every direction at all times. a.k.a. my car can’t fly or travel on water (VW bugs are one of the few exceptions).
Is that why so many of his don’t move?
You’ve been down to Peru with Aaron Rodgers again, haven’t you?
Thanks to my Detroit Lions, he could be in Peru with A-A-Ron right now!
#Kneecaps #IfWeAintGoingYouAintGoing
The term “self-propelled” does not include the concept of “self-fueled”, IMHO. If something is self-propelled, it has the ability to move itself (not refuel itself) without outside agency. If you attach the requirement to be self-refueled, that rules out everything that we think of as self-propelled except living organisms.
To answer your question, Jason, no: sailboats (and cable cars and elevators, etc.) are not self-propelled because they are propelled (given motive force) by an external agency.
So… a cable car is not self propelled because the motor is not in the car, but a electric trolley car is, because although its power comes from an external source the motor is inside it?
I was reading about sailing ships the other day in a very old book and the author said that the wind is the fuel but the sails are the engine that turn the fuel into motion.
If an automobile is out of fuel temporarily can it no longer be claimed to be a self propelled vehicle? I’d say no: it is a self-propelled vehicle that is out of fuel. Additionally, one could say the same of a horse: it you don’t feed it adequately it can’t move.
So a sailboat is indeed a self-propelled vehicle because it has its motor contained in it. It simply runs out of fuel more frequently than an automobile.
The term “self-propelled” is a funny sticking point. The more important issue, IMO, would be to determine if the vessel is in control of it’s means of conveyance, be it machinery, sails, oars, etc. In this case, a sailing craft is 100% (inasmuch as any vessel can be within the limitations of it’s design) in control and could therefore be deemed “self-propelled”.
Definitions from COLREGS, aka “Rules of the Road”
(a) The word “vessel” includes every description of water craft, including nondisplacement craft, WIG craft and seaplanes, used or capable of being used as a means of transportation on water.
(b) The term “power-driven vessel” means any vessel propelled by machinery.
(c) The term “sailing vessel” means any vessel under sail provided that propelling machinery, if fitted, is not being used.
“I think now that a sailboat is self-propelled, and it does have an on-board mechanism for turning energy into motion”
That’s the big thing. The cable car is not, in my estimation, self-propelled. It is not converting potential energy of the cable to motion, but being pulled by the cable. I would contrast that with a bus that pulls electricity from overhead but converts that energy via motors. Arguably, a sailboat, by taking the wind but being able to redirect it and travel at different speeds than the wind speed, should be categorized as converting energy. But I also get the reason some would say that it is not. Not only is it moved by the wind, but the sails must be manually adjusted to catch that wind appropriately. After all, the reins on a carriage allow the driver to redirect the horse (though the vehicle is actually not converting energy to movement or redirecting the horse).
My (clearly unofficial) rulings:
Elevator: not self-propelled. The mechanisms are separate from the vehicle (even though the shaft and equipment are part of the elevator, they are not the parts in motion). I could conceive a self-propelled elevator, but it would be very different from our cable-pulled cars.
Hot air balloon: partially self-propelled. The up/down is quite obviously self-propelled, but it is my understanding that it can only follow the direction and speed of the wind for horizontal movement.
Horse: self-propelled, obviously.
Glider: probably not self-propelled. While it is arguably converting gravity into horizontal movement, it is largely just directing its own fall in some direction. That said, I would accept the argument that at least very efficient gliders could be considered self-propelled. Hang gliders are not, due to the human movement being the direct steering, but a glider that is efficient and can steer via controls vs direct intervention could be, as it does direct its movement.
Raft: not self-propelled. Not only does it not actually convert the water speed into any other movement, even the steering within the range of that is done with outside implements. It is always either carried along by currents or human-propelled.
Pedal-assist E-Bike: partially self-propelled. Converts electricity into some of the motive power.
Bicycle: not self-propelled, but close. By using gearing to increase the efficiency, a bicycle comes close to converting energy to motion, but it is still human-powered and the human is directly inputting kinetic energy.
Bicycle with humanoid robot: the robot is self-propelled, the bicycle is not.
Bicycle with permanently attached humanoid robot: self-propelled. The robot is now a part of the vehicle, making it the engine for this bicycle. But why? This cannot be efficient.
As a hang glider pilot, I would say your knowledge is incomplete. Gravity pulls us down, yes absolutely. But lift, lifts us up, and on good days we can fly for hundreds of miles. Sailplanes can fly for thousands of miles. Finding lift from thermals, from ridge lift, wave lift and convergence zones is as much an art as it is a science, but a flight where we merely descend from launch altitude, (A sled run, in the argot of the glider pilot) is the most basic, and worst case scenario that doesn’t involve a crash. Many glider pilots won’t even take off if the weather conditions indicate there is no lift to be found. Gliders are at least as much a self propelled vehicle as sailing ships.
Fair. I definitely do not know much about gliders.
Although not technically an elevator, what about a Wonkavator?
“So, back to my original question: do any of these count as self-propelled?”
Nope.
Next!
Propulsion is the necessary component of “self-propelled”. I don’t think a sail counts as a form of propulsion, unless you think kites are also self-propelled. On the other hand, a windmill that turns a propeller under water to move a boat would be self-propelled.
To put it another way, F=ma. The F must be generated by something on the m to cause the a.
What about on a windless day? Is your windmill driven propellered craft still self-propelled? I think it wouldn’t be because it cannot move and stop at will.
Now, a windmill attached to a generator that stored electricity into a battery which then powers a motor to drive a propeller, that would be self-propelled.
Upon first thought, I was thinking that the only things in life that are self-propelled are living creatures. And yet, there still needs to be an energy source, whether it comes from food or cocaine is almost irrelevant.
So I guess the larger question of “is anything in life self-propelled?” Even then we can get into all sorts of topics regarding gravity and mass, and that is a whole other wormhole. With that said, I propose that the answer is a definitive “No!, there is no such thing as self-propelled.”
I started off thinking you can’t call a sailboat self propelled because it does not fully contain the means of its own propulsion. A motor vessel carrys its fuel in addition to the motor, gears, and propellers that allow it to move independent of the winds and currents. However, it does not supply its own fuel now does it? Someone has to add fuel periodically to keep it moving. The motor vessel gets fueled by people, an external factor. The sailboat gets fueled by naturally occurring winds. The masts and sails are the machinery. If a barge that can’t get to its destination at all without being pushed or pulled by another vessel is not self propelled.
Let’s explore this further, even though there is absolutely no good reason to do so. Self-sufficient humans are self propelled because we fully contain the means of obtaining and processing our fuel. We eat and breathe on our own. This means infants and children cannot be considered self propelled until they are old enough to independently consume AND prepare food. Your 3 year old is not self propelled because they cannot reach the can of Spaghetti’ohs in the pantry. Sorry kid, but you are technically inert until you can use a step stool and operate the microwave on your own. I don’t give a shit if you can hold the spoon. A house plant can “hold” a spoon if I place it amongst the leaves. A person who is paralyzed from the neck down and has a monkey bring them food is self propelled. Why? Because they command the monkey.
Damnit, that means toddlers really are self propelled because adults are essentially their trained monkeys. Shit. I’ve got some more studying to do.
I’m really trying but I seriously cannot find any flaw in your logic.
By this logic, my car needs to add gas to itself. Spock would not approve.
Correct, your car cannot propel itself unless you obtain fuel and then add said fuel to the tank. That means cars are not self propelled unless you want to say we are a vehicle’s equivalent to the trained monkey. The damn monkey conundrum has made this a lot more complicated than I had hoped.
“…even though there is absolutely no good reason to do so.”
I beg to differ! I’ve enjoyed the last hour of my time this has consumed! Reason enough for me!
Self-propelled-
Cars
Trains
Motorcycles
Airplanes
Helicopters
Dirigibles
Watercraft with an engine and propeller(s) or paddlewheel
Not self-propelled-
Sailboats (wind)
Canoes/rowboats/rafts (oar powered)
Cable cars (separate powerhouse)
Ski lifts (separate powerhouse)
Elevators (separate powerhouse)
Hot air balloons (wind)
Bicycles/big wheels (pedal power) (except motorized bicycles)
Skateboards (except motorized)
Roller skates
Skis
Subarus (after the valve train fails)
cotd
I take issue with excluding human-powered conveyances. Nothing in the article is considered absent human participation. Canoes, Bicycles, Skates, etc. are powered within the closed system which includes the human as the engine. Cable cars, for instance, convey humans but their power comes from outside the closed system of conveyance and person. Maybe in some instances like canoeing on a river, gravity provides an assist. But that’s true of a car going down a hill and we consider a car as self propelled.
So, I propose self-propelled means propelled within the closed system of a human(s) and convenance.
I can’t agree. A roller skate with no foot in it is not self-propelled, it’s merely a shoe with wheels. A bicycle with no rider is not self-propelled, but an electric motorized bicycle is, even after a human has fallen or jumped off of it, for so long as it continues to stay upright.
The “closed system” isn’t closed because the human isn’t a permanent, integrated part of it.
After watching the cable car video, I am way smarter.
After reading Torch’s twisted logic, I am way more confused.
I would defined ‘self propelled’ as having the means to convey oneself IN A DESIRED DIRECTION using whatever environment is available. Therefore sailboats are self-propelled, as are cable cars, gliders, and balloons (mostly). But tumbleweeds are not.
David didn’t immediately tell you to draw your bounds around the system and determine what is included within the system and what isn’t?
Bad engineer! Bad! :shakes rolled up newspaper at David:
The cable cars vs electric buses is easy. You’ve determined that the motive force for the cable cars is the important thing, the motor being on the bus is the key there. The electricity coming from outside the system doesn’t matter, we fill our fuel tanks with fuel from outside the system. Without that external system then a gasoline vehicle wouldn’t be self-propelled, so an electric bus that isn’t hooked up to a grid is still self propelled, it just lacks the necessary support system.
Elevators are difficult. If you build a building and spec out that it has to have an elevator, you’re going to be very upset if you just get a box that opens and closes, doesn’t have a counterweight system, rails, drive motor, etc. At the same time, its the exact same argument for the cable cars. A cable car without the drive cable isn’t truly a cable car.
Define the bounds of the system better and we can talk.
As a final thought: I think you need to redefine what self propelled means.
As a start, maybe “if I vehicle can go against the forces acting on it, it is self propelled”
Sailboats: can tack into the wind, self propelled.
Gliders/hot air balloons: limited by gravity and wind, cannot go against one or both.
Cable car: cannot operate against gravity or the motive force of the cable, not self propelled.
“if a vehicle”
Damned no-edit-button-havin-comments.
As a second final thought: It sounds like we need classifications as to what level of self propelled something is. Similar to the wagon classification system that was developed
I propose 5 levels of self-propulsion:
Level 0 (No Self-Propulsion)
Level 1 (Driver Assisted Self-Propulsion)
Level 2 (Partial Self-Propulsion)
Level 3 (Conditional Self-Propulsion)
Level 4 (High Self-Propulsion)
Level 5 (Full Self-Propulsion)
Obviously, full Level 5 is the goal but it takes a lot of work and technology to get there. Depending on the mode of transport, we’re stuck at Level 2 in a lot of ways. Maybe someone can write a book about these challenges. Working Title: “Energy Source, Take the Wheel”
Sailboats can tack into the wind within limits. More than once I’ve spent half the day going in the wrong damn direction because of the wind. (Only to later be approached by Homeland Security asking me why I’m meandering around the Gulf instead of going directly where I said I was going.)
You bring up a good point, and thinking about it they aren’t necessarily going against the wind, as some portion of them is moving with the wind. If that is true, then they aren’t actually going against the force(s) that naturally act upon them
Sailboats (except square riggers) use the aerodynamic shape of the sails to create a low pressure zone on the curved side which pulls the boat along. You still need to have a little bit of wind hitting the back of the sail to keep it from luffing. The configuration of the boat and how strong the wind is decides how high it can point upwind, monohulls typically can point higher than multihulls for instance and you can’t point as high in low wind, but the best are still about 40degrees off the wind to one side or the other.
Therefor the sailboats are never acting against the force of the wind, not without deploying the ironsail that is.
Elevators add a different wrinkle, because there are a couple very different elevators.
Most low-rise elevators are hydraulic – a box pushed by a piston.
Most high-rise elevators are traction – vertical cable cars.
I’d ague that neither are self-propelled, which also means cable cars aren’t. But if you take the position that cable cars are self-propelled, traction elevators are too. That logic doesn’t necessarily apply to hydraulic elevators. If it does, does that mean a excavator bucket is self propelled outside of the excavator?
I think it also comes down to how the items are being identified as.
Most people, if they know what a cable car is, will just say “its the trolley that goes up and down the hills in San Fran.” and won’t point to the cable portion of it, or the drive section for the cable. Hell, I knew they traveled by being drawn along cables, but I didn’t realize that there was a little gripping clamp that grabbed it, I thought there were blocks attached to the cable that the system could grip or not grip, similar to the belt on a drive-through car-wash.
Comparatively, the public has an understanding of an elevator (from TV, movies, and other popular media) as a box that goes up and down on rails, and has cables and stuff to help it go up and down, “and there’s other things in there like a motor, but I’m not really sure?”
So, should we look at it as the more of the system may be known and described by an individual, the more well classified it can be? If you can drill down to hydraulic or traction, each can have its own classification, but if you only know enough to say “of course I know what an elevator is, do you think I’m an idiot?” then it gets a broader and less nuanced classification.
a few commenters have identified the boundaries of the system as a key aspect of JT’s dilemma. By analogy, the Second Law of Thermodynamics applies to CLOSED systems. the bounds of this system haven’t been clearly defined.
Another aspect of this dilemma has been touched upon by Stephen Jay Gould in some if his books (i forget which) that concepts like “self propelled vehicles” are a human construct we use to understand reality (Gould’s example is whether a portuguese-man-of-war is an individual animal or a colony- his conclusion was neither, it’s not a yes/no) there is no platonic ideal of SPV in reality, it’s an idea we use. in this case, as other commenters have built upon, the definition of SPV needs to be more detailed.
My $.02…
I hadn’t specifically heard of Gould before, briefly looking into him I can see that I definitely need to change that.
Thanks for that.
The Flamingo’s Smile
ch.5 “A Most Ingenious Paradox”
is the one I was thinking of.
Correct take, as I see it
Sailboats? Nope, unless you also think a horse drawn carriage is as well.
I would consider a “horse drawn carriage” as a system. You can “fuel” the horse and then go and stop mostly as you please. In my mind the wind is not part of the sailboat and you cannot store its energy in the sailboat to go and stop as you wish.
I think there’s an easy definition, which is that both the energy source and the motive source need to be self contained units stored aboard the vehicle to be considered self powered. That covers battery vehicles, ICE vehicles and marine power plants but not direct drive wind, solar or external power motors. If you put a wind turbine on a ship attached to a battery and a motor it would be self powered, but a traditional sailing boat wouldn’t. You needn’t control the method of refuelling but you do need to be able to independently stop and go.
It could be argued that an ICE vehicle would not be considered self powered as it needs the outside source of oxygen to run. If we are limiting the definition to Earth bound vehicles then they can be included, but I wouldn’t expect any moon buggies to be ICE (unless you fitted them with oxygen tanks for the purpose of combustion of course).
Captain Pike himself is not self-propelled, but his wheelchair is.
Of as he would say, “Beep. Beep.”
#HashtagTooSoon
I think that one could surmise what is considered to be self-propelled is if the unit contains both a means to store energy, and a mechanism to turn the stored energy into a motive force. Ergo, anything that relies upon an externality for energy capture is inherently not self-propelled.
Therefore, sailboats, cable cars and trolley busses are not self-propelled. The boat’s externality for energy capture is wind, cable car’s is a moving cable to which it may attach, and the trolley bus uses the pantograph to capture electricity.
To summarize, the key differentiator here is a means to store energy on-board the vehicle that is useable by the motive force mechanism.
This is the way
Anybody who has been stuck offshore on a windless day can tell you that no, a sailboat is not self-propelled. Not unless it also has an auxiliary engine but that’s most likely an old Atomic 4 with bad points and a prop shaft that just slipped its key again so still, not self-propelled. Now, if your vessel has a tiller and enough rudder and you’re not fighting a current and you have at least 1 arm you can attempt sculling at which point your sailboat is finally self-propelled.
Eh….could make the same argument about running out of fuel. In the end, the energy comes from outside.
That’s arguing semantics over storage. I consider myself to be self propelled but if I run out of Twinkies I’ll eventually stop as well.
According to the dictionary self-propelled is an adjective which is defined as “moving or able to move without external propulsion or agency”. It doesn’t mention storage of energy which is what internal combustion and battery electric vehicles do. A sailboat does not store its wind onboard (though Mythbusters did prove that to be plausible).
A traditional elevator is not self propelled because the motor and its power source pulling the cable is external to the vehicle. However if the cable or track is static and the motor is affixed directly to the elevator car to traverse the track then it is self-propelled.
The horse and buggy is a tricky one. The buggy certainly is not self-propelled. The horse certainly is self-propelled. But once you hitch the buggy to the horse it becomes a single unit “horse-and-buggy” and that combined unit is self-propelled until the yoke breaks.