Difference between revisions of "3244: Pullback Drive"
(→Explanation: A bit of further detail about pull-back motors.) |
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{{incomplete|This page was created by A STOMP ROCKET POWERED CAR. Don't remove this notice too soon.}} | {{incomplete|This page was created by A STOMP ROCKET POWERED CAR. Don't remove this notice too soon.}} | ||
| − | This comic is a reference to toy cars with {{w|pullback motor}}s. Normally used for small toy cars, the spring motor stores potential energy when the car is pulled backwards, and the potential energy is immediately released as kinetic energy when the spring is | + | This comic is a reference to toy cars with {{w|pullback motor}}s. Normally used for small toy cars, the spring motor stores potential energy when the car is pulled backwards, and the potential energy (including the final energy used in holding the car against its spring) is immediately released as kinetic energy when the car is released. |
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| + | A very simple version of pull-back car will only go as far forward as it is drawn backwards in the first place, although by the use of free-wheel gearing at the end of its 'powered' phase and change in effective gearing (between 'charging' the spring by back-pulling, and thenetting it 'expend' in the forward direction) can store a lot of torque from a little distance and expend it in more speed/distance for the very light toy, which then may run on 'unpowered' for a significant further distance in the right circumstanes. On the other hand, they do not have the ability to store indefinite degrees of energy in their spring, they may hit a hard limit whereby the spring cannot be wound any firther, or (commonly for such toys) a slip-gear will audibly produce rapid 'click's as the mechansim no longer tries to convert pull-back movement into sprung potential (letting the child know that their toy is at maximum readiness). | ||
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| + | In this comic, [[Hairy]] suggests a full-scale version of a pullback car. Making this type of energy store work on the scale of a full-size car would be extremely impractical, due to the {{w|Energy density#In material deformation|low power}} and the requirement to pull it back far enough to then go anywhere meaningful. Hairy tries to sell the car by saying that [[Cueball]] won't need to worry about gas or electricity prices. This is technically true, but cars that run on petroleum or electricity have the advantage of their energy supply being refillable, while this pullback car presumably does not. Also the power relies on the car 'being pulled back '''''really''''' far', which would require a lot of difficulty, and would not go very far at all unless - as pointed out by Hairy in the title text - it was pulled back very far (though how they intend to do that is unclear). | ||
The entire reason for Hairy attempting this new type of propulsion is the rising electricity and gas prices as a result of the closure of the {{w|Strait of Hormuz}} due to the {{w|2026 Iran war}}. The strait was a very common waterway used for the international trade of natural gas and petroleum from the Middle East, but the Iranian government is currently not allowing any foreign ships to pass through it. If this type of propulsion works, this would negate the need to fuel the car, making it a good energy-efficient alternative if implemented correctly. | The entire reason for Hairy attempting this new type of propulsion is the rising electricity and gas prices as a result of the closure of the {{w|Strait of Hormuz}} due to the {{w|2026 Iran war}}. The strait was a very common waterway used for the international trade of natural gas and petroleum from the Middle East, but the Iranian government is currently not allowing any foreign ships to pass through it. If this type of propulsion works, this would negate the need to fuel the car, making it a good energy-efficient alternative if implemented correctly. | ||
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It would be possible to "recharge" such a car by repeating the process of pulling it backwards. However, the energy being stored in the spring motor would have to come from somewhere. A flywheel connected to the motor could be occasionally lowered onto the road when the car is under braking and then automatically raised, which may work as a form of charging if the released kinetic energy could be diverted to the main wheels. However, the automatic lowering and raising of the flywheel would require an external energy source, and it would be much simpler to just use an electric car at that point. Plus, this would produce diminishing returns and the car would need to be "recharged" every so often. | It would be possible to "recharge" such a car by repeating the process of pulling it backwards. However, the energy being stored in the spring motor would have to come from somewhere. A flywheel connected to the motor could be occasionally lowered onto the road when the car is under braking and then automatically raised, which may work as a form of charging if the released kinetic energy could be diverted to the main wheels. However, the automatic lowering and raising of the flywheel would require an external energy source, and it would be much simpler to just use an electric car at that point. Plus, this would produce diminishing returns and the car would need to be "recharged" every so often. | ||
| − | In the title text, Cueball points out that such a motor would store very little energy and would run out almost immediately compared to a traditional combustion or electric engine. Hairy says that to counteract this, they "pull it back '''''REALLY''''' far," which would not actually solve the problem of it being a single-use and incredibly inefficient energy source. However, how they propose to do that is unclear, but to do it manually would be very difficult to pull off{{citation needed}}, and if pulled by a kind of mechanical device it would defeat the main purpose of the pullback car - That it doesn't rely on various fuels to keep it going. | + | In the title text, Cueball points out that such a motor would store very little energy and would run out almost immediately compared to a traditional combustion or electric engine. Hairy says that to counteract this, they "pull it back '''''REALLY''''' far," which would not actually solve the problem of it being a single-use and incredibly inefficient energy source. However, how they propose to do that is unclear, but to do it manually would be very difficult to pull off{{citation needed}}, and if pulled by a kind of mechanical device it would defeat the main purpose of the pullback car - That it doesn't rely on various fuels to keep it going. |
==Transcript== | ==Transcript== | ||
Revision as of 15:00, 12 May 2026
| Pullback Drive |
 Title text: "How does the spring not run out almost immediately?" "We pull it back REALLY far." |
Explanation
|
This is one of 48 incomplete explanations: This page was created by A STOMP ROCKET POWERED CAR. Don't remove this notice too soon. If you can fix this issue, edit the page! |
This comic is a reference to toy cars with pullback motors. Normally used for small toy cars, the spring motor stores potential energy when the car is pulled backwards, and the potential energy (including the final energy used in holding the car against its spring) is immediately released as kinetic energy when the car is released.
A very simple version of pull-back car will only go as far forward as it is drawn backwards in the first place, although by the use of free-wheel gearing at the end of its 'powered' phase and change in effective gearing (between 'charging' the spring by back-pulling, and thenetting it 'expend' in the forward direction) can store a lot of torque from a little distance and expend it in more speed/distance for the very light toy, which then may run on 'unpowered' for a significant further distance in the right circumstanes. On the other hand, they do not have the ability to store indefinite degrees of energy in their spring, they may hit a hard limit whereby the spring cannot be wound any firther, or (commonly for such toys) a slip-gear will audibly produce rapid 'click's as the mechansim no longer tries to convert pull-back movement into sprung potential (letting the child know that their toy is at maximum readiness).
In this comic, Hairy suggests a full-scale version of a pullback car. Making this type of energy store work on the scale of a full-size car would be extremely impractical, due to the low power and the requirement to pull it back far enough to then go anywhere meaningful. Hairy tries to sell the car by saying that Cueball won't need to worry about gas or electricity prices. This is technically true, but cars that run on petroleum or electricity have the advantage of their energy supply being refillable, while this pullback car presumably does not. Also the power relies on the car 'being pulled back really far', which would require a lot of difficulty, and would not go very far at all unless - as pointed out by Hairy in the title text - it was pulled back very far (though how they intend to do that is unclear).
The entire reason for Hairy attempting this new type of propulsion is the rising electricity and gas prices as a result of the closure of the Strait of Hormuz due to the 2026 Iran war. The strait was a very common waterway used for the international trade of natural gas and petroleum from the Middle East, but the Iranian government is currently not allowing any foreign ships to pass through it. If this type of propulsion works, this would negate the need to fuel the car, making it a good energy-efficient alternative if implemented correctly.
It would be possible to "recharge" such a car by repeating the process of pulling it backwards. However, the energy being stored in the spring motor would have to come from somewhere. A flywheel connected to the motor could be occasionally lowered onto the road when the car is under braking and then automatically raised, which may work as a form of charging if the released kinetic energy could be diverted to the main wheels. However, the automatic lowering and raising of the flywheel would require an external energy source, and it would be much simpler to just use an electric car at that point. Plus, this would produce diminishing returns and the car would need to be "recharged" every so often.
In the title text, Cueball points out that such a motor would store very little energy and would run out almost immediately compared to a traditional combustion or electric engine. Hairy says that to counteract this, they "pull it back REALLY far," which would not actually solve the problem of it being a single-use and incredibly inefficient energy source. However, how they propose to do that is unclear, but to do it manually would be very difficult to pull off[citation needed], and if pulled by a kind of mechanical device it would defeat the main purpose of the pullback car - That it doesn't rely on various fuels to keep it going.
Transcript
[Hairy and Cueball are standing to the right of a medium-size car. Hairy has raised one hand slightly to point to the car.]
Hairy: You won't have to worry about gas prices or electricity prices with our new pullback drive model.
Hairy: At the factory, we put the car on the ground and tow it all the way backward until it starts clicking.
Hairy: To drive forward, you just release the brake and it goes.
Title text: How does the spring not run out almost immediately? We pull it back REALLY far.
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Is that supposed to be Elon Musk? 185.114.120.233 (talk) 09:24, 12 May 2026 (UTC) (please sign your comments with ~~~~)
There are toy cars that work like this, or that use a flywheel to store energy in a similar way, for example the Fisher-Price Rev 'N Go Stunt Vehicles. The salesman is offering a full sized car on the same principle. The toys don't go very far. Neither will the full sized car, though he implies it will go "far" before stopping. He doesn't offer any practical way to rewind the spring. 2A12:F43:1462:CC00:583C:B3A7:2A0B:2140 09:56, 12 May 2026 (UTC) dww
- Pull-back and Rev-up toys work significantly differently (though a pull-back toy may have a flywheel effect, it doesn't usually rely on this). Both are, of course, ways in which a child puts their effort into a much smaller vehicle that then expends that effort into forward motion (from my childhood, there were 'friction-toys' or even the Evel Knievel Stunt Bike, on one hand, and things like the Penny Racers, on the other).
- The Rev'N'Go type perhaps can be far more indefnitely charged with energy, upon being released (barring mechanical failures and stripping/melting the plastic cogs), but would not give you the described Clicking that the comic says is happening, which is a sign of a sprung-toy with basic overwind-protection designed in.
- Also, riding a (for example) full-sized Evel Knieval flywheel bike and applying the brakes (assuming they could stop it in time!) would probably just stop it, and leave no more energy to move off again (unlike the spring-powered car, halted before too unwound). I suppose you could make the brakes disengage the drive from the still-running flywheel, then 'clutch back on' when you released them again, but still not something that mofe pulling back at the factory is going to help reduce your range-anxiety with. 82.132.221.157 16:00, 12 May 2026 (UTC)
Energy storage. The devil is in the detail, and the magnitudes. It turns out a rubber spring (aeroplane elastic) stores rather more energy weight for weight than a steel 'clockwork' spring. However batteries, and hydrocarbons, store orders of magnitude more. This subjectwould be good for one of Randall's 2D graphs, plotting use case against energy stored. For instance, a diver's harpoon gun uses a pull-back mechanism quite effectively. 82.19.218.32 (talk) 10:22, 12 May 2026 (UTC) (please sign your comments with ~~~~)
I italicized the "or" in the first section of the transcript SomebodyElse (talk) 11:09, 12 May 2026 (UTC) SomebodyElse 12:08, 12 May 2026 (UTC)
- Isn’t it also bolded?Commercialegg (talk) 12:51, 12 May 2026 (UTC)
- Looks like it is. :) SomebodyElse (talk) 18:09, 12 May 2026 (UTC)SomebodyElse 17:08, 12 May 2026 (UTC)
Is the mention of worries about gas prices a reference to Trump's war on Iran? SectorCorruptor (talk) 14:52, 12 May 2026 (UTC)
- Almost certainly. I've added it in. --DollarStoreBa'alconverse 14:38, 12 May 2026 (UTC)
Does this count as a Tuesday comic? Not sure when it went live but it hit explainxkcd at 0900 UTC, which was 2AM Tuesday morning California time. It was still Monday in Hawaii (UTC-1000) though. 64.201.132.210 15:18, 12 May 2026 (UTC)
Probably the real vehicle getting most close to the pullback drive is the Gyrobus: https://en.wikipedia.org/wiki/Gyrobus 2a02:3100:8bac:fe00:1e1b:dff:fe9f:401d (talk) 20:40, 12 May 2026 (please sign your comments with ~~~~)
I'll let another editor handle the writeup and citations, but here are some order-of-magnitude comparisons: The springs actually in your car's engine store a few joules. A garage door spring might store a few kilojoules. An eight-ton chunk of rubber can absorb 5 megajoules, and a single gallon of gasoline stores >120 megajoules. Even if you have some incredibly machinery to get that energy out, there's several orders of magnitude between (the spring energy you can store inside a car) and (the spring energy needed to make a car go even one mile). 206.209.15.112 (talk) 21:02, 12 May 2026 (please sign your comments with ~~~~)
- You can make springs out of petrol? 2001:569:FBCA:1700:986:CE3B:3243:855 00:47, 13 May 2026 (UTC)
Just reading this article and seeing this sentence:
> This is technically true, but cats that run on petroleum or atomicity have the advantage of their energy supply being refillable, while this pullback cat seemingly does not (without another factory-style 'pull back' facility).
82.196.111.48 19:06, 13 May 2026 (UTC)
- I think you needed to paws and read those clawses again. 82.13.184.33 08:30, 14 May 2026 (UTC)
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