3244: Pullback Drive

Pullback Drive

|< < Prev #3244 (May 11, 2026) Next > >|

Title text: "How does the spring not run out almost immediately?" "We pull it back REALLY far."

|< < Prev Random Explanation Next > >|

Explanation

This is one of 48 incomplete explanations: This page was created recently. Don't remove this notice too soon. If you can fix this issue, edit the page!

Transcript

This is one of 45 incomplete transcripts: Don't remove this notice too soon. If you can fix this issue, edit the page!

[Hairy & Cueball are talking in front of a white car. Hairy has his hand raised]

  Add comment        Create topic (use sparingly)       Refresh 

Discussion

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'al^converse 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)
        Add comment