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How does a pull-back car work? Illustrated teardown

Muhammad523 · 219 points · 38 comments · 前天
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matt-attack昨天

This really needs to be done for a GLP-1 auto injecting needle. Pretty sure it’s the same as an epi-pen as well. It blows my mind. It’s a disposable, single use device that at the press of button: 1. Inserts the needle in your skin, 2. Slowly presses the plunger until the dose is injected 3. Then retracts the needle with plunger Three distinct and seemingly opposing motions. With timing. All in a little plastic enclosure. It sure I can think of a toy with that kind of mechanism.

arjie13小时前

Oh, is that why when you "overwound" it it would make that rapid ticking sound? The outer end of the spring is falling into the next little slot, huh. Fascinating stuff.

asdff15小时前

What is the name for the sort of toy car you push in one direction and it continues slowly in that direction? These ones were usually styled as 4x4 vehicles and almost moved like a rock crawler with the 4wd set to low. They could be pushed forward or in reverse (and then would go in reverse).

0zer03小时前

Fascinating animation. But there is one thing I don't understand. What is the purpose of the left axle gear (green)? It is not fixed to the axle because it rotates in the same direction in both modes. Wouldn't is be more efficient to connect the wind-up gear directly to the right axle gear (blue) and through pushing to the left spring gear (red)?

reactordev15小时前

I learned this when I was 4. We even had ones that shot sparks. America. The animations on this are really well done and I loved that trip back to childhood of pulling the car back and letting it rip. However, given the popularity, you should simulate what happens when you pull it back to the extremes over and over again and the spring gets stretched. It no longer kicks as fast as it used to and in some cases, it won't go at all.