How does a pull-back car work? Illustrated teardown

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.

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.

I guess as a kid I only had access to the cheap ones? Would pull back, not knowing where to stop, and there was eventually a crunching noise. Then I'd worry I'd ruined the thing!

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).

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.

Why is the wind-up gear needed? Couldn't the axle be connected directly to the spring gear?

I really love this site, it is obivous that the owner puts a lot of effort into this

If you have access to a 3D printer, this helps explain the basics too: https://www.thingiverse.com/thing:3308710

Wow. I love being reminded of stuff like this. Those cars were so cool.

Edit: I took one of these cars apart as a kid to see how it worked. This site brought back a lot of memories. The little coil spring inside the gear. I have to get my hands on one of these now…

absolutely love it! Gorgeous drawing, meticulous detail.

Great site!

Love this site! Well done!

Please leave my browser history alone