alt.hn

6/28/2026 at 10:16:20 PM

How does a pull-back car work? Illustrated teardown

https://mechanical-pencil.com/products/car

by Muhammad523

6/29/2026 at 4:38:38 PM

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.

by matt-attack

6/28/2026 at 10:16:20 PM

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

by Muhammad523

6/29/2026 at 4:58:01 AM

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…

by donkey_brains