Every machine is a time machine.

The movie Primer has a very limited time machine that works at -2X. You turn the machine on at, for instance, 2PM, and walk away, coming back in, say, eight hours. You then go into the machine, and you stay in there for eight hours. When you come out of the machine, it is now 2PM, the time when you first turned the machine on. It is a one-way machine; you can only ever use it to go backwards, and you have to go forwards in time the old-fashioned way.

It was made on a budget of $7000 and it's one of the best sci-fi movies ever made.

the dinos would get you first so very.

About half as difficult as it would be for the 220/240V one it needs.

there was an episode where they created a dynamo generator and batteries.

that took them something like six months with many people helping.

unfortunately dynamos(like above) and batteries work on DC current. that time machine works on AC.

so you would need to do two things.

1. create a mechanical DC>AC inverter that preferably is powered from the physical input of the dynamo
2. create batteries in both series and parallel to ensure a 120v voltage is maintained at the required amperage.

also consider that north American standards require electricity to run at 60hz. this means the AC signal flips the DC signal 60 times per second. creating a mechanical inverter would need to take into account the size of the circle for a complete rotation in 1 second as well as the speed at which the dynamo must spin in order to get 60 alterations per second. the rough formula would look something like: frequency = speed/(diameter*3.14). speed can be variable depending on the size of the copper wheel used as well.

to sum everything up, for just the two people there, it's probably going to take them too long and they'll die from exposure or predators.

get excited

Assuming Dr. Stone is some kind of MacGyver regen:

Two obvious approaches to me that I'll run through in high level: build a wind/watermill generators or potato/lemon batteries

First thing you'll need to figure out for both is how to make some wire. That's going to require finding some metal ore and a hot furnace, and creating a few tools out of stone to work with it.

The biggest difficulty with the former two is going to be finding some ferrous metal to turn into magnets. You can make a magnet without electricity by smashing the shit out of some iron as it's aligned with the earth's magnetic field, and it'll become a weak magnet. From there with enough wire, you can build a generator. With the sails of the mill, you can build that out of wood and foliage.

For potato or lemon batteries, you're going to need a shitload, as they give you about a volt and a pretty tiny current, but theoretically you could figure something out that way with enough. I imagine some things may want to eat your batteries though

trash can. remember a trash can.

I don't know this movie called "Back the the Future"

That's heavy doc

I was thinking chron-o-john

Pshaw, merely requires a minor positional adjustment, and of course the entire historical location of every planetary body in the galaxy.

Maybe it's back in the same spot. I'm feeling lucky.

between the planet revolving around the sun, the solar system revolving around the galaxy, and space expanding, we're moving at hundreds of thousands of km/h. Good luck getting back to where you started.