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  • - [Narrator] Some toy cars have a wind up mechanism inside.

  • Pull it back and then release the car to watch it go.

  • In this video, we're gonna look at the gears,

  • the spring, and that clicking noise you hear

  • when winding up the car.

  • (spring clicking)

  • That's coming up.

  • (electric buzzing)

  • (lightning explosion)

  • (upbeat music)

  • If you want one of these toy cars to move forward,

  • you can either push it.

  • You could build a track

  • and use gravity to move the car forward.

  • Or my personal favorite are the cars

  • with the pull back mechanism.

  • No batteries required.

  • Just firmly press down,

  • pull back the car to wind it up.

  • Now release it and watch it go.

  • Let's take a look at how this works.

  • Take the case off the car and we're left with the chassis,

  • four wheels and a motor.

  • The front wheels spin freely.

  • There's nothing special about them.

  • The motor is only connected to the back wheels.

  • Now if you wind it up,

  • you can see some of the gears moving.

  • Let's open this up to see what's going on.

  • There's five gears here.

  • And right behind the biggest gear

  • is a twisted piece of metal.

  • It's called a Torsion Spring.

  • The more you twist this, the tighter it gets

  • and the more energy it stores.

  • Once released, it will quickly unwind

  • if allowed to do so.

  • This spring fits quite snug inside the circular hole.

  • If I pull it out, then the spring immediately expands.

  • And it's not so easy to put back in.

  • So be warned if you try this on your own toy car.

  • On the large gear, there are some curved extensions

  • sticking out the side.

  • These fit right around the center of the spring

  • as the gear turns, the spring does too.

  • When the car is pulled back, there's a chain reaction

  • of gears turning.

  • This is called the gear train

  • and it's what causes the spring to wind up.

  • Let's take a step back for a moment

  • and talk about gear ratios.

  • I have two gears here of different sizes.

  • If the big gear turns once, the small gear

  • will turn around more than once.

  • Now imagine the small gear

  • had another larger gear attached to it.

  • We could repeat this again with another smaller gear here.

  • Turn the first gear just a little

  • and the last gear turns a lot.

  • This concept is used in the mechanism

  • for a pull back car.

  • Now let's take a look at the car gears.

  • There's one attached to the axle

  • and there's one right next to it.

  • These always move together whether the car

  • moves forward or backwards.

  • We've seen the large gear.

  • Now these two gears have a mind of their own.

  • This one helps winding up the car.

  • And this one helps unwind the spring

  • and push the car forward.

  • The wind up gear can slide up and down

  • to engage or disengage with the teeth

  • on the large gear.

  • On the side, there's a diagonal slot

  • that makes the sliding possible.

  • When we start pulling back the car,

  • the wind up gear engages with the large gear.

  • When the car is released and starts moving forward,

  • the gears move the other way

  • which disengages the wind up gear

  • so it's no longer in contact with the large gear.

  • Now during this time, the wind down gear

  • is doing the exact opposite.

  • The car is pulled back, the wind down gear

  • is disengaged from the large gear.

  • You can see it doing a little dance

  • while it tries to stay out of the way.

  • When the car is released, the wind down gear

  • slides into place just as the wind up gear

  • slides out of place.

  • The Torsion Spring is causing the large gear to spin

  • which then moves the gears

  • which then turns the wheels on the car.

  • This is where the gear ratios come into place.

  • The largest gear moves only a little

  • and the back wheels of the car turn a lot.

  • This is part of why the car can travel so far on its own.

  • When the spring has released all of its energy,

  • the car keeps going on its own momentum.

  • The large gear will stop

  • and the wind down gear will disengage again.

  • This time, both of these gears are out of place.

  • This way, the car continues to move forward

  • with minimal interference from the large gear.

  • Imagine if the car abruptly stopped when this happened.

  • It wouldn't be a very fun toy.

  • Now because of the gear ratios,

  • you can move the car back and forth

  • while firmly pressing down and it's still winds up the car.

  • Watch the large gear here.

  • Pull back the car and the large gear winds up a lot.

  • Push the car forward the same amount,

  • and the large gear only unwinds a little.

  • Back and forth.

  • Back and forth.

  • Overall, the spring is still winding up.

  • One last mystery is that clicking noise you hear

  • when you pull back the car far enough.

  • (spring clicking)

  • This is actually a clever fail safe

  • to prevent you from over winding the mechanism

  • which might damage the spring or the gears.

  • On the outside of the spring, you'll see a little loop

  • which fits into these slots around the outside.

  • When the spring has enough tension,

  • the loop will slip into the next slot.

  • This is what causes the clicking noise.

  • The sound means your car is just about wound up

  • as far as it'll go.

  • My name's Jared and I'm a 3D animator here on YouTube.

  • I like making videos about how things work.

  • If you'd like to help me make more videos,

  • click here to visit my Patreon page.

  • Thanks for watching and I'll see you next time.

  • (upbeat music)

- [Narrator] Some toy cars have a wind up mechanism inside.

Subtitles and vocabulary

Operation of videos Adjust the video here to display the subtitles

B1 US gear wind large pull toy winding

How does a Pull-Back Toy Car work?

  • 2 1
    Siao-shen Jhu posted on 2021/05/09
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