Why Don’t Tree Houses Have These?
Why Don’t Tree Houses Have These?

[Captions by Mary V. at Y Translator]
In today’s video, we’re going
to be taking a look at pulleys. One of the classic six simple machines. We’ll take some measurements,
demonstrating how they work, and then we’ll try building a scale model
of an electricity free elevator. A pulley is one of what
renaissance scientists referred to as the six basic machines. Six mechanical devices that
helped you change the direction or magnitude of a force. The other five are a lever, a wheel and axle,
an inclined plane, a wedge and a screw. Today, we’ll be looking at pulleys
and taking some measurements with this fish scale to see what
happens to the different weights on a rope as it runs
through one or more pulleys. After that, the plan is to build a scale
model of something I came up with a few years ago and maybe
other people have come up with it hundreds of times before me. But the idea is to make an elevator
that uses just weights, ropes and pulleys and no electricity. Here’s the idea. A fixed weight will have two separate
pulley systems attached to it. One that makes it so you could
ride the other end of the rope up. And one that makes it so you
could write it back down. First off, we need a frame
that we can attach stuff to. So I’ve got a bunch of scrap
wood and we’re going to start throwing some stuff together. [Music] This is not the most
official-looking construction ever. Some pieces are kind of twisted
and warped and it’s just not flat. That’s because this is literally
just thrown together from pieces that I already had just in my scrap
pile but it should work pretty well. The important thing is that this end
over here can take a good amount of weight and we can do our tests on this. Here’s the first pulley we’re
going to do some tests with. It’s designed to just be permanently
attached onto something. It doesn’t move around
like some other kinds of pulleys. It just stays in one spot
but that’s exactly what we want at first. [Music] We’ve got our pulley attached
and we’ve got a thin cord running through the pulley. We’re now going to attach
that on to this little clip. That’s just to make
things a little bit easier as we’re disconnecting
and reconnecting stuff. We have here a fishing scale. We’ve got here what is
supposed to be a 10-pound weight. This is just sort of
a barbell exercise weight. We’re going to just hook that on
with this little rope and see what measurement
our scale gives us. 10.17 pounds for those who are curious. That is 4.6 kilos, so we can see just over 10 pounds. It could be that the weight
has a little bit of extra on it. It could be that this fish scale is
not 100% accurate but it’s pretty close. It’s supposed to be 10 pounds. It’s showing up as almost 10 pounds. Now let’s see what happens if we
connect this to our pulley system and then use our scale to pull on that. All right. Let’s add a little bit of a loop
into our rope right here so that we can hook our scale on to it. Pull on the loop, weight goes up. All right turn our scale on. The scale is going to be upside down, but we should still be
able to see the numbers. So it was 10.17 pounds. 10.17. We got exactly the same read out. A single fixed pulley does
change the direction of the force but it doesn’t change
the magnitude of the force. I’ve now got a 7.5 pound weight
with a hook attached to it, and we’re going to put that
through the loop instead of our scale, and what we’re going to see is that it’s not
heavy enough to pull the 10-pound weight. Of course it’s not. 10 pounds is more than 7 and 1/2 pounds. Drop it the other way. We can see that the 10-pound weight is
of course enough to lift the lighter weight. With our 7 and 1/2 pound weight
attached to one end, if we now attach the fish-scale to the same
spot, it’s not going to take as much pull because it’s already got the weight. Same deal. We’ve got static friction coefficient to
overcome but we can see that what we’re getting on the scale varies
between about one and a half pounds and well I think we got up to 6 there. But an equilibrium does seem to
be at about two and a half pounds, which is exactly what
we would expect to see. Let’s change things up and try
attaching a single movable pulley to our weight instead of one fixed pulley above. We’ve got our 10-pound weight,
we have a pulley attached to the top of the weight. On one end, our cord is
just attached to the beam. It’s not running through this pulley. It’s just on the beam. Separate from that. And the other side we can
just pull with our hands. So how hard are we going to have to
pull on this rope in order to get that weight to lift off the ground? Well let’s look at it. If it’s just suspended in the air. We know we have 10 pounds
of weight hanging down, and we’ve got two cords, that means each cord
should have five pounds on it. And that’s not really going to change. Even if we’re pulling it up and down. We should still have five pounds
are suspended in this cord, and five pounds suspended in this cord. Here we go. Here’s our scale. Pull till the weight starts
lifting and we are at about 5 pounds. We pull really fast for a second. It might register as even higher
but for the most part we get approximately five pounds of force
necessary to lift this 10-pound weight. Now with our single movable pulley
system it cuts the weight down in half but of course there has
to be a trade-off. You can see that if I move my hand,
I’m grabbing the rope right at the pulley. If I lift it from here,
all the way up to this beam, the weight didn’t move
the whole distance to the beam. The weight moved half
of the distance to the beam. So it only takes half as much
force to lift this weight off the ground but it only moves half as far. There has to be a trade-off and you
can’t remove the amount of work it takes to get that weight
up to its final height. And see to raise it all the way up, my hand has to travel
twice the height of the weight. But now we have an issue back to where
we first started before we’d even come up with the pulley in the first
place is that we’re lifting up. Sure it’s easier to lift up than it was
before but we’re still pulling up which is not as easy
of a motion as pulling down. So we can run it
through the fixed pulley again. And now we can pull down. And lift the weight up. The fixed pulley doesn’t
change the magnitude but it does change the direction. So this takes five pounds pulling up. That means this takes
five pounds pulling down. And of course if we move the entire
distance from the top pulley to the bottom pulley, our weight moves
approximately half that distance. I have to go back and pull it a
second time to get it all the way up. I’ve got a couple more pulleys so I’m
going to add another one to the top, another one to our weight and see
if we can reduce how much we have to pull on this even more. All right. The cord starts fixed
on one end of the beam. It’s going down through the first pulley
up through the fixed pulley on the top. Now we’re going to come back down
through the second movable pulley on the weight. And then we’re going to go back
up to this newly fixed pulley. It’s feeling pretty lightweight to me. Let’s check how much it takes
to move this with two moving pulleys and two fixed pulleys. It’s showing up as anywhere
between one and a quarter pounds, and almost four and
a half to overcome friction. But what we should be looking at is
one quarter of the total weight that would be two and a half pounds. Previously we attached our
seven and a half pound weight to a single fixed pulley system. And of course the 10-pound
weight lifted it right up. But now we’ve got a
system of moving pulleys, and we should see the opposite effect. Quite a bit in fact. There is very little resistance
there the seven and a half pound weight just plummets to the ground lifting the 10-pound weight 1/4 of
the distance to the pulleys at the top. Several years ago while I was just
doing some doodles, drawings, messing around with how
pulleys systems work, I thought of this idea that you might be able to use
pulleys and weights to build a sort of elevator. The concept I thought was pretty fun. And so what I wanted to do
is build a scale model. And it’s not just one weight
that would lift you back up. It’s a weight that has two
separate systems attached to it. One where the weight is
attached to a single fixed pulley, so the weight would pull you up, and another system
run at the same time that has a movable pulley
and a fixed pulley. So your weight would
overcome the counterweight, and you could ride it back down. [Music] We have our system all set up. We’ve got a 10-pound weight with two
separate pulley systems attached to it. The black one is a single fixed
pulley so it’s not changing the magnitude. It’s still an even ten pound pull. But it is changing the direction. The weight goes down,
it pulls the rope up. The movable pulley changes our
magnitude dividing it in half and the fixed pulley
changes the direction so that it’s still the opposite direction
as the movement of the weight. So imagining that this whole thing
is a scaled-down tree-house, this weight represents the weight, this 7 pound weight represents the
person or you know, we’ll say me, and this represents
the little ledge in the treehouse of the treehouse itself. This is actually non-functional. It’s just there to prove a point. The black cord which is on the fixed
pulley and that is currently tied to something on the ground. And this little loop is where
our person can grab a hold. Now as we untie the rope from
where it’s wrapped around this screw, the heavier weight takes over. Lifting this weight well almost
all the way up to this platform. Like I said this is just illustrative. We can just say that they
can climb on from there. Yay! We have climbed up onto our platform. Just as we wanted. But now you need to get down
in the weight is all the way down there. So what you do, is you
clip into the other system, and climb out of the treehouse. You are now gently lowered down to the
ground by the pulley system and the weights. Of course the weight is now only
halfway there in the loop to get back up is way out of reach. So what you need to do is just keep
pulling on the orange cord, lift your weight all the way back
to the top until you can reach the loop for the other side again. This is actually one set up where
you would be glad that the pulleys aren’t 100% frictionless. If they were perfect pulleys then
as you jumped out of the tree house, you would actually still
drop at the full speed of gravity. You would hit the ground holding
a rope that took a whole bunch of your weight off so it wouldn’t be
like hitting the ground full speed normally jumping out of the tree house. Your legs wouldn’t be supporting
your whole weight but it’d still probably be pretty scary to be
rushing in at the ground that quickly. Overall, the idea does work pretty
well and I hope that I get a chance in the future to try this out
as a full-scale treehouse elevator. Guys thanks for watching,
and we’ve got more for you to see. The box up at the top will
take you to our last video. You should go check that out. The bottom box will show you what
YouTube thinks you need to be watching next, and if you hit this bomb in the middle, you’d be subscribed to our channel
so you never miss out on a video. Don’t forget to ring that bell
and we will see you in the next one. Talk to you then.

100 thoughts on “Why Don’t Tree Houses Have These?”

  1. Johnathan Conaway says:

    I'd love to see a full scale of this, I'm all for seeing mechanics overcome electricity. I'm really tempted to try this, just didn't exactly know how it'd be done.

  2. Brian says:


  3. ya boy jack says:

    i thought this said "why dont tree houses have trees?" and i was ready to build a tree house on a street lamp

  4. s c says:

    or….. you could just use a ladder

  5. Shreshth Mohan says:

    Sure, that's what "scrap" wood looks like.

  6. Peaky43 says:

    "This is my scrap wood pile that just happens to fit together into this rack and still has the labels on it"

  7. dr00by says:

    The kid has one of these setups in Cop and a Half (1993) so he can jump off his balcony

  8. matt hombre says:

    2:33 1017 briksquaaaa

  9. Hunter Dean says:

    Before whatching I’d like say my tree house had a pulley since 05’

  10. Dan O'Connell says:

    I had a sort of pully on my treehouse. It wasn't an atuall pully, but a rope slung over a branch. What I found fascinating is that when you pull yourself up this way, by putting a loop at the the bottom for your foot… The effort to pull is lessened more than you'd think.

    When you're standing with your foot in the loop at the end, 100% of your weight is there. Then when you pull you're not just lifting your total weight, you're also taking weight off your foot, because you're pulling yourself up at the same time. The net effect is really fascinating.

  11. Geoffrey Marsh says:

    Had started sketching this up for the boys' treehouse, but was having trouble figuring out how to account for the very different weight of the two boys. My solution was to grab a gri-gri belay device and weights heavier than their combined mass to let them control their ascent/descent (depending on which way I rig it up)

  12. Bradley Bates says:

    bro your screws are not long enough

  13. indyjons321 says:

    I want to see this full scale.

  14. Relly says:

    I wanna see this in full real life scale

  15. Corl Franco says:

    Wtf is a pound… use real world units

  16. Mit Mit says:

    do this to scale.

  17. Jamie P says:

    I live up in the mountains in a cabin you have any ideas on how to real up groceries there's 30 stairs I have to go up before I get to my front door LOL

  18. Ninjabreadman says:

    How would you calculate how much the counter weight needed to be based on your weight?

  19. Pain & Discomfort says:

    Making that full size would be dope. Also afraid of the day you get a paper cut.

  20. Hammer ToeNail says:

    I want to hang myself with that system

  21. Emberson Gaming says:

    Make a bugger scale with hevy dumbels and other thung an see how light u can make them

  22. clump of poo says:

    jezz his hand are veiny

  23. Gabe Porter says:

    2:30 Jeeze I didn’t know you hated us

  24. zGilly 9020 says:

    I'd like to see a full scale build on the mechanical elevator

  25. Sean Mathias says:

    Do a full scale please

  26. Marco Ayala says:

    your machine looks like hang man lol

  27. 10CC says:

    My wife designed a carabineer to get groceries two stories up.
    She's very proud of her accomplishment,. . I am too.

  28. Clint Bland says:

    What a cool idea! I really hope you do a full scale version.

  29. Anything under the sun says:

    For the smaller pulleys he should of used I bolts or fencing staples and a cable tie. It wouldn’t effect the performance but it would look better that that black string.

  30. Justin David says:

    The pulleys need to go below ground

  31. EB13LDK says:

    i watched this at the library and a girl walked by and nervously asked why i was watching a tutorial on how to build a gallow

  32. jan kolář says:

    nice video, but i we learned about this in physics, so it is not much interesting for me

  33. Matthew Bishop says:

    Go for it, fulfill all our treehouse dreams

  34. Mike Rogge says:

    both wedge and screw are inclined planes-there are only four.

  35. Chenwei Ku says:

    This was a great video. Keep up the educational teaching videos. Great Job!


    The king of random:ELEVATOR
    That one emo kid:I COULD HANG MYSELF WITH THAT

  37. Adam says:

    Make or invent an instrument

  38. Christo van Niekerk says:

    Make the full scale tree house and elevator

  39. josh pentalin says:

    best video ever. This is so cool with the physics and mechanical engineering. Make more like this! Great job Nate!

  40. jacob shaw says:

    can you please try making cast iron skillets or melting

  41. Michal Štein says:

    For those who are curious? Did you mean from the rest of the world?

  42. DEEVIEDIE says:

    Please make that tree house

  43. bus boy struggles says:

    lmao it looks like a hangman stand

  44. Zio Lan says:

    Now it's time to build The Prince of Random Tree House

  45. Hero Animations says:

    Am I actually the only one that doesnt understand anything?

  46. Mr says:

    Make it full sized

  47. 209chevymon says:

    Man i cant wait to see the full scale of this project

  48. Nikiezekiel Gasis says:


  49. RoadRunnerLaser says:

    Did you have to guess a letter before adding each piece to that construction???

  50. xTony92 says:

    Nate is the best 👍👍

  51. FarmallRed 221 says:


  52. FarmallRed 221 says:

    NO MIlwauike

  53. Bradley Whais says:

    this would be very weight sensitive.

  54. Juhn-wel Gula says:

    Try to make a gigantic of that thing, that would be awesome

  55. iCoffeeGT Gaming says:

    2:30 fk u wood structure

  56. Jacob Alford says:

    What will happen if u put oblek or slime maybe both in the vacuum chamber ????? Please do a video on this!?!?

  57. KittyKat Allen says:

    When are you going to do the full size?

  58. ThePrufessa says:

    I'm getting a liquid retina display installed on my Stylo 4.

  59. ThePrufessa says:

    2:24 so, if it's not actually a ten pound weight and it's just "sorta" a barbell weight then what exactly is that big piece of metal that looks like it is EXACTLY a ten pound "barbell exercise weight"? Man you narrate in such a douche bag way. But great videos otherwise. At least most of them.

  60. Mac STRANGE says:

    Interesting test and experiment

  61. Sawer says:

    Try it fullscale and make a video about it, also make sure people are aware of the risks, it might work a bit too fast on full scale.

  62. lovegrape kitty says:

    I'd like to see the full scale version

  63. Keshav Bodhee says:

    Tree house with elevator please

  64. Kenneth Thygesen says:


  65. Noah Durling says:

    Behold unnecessary scientific knowledge

  66. Edvards Krastiņš says:

    Its called mechanical advantage

  67. Minh Huynh says:

    someone give this man a tree mansion

  68. HeyItsTim says:

    Now i understand a compound bow/crossbow

  69. th3cause says:

    Ok let's go build the great pyramids of giza

  70. Elliot Borkenhagen says:

    Build a tree house with an Elevator.

  71. Joshua Lewis says:

    U should make that bigger and actually ride it up and down

  72. Kaymen Lewis-Johnson says:

    this is mechanical advantage isnt? same as a mousetrap car?

  73. John Altenburg says:

    I like all your other vids, But this video seems haphazard and thrown together. Like a kid would do.

  74. Christopher Hawker says:

    Doesn't the wooden frame remind anyone of a game of Hangman?

  75. Czech game player says:

    Why i didnt watch this video when i was learning about pullies, levers and that stuff

  76. Chris Fesko says:

    Yeah when are you going to make this full scale? I would really like to see this work to carry human beings up and down!

  77. kingpatch95 says:

    It’s time to scale this up a bit

  78. Charlie Parr says:

    can you make rope from leaves 🙂

  79. Instant Tech says:


  80. BigAppleGaming ! says:

    Make a big tree house with this idea

  81. Bobby8nyc/Daddy_fit says:

    Bro why does it look like you’re gonna hang a dwarf

  82. Daxelin901 says:

    the testing of how pulleys affect the weight exerted on a scale was the exact project I did for a science fair in 5th grade. I was one of the top scorers at my school with it

  83. David Rodriguez says:

    Please try this out as a full scale.

  84. Mason Green says:

    Actually our tree house had something like that. A friend of the family came up and saw we was haveing trouble getting down from the tree house.. Any way he came up with this contraption kinda like what climbers have that makes the fall not so fast and hard.. Only used as a safty. But still fun to bounce around on 😏

  85. Jack Debney says:

    I would love to see you build a tree house

  86. Leepu pelaa10 says:

    Do treehouse that has this

  87. Budi Darmawan says:

    I study this mechanism of catrol in elementary school.

  88. Big comedian Scammer gets scam says:


  89. Bruno Rivas says:

    you should make a fort in the woods and max it out with your inventions

  90. Aleks Rocha says:

    This was my first tkor video many years ago

  91. Missy & Derek Davison says:

    You need the black rope to have the same amount of pillows and same length of rope so both ropes hit the top and bottom and the same time.

  92. Heather Stock says:

    Bob @iliketomakestuff just finished a treehouse. You two should collaborate on this project. It would be so great for making treehouses more accessible for kids with muscular disorders, like my nephews.

  93. Kieran Joshi says:

    You can simply use two hands to pull

  94. Ali_opowerful 510533 says:

    0:54 looks like someone’s getting hanged

  95. Jacob Limbaugh says:


  96. Rolf Poelman says:

    Where is the next promised video, of making a tree house lift with this pulley idea?

  97. Rolf Poelman says:

    I might need more detailed instructions, and especially to use on a tree.

  98. Jacob Thompson says:

    Pon pine does not need predrilled holes… But i guess you may have needed some b roll footage.

  99. papriel dreemur says:

    WAIT, could you possibly make one of these and exercise and get power?
    that would be really cool! one day imma get a trree house and do this for the entrance AND imma have one of my own versions of this to get power from my own strength!

  100. Patt Adams says:

    Kinda fun how elevators are not a new invention but the elevator brake is.

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