- 5 ay önce
The Smart Tricks Inside Telescopic Machines
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00:00Have you ever wondered how telescoping mechanisms actually work?
00:04Because there's quite a few interesting challenges when you want something to become more than
00:08twice its original length.
00:11Let's take a look at a few completely different types of telescoping mechanisms.
00:17Krommenhoek in Apeldoorn is letting me film in their amazing showroom and Flexispot sent
00:21me one of their legs which uses a completely different mechanism.
00:25Let's look at hydraulics first.
00:27A regular hydraulic cylinder can extend to a little bit less than twice its length.
00:33The simplest idea to go further is to make a telescoping cylinder and just fill the whole
00:38thing with oil.
00:40This works great on a small scale like this cute little jack, but you can imagine that
00:45you need way too much oil to fill a cylinder that can stretch the length of a boom lift
00:50or even a telescopic crane.
00:52Partly because of the length, but mostly because the stacked walls will eventually force
00:58you to build a cylinder with an enormous diameter even though you are limited to the power of
01:05the smallest section.
01:06Another problem is that telescopic cylinders are usually single acting.
01:11They have just one place for the oil to go, so they can only extend under their own power,
01:16but they need external forces to retract again.
01:20And that's on top of the fact that the whole thing would basically be a bunch of hollow piston
01:24rods.
01:25This shiny part, which is super hard and super precise and rust resistant.
01:31So, yeah, it gets expensive really quick.
01:34Telescopic cylinders like this are regularly used in dump trailers and that kind of stuff,
01:39but if you really want to go far, there are definitely better options out there.
01:44Another way you might think of to go further is to just add another cylinder on top.
01:49And when the first one is extended, you extend the second one.
01:52This lovely little electric forklift uses this technique.
01:56What makes it interesting is how the hydraulic fluid gets to where it needs to go, because
02:01the hydraulic lines are not very stretchy, of course.
02:04Let me preface this with the fact that I haven't seen a diagram of this model or anything like
02:09that, but this seems to me what's going on.
02:12Even though these cylinders are not telescopic, they are still single acting, because they can
02:16always rely on gravity to push them down again.
02:19This is also partly why they are so incredibly slim.
02:23There is just space for oil underneath the piston.
02:25They don't need room on top, between the piston rod and the cylinder wall.
02:29As a first fun side note, did you know that regular double acting cylinders can push harder
02:35than they can pull, because the cylinder rod takes up space on the piston, so on one side
02:41there is less surface area for the oil to push against.
02:44Anyway, as you can see, these single acting cylinders on the forklift still have two ports.
02:51And that's where the smart tricks come in.
02:53The piston rod is hollow, so the main port is located there on top.
02:58But, and this is just the chef's kiss, when the piston reaches this point, a port opens
03:04out that goes to the second cylinder.
03:06And because the hollow piston rod of the second cylinder moves up together with the body of
03:11the first cylinder, they can just use a tiny bit of hard line between the two.
03:17Just, just so good.
03:19But it gets even better.
03:21Let's move on to the most used, and most brilliantly simple way of extending the reach
03:26of your cylinder.
03:27If you put a pulley on top of a cylinder with a chain over it, and you bolt one side of the
03:32chain to the cylinder housing, the other end of the chain now has to move up twice the
03:37distance of the extending cylinder.
03:39You can think of it like this.
03:41When the chain doesn't roll, it moves up the same amount as the piston.
03:46And now, if you pull one side back down, the other side moves up the same amount again.
03:51That's basically what happens, but in one continuous motion.
03:54This chain also hides the length of the cylinder.
03:58Now the forks can touch the ground.
04:00They are the lowest part of the machine.
04:02And when it's up, the forks, or the load, are also the highest part of the machine instead
04:07of the piston rod, which allows you to go through lower doors and such.
04:12This chain mechanism is used in most, if not all, boom lifts and forklifts.
04:16With boom lifts, the cylinder is mounted in reverse, so that we can mount the second section
04:22to the cylinder housing without making holes in the third section.
04:26The chain is connected to the first section, goes over the pulley that moves together with
04:31the second section back to the third section.
04:34But chains can only be in tension of course, so there's another chain that goes over another
04:38pulley on the back of the second boom section to pull the third section back down.
04:43The hydraulic lines are folded over on the outside of the machine.
04:47They come back from the end of the first section and lay straight along the third section.
04:52So only the length of the second section needs this rolling hardness to prevent kinks in
04:56the line.
04:57As a bonus fact, this small cylinder here isn't there to help the huge one out.
05:06No, when the arm goes down, it pushes oil into the cylinder there, which keeps the forks
05:12level.
05:13Okay, back to the telescoping mechanisms.
05:15One downside of this chain technique is that your cylinder also needs to be twice as strong,
05:20which is why this cylinder in the front is actually wider than these long ones in the back.
05:25You can also use this technique for a larger amount of boom sections by chaining them together.
05:30If you connect another chain to the second section, put a pulley on the third section,
05:36you could mount a fourth section to the other end of the chain.
05:40And you can go on and on and on.
05:42But you will run into the limits of this technique pretty quickly, because you are just spreading
05:47out the power of one cylinder over a longer and longer distance.
05:51Eventually, the strength of the cylinder, the strength of the chains, or the resistance
05:55from the pulleys will become a problem.
05:58So it's generally not used for more than five sections.
06:01Pam, pam, pam.
06:03Introducing, introducing.
06:05Telescopic cranes.
06:07Telescopic cranes often use a locking mechanism and just go one by one.
06:11Lock the piston to the smallest boom section, extend, lock the boom section in place, release
06:17from the piston, retract, lock to the second smallest section, to the piston, and so forth.
06:23And in contrast to forklifts, most of the lifting itself is not done by extending the
06:28boom, but just with a cable when the boom is locked in place.
06:31This is what allows you to use a relatively slow mechanism for the boom.
06:35How the locking and unlocking actually works in practice is a bit of a mystery, and it probably
06:40depends on the manufacturer.
06:42If anyone is watching, I'd love to do a factory tour or something.
06:46But that's the gist of it.
06:47With this system, you can just keep on stacking.
06:50However, hydraulics are expensive and messy.
06:54You need a pump, you need a motor for that pump, you need hoses, you need cylinders, you
06:59need pfff.
07:00And even if you make it nice and expensive, it will eventually leak somewhere.
07:05That's basically a given with hydraulics.
07:07So for consumer goods, like adjustable standing desks, that should be affordable and clean,
07:14screwing mechanisms are much more appropriate.
07:17But these legs still need to extend more than twice their length.
07:20So you can't just have nut on a piece of all thread.
07:23You need something a little bit smarter.
07:26Lucky for us, Flexispot wanted to sponsor this video.
07:29And I happily agreed on the condition that they would send me an extra leg to take apart.
07:35And they did.
07:36In fact, they sent me a whole extra desk.
07:39After taking apart one leg for the video, which we'll get to in a second, I still had
07:43two left.
07:44And I am enjoying my adjustable desk so much that I wanted to surprise my old man by changing
07:50out his current desk legs with these adjustable ones.
07:53And so I did.
07:55This specific controller was made for three legs and not the two I still had left.
08:00But with some simple soldering, I could just use the power supply directly and mount a
08:03simple switch in between.
08:05Needless to say that this obviously doesn't fall under their warranty.
08:09But it works.
08:10And my dad was very happy.
08:11And so am I.
08:12They had great instructions.
08:14It lifts me like it's nothing.
08:16It has easy controls where you can preset heights and all that kind of stuff.
08:19And they are really stable.
08:21In fact, they are way more stable than my old, non-adjustable desk.
08:25And they are surprisingly affordable.
08:27Flexispot has an October sale going on with up to 50% off.
08:30Check the description for my promo code and all the details.
08:33Oh, and they also sent me their C7 ergonomic chair.
08:36Very happy with it.
08:37Super adjustable.
08:38Good wheels.
08:39Can recommend.
08:40Alright, let's take that leg apart.
08:41First, we have the three tube sections on the outside.
08:45These keep the whole thing stiff and keep it from rotating, as you will see later.
08:50They also slide into each other with little pieces of elastic and some kind of lubrication.
08:54The lube is perfectly kept inside, and I'm not sure how.
08:58But the forbidden icing is not what we are here for.
09:01Inside the main tubes is another set of smaller tubes with the actual screw mechanisms inside.
09:07It's 55 centimeters long, but fully extended is 125 centimeters long.
09:13More than double.
09:14So these two sections on the outside are not touching each other when fully extended.
09:18There is something else inside here.
09:20It's a pair of telescopic screws.
09:23Check how beautiful this is.
09:25Ladies and gentlemen, if this doesn't give you the fizz, I don't know what to tell you.
09:29And you can see that this thread seems to be at a lower angle than this thread.
09:34That's so that every rotation, they extend the same amount.
09:37So in fact, the threads per centimeter are exactly the same.
09:40But I'm getting ahead of myself.
09:42How does it actually work?
09:43How do these screws interact with each other?
09:45Well, we have two screws with two nuts that are attached to two nesting tubes.
09:52If we turn the screws while keeping the nuts from rotating, the nuts move up, of course,
09:57taking the tube sections with them.
09:59Pretty basic stuff.
10:00The big question is, of course, how do we turn the second screw?
10:04And the answer is, with the first screw.
10:06Inside the second screw, there are straight splines that the first screw grabs onto with
10:12a splined tip.
10:13It can move in and out, but it makes the screws turn together.
10:17While the nuts do the opposite.
10:19They are free to turn, but cannot slide.
10:22So let's look at the whole system.
10:24Everything that moves together has the same color.
10:27The motor is fixed to the tabletop and the big blue tube section.
10:31It turns the blue screw.
10:33The green nut is attached to the small green tube, which cannot rotate because it's connected
10:39to the big green tube section.
10:41So the green nut starts moving along the blue screw.
10:44Meanwhile, the green screw is rotated by the splined tip inside.
10:49This green screw is mounted to the green nut with a bearing, so it moves in the same direction
10:54but it's free to rotate.
10:56Then, there's a red nut on the green screw, which is mounted to the small red tube section,
11:01which is connected to the big red tube section and the table feet, if that's the word.
11:06As you can see, the blue pushes off of the green, and the green pushes off of the red.
11:11And that's it.
11:12Thanks Flexispot for sponsoring this video.
11:16They have all types of standing desks and accessories you could ever want.
11:20Go to the link below and use my promo code to enjoy extra discounts.
11:23And thanks to Crommelhoek for showing me around and letting me play with their machines.
11:27I hope to see you in the next video.
11:29Have you ever wondered how...
11:30Keep the camera still, damn it.
11:32Zoom out, zoom out, zoom out.
11:33This interface is short and we want to see the whole boom.
11:36Okay, we will fix it in post, I guess.
11:38Scrum?
11:39Hello.
11:40Push the camera still to the pulled stud employee, which is potentially perfect,
11:43where we got a jackhammer from the beginning of the blog,
11:45right?
11:45What?
11:47God shook himself.
11:47Thy's director Peter.
11:48Daddy is a very good captain about the video of the video.
11:50Sorry to take the camera.
11:53I heard the crew.
11:54I忘れない eye interview.
11:56I saw it all when the camera went to a pen.
11:58Then, I did not meet the camera.
11:59I thought we were justangle-by-by-to- theta, isn't it enough, there's been a guy down too tall and
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