Trainers, educators, welcome to the fourth in the series of webinars that we're having for the foundation and instructors. I'd like to thank Tim Dell again for taking time out of his day to talk about planetary gear sets and I wanted to talk a little bit about our webinar that we're having on Thursday. We'll be hosting a webinar to talk about the future of the foundation. We've got a lot of good things percolating in the foundation, talking about evaluating standards, looking at we've got an instructor's conference we're gonna be kicking off in the in the spring. So we have a lot of great stuff we want to share with you and take a historical look at where the foundation is and where it's going. You don't want to miss this because they'll give you a lot of information. We're gonna be offering a lot of different opportunities for instructors in the future. We'll be hosting webinars like this throughout the year. We're offering credits. In addition to that, we'll be having networking events at some of our other events that we have with our regular members. So lots of great things happening in the foundation and so I look forward to talking a little bit more about that on Thursday. I will pass this over to Tim at this point to talk to go in depth on planetary gear sets and thank you so much for attending this webinar today. Tim, it's all yours. Great, great. So welcome everybody. Today we're going to jump straight into planetary gear sets. This is taken primarily from Chapter 9 of my Heavy Equipment, Power Trains, and Systems textbook that is published by Goodhart Wilcox. So if you want to follow along in Chapter 9 and go ahead. So first of all in terms of simple planetary gear sets, you can find them in lots of different locations. So the construction industry, the ag industry, the on-highway truck, automotive. So we find them a lot in transmissions. Specifically, you can find them in power shift transmission. You can find them in automatic transmission, continuously variable transmissions, lots of different final drives. But that doesn't mean that all transmissions or final drives use simple planetary gear sets or even compound planetary gear sets. But they're used in a lot of different locations. So why would a manufacturer or designer or engineer choose to employ, I guess, planetary gear sets? Well, they're compact in design. So that's one reason as compared to traditional, let's say, countershaft design. And then if you just take a single simple planetary gear set, it can produce eight different configurations. And I'm cautious on how I say that. I don't like to say eight power flows. I like to say eight configurations. We'll elaborate on that in a minute. So based on that, we need first say, okay, what is a simple planetary gear set? So if I can get my pointer out here, we know that it has one sun gear that's kind of buried underneath this carrier. Then in this case, we have kind of a triangular shaped planetary carrier. We can have rectangle shape. We'll talk about that in a minute. But basically, a planetary carrier has these planetary pinions that are pinned to the actual carrier assembly. And then you have this large internal tooth ring gear, which could also be called an annulus gear. So basically, those three components, the sun, the planetary carrier, and the ring make up a single simple planetary gear set. And I'm not going to elaborate on the planetary pinions at the moment. We'll talk a little bit about them after a while. But for now, we'll just move on. So I mentioned a second ago that a simple planetary gear set can produce eight configurations. And that's what's listed here on this slide. So the first two, well, actually the first six, you'll notice that I say slow, fast, slow, fast, slow, fast. So the first pair, you could call torque multiplication. Notice that I qualify it with forward torque multiplication. You could call it speed reduction. You could call it underdrive if you want. But basically, you have a slow and a fast. If you wanted to only focus on this single simple planetary gear set and nothing else, then you could share with the students, then this would be an example perhaps of a first gear. And that this would be an example of perhaps second gear. So this could be anywhere from a three to one, four to one ratio. This might be one and a half to one ratio. Then the second pair would be overdrive. And again, notice I qualify that with forward. Forward overdrive, which again, this could be a slow. This could be a fast. And so this might be a ratio of about, let's say, 0.6 to one. It really depends on the teeth of the sun gear and the teeth of the ring gear. I'll elaborate on that in a minute. And the fast overdrive might be, I don't know, an example of 0.33 to one ratio. I'll elaborate that as well. So then the next set would be reverses. Now when you look at the slow fast reverses, slow would be a reduced speed, an underdrive reverse. Maybe, I don't know, two to one, one and a half to one, something of that nature, 2.2 to one. But the fast reverse technically is an overdrive reverse. And that is why up here I qualify these as forward overdrive. I've taught this for many years and just said, okay, we have basically two torque multiplications. We have two overdrives, two reverses. But honestly, you have to think about these are forward torque multiplications. These are forward overdrive. This is a slow reverse, which is underdrive reverse, as well as this is an overdrive reverse. And then the last two are direct drive and neutral. And that's why I call these configurations, because neutral is really not a power formula, really. I mean, you're not getting anything out of the gear set. It's just neutral. And so that's why I like to say these are eight configurations. Now here in a minute, when I start talking about how I deliver the simple planetary laws, you'll hear me say in class, and I can sometimes rattle this off way too fast and tell the students back, tell me to back up, slow down, etc. You'll hear me say, okay, in order to get a change of speed and or change of direction, that's way too fast, right? So that doesn't mean anything to, let's say, students that are brand new. If you say, okay, if I want to change a speed and or a change of direction, then there are two ways of getting that in a simple planetary gear set. But again, they're saying, well, what the heck does that mean? A change of speed and or change of direction? Well, that is the first six configurations we're looking at. These two are a change of speed. These two are a change of speed. And these two are a change of speed and a change of direction. So when I say, okay, if we want to obtain a change of speed or a change of direction, then the students need to know we're talking about these first six configurations. Let's jump into planetary laws. So to me, you can kind of teach this like math. In other words, you got to start with the fundamental foundations, and then once you get that, then the students can actually do the work themselves and tell you how to achieve those eight different configurations. So first of all, if we want an output, we obviously got to have an input. So that means we have to have an input member if we expect this planetary gear set to produce some type of an output. So that's fairly straightforward. And then the other additional principles here, one would be that we're going to focus on the three planetary members, specifically the Sun, the planetary carrier, and the ring. And in order to get those changes of speed and or those changes of direction, not only do we need to have an input, which is the driving, then we typically will have to have a held member or a coupled member in order to get an output or another driving member. So first of all, you know, students can get this confused. So driving is our input, driven is our output, and then a lot of times students will think, okay, held means coupled. No, it does not. They are definitely different. So held means where we're physically holding one of those members, the Sun, the carrier, or the ring, to the transmission housing, to the case, to the final drive housing, etc. Coupling means when we are physically attaching two of those members to each other. So I kind of say in class, what's kind of the equivalent of welding the planetary carrier to the ring? That would be coupling. They're not attached to the case, they're not grounded to the case, they're only grounded to the case when they're held. And so that's the challenge for some of our students to think about at times. And so then here I am now focusing on that comment earlier. How do I get a change of speed and or a change of direction within a planetary gear set? Well, you have to have either one member as an input and one member held. And this is the easiest, most common way, and that's what I'll focus on for 20-25 minutes of this presentation. But technically you could achieve a change of speed or a change of direction by having two input members, and this is where I slow down. Because normally when somebody says two inputs, hey, I've been taught two inputs equals direct drive. And I'll say, whoa, whoa, whoa, whoa, wait a second. You only get direct drive with those two inputs if you qualify in a certain way. So if you have two different input members that are driving at different speeds and or different direction, that is also going to deliver a change of speed or a change of direction. So, and I have a trainer here that I'll show that demonstrates that. So the next principle is probably the most fundamental foundation principle that I focus on the most. And I tell students that this is by far the most important. As an instructor, it might be very helpful to ask or require, I should say, the students to be challenged on this slide the next class period before they walk in to the units on planetary gear sets. So let's say tomorrow you're going to cover planetary gear sets in class. Today's students, we're all going to learn planetary gear sets, the eight different configurations. But first thing, when you show up to class in the morning is I'm going to challenge you on this slide and you have to be able to tell me what the planetary carrier is doing for these different, three different configurations. And make it high stakes. Don't just say okay for five points because they won't take it serious and etc. So because if they cannot tell you what the planetary carrier is doing for reverse or multiplication or overdrive, then we're done. We're not going to be able to get anywhere. They're going to be lost. They're going to be confused. They're going to be frustrated. And we're just going to be spinning our wheels. And so it's, to me, it's kind of equivalent of math saying okay we're going to talk about algebra today. And the students saying well I don't really have my multiplication tables figured out and I struggle with addition and subtraction. Well there's no reason to move on to algebra if we don't have those fundamentals. So this slide is the fundamental foundation. Now I think most students, we can get them to understand that when the planetary carrier is held, that it will indeed reverse the power flow. That one to me is not a huge challenge. But the next two can be a challenge. And so I like to use this slide as a way, as a crutch, for assisting them in trying to remember what the carrier is doing in a torque multiplication mode. So you could share with the students, hey what are we looking at here? This is a final drive. Specifically an inboard planetary final drive. And this is found in ag. This is found in construction. Lots of different applications. So they could say okay I'm looking at this. What is this? What is it? Well here's your ring gear. And you can see these bolt holes on the ring gear and how it's going to be bolted with this trumpet housing to the side of your axle or differential case if you want to say that. You could say okay here's my sun gear. It's basically the input to this simple planetary that's coming from the differential. So the side gear of the differential is going to provide the power to this sun gear as the input. But what's key and critical to this slide is you could ask the students, okay this is an axle. All right yeah. So here's the carrier. Okay yes. Well what's that carrier attached to? Well the carrier is attached to the axle shaft. Oh it is. Yes it is. All right. And so if that carrier is attached to the axle shaft, then why is that? Well because we need to multiply torque. Well anytime we have a final drive we're multiplying torque right? And so that means that the carrier is part of the output and that's how I'm hoping that they will be able to remember that when the carrier is the output we are building torque which means we're also reducing speed. So that's the crutch that I'm hoping that they visualize in their mind when we're going through it. And then the last one is just the carrier whatever it's the input we're going in an overdrive mode. Let's back up one more time on this particular slide. This slide can be a challenge for students because in their mind they might be saying wait a second on torque multiplication isn't that slow? Yeah. Well then how can I have a slow slow and a fast slow? Well that's why I said it might be better to say well this is kind of a first year example. This is kind of a second year you know 3.0 to 1 ratio 1.5 to 1 ratio. And then they could say well is it overdrive fast? Yeah overdrive is fast. Well how can I have a slow fast and a fast fast? Well that's why it's sometimes helpful to say well this might be an example of about a 0.6 to 1. This might be an example of a 0.3 to 1. I could get off on a tangent here and talk about you know that gear set by itself is not super usable with a fast overdrive but then you could share with them well you know on a cat d6 and third gear that technically we take a slow forward torque multiplication with the first gear set take a fast forward overdrive at the second gear set and put those two together and we get direct drive. But for now let's not go off on that tangent and let's just keep focusing on simple planetary laws. And so again you've got to start with foundation the carrier the carrier the carrier. In other words if they can't tell you what the planetary carrier is doing for reverse torque multiplication or overdrive we're in trouble we're not going to be able to really go any farther. So then the last thing is that we could say okay how do we get direct drive? Well you can achieve direct drive two different ways. You can say that if you have two input members that are at this notice I'm qualifying it two input members at the same speed in the same direction that is direct drive. And I'll show that on a trainer here in a second. The other way of getting direct drive is basically having an input and then coupling two of the gears together. So you can say I'm going to drive the carrier and I'm going to attach the Sun to the ring. I'm going to drive the ring and attach the carrier to the Sun. Whatever you want to say it doesn't matter. Anytime you couple two members you're basically going to have direct drive given that you have an input. So you could also share with the students that if you had a noise in the gear set and if that noise mysteriously goes away during direct drive then that's a pretty good telltale sign that you have a chipped tooth. And so like I teach also automatic transmissions for automobiles and so after the students reassemble the transmission I put them on a dynamometer and we run them to make sure that they put them together correctly. And one of them does have a chipped tooth on the Sun gear and so the students will literally hear noise in first and second and reverse and fourth but when we go to third which is direct drive they'll basically hear that noise goes away. So that's something to keep in mind. And of course we know that direct drive produces same speed, same torque, same direction. So and then lastly we can talk about that if we only get an input by itself nothing else then I have neutral. What does that mean? That means if you have an input and you want an output and that's going to require one of three different things. You're going to have to have a second input or you're going to have to have something held or you're going to have to have something coupled. Now let's jump into my actual screen here. So the next thing is is I like to share the size of the actual gear set. So I'll bring this back here and when I'm in a classroom I'll say okay guys let's just think about what size are each of the gears and then I'll actually just pull the gears out of this particular trainer and say okay tell me the size. So in this case if you look at these two gears I'll say which one is the larger one? They'll say well the carrier is larger. Okay so the carrier in relationship to the Sun is larger than the Sun. And then I'll say okay what about the ring? Which is larger the carrier or the ring? The students say okay the ring is larger and so I like them to actually just see the relationship that the ring is the largest, the carrier is the middle size, the Sun is the smallest, and that we are not focusing on individual pinions at this particular time. Okay I can move this slide here. So the one thing that you could say about those planetary pinions if they're wanting to say well why is it important to have three planetary pinions or four versus three is the more planetary pinions we have then the heavier amount of torque we can produce in the gear set. So for instance we're delivering a thousand pounds of torque through that planetary gear set and you only have two planetary pinions they have to share half the load 500 pounds versus if you have five planetary pinions or in this case four then it distributes the power and makes it a stronger gear set. Another thing we talk about is that sometimes planetary gear sets are called epicyclical gear sets. You could say well where does that come from? Well you got to go all the way back to second century astronomer Claudius Ptolemy basically he hypothesized that the planets were spinning on these small little axes. He called those epicycles and then he said basically they follow a large circle circumference and at that time he thought that it basically was was surrounding the earth not the Sun and so anyways that's how we come up with epicyclical as a term for today's planetary gear set that these pinions are revolving around the Sun. And then the last I think the last principle that I like to go back and re-review with students that they should have already known by now is what I call big gear small gear and so on big gear small gear basically I will draw on the board that what happens and I'll ask the students this is kind of review from manual transmissions or from let's say belts and pulleys or chain drives etc and I'll ask the students okay what happens if I have a small input in a large output gear? The students typically at this stage are pretty good about saying well I know that that gives me a speed reduction a slower speed. You could also put an arrow up for an increase in torque but I don't want to focus on torque today right and so then you could say okay again going back to big gear small gear is well what happens if I have a large input gear and a small output gear? And the students of course hopefully by then know that this is an increase in speed that's how I get an increased speed. This is a fundamental foundational type way of delivering this content to our students and I sometimes would like to ask them well how do you remember that? How do you visualize that in your mind? You know a lot of us will hear students say well I think of my bicycle when I get on my 10-speed bicycle I'm going up a hill and I need a whole lot of torque in a reduced speed they'll notice that the front little sprocket is small and then I got a big sprocket in the back and then when I'm going down the hill I noticed that the front sprocket basically goes to a larger size and the back sprocket goes to smaller. Personally myself I don't think of bicycles I just think of a ring and a pinion like in an axle right so here's pinion here's the ring for whatever reason that's just the way I keep that in mind. Now this is where I like to get into the actual delivery of simple planetary gear sets and having students learn it and you will probably know that there are some students out there and they'll just memorize a matrix for the portion of this part of the semester and then they'll forget it and never remember it the rest of their life right whereas if they can just simply remember big gear small gear and what the carrier is doing it's all downhill it's really that simple and that easy and so to me I think it's not too difficult for a student to know that anytime we are in reverse with the simple planetary gear set that the carrier and I will ask them I'll make them tell me what's the carrier doing they'll say okay when I'm in reverse that my planetary carrier is held and so I'll put planetary carrier is held and I'll write that on the board and you can write reverse over there as well and again this is on page 289 in the text but when I'm doing this in a class I tell them put up your textbooks for now just pay attention follow along and let's let's not use the book as a crutch I want them to understand the process and so then I'll say okay now let's figure out how do we achieve a slow reverse and fortunately they have already provided the information to the class they told the class each other they'll say well I knew that I needed a small input and a large output in order to achieve a slow speed and so in that case I'll ask them so what do I want for an input and they'll say well I want something small and I'll say well keep telling me what is that I'm not giving them the answer they're telling me and they'll say well something small must mean the Sun and so they'll share that with me and I'll say okay that's great and then I'll say okay well what size output do I need if I want something slow then they'll say well if I want something slow I must need some type of a large item in that case that must be the ring and so there it is they legitimately told me they taught me the instructor how to actually achieve a slow reverse and so you'll notice on this gear set that there are three lines that are aligned there and so the gear set does have a mechanism to physically hold each of those if you want I did not produce this I inherited this I guess you'd say when I started teaching here a long time ago and so now I've used this trainer for whatever reason a long long time it just seems to work for me but anyway so the students can again tell us that the carrier is held in reverse anytime the carrier is held I'm going to reverse power flow now the choice is am I going to have a slow reverse if I want a slow reverse I need a small input they'll tell me which is the Sun so what I'm doing this I want the students to remember how many input revolutions it takes to make an output because that is the ratio and so in this case if I turn this the Sun gear let's say I turn the Sun gear backwards we'll notice that the ring is going in the opposite direction and so in this particular case if I keep spinning and keep spinning there's one input and I keep spinning in this case I made it finally a total revolution and you'd say it looks like you had to spin that Sun gear approximately I want the students to estimate because I have an exercise they'll say well let's say that it was approximately 1.66 to 1 ratio it took about 1.66 revolutions to make one output if it's a reverse you can actually put a negative on there if you like okay then I'll say all right guys let's let's move on let's go to fast I'll say all right where do we start got to start at the foundation and they'll say carrier the planetary carrier okay well we're still in reverse yes what's the carrier doing let's say it's held okay then if I want something fast tell me what I need to know and they'll say okay I want something fast they'll say I need a what I don't tell them they tell me I need a large input what is that they'll say well that's a ring okay because they can see on the board we've already put the big gear small gear on the board okay the next then what else do I need I need an output if I need a fast power flow what size of output do I need and say well I need something small well that would be a Sun so again I I did not provide that information to them they taught me that information right and so then we can get our gear set back out and basically test test our theory so they'll say the carrier is held basically tighten the carrier down I'm gonna then turn the ring and so if I turn the ring in this direction look how much faster that some gear is spinning so in this particular case my Sun gear has already made a revolution I already got an output and I haven't even made an entire input so in that case I could say that my estimated ratio is I don't know let's say 0.66 to 1 approximately okay that is my estimated ratio and then I'll talk about calculating these here in one second. So that would be the way that we will get through reverse. Now let's go on to the next set of power flows. And so on my board, I will leave some of this up on the board. So you can leave the carrier, definitely wanna leave the big gear, small gear. You can leave the slow on there, the arrows on there, leave the fast on there. And then we're gonna say, let's move on to what I think is the next one that's not as challenging. That's torque multiplication. I'll say, okay, students, I showed you a slide earlier and it was of a final drive. They say, yep. So let's talk about that final drive. Is it increasing speed or decreasing? No, it's decreasing speed. It's multiplying torque, okay? So it's torque multiplication. Yeah, well, what was that planetary carrier attached to? Well, it's the axle shaft. So what does that mean? And they should be able to say, well, that means the carrier is the output anytime we're in torque multiplication. And so they are able to tell you that as the students. And so we'll say when the carrier is the output, that we are in torque multiplication. So they, and I'll just abbreviate that for now. So they are able to share that. Now, this is where I say, let's slow down. And I share with them the critical junction at this time is being able to ask the correct next question. Because if they try to go too fast, they're gonna stub their toe and make a mistake. And as instructors, we easily stub our toe in class and I'll say, hey, wait, I misspeak. If I write something down wrong, if I said something and I was thinking something else, stop, back up. Anyways, so we know the output. But let's look at big gear, small gear for a second. Do you see anything on big gear, small gear that says anything about held? No. So on the big gear, small gear, the only two things that we care about are what? Input and output, okay? And if we know what the output is, I'll ask the students, then tell me what's the right question. Don't move on until you know the right question. And they'll say, well, the right question is, what is my input? That's all I care about. And so in that case, if I want something slow, because the output is known, I have to ask the question, what size of input do I need for something slow? And so they'll say, well, for something slow, they'll tell us I need a sun because it is small. Okay, then what remains? I have an input, I have an output, then basically by default, the only thing left would be held. And that held, in this case, it can't be the sun, it can't be the carrier, it must be the ring. And that honestly is that final drive that we looked at just a second ago. So again, we want to look at this trainer, try to put all this back together. And I'm going to hold the ring. I'm gonna try to drive that sun. I don't have enough torque there. There it is. See there, I've already stubbed my toe. I said I was gonna hold the ring and you see what I did. I was holding the carrier. So, okay, let's hold the ring and I'm gonna drive the sun. And notice the carrier's falling behind at a slower pace. There's one input, two inputs, and let's say that's about 2.66 to one. For this gear set, we'll say that that was about 0.266 to one on our estimation. Just for grins, in case you want to make a mental note and do some computations, this sun gear has a 41 teeth, the ring gear has 67. We could do the actual computations here in a second. Okay, then we could say that kind of appears like a first gear power flow, right? Or close to that. Let's go on to fast torque multiplication. You got to start with the foundation. What's the foundation? The foundation is always the carrier. And so what's the carrier doing anytime we're in a torque multiplication mode? The students will tell us, well, it's the output. Okay, if I know what the output is, then if I want to try to find, excuse me, a fast torque multiplication, then I'll say to students, tell me the right question. And they'll say, well, I need to know what the input is. Well, if I want something fast, what type of input do I need? In that case, I need a large input. And so they'll say, that must be a ring gear. Okay, and then by default, I got a carrier, I got a ring, I got an input, I got an output. That means last thing would be held. And then that would be basically the sun. So, unless I made a mistake here, I push these back together, I'm gonna hold the sun, and I'm gonna drive the ring. Notice that the carrier is behind again, because we're in a torque multiplication, it's a reduced speed, it's behind, but it's not to the same slow speed as what we just had a second ago. So there's one revolution. We're trying to see what it takes to get that up to the top. And you would say, in this case, it's about 1.66 to one on our estimated ratio. So 1.66 to one is our estimate for our ratio, not our computed, but just our estimate. And so therefore, students just shared with us, the instructors, and told us how to get fast reverse, slow reverse, fast torque multiplication, slow torque multiplication, and now we can move on to the next ratio, which would be the overdrive. So again, we're gonna go down that road, we'll get rid of this, we'll get rid of this, we'll get rid of this, and this, and that. We still have fast, slow, still have our arrow, still have our carrier, still have our big gear, small gear, and say, okay, students, tell me now, I want an overdrive. Yep, what's my carrier doing? I can't do anything unless I know what the carrier is doing. And hopefully they'll say, oh, for overdrive, my carrier is the input. And so if they can do that, and we can say, okay, we know that the carrier is the input for overdrive, then we can back up and say, okay, slow down, slow down, what's the right question to ask? And hopefully, your students will say, well, if I know the input, the next question is what size of output? Okay, and that's the key, right? So if I want something slow, I'm gonna ask what size of output? For big gear, small gear, what size of output do I need for something slow? They'll say it's the ring. So if I got a ring here, what's left? I got a ring output, a carrier is an input, and the last thing would be something is held, and that must be the sun, which is gonna be allowing us to have a slow overdrive. So if I put these back together, there's my gear set, I'm gonna hold the sun, I'm gonna drive the carrier, and we're gonna see the ring get ahead. The ring gear gets ahead, we're trying to find out how much it takes to get one output we find our output has already made a revolution, and we only turned it about 0.66 to one. Well, that means our estimated ratio is about 0.66 to one on the actual overdrive, not our calculated, but our estimated. Okay, well, let's go to a fast overdrive. You always start with the foundation, and the foundation is what's the carrier doing? What are we in? Overdrive. So the student should say, well, if I'm in overdrive, my carrier must be the input. Okay, well, if it's the input, then the next thing is what's the question I must ask myself? Well, if I know the input, the question is, I like this long pause, what's my output? Well, if I want something fast, what size of output do I need? I need something small, right? Based on that, so the students will say, that must be a sun, and what's left is held. And so if I got a sun, a carrier, this must be the ring, and this should give me a fast overdrive. So if I align these again, and it says I'm going to hold the ring, and I'm going to spin the carrier, look how fast that sun is. The sun is very fast, it gets way ahead of us, and it already made one revolution, and I only turned it about a third. So you could say that that estimated ratio is about 0.33 to one on that fast overdrive. And those are the difficult, I would say, not difficult, but the six different changes speed and change of direction in terms of planetary gear set. Now, we can go back to direct drive. And on direct drive, I shared with you that we know that it takes two inputs in the same speed, in the same direction to get direct drive, or that it takes one input and a couple, two members coupled. So a couple things. One, if you look at this and we put these together, say, let's talk about direct drive. Let's say I'm going to turn the carrier in the ring at the same speed, in the same direction, at the same time. Well, if you're able to look really, really closely, you'd say, hey, Tim, I don't see those little pinions spinning. That's right, because it's an entire assembly in direct drive, those planetary pinions don't spin on their axis. The whole assembly rotates together in direct drive. We have the same speed, same torque, the same direction, and those small little pinions quit spinning. And that's because we have two inputs. And for this example, I'm just sharing, it's the ring and the carrier, same speed, same direction. Or you could say, I'm physically going to weld the carrier to the ring and then drive the sun, and that would also produce a direct drive, okay? Now, this is where I basically share with the students how it's possible in our world that we have two inputs that are not the same speed and not the same direction. So you can find that in a torque divider on a cat dozer. You can find that a little bit, I guess I'll say, on an excavator final drive, and I'll elaborate on that. I want to be very cautious when I say that. And then where we find them very, very commonly are in continuously variable transmissions. This is a Case IH Harvester continuously variable transmission simulator. I have a part number for it. If you want to go to a case dealership to buy it so you can have it in your classroom, I think it's 400 bucks. I think it says C-I-H-1-2-1-51-0-0-1. That's the part number, but it's an excellent trainer for teaching this principle with simple planetary gear sets. So first of all, inside of here, underneath you have basically batteries that are delivering power to the ring gear. It's emulating the engine, that the engine's producing a fixed speed based on your engine speed. And that is basically the input is the ring gear. And then you'll also have this little handle which emulates a hydraulic motor that's attached to the sun gear. And so on the backside, you can place it right here and lock it in place so that the motor is fixed and stationary, okay? And in that case, if you turn it on, I'll keep my fingers out of here. You'll see that the motor is fixed. The sun gear is stationary. The ring gear is an input and the carrier is an output. So what happens when you take that hydraulic motor and you change the speed as a second input in a different direction or a different speed? Notice that the output changes. You can spin it fast in one direction, you can hold it, or you can go fast in an opposite direction. Those are examples of two different inputs at different speeds, two different inputs at different speeds or in different directions that gives you a change of speed and or a change of direction based on that principle. Okay, we can also just re-say as I said earlier that if you have an input by itself, then basically you just have neutral because it requires a second input or something held or something coupled, right? You can also mention that some transmissions, they will actually have a planetary control applied in neutral just because it's advantageous. It's not always that way, but it's advantageous. So like for instance, on Allison 1000, 2000, 3000, 4000 series transmissions, you'll find a neutral that the clutch number five is engaged and it's advantageous because when you leave neutral, you're gonna go to what? Reverse or first. And when number five clutch is engaged, that's what's used for first or reverse for holding the number two carrier or the number three ring. So that's why sometimes you'll see manufacturers of transmissions advantageously basically apply a certain planetary control. Now, one thing that's a little different on that is CAT on their three speed dozers, they have the third speed clutch engaged in neutral. And that's a little different in that scenario. So I will try to go back to share my screen here. Hopefully I'll have the right screen up here. Right now you're looking at page 287 of the textbook that shows a matrix on how to compute the actual planetary gear set ratio. And you can follow along there on the matrix. But basically what I want students to do is one, remind me, say, all right, we've been through manual transmissions. How do we compute the ratios? And hopefully we can somehow come up with in class that we put the output T over the input T. So we divide the input teeth into the output. So again, I think of the ring and pinion, let's say a ring gear, 41 teeth, pinion, let's say nine, five, nine and 41, get a ratio of 3.77, 4.11, whatever. So that's how we get our ratios. And then the second thing we have to know, which is fairly simple, is that we only have to count the teeth on the sun and only have to count the teeth on the ring. And that's because the carrier, those teeth are basically the sun plus the ring. So on this previous slide, it's just a theoretical transmission or theoretical planetary. I said, all right, in theory, let's just say the sun had 20 teeth and the ring had 60. Well, in that case, I could say, well, what's the carrier? The carrier is the sun plus the ring. So the carrier is 20 plus 60, which equals 80, right? And so like in torque multiplication, we know that the carrier is the output, you put the output on top, you divide the sun into it, and that's how you came up with a four to one ratio. So here's a slide that shows an example. Let's say reverse. In this example, let's say the sun is 20 teeth. Let's say the ring is 36 teeth. And if then we want to do the ratio, basically it's just sun divided into the ring. And then we'd have a ratio of a 1.8. And so if you want to go to a fast reverse, we divide the ring into the sun and you'd see this looks like an overdrive ratio for reverse. Well, what happens when you start getting into torque multiplication or overdrive? Again, we have to come up with the carrier. So the carrier is sun plus ring. And basically, if we have a torque multiplication, we know the carrier is the output. So it goes at the top. How do I get the slowest to slowest? I got the smallest to smallest input. And so sun divided into the carrier would give me a 2.8 to one on this gear set. How would I get, let's say that second gear ratio, that second gear ratio, you have the output as the carrier. So sun plus ring. And then you divide the bigger gear into it, which is the ring. And they give you an approximate 1.55 to one. I'm cautious about saying that this would be a first and this would be a second gear, because when we get into compound planetary gear sets, then things change, you know? And so this is just only if we're only dealing with a simple planetary gear set. And so this shows an example of overdrive. Again, we know that the carrier is the input in overdrive. So the carrier is on the bottom and it's being divided into the other gear. So for slow, we're dividing it into a big ring. So carrier divided into ring, this would be an example of that ratio. What happens if we want something fast? We divide the carrier 20 plus 36, which is sun plus ring into a small gear, which is the sun 20. And that gives you a ratio of about 1.36 to one. So what I do is basically I walk through this whole process in class. And then when it comes to lab time, I say, okay, this is your worksheet. This is your exercise. And I have them put everything away. And I get out a simple planetary gear set and I'll get off my share screen here again in a second. And I have them put all their training needs aside except for a simple planetary gear set. And then I have them first walk through here and tell me in fast overdrive, what's the input, what's held, what's output. And I do that for all six configurations. And then I'll go around, I'll check, make sure that they haven't made mistakes. There'll be a mistake or two, right? And then next I'll have them do the actual ratio, which is estimated. And so this is where they're lining up the teeth on the actual gear sets and the marks. And they have to figure out how many input revolutions it takes to make an output. And I want them to estimate that. And then I'll go and double check that as well, see if it's all correct and accurate or whatever. And then lastly, then I'll have them get out a calculator and I'll have them count the actual teeth on the sun and the ring. And then I'll have them physically calculate to see how close their estimation was with the true calculated gear ratio of that simple planetary gear set. And then I'll have them tell me exactly what are the two methods for achieving direct drive. As a review, they can look back at chapter eight and see that we use mechanical symbols for schematics. So not only do they learn about hydraulic schematics, electrical schematics, but they also get to learn about mechanical schematics. And so they can see that this is a clutch and this is a held member and this is a band. So we spend time about that. And then based on all of that we've talked about is the introduction to compound planetary gear sets. And this is where it gets a little bit challenging for students. And we know that when we have two planetary gear sets that are connected together, then we start to have compound planetary gear sets. So examples are final drives, right? Let's say on a large elevated dozer on a cap machine, then they basically have a shared ring. They have a small sun for the first stage causes the carrier to be an output, which drives the small sun of the second stage. And then the carrier is basically of the second stage is gonna drive the actual sprockets. And on this style of final drive double reduction, you can actual apply simple planetary laws because you truly have one input, one held and one output of the first gear set. And you truly have one input, one held and one output of the second gear set. And so you can go through, let's say a D9T, compute the ratio of the first, the second, and multiply those together and find an overall ratio or a D11T or a 797F because those planetaries, let's say are such, right? So what happens when you get into compound planetary gear sets when you now have multiple T, excuse me, multiple gears that are spinning at the same time? Well, here's an example on page 587 of a double reduction excavator final drive. You'd say, okay, I have a hydraulic motor and it's gonna drive the first stage sun gear. And that sun gear is then gonna provide an input, right? And so we could say if we haven't started moving that this ring gear is initially held. Well, if that ring gear is initially held, the cause of the carrier would be an output which drives the sun of the second stage. And then if you get to this stage here, you'd say, okay, the carrier is held. So that means it's gonna reverse the power flow of the ring gear and it's gonna rotate in the opposite direction of the hydraulic motor. But the challenge is once we start spinning, we now have a ring gear rotating backwards and we also have a carrier, excuse me, we also have a sun gear spinning. And so now we actually have two different inputs or two different rotating members and then you don't apply those simple planetary laws. You could say, well, this ring acts like a held member because it is rotating slower than the carrier and we can go down that road and talk about that as well. So I guess just lastly, the other thing that I do when I talk about simple planetary gear sets is I share this picture that's on page 289 and 290 of the textbook. And I say, well, let's consider a theoretical transmission that's very simple where basically we just have three clutches and three brakes. So brake A holds the carrier. The students should say, okay, that's gonna reverse power flow. And they could say, okay, if we have three clutches that are coupling two members, that this clutch and this clutch creates direct drive because it's coupling the ring to the carrier, the ring to the carrier, the ring to the carrier. Okay, that's simple enough. And then they could say, okay, brake B and brake C holds the ring so that if the sun is the input, it causes the carrier to be an output, which gives you torque multiplication. And so if you remind them what's in the literature that, okay, let's say the sun is 28T, this ring is 80, the sun is 36, this ring is 80, the sun is 46, and this ring is 60, then you can go through here and compute your actual ratio. So in reverse, you hold brake A, you get a 2.86 to one ratio. If you hold the ring of the second gear set, you get a 3.22 ratio, gear set C, and so on. And so then you can actually talk about the actual clutch apply chart if you want, and then go through the process and say, okay, let's have clutch A apply, brake B apply, and brake C apply. They should be able to tell you that this would be a ratio of a one-to-one direct drive, right? And then they should be able to, again, compute this ratio and say, okay, that's approximately 3.22 to one ratio. And then of course, this ratio, if we have brake C apply is a 2.3 to one ratio. And so if we multiply all three of those together, they'd see that that theory is we have about a 7.4 to one ratio. Unfortunately, our gear sets are not that simple. The compound planetary gear sets are a little bit more challenging, but it's a good exercise to go through the process of having students tell me, you know, the power flow and let them physically go through the actual ratios. And as they do this, let's say, when we get into reverse and say, okay, brake A is applied. Well, brake A is applied, gonna reverse the power flow because the carrier is held. And as they go from first reverse to second reverse, they could start to say, well, it looks like brake A appears to be like the reverse brake. Well, that is true in this scenario. That is correct. But if you wanna go to this case and say, let's take this gear set and duplicate it on the back, then brake A is no longer the reverse gear set per se, because it could also be used if we have brake A engaged and brake D engaged, because even though this reverses the power flow, this one would reverse it back to the correct direction. And that actually does happen at times in transmission. So, and then of course, this would be the actual matrix or the apply chart in that case. So I'm probably not gonna bore you guys with a lot more. I could go into compound planetaries if we wanted, if you wanna stay on afterwards, if you want, that's fine. And if you've got questions, I'd be happy to answer them. My email is tdell.pittstate.edu. As a reminder, we're planning to offer three hydraulic sessions starting in December and January and March that are four days long. If you wanna get some hands-on training, then go to this KCCTE website where you can sign up for these three sessions. So Lindley, I will turn it back over to you to see if you guys have any questions. All right, Tim, thank you so much for everything today and thank you for listing your email address. No questions have come in thus far, but I wanted to thank all participants for attending today, all of Tim's sessions. Thank you, Dr. Dell. And thank you to everyone for their participation in the instructor series. And we're looking forward to seeing you all again on Thursday at 11 a.m. for our final series. So I hope everyone has a great rest of their day and we'll see you on Thursday. Thank you.

webinar

Tim Dell

planetary gear sets

sun gear

planetary carrier

ring gear

gear configurations

gear ratios

compound gear sets