Man!!!!that was an awesome explanation, I'm 53yr old, been running and repairing heavy (and smaller) equipment 34+yrs ....often wondered but never knew, I appreciate you taking the time to break down and explain, I'm saving your channel. You'll definitely be another one of my go toos:)
I just love the amount of entusiasm when explians the math of the transmission. And at the end, as a final conclussion, he finishes it with a "pretty cool". Love it.
You should have seen when I first took it apart. I said WOW a lot of times. I'm sure there are a lot of people who know all about this kind of stuff already, but I totally love seeing something new for the first time. It makes learning really fun.
Appreciate the explanation. How these mechanisms are conceptualized and manufactured is amazing. I have a compact tractor with a hydrostat, which is super convenient and smooth compared to the traditional gear transmission. I could picture early farmers being skeptical of this incredibly complex mechanism initially though. The whole rotation mechanism is similar in concept to a helicopter rotor hub with the awash plate, connecting rods and bearings. I’m going to go easier on my ride on mower and tractor now, keep ‘em in low gear. Stuff is intricate.
I’ve been using my zero turn lawnmower for 3 years now and I always wondered how the transmission works. I do believe those have 2 small transmissions (one for each wheel) but this explained perfectly and very clearly how the magic happens. I love knowing how things work!
My friend rebuilt the powertrain for a 15” gauge miniature train locomotive. The train as built in 1947 used a simple clutch between the gas engine and the driveshafts for the trucks. Obviously, it had no reverse! When the clutch suffered a catastrophic failure, we could not find a direct replacement for it or even parts to repair it. The most recent parts list from the manufacturer was dated 1963. So we swapped the ancient, smoky Onan motor for a new Honda 25HP and, instead of the clutch, used an Eaton Series 11 hydrostat. All it took was moving to motor mounts forward a few inches and fabricating a couple of brackets for the transmission. We got excellent power throughout the speed range, plus a reverse. No more pushing the train backwards 400’ to put it away at night! It helped that the company I worked for was an Eaton distributor, so I got him the employee price of cost + 10%.
He sort of mentioned it, but this transmission idea was a marriage of a variable displacement swashplate type hydraulic pump and then using that same design in reverse as a hydraulic motor. A variable displacement pump is a very common design in hydraulic actuated machinery but with a couple important differences. Firstly, the swashplate generally is not able to go into a reverse position. Secondly there is no manual control of the swashplate angle. Instead a spring acts to tilt the plate to maximum and the output pressure works against the spring to bring the plate back to the neutral position. So if you block off the output flow the pressure rises to bring the plate to neutral while holding pressure at maximum. If there is no back pressure the plate tilts to its maximum position to deliver the maximum flow rate.
As said there is nothing new under the sun it is all ready here it just has to be thought up and that is what the engineer done it was in his mind of what he wanted to achieve that my friends is God he is the infinite mind that's why nothing is impossible with the infinite mind of God and we all are created with a mind as hydruclics fascinates me I see how this works
Yep. Most normal people, when they need to haul something to the dump, they just load it up and take it to the dump. Not me. I take it apart. So instead of 1 easy big thing to haul to the dump, I have like 1000 little nuts and bolts and parts to collect first...
Thank you for this video, I am a very mechanical person, but I’ve never given a hydrostatic transmissions a second thought, thank you for this! Perfect
Thanks! Just got my first lawn-mover. As it is a bit jerky - trying to understand how things work under the hood before fixing. Hydrostatic is a new thing for me.
When I was growing up in the mid 70's we had a Wards 16 horse garden tractor that had hydrostatic drive and I knew it was a hydraulic pump and motor but watching this video it was more simple than I thought
Careful on your terminology - statics does not always mean there is no motion at all, but rather that input forces and output forces equal each other, so there is no change in motion. Dynamics is when an acceleration results from forces that are not equal - as we see in normal geared transmission when the input shaft (engine) speed must change between abrupt gear shifts. It's true though, the terms have gotten a bit simplified over time when usually we use static to mean 'stopped' in most everyday use.
@@PetersonBrosAutomation 'Static' in reference to pressure and fluid systems actually means 'stable'. Where there is flow, there is instability. No one would consider the wind being static - but obviously the overall pressure remains constant. As for input and output forces equalling each other, I doubt you'll find a case where that is true. There are nearly always 'losses' - commonly as heat. A fluid providing movement transmission will be very much like the wind - will contain pockets of higher pressures and pockets of lower pressures - just like the wind. I see where 'static pressure' terminology is coming from but it's being misapplied.
My friend’s family had that same Montgomery Wards tractor. My friend was always so proud of how cool the transmission technology was. This video explains why!
This is all new to me, but I got a 2-wheel tractor and wanted to understand how it works. Your explanation of a challenging subject is exceptionally clear. Thanks.
Great, glad to hear it! If you ever do get to tear one down, I'd suggest having a bucket of cleaning solvent handy, and a space to work that is prepared for cleanup. They are really cool, but super messy until you get all the oil cleaned and dried. And the whole place will smell bad. Do NOT, repeat do NOT attempt this on the dining room table. You will be kicked out of your house until you learn to shape up. (written from my shop computer)
This was a great video. I had a vague idea of how hydrostatic transmissions work but this really clarified it. Swash plates are such a cool mechanical design. Their uses are almost endless. What really blows my mind tho is how someone created this without the use of computers.
The human mind was once more powerful than any computer but we have been dumbed down over the ages. The lie is that we are more intelligent than our ancestors.
I'v spend some time attempting to learn the ins-and-outs of HST and this video has certainly helped but I also recommend for your viewers watching as much about Piston pumps and shwach plates as you can to further your understanding
I searched for shwach plates . No sensible related result found ! Then I tried searching for 'bearing shwach plates' , ah , bliss ! Hope that helps someone else .
Excellent presentation! Very concise, well communicated, good use of the transmission to demonstrate concepts and obviously you know your subject matter. Have used my Hydra Gear ZT-2800 equipped Toro for over 600 trouble free hours and always wanted to know how they work - now I do. Thanks a bunch!
Fascinating - And a convincing assessment of how it worked, however, I still maintain it is black magic. As for taking it apart myself, I would not have understood it but merely compiled a hydrostatic gearbox kit.
Excellent video sir ! I don't believe anyone could possibly improve upon your presentation verbally or visually to inform me . I knew absolutely nothing about the inner workings of these mechanisms before watching your video. I watched it one time and have a complete understanding . Im not saying im an instant expert or couldn't learn anything else on the subject but man you did an excellent job. This is the first time I've seen your work and am excited to see what else you have on here. I don't mean to sound like a gushing school girl i was just very impressed. Thank you
Yes it was, but…. My question is about the difference in being able to move shifter while in motion easily, versus the ones that you have to change the speed position which is not easy unless unit is standing still. Therefore they are either automatic or hydrostatic?
I have an early Murry with such a drive and am totally spoiled. I have often wondered how it worked, but I wasn't about to take it apart just to see. I think it's absolutely brilliant. Kudos to Mr. Hydro. LOL Thanks for sharing.
This made me so nostalgic 🥺 seeing that 0510 and even having original (i believe) style bull gear and miter gears. Literally makes me so happy to see this!
I have a John Deere LX 289 with 17 hp hydrostatic transmission when I first bought it I did an oil change on the engine are used Amsoil 0W 30 and I contacted the tech people at Amsoil and he said use a 0W 30 in the transmission also and when I did man made it a lot quieter ha ha people neglect maintaining those transmissions they need to be maintained better by changing the fluid not every year but at least every 200 hours of usage it’s not hard to do but when you do it, you drain it with the new fluid and get the back wheels off the ground start the engine up and let idle and then work the forward and reverse. That way you fill everything up real good and then you’re ready to go after you check the fluid level all right you guys this is a really good video. I’ve seen some of this guys videos before he’s good. He’s a real good man all right you guys have a good day now this is a Jim Mungai from Kennerdell, Pennsylvania.
Swash plate pump, swash plate motor. Lucas improved the efficiency of fuel pumps on gas turbines engines with their swash plate pumps, instead of the gear pumps that were being used. They pump the amount of fuel required as opposed to the gear pumps which pump the maximum amount of fuel which is bled off when not required.
A variable displacement hydraulic pump on an excavator works very much the same . By changing the angle of the cylinder increasing the stroke of the pistons changes the oil flow speed . But thanks for this because i had never seen a hydrostatic transmission apart or describe before . Well done thank you
You bring up a good point about pumps, and valves (like the kind used in hydraulic joystick bucket and boom controls) use the same swash plate concept to open and close spool valves to change the fluid flow rate. Funny how there are so many mechanical inventions out there... But so many of the concepts are related. Brilliant inventors, way smarter than I'll ever be.
Awesome vid! This principal is very akin to power steering works. On a car, the pump is separate, but the steering wheel vanes/ valves built into the steering shaft are the input/ output PID. This is relatively weak. The pumps on this are interictal to the input/ output PID. This gives the power to drive the mower and not just turn steering on a car... Very cool engineering. It is also akin to how the cyclic on a helicopter works for steering...
I searched for Hydrostatic transmission and found your video and i must say that you really explain how the whole system works on a easy understandable level, Thanks for that! It's a fantastic little system that really works well and for a long time if taking care of. You have a new Subscriber. Good work 👍👊
I was repairing a new skid steer, where one side had no power. Took it apart twice, without finding anything. The factory sen.t out an expert, who found nothing. The company sent out a new unit, and the old unit sent back. A few weeks later they diagnosed the issue. The pump and motor use the same size pistons, but the slippers are different. Someone put pump pistons in a motor assembly. There was .0001 difference in diameter in the lube holes in the slippers on the pistons.
@Robert Heinkel that’s interesting, I have a situation on a JD riding mower but no one swapped any parts around. Why would one of these transmissions suddenly have no reverse then go to the shop for a fluid and filter change and end up with reverse working now but no forward? We have a John Deere 265 that reverse got real weak and stopped working then it was taken to a tractor shop where they recommended a hygard fluid (John Deere product) and filter change and came back with no forward drive. It’s got me baffled as to how the situation literally reversed itself. I’m trying to understand how these work before I just start pulling it apart. No reverse with functional forward to no forward with functional reverse... crazy 🤔
@@paulbeldenbush yeah I’m not a fan of John Deere because they make it hard to get parts and self repair very limited. My dads jd that I commented about got worse and barely goes forward or backwards once it warms up. I think parts in the hydro are worn. Trying to keep an eye out for a parts machine jd 265 series but in the meantime 300 bucks bought another machine that climbs hills no problem. Sad thing is the jd has a snow blower, mower, plow etc that can’t be used now. Oh well JD f**ked themselves out of a future customer. Hell, farmers get screwed by them all the time, big combines that are hundreds of thousands and they will disable them by the touch of a button. It’s time we fight for right to repair for all. Louis Rossmann is the man fighting for us on R2R
Thanks. This video helped me understand some of the components that go into my hydrogear. I am losing power when any load is put on the system. The motor seems to be running fine, but the transmission lags behind. I am ordering parts to break open and rebuild them. The pump seems to wear groves that can sometimes cause strain and loss of power.
Thanks for a very well done explanation... I have had several hydrostatic lawn mowers and now I have a layman's understanding of this mechanical marvel.
Perfect! Thank you very much! Before I saw this video, I had no idea what is a hydrostatic transmission. You explained it so well, that I can go teach it (but not like you).
I appreciate all of your knowledge and taking time to explain this I might be getting a job soon or I'm maintaining a small Amusement train that is a biodiesel hydrostatic hybrid motor and in looking up hydrostatic Transmissions I was also very fascinated
Thank you this is a very well explained description of hydrostatic transmissions that I never knew before. As I think about the rotational forces generated by this mechanism of fluid dynamics I wonder if these transmissions are prone to wear out either from piston wear or bearing wear. Some of these small garden tractors are designed to pull, say, a tilling attachment or push snow. And so, these situations create much more stress on these pistons and bearings, it seems. What is the expected life of these transmissions (TBF, time before failure)? Thanks again for sharing this well thought out video.
Yea a pump and motor. The part that pivots is called the wash plate. It's called a variable volume pump. That is what is used on large stamping hydrolic presses. The ones I work on are huge. I think using the word transmission kind of throws people off. At 10:00 you say it sounds kind of weird lol thars the first time you describe the system the way a hydrolic tech would. Still on nice video for the laymen.
nice teaching. I would recommend setting up your channel like channel art, Tell yourself in the about section to increase your views, ultimately your business. Your way of teaching is so amazing. Keep it up and keep shining also.
Bought a Spartan Zero Turn, has these hydro static transmissions in them. How interesting your instructional video is. Parker loves you you, I’m sure on that. Great video. Thanks. Enjoyed it very much.
hola...amigo precisamente tengo una de esas que compre para un proyecto de go kart y no sabía como funcionaba y aunque No entiendo un comino de Inglés por lo menos me diste una idea de como funciona .. aún tengo ciertas dudas de como probarla y todo eso y como.saber si esta en buen estado pero te aseguro que ti explicación fue tan CLARA Y PROFUNDA que incluso sin conocer tu idioma lo entendí mil gracias la toma que no tengan subtítulos tus vídeos y los comentarios tampoco tienen la opcion de traducirlos al español
On Royal Navy ships in the '60's, some had Denny-Brown fin stabilizers. The hydraulic mechanism was similar to your description but with radial 12 piston-and-rod units in each of the 'A' transmitter (compressor) and 'B' receiver (motor). Angled actuators, like yours, determined speed and amount of fin movement ultimately ordered from gyroscopic master controller.
Great teardown & explanation, My old Stiger has this type of transmission & it starts to slip when hot. Now I know that maybe if I just put a heaver grade of oil it may solve the problem & extend it life a little more. I thought it must work by clutch packs & they had worn out. But the hydraulic pump & motor must be just a little worn, so not likely to harm anything by going to a thicker oil within reason.
So did that work? One suggestion.I had real success with power steering and other systems with appropriate Lucas oil additive. Had advice from a Lucas rep to add two bottles instead of one,he was right,for a power steering system that was genuinely tired. Got a year out of it I really do not think I would have otherwise.
@@paulmanson253 I changed it to 80/90 oil & it improved it but it still starts to slip after more than about 1 hour mowing in hot weather. It is difficult to get the oil in it after draining, But if I do change it again, I will try the Lucas oil but not sure I would be able to get it into the long tube like small inlet.
@@calthorp There are ATF funnels with a very narrow end to them. Also,just looked at one item I have. Made by Hopkins Manufacturing,Emporia Kansas. No doubt they have other items ,but the one I have should serve. No doubt they will be online. Cheers.
@@paulmanson253 The catch with filling it is its a long tube filler but there gear box is sealed so it takes forever for the oil to slowly make it way down. If you tip it too fast it just air locks & stops. It is not designed to be serviced.
My mower quit moving. I am far from a mechanic, but this helped a lot! Even if I still have to take it to a mower mechanic at least I have some background knowledge of what all needs to be done and why it costs what it costs. I wish I could check the oil on mine without draining it.
I believe this kind of pump arrangement is called a 'swash plate' pump. A very similar arrangement is used for some ship's steering gear. Instead of forwards and backwards control, it moved the rudder port and starboard by moving the control rod via the steering wheel. This allowed the steering pump motor to run at a constant speed and only move the rudder, when the steering is moved from midships. It's a very old system.
@@billythekid2281 Yes, the same pump arrangement with a fixed swash plate. They don't have the variable control. AC pumps are switched on and off, with a magnetic clutch.
These are pretty cool. It all relies on that split second advance/retreat offset difference along with brute force. Timing is everything. Good video !!
So am I understanding this correctly: The pistons on one side of the set of pistons (in the output set that is connected to the output shaft) are pushed against the fixed angle part of the transmission case by the pressurized fluid and that is what forces the whole set of pistons (and thus, the output shaft) to rotate?
This is the one part he really didn't explain, maybe he thought it was obvious. But yes, the pistons pushing against the fixed angle plate cause rotation of those pistons....it's almost like the angled plate is a crankshaft, as the pistons push on the plate they go from the closest point to the farthest point possible, but rather than turning a crank, the pistons move instead.
I just bought a 2016 Craftsman T2400 for $750 in perfect running condition and it has this type of transmission. When mowing yesterday, I liked how I can control the speed on the fly just by moving the lever. With my old mower, I had to jab the clutch to change speeds. With how bumpy and uneven my yard is, I have to do this a lot. With this new mower, I was curious to know if I should be pushing the clutch in to change from forward to reverse and vice versa. Now that I have a better understanding how this transmission works, it seems unnecessary to push in the clutch before changing directions.
What happens to the pressure of the fluid on a very steep hill when you go for maximum angle but the tractor cannot move because it’s too steep? (It’s not recommended of course, one should back off of the lever / pedal)
What a great explanation of a mystery box , at least to me. How often should you change this hydraulic fluid ? Is there a drain /refill on my Cub Cadet 50" lawn tractor ? Thanks !!
Silly question: Could this principle be designed for use as a drive train for a bicycle? Ignoring the cost, of course. Or would the losses at pump and motor be prohibitive for such an application? Infinite gears, ground clearance, low maintenance - that kind of advantages...
Excellent presentation. Simple explanation of complicated concepts. I actually understood the information presented and now have more knowledge of hydrostatic transmissions. Thank you. Could we use this in an automobile?.. I know my JD sprayer will travel 30 mph...a car could do more . .. just wondering. Any takers?
I'd like to know how the hydraulic fluid doesn't escape the gap between the rotating cylinder thing that holds the spring-loaded cups and the stationary section with the slots for the fluid. If the cylinder is spinning, it's hard to seal the gap between that and the stationary plate well enough the hydraulic fluid doesn't escape, I think. Or does the hydraulic fluid leak into the case during normal operation?
Hi, good video, mine hydrostatic transmission is making noise like pieces of metal inside, I opened it and it seems that the noise is coming from the pump, how can I remove the pump? Cheers Ray from Sydney Australia
If i understand correctly, these are "Continuously Variable Transmissions" in that any movement, no matter how small, of the swashplate changes the displacement of the pistons and thus the "gear ratio" of sorts. Not too important for this application, but can be neat for vehicles, especially if optimizing efficiency, as you can have the engine in the "perfect gear ratio" all the time, with no shifting.
I think most production systems use belt+cone, or sphere based CVTs, but hydraulic is simpler (in my armchair opinion). I think the losses are the main concern? I need to look into it more/hear from others to be honest.
Another benefit to this system is not inside the transmission, but rather the driving engine - it does not need to change RPM up or down, because it doesn't shift between discrete gears, allowing you to run the engine very close to its most efficient RPM all the time!
You did a great job of explaining how this works, but I'd like to add a few thoughts. The apparatus that tilts back and forth is commonly called the swash plate and as you said, it's on the pump in this example. Not only can it control the volume and direction of the oil flowing into the hydraulic motor, when the swash plate angle is set to 0 degrees or perpendicular to the radial pistons of the pump, the pistons do not reciprocate at all and that creates zero flow and provides a neutral for the transmission. The beauty of this sort of drive system that makes it radically different from geared speed systems is that the torque from the hydraulic motor stays constant no matter the speed that the vehicle is being driven at. There is another arrangement wherein the pump output volume is fixed and the swash plate angle on the motor is movable. If you use vector analyses you can see that changing the incline of the swash plate away from zero will increase the volume of each piston's displacement, thus causing the motor to slow, but it will turn more easily so you get more torque at the output shaft. This lets the mower keep going up a steep incline, although at a slower speed, rather than stalling. Of course internal pressure relieving devices will set an ultimate limit to the torque available to keep from killing the engine. Typically a variable displacement radial piston pump will not require a separate relief valve like a fixed displacement pump would. The design of the pump would have a provision that flips the swash plate to 0 degrees if an overload is created. This tranny may not be built that way or the springs inside the pistons may accomplish that.
Question... I noticed, before you disassembled it, one axle had a shiny spot near the case. As if it may be walking out. My 7 yr old Poulan exhibits the same . Is this something that I should be concerned about ? It functions properly.
I've been wondering how to tap into the output side of a hst to run hydraulic cylinders for a snow plow and small (cat 0) 3 point hitch on a garden tractor.
Excellent; I have a Scotts S2046 Lawn Tractor with hydrostatic drive which is a far cry better than the silly geared machines, and with infinitely variable speed is a joy to drive, but I did not have a clue how it worked, even though I am a design engineer. Great video!
Great video. I have a question you might be able to help with. I have a 1990 Ariens tractor that is have a issue. The mower wont move forward and make a whining sound...it move backward strong and fast...just not forward. The belts seem to be tight, the fluid seem to be full, the linkage seems to be moving. The mower is in super good condition and hope to save it. Any help would be great...Thanks
Hey great job. I didn't imagine the pistons being so small like a toy 😂 Anyway, this video made me recognize the importance of the factory-set constant angle of the swash plate in the hydraulic motors. If their constant angle is relatively low, you'll be preferring torque over speed. If their constant angle is relatively high (steeper swash plate), you'll be preferring speed over torque. And although I haven't checked, I'm certain there are machines that allow some adjustment of that final drive swash plate angle.
So what would be the max RPM for one of these? I suppose a better question would be theoretically how how fast could you go on a lawn mower with a hydrostatic transmission before doing any damage
Not motor oil - at least not the viscosity I would use in my car. It may be a heavier weight oil, but I would definitely recommend going by manufacturer's info, from manuals, etc.
Trust me, I had to take this apart a lot of times before I really figured anything out. And now I think I understand it, but I'm sure there's still a lot I don't get. It amazes me how somebody once figured this up out of their head. Incredible.
That was great! I'll need to watch a dozen more time to fully comprehend but you did a great job explaining. My first machine with a hydrostatic transmission was a Honda snowblower. I always marvelled at how smoothly it transitioned from forward to reverse. You did a great job of explaining the mechanic and dynamic workings. This device sure beat the old fashioned planetary gear, Thank you!
Videos like this are what make UA-cam worthwhile.
As a 'mechanical layman', this explained how hydrostatic transmission works simply & clearly - well done, and thank you!
Man!!!!that was an awesome explanation, I'm 53yr old, been running and repairing heavy (and smaller) equipment 34+yrs ....often wondered but never knew, I appreciate you taking the time to break down and explain, I'm saving your channel. You'll definitely be another one of my go toos:)
I just love the amount of entusiasm when explians the math of the transmission. And at the end, as a final conclussion, he finishes it with a "pretty cool". Love it.
You should have seen when I first took it apart.
I said WOW a lot of times.
I'm sure there are a lot of people who know all about this kind of stuff already, but I totally love seeing something new for the first time. It makes learning really fun.
What an interesting way to create a continuously variable transmission.
Thanks for taking the time to rip one apart and dig into the subject!
Appreciate the explanation. How these mechanisms are conceptualized and manufactured is amazing. I have a compact tractor with a hydrostat, which is super convenient and smooth compared to the traditional gear transmission. I could picture early farmers being skeptical of this incredibly complex mechanism initially though.
The whole rotation mechanism is similar in concept to a helicopter rotor hub with the awash plate, connecting rods and bearings.
I’m going to go easier on my ride on mower and tractor now, keep ‘em in low gear. Stuff is intricate.
I’ve been using my zero turn lawnmower for 3 years now and I always wondered how the transmission works. I do believe those have 2 small transmissions (one for each wheel) but this explained perfectly and very clearly how the magic happens. I love knowing how things work!
My friend rebuilt the powertrain for a 15” gauge miniature train locomotive. The train as built in 1947 used a simple clutch between the gas engine and the driveshafts for the trucks. Obviously, it had no reverse! When the clutch suffered a catastrophic failure, we could not find a direct replacement for it or even parts to repair it. The most recent parts list from the manufacturer was dated 1963. So we swapped the ancient, smoky Onan motor for a new Honda 25HP and, instead of the clutch, used an Eaton Series 11 hydrostat. All it took was moving to motor mounts forward a few inches and fabricating a couple of brackets for the transmission. We got excellent power throughout the speed range, plus a reverse. No more pushing the train backwards 400’ to put it away at night! It helped that the company I worked for was an Eaton distributor, so I got him the employee price of cost + 10%.
Bravo...well done! What's amazing is the mind of the engineer that created machinery like this.
He sort of mentioned it, but this transmission idea was a marriage of a variable displacement swashplate type hydraulic pump and then using that same design in reverse as a hydraulic motor. A variable displacement pump is a very common design in hydraulic actuated machinery but with a couple important differences. Firstly, the swashplate generally is not able to go into a reverse position. Secondly there is no manual control of the swashplate angle. Instead a spring acts to tilt the plate to maximum and the output pressure works against the spring to bring the plate back to the neutral position. So if you block off the output flow the pressure rises to bring the plate to neutral while holding pressure at maximum. If there is no back pressure the plate tilts to its maximum position to deliver the maximum flow rate.
As said there is nothing new under the sun it is all ready here it just has to be thought up and that is what the engineer done it was in his mind of what he wanted to achieve that my friends is God he is the infinite mind that's why nothing is impossible with the infinite mind of God and we all are created with a mind as hydruclics fascinates me I see how this works
Outstanding video. I always wondered how a hydrostatic transmission works. Clear, concise and great use of actual transmission parts.
Yep. Most normal people, when they need to haul something to the dump, they just load it up and take it to the dump.
Not me.
I take it apart.
So instead of 1 easy big thing to haul to the dump, I have like 1000 little nuts and bolts and parts to collect first...
If I had had you as a teacher I would have definitely gotten better grades. Thanks for your thorough explanations.
Thank you for this video, I am a very mechanical person, but I’ve never given a hydrostatic transmissions a second thought, thank you for this! Perfect
Thanks! Just got my first lawn-mover. As it is a bit jerky - trying to understand how things work under the hood before fixing. Hydrostatic is a new thing for me.
Thank you, for enlightning me on the hydrostatic system, you do good!
I am happy to help - learning brings me a lot of joy!
When I was growing up in the mid 70's we had a Wards 16 horse garden tractor that had hydrostatic drive and I knew it was a hydraulic pump and motor but watching this video it was more simple than I thought
Brilliant misnaming a hydrodynamic unit as 'hydrostatic'. This terminology appears to have gone through thousands of clueless brains !
Careful on your terminology - statics does not always mean there is no motion at all, but rather that input forces and output forces equal each other, so there is no change in motion. Dynamics is when an acceleration results from forces that are not equal - as we see in normal geared transmission when the input shaft (engine) speed must change between abrupt gear shifts.
It's true though, the terms have gotten a bit simplified over time when usually we use static to mean 'stopped' in most everyday use.
@@PetersonBrosAutomation 'Static' in reference to pressure and fluid systems actually means 'stable'. Where there is flow, there is instability.
No one would consider the wind being static - but obviously the overall pressure remains constant.
As for input and output forces equalling each other, I doubt you'll find a case where that is true. There are nearly always 'losses' - commonly as heat.
A fluid providing movement transmission will be very much like the wind - will contain pockets of higher pressures and pockets of lower pressures - just like the wind.
I see where 'static pressure' terminology is coming from but it's being misapplied.
My friend’s family had that same Montgomery Wards tractor. My friend was always so proud of how cool the transmission technology was. This video explains why!
Ive got one with a pto
This is all new to me, but I got a 2-wheel tractor and wanted to understand how it works. Your explanation of a challenging subject is exceptionally clear. Thanks.
I enjoyed the way you taught this. I don't plan on taking one apart but now understand why it cost so much to repair.
Great, glad to hear it! If you ever do get to tear one down, I'd suggest having a bucket of cleaning solvent handy, and a space to work that is prepared for cleanup. They are really cool, but super messy until you get all the oil cleaned and dried.
And the whole place will smell bad. Do NOT, repeat do NOT attempt this on the dining room table. You will be kicked out of your house until you learn to shape up.
(written from my shop computer)
Absolute best video explaining anything about these seemingly mysterious mower transmissions
This was a great video. I had a vague idea of how hydrostatic transmissions work but this really clarified it. Swash plates are such a cool mechanical design. Their uses are almost endless. What really blows my mind tho is how someone created this without the use of computers.
The human mind was once more powerful than any computer but we have been dumbed down over the ages. The lie is that we are more intelligent than our ancestors.
Imagine the brain power it takes to dream up an invention like that.
I'v spend some time attempting to learn the ins-and-outs of HST and this video has certainly helped but I also recommend for your viewers watching as much about Piston pumps and shwach plates as you can to further your understanding
I agree. This is a very confusing explanation.
I searched for shwach plates . No sensible related result found ! Then I tried searching for 'bearing shwach plates' , ah , bliss ! Hope that helps someone else .
Excellent presentation! Very concise, well communicated, good use of the transmission to demonstrate concepts and obviously you know your subject matter. Have used my Hydra Gear ZT-2800 equipped Toro for over 600 trouble free hours and always wanted to know how they work - now I do. Thanks a bunch!
Amazing how something can be so simple to understand yet so complicated in it's operation!
Fascinating - And a convincing assessment of how it worked, however, I still maintain it is black magic. As for taking it apart myself, I would not have understood it but merely compiled a hydrostatic gearbox kit.
Excellent video sir ! I don't believe anyone could possibly improve upon your presentation verbally or visually to inform me . I knew absolutely nothing about the inner workings of these mechanisms before watching your video. I watched it one time and have a complete understanding . Im not saying im an instant expert or couldn't learn anything else on the subject but man you did an excellent job. This is the first time I've seen your work and am excited to see what else you have on here. I don't mean to sound like a gushing school girl i was just very impressed. Thank you
I have to agree with your entire comment!
Yes it was, but…. My question is about the difference in being able to move shifter while in motion easily, versus the ones that you have to change the speed position which is not easy unless unit is standing still. Therefore they are either automatic or hydrostatic?
I have an early Murry with such a drive and am totally spoiled. I have often wondered how it worked, but I wasn't about to take it apart just to see. I think it's absolutely brilliant. Kudos to Mr. Hydro. LOL Thanks for sharing.
This made me so nostalgic 🥺 seeing that 0510 and even having original (i believe) style bull gear and miter gears. Literally makes me so happy to see this!
Your time is Appreciated I’m trying to figure out how to make this transmission more powerful this really helped a lot
That's pretty cool. Never understood or even wondered how a hydrostatic trans worked, but now that I see how it works it's pretty simple.
I have a John Deere LX 289 with 17 hp hydrostatic transmission when I first bought it I did an oil change on the engine are used Amsoil 0W 30 and I contacted the tech people at Amsoil and he said use a 0W 30 in the transmission also and when I did man made it a lot quieter ha ha people neglect maintaining those transmissions they need to be maintained better by changing the fluid not every year but at least every 200 hours of usage it’s not hard to do but when you do it, you drain it with the new fluid and get the back wheels off the ground start the engine up and let idle and then work the forward and reverse. That way you fill everything up real good and then you’re ready to go after you check the fluid level all right you guys this is a really good video. I’ve seen some of this guys videos before he’s good. He’s a real good man all right you guys have a good day now this is a Jim Mungai from Kennerdell, Pennsylvania.
This is a video I've always wanted to see. Thanks for making it! Now I have to go check out your others.
Thanks, just bought a used Craftsman riding mower with hydrostatic. Good to know how they work, and now I think I could do repairs to it if needed
Ty, that's exactly the info i was looking for. No gimmicks and straight to the point.
Thanks! Understanding how something works is sometimes better than a video showing you how to fix it. Heading out to the garage with confidence now!
Every time I do that, it leaves me with new things that need fixing :) Good luck!
It's a simple concept, brilliantly executed.
Swash plate pump, swash plate motor. Lucas improved the efficiency of fuel pumps on gas turbines engines with their swash plate pumps, instead of the gear pumps that were being used. They pump the amount of fuel required as opposed to the gear pumps which pump the maximum amount of fuel which is bled off when not required.
A variable displacement hydraulic pump on an excavator works very much the same . By changing the angle of the cylinder increasing the stroke of the pistons changes the oil flow speed . But thanks for this because i had never seen a hydrostatic transmission apart or describe before . Well done thank you
You bring up a good point about pumps, and valves (like the kind used in hydraulic joystick bucket and boom controls) use the same swash plate concept to open and close spool valves to change the fluid flow rate.
Funny how there are so many mechanical inventions out there... But so many of the concepts are related. Brilliant inventors, way smarter than I'll ever be.
Awesome, your disassembly was the most intuitive way to visualize it, well done
Awesome vid!
This principal is very akin to power steering works.
On a car, the pump is separate, but the steering wheel vanes/ valves built into the steering shaft are the input/ output PID.
This is relatively weak.
The pumps on this are interictal to the input/ output PID.
This gives the power to drive the mower and not just turn steering on a car...
Very cool engineering.
It is also akin to how the cyclic on a helicopter works for steering...
This is fascinating, I've never heard of anything like this before! What a neat mechanism!
terrific explanation of a hydrostatic transmission
First time I understand (basic) hydrostatic operation! Thanks
I searched for Hydrostatic transmission and found your video and i must say that you really explain how the whole system works on a easy understandable level, Thanks for that!
It's a fantastic little system that really works well and for a long time if taking care of.
You have a new Subscriber. Good work 👍👊
I was repairing a new skid steer, where one side had no power. Took it apart twice, without finding anything. The factory sen.t out an expert, who found nothing. The company sent out a new unit, and the old unit sent back. A few weeks later they diagnosed the issue. The pump and motor use the same size pistons, but the slippers are different. Someone put pump pistons in a motor assembly. There was .0001 difference in diameter in the lube holes in the slippers on the pistons.
They actually cared to find out what had gone wrong? That's great!
@Robert Heinkel that’s interesting, I have a situation on a JD riding mower but no one swapped any parts around. Why would one of these transmissions suddenly have no reverse then go to the shop for a fluid and filter change and end up with reverse working now but no forward? We have a John Deere 265 that reverse got real weak and stopped working then it was taken to a tractor shop where they recommended a hygard fluid (John Deere product) and filter change and came back with no forward drive. It’s got me baffled as to how the situation literally reversed itself. I’m trying to understand how these work before I just start pulling it apart. No reverse with functional forward to no forward with functional reverse... crazy 🤔
@@lh98 A classic John Deere story, and why I switched to a Cub Cadet dealer model tractor.
@@paulbeldenbush yeah I’m not a fan of John Deere because they make it hard to get parts and self repair very limited. My dads jd that I commented about got worse and barely goes forward or backwards once it warms up. I think parts in the hydro are worn. Trying to keep an eye out for a parts machine jd 265 series but in the meantime 300 bucks bought another machine that climbs hills no problem. Sad thing is the jd has a snow blower, mower, plow etc that can’t be used now. Oh well JD f**ked themselves out of a future customer. Hell, farmers get screwed by them all the time, big combines that are hundreds of thousands and they will disable them by the touch of a button. It’s time we fight for right to repair for all. Louis Rossmann is the man fighting for us on R2R
@@lh9815:21
Thanks. This video helped me understand some of the components that go into my hydrogear. I am losing power when any load is put on the system. The motor seems to be running fine, but the transmission lags behind. I am ordering parts to break open and rebuild them. The pump seems to wear groves that can sometimes cause strain and loss of power.
Update for resolution. It was the tension on the drive belt causing all my problems. Sometimes its the simple things.
Nicely done. Great to listen to someone explain things efficiently.
Thanks for a very well done explanation... I have had several hydrostatic lawn mowers and now I have a layman's understanding of this mechanical marvel.
Absolutely brilliant, I have the same transmission that stopped producing power and think this may have solved the problem.
This is interesting - I'd love to hear what part of the system was causing the power loss. I hope you find the issue!
Perfect! Thank you very much! Before I saw this video, I had no idea what is a hydrostatic transmission. You explained it so well, that I can go teach it (but not like you).
I'm glad you found it helpful! Before this video, I really had no idea myself, so it was quite interesting to tear it apart and learn.
Simple principles in complex arrangements, really an impressive design
Thanks, this was the most accessible explanation I've seen.
I'm so glad I found your channel! Your excitement for all things mechanical is exactly like how mine is, so I can totally relate! You've earned a sub!
I appreciate all of your knowledge and taking time to explain this I might be getting a job soon or I'm maintaining a small Amusement train that is a biodiesel hydrostatic hybrid motor and in looking up hydrostatic Transmissions I was also very fascinated
Thank you this is a very well explained description of hydrostatic transmissions that I never knew before. As I think about the rotational forces generated by this mechanism of fluid dynamics I wonder if these transmissions are prone to wear out either from piston wear or bearing wear. Some of these small garden tractors are designed to pull, say, a tilling attachment or push snow. And so, these situations create much more stress on these pistons and bearings, it seems. What is the expected life of these transmissions (TBF, time before failure)? Thanks again for sharing this well thought out video.
Yea a pump and motor. The part that pivots is called the wash plate. It's called a variable volume pump. That is what is used on large stamping hydrolic presses. The ones I work on are huge. I think using the word transmission kind of throws people off. At 10:00 you say it sounds kind of weird lol thars the first time you describe the system the way a hydrolic tech would. Still on nice video for the laymen.
back in the 70's i used to drive a IH 656 Hydro tractor and always wondered how that worked... now i know... Thanks
nice teaching.
I would recommend setting up your channel like channel art, Tell yourself in the about section to increase your views, ultimately your business. Your way of teaching is so amazing. Keep it up and keep shining also.
Thanks for the tip, good advice! And I am glad you enjoy the teaching. Obviously, I kinda like it as well!
Bought a Spartan Zero Turn, has these hydro static transmissions in them. How interesting your instructional video is. Parker loves you you, I’m sure on that. Great video. Thanks. Enjoyed it very much.
very clearly explained. You are an excellent teacher !
hola...amigo precisamente tengo una de esas que compre para un proyecto de go kart y no sabía como funcionaba y aunque No entiendo un comino de Inglés
por lo menos me diste una idea de como funciona ..
aún tengo ciertas dudas
de como probarla y todo eso
y como.saber si esta en buen estado
pero te aseguro que ti explicación fue tan CLARA Y PROFUNDA que incluso sin conocer tu idioma lo entendí
mil gracias
la toma que no tengan subtítulos tus vídeos
y los comentarios tampoco tienen la opcion de traducirlos al español
On Royal Navy ships in the '60's, some had Denny-Brown fin stabilizers. The hydraulic mechanism was similar to your description but with radial 12 piston-and-rod units in each of the 'A' transmitter (compressor) and 'B' receiver (motor). Angled actuators, like yours, determined speed and amount of fin movement ultimately ordered from gyroscopic master controller.
What a brilliant device!
Great video for an even better explanation!
Great teardown & explanation, My old Stiger has this type of transmission & it starts to slip when hot. Now I know that maybe if I just put a heaver grade of oil it may solve the problem & extend it life a little more. I thought it must work by clutch packs & they had worn out. But the hydraulic pump & motor must be just a little worn, so not likely to harm anything by going to a thicker oil within reason.
So did that work? One suggestion.I had real success with power steering and other systems with appropriate Lucas oil additive. Had advice from a Lucas rep to add two bottles instead of one,he was right,for a power steering system that was genuinely tired. Got a year out of it I really do not think I would have otherwise.
@@paulmanson253 I changed it to 80/90 oil & it improved it but it still starts to slip after more than about 1 hour mowing in hot weather. It is difficult to get the oil in it after draining, But if I do change it again, I will try the Lucas oil but not sure I would be able to get it into the long tube like small inlet.
@@calthorp There are ATF funnels with a very narrow end to them. Also,just looked at one item I have. Made by Hopkins Manufacturing,Emporia Kansas. No doubt they have other items ,but the one I have should serve. No doubt they will be online. Cheers.
@@paulmanson253 The catch with filling it is its a long tube filler but there gear box is sealed so it takes forever for the oil to slowly make it way down. If you tip it too fast it just air locks & stops. It is not designed to be serviced.
My mower quit moving. I am far from a mechanic, but this helped a lot! Even if I still have to take it to a mower mechanic at least I have some background knowledge of what all needs to be done and why it costs what it costs.
I wish I could check the oil on mine without draining it.
@Hannah Danielle did you resolve your mower issue?
Great teardown and explanation.
I believe this kind of pump arrangement is called a 'swash plate' pump. A very similar arrangement is used for some ship's steering gear. Instead of forwards and backwards control, it moved the rudder port and starboard by moving the control rod via the steering wheel. This allowed the steering pump motor to run at a constant speed and only move the rudder, when the steering is moved from midships. It's a very old system.
Same as a AC Compressor in cars too.
@@billythekid2281 Yes, the same pump arrangement with a fixed swash plate. They don't have the variable control. AC pumps are switched on and off, with a magnetic clutch.
This is the same idea as a variable piston pump only one pump drives the other. Wild
Swatch plate action is powerful, especially in hydraulic applications, and this an ingenious invention.
Very good job in explaining how the trany works. 👍🏻👍🏻👍🏻
These are pretty cool. It all relies on that split second advance/retreat offset difference along with brute force. Timing is everything. Good video !!
So am I understanding this correctly: The pistons on one side of the set of pistons (in the output set that is connected to the output shaft) are pushed against the fixed angle part of the transmission case by the pressurized fluid and that is what forces the whole set of pistons (and thus, the output shaft) to rotate?
This is the one part he really didn't explain, maybe he thought it was obvious. But yes, the pistons pushing against the fixed angle plate cause rotation of those pistons....it's almost like the angled plate is a crankshaft, as the pistons push on the plate they go from the closest point to the farthest point possible, but rather than turning a crank, the pistons move instead.
Search "axial piston motor" or "variable displacement axial piston pump".
I just bought a 2016 Craftsman T2400 for $750 in perfect running condition and it has this type of transmission. When mowing yesterday, I liked how I can control the speed on the fly just by moving the lever. With my old mower, I had to jab the clutch to change speeds. With how bumpy and uneven my yard is, I have to do this a lot. With this new mower, I was curious to know if I should be pushing the clutch in to change from forward to reverse and vice versa. Now that I have a better understanding how this transmission works, it seems unnecessary to push in the clutch before changing directions.
What happens to the pressure of the fluid on a very steep hill when you go for maximum angle but the tractor cannot move because it’s too steep? (It’s not recommended of course, one should back off of the lever / pedal)
What a great explanation of a mystery box , at least to me. How often should you change this hydraulic fluid ? Is there a drain /refill on my Cub Cadet 50" lawn tractor ? Thanks !!
Silly question: Could this principle be designed for use as a drive train for a bicycle? Ignoring the cost, of course. Or would the losses at pump and motor be prohibitive for such an application? Infinite gears, ground clearance, low maintenance - that kind of advantages...
Best explanation of a hydrostatic transmission I have seen, bar none.
Thanks!
You know, no matter how much stuff I take apart, there's always so much new stuff to learn!
Excellent presentation. Simple explanation of complicated concepts. I actually understood the information presented and now have more knowledge of hydrostatic transmissions. Thank you.
Could we use this in an automobile?.. I know my JD sprayer will travel 30 mph...a car could do more . .. just wondering. Any takers?
Wonderfully done! Thank you!! What a great instructional video!
You deserve more than a 100k subs mate !
Keep creating more content. Hopefully you could be the next ChrisFix 😇🤞🏼🤞🏼
I appreciate getting to see how the inside of one of those transmissions actually work what do I have to take my apart myself
Nice to see the inside of one of these without desecrating my own mower (Electric converted Cub Cadet :) )
so glad to come across your explanation. great video. thanks for sharing
I'd like to know how the hydraulic fluid doesn't escape the gap between the rotating cylinder thing that holds the spring-loaded cups and the stationary section with the slots for the fluid. If the cylinder is spinning, it's hard to seal the gap between that and the stationary plate well enough the hydraulic fluid doesn't escape, I think. Or does the hydraulic fluid leak into the case during normal operation?
Hi,
good video, mine hydrostatic transmission is making noise like pieces of metal inside, I opened it and it seems that the noise is coming from the pump, how can I remove the pump?
Cheers
Ray from Sydney Australia
If i understand correctly, these are "Continuously Variable Transmissions" in that any movement, no matter how small, of the swashplate changes the displacement of the pistons and thus the "gear ratio" of sorts. Not too important for this application, but can be neat for vehicles, especially if optimizing efficiency, as you can have the engine in the "perfect gear ratio" all the time, with no shifting.
I think most production systems use belt+cone, or sphere based CVTs, but hydraulic is simpler (in my armchair opinion). I think the losses are the main concern? I need to look into it more/hear from others to be honest.
Another benefit to this system is not inside the transmission, but rather the driving engine - it does not need to change RPM up or down, because it doesn't shift between discrete gears, allowing you to run the engine very close to its most efficient RPM all the time!
Thank you so much for your demonstration! I have wondered about hydrostatic drive principles, but never have delved into it.
More utubers should be making videos like this , great overview
You did a great job of explaining how this works, but I'd like to add a few thoughts. The apparatus that tilts back and forth is commonly called the swash plate and as you said, it's on the pump in this example. Not only can it control the volume and direction of the oil flowing into the hydraulic motor, when the swash plate angle is set to 0 degrees or perpendicular to the radial pistons of the pump, the pistons do not reciprocate at all and that creates zero flow and provides a neutral for the transmission. The beauty of this sort of drive system that makes it radically different from geared speed systems is that the torque from the hydraulic motor stays constant no matter the speed that the vehicle is being driven at.
There is another arrangement wherein the pump output volume is fixed and the swash plate angle on the motor is movable. If you use vector analyses you can see that changing the incline of the swash plate away from zero will increase the volume of each piston's displacement, thus causing the motor to slow, but it will turn more easily so you get more torque at the output shaft. This lets the mower keep going up a steep incline, although at a slower speed, rather than stalling. Of course internal pressure relieving devices will set an ultimate limit to the torque available to keep from killing the engine.
Typically a variable displacement radial piston pump will not require a separate relief valve like a fixed displacement pump would. The design of the pump would have a provision that flips the swash plate to 0 degrees if an overload is created. This tranny may not be built that way or the springs inside the pistons may accomplish that.
Question... I noticed, before you disassembled it, one axle had a shiny spot near the case. As if it may be walking out. My 7 yr old Poulan exhibits the same . Is this something that I should be concerned about ? It functions properly.
I've been wondering how to tap into the output side of a hst to run hydraulic cylinders for a snow plow and small (cat 0) 3 point hitch on a garden tractor.
Excellent; I have a Scotts S2046 Lawn Tractor with hydrostatic drive which is a far cry better than the silly geared machines, and with infinitely variable speed is a joy to drive, but I did not have a clue how it worked, even though I am a design engineer. Great video!
Great video. I have a question you might be able to help with. I have a 1990 Ariens tractor that is have a issue. The mower wont move forward and make a whining sound...it move backward strong and fast...just not forward. The belts seem to be tight, the fluid seem to be full, the linkage seems to be moving. The mower is in super good condition and hope to save it. Any help would be great...Thanks
Thnx! I have been looking for this info for two days.
Hey great job. I didn't imagine the pistons being so small like a toy 😂 Anyway, this video made me recognize the importance of the factory-set constant angle of the swash plate in the hydraulic motors. If their constant angle is relatively low, you'll be preferring torque over speed. If their constant angle is relatively high (steeper swash plate), you'll be preferring speed over torque. And although I haven't checked, I'm certain there are machines that allow some adjustment of that final drive swash plate angle.
interesting, wanted to understand as i never heard before and was planning to buy a tractor with HST, well done
So what would be the max RPM for one of these?
I suppose a better question would be theoretically how how fast could you go on a lawn mower with a hydrostatic transmission before doing any damage
good video. is hydrostatic trans fluid regular motor oil?
Not motor oil - at least not the viscosity I would use in my car. It may be a heavier weight oil, but I would definitely recommend going by manufacturer's info, from manuals, etc.
I still don't quite understand it (It's me, not you). But I can watch this until I get it. Thanks for making this video.
Trust me, I had to take this apart a lot of times before I really figured anything out. And now I think I understand it, but I'm sure there's still a lot I don't get.
It amazes me how somebody once figured this up out of their head. Incredible.
That's some creative ingenuity how this all works. Real cool.
That was great! I'll need to watch a dozen more time to fully comprehend but you did a great job explaining. My first machine with a hydrostatic transmission was a Honda snowblower. I always marvelled at how smoothly it transitioned from forward to reverse. You did a great job of explaining the mechanic and dynamic workings. This device sure beat the old fashioned planetary gear, Thank you!