How Does a Hydrostatic Transmission Work?
2024 ж. 7 Мам.
455 871 Рет қаралды
I've driven many hydrostatic mowers and lawn tractors - but I've never taken one apart until today!
The basic job of this transmission (and the concept of Hydrostatic power) is converting constant velocity power through a hydraulic pump into a matching hydraulic motor with a variable speed.
But to see the process and the parts...
That's a whole new level of understanding.
Here is a link that was shown to me with an excellent animation of the fluid flow process since it's impossible to operate with the transmission disassembled - • Hydrostatic Transmission .
Enjoy!
As a 'mechanical layman', this explained how hydrostatic transmission works simply & clearly - well done, and thank you!
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%.
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.
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.
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!
What an interesting way to create a continuously variable transmission. Thanks for taking the time to rip one apart and dig into the subject!
If I had had you as a teacher I would have definitely gotten better grades. Thanks for your thorough explanations.
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.
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!
Nicely done. Great to listen to someone explain things efficiently.
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
Awesome, your disassembly was the most intuitive way to visualize it, well done
Thank you so much for your demonstration! I have wondered about hydrostatic drive principles, but never have delved into it.
Thanks for this video. I've seen 3d animations of these, but your process of going through it step by step really helped me get a better understanding of these.
Your time is Appreciated I’m trying to figure out how to make this transmission more powerful this really helped a lot
This is a really good video explaining how the hydrostatic transmission works. What a really cool, amazing technology!
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
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.
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
These are pretty cool. It all relies on that split second advance/retreat offset difference along with brute force. Timing is everything. Good video !!
This is fascinating, I've never heard of anything like this before! What a neat mechanism!
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.
Thank you, for enlightning me on the hydrostatic system, you do good!
I am happy to help - learning brings me a lot of joy!
You did an excellent job of explaining how it works. Thanks.
Amazing how something can be so simple to understand yet so complicated in it's operation!
Videos like this are what make KZhead worthwhile.
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 👍👊
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 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)
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!
very clearly explained. You are an excellent teacher !
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
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.
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...
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!
This is the same idea as a variable piston pump only one pump drives the other. Wild
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.
@@lamedisclaimer4978 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
What a brilliant device! Great video for an even better explanation!
Great teardown and explanation.
A good explanation , good video.
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!
This is a video I've always wanted to see. Thanks for making it! Now I have to go check out your others.
It's a simple concept, brilliantly executed.
Imagine the brain power it takes to dream up an invention like that.
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.
Simple principles in complex arrangements, really an impressive design
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.
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.
terrific explanation of a hydrostatic transmission
You deserve more than a 100k subs mate ! Keep creating more content. Hopefully you could be the next ChrisFix 😇🤞🏼🤞🏼
That's some creative ingenuity how this all works. Real cool.
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.
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
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 .
Well done 👏. Great explanation and demonstration.
Fantastic video. Great channel! 👍
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!
Thanks, this was the most accessible explanation I've seen.
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?
Very good demonstration & explanation. My channel is a DIY small engine & various DIY projects. I worked on a couple of these transmissions & have read up on these transmissions & studied many diagrams. You by far give the best clear explanation that I came across. It has been a few years before you made this video but it would have saved me so much time. If get any questions on my channel about transmissions I will direct them to your channel. With 16,560 views & 238 likes in less than a year what else can I say. I just subscribed & hit the 239👍 for you. Stay safe, Joe Z
Very good job in explaining how the trany works. 👍🏻👍🏻👍🏻
very detailed. Exactly what what I needed to understand this thank you.
Excellent explanation. Thank you for sharing!
Such a good video man! Very informative!
Thnx! I have been looking for this info for two days.
Brilliant explanation.
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.
Thanks for the video, it was very interesting and it made me understand exactly how that my old Ford lawn and garden tractor works, I sort of had a little bit of an idea, but you made me understand it completely . 🤗👍💖💫
I really loved this video and thanks for putting your efforts to make this wonderful video .
Thanks! I'm glad you enjoyed 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.
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.
Excellent Video. Great explanation.
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...
Well done. You are a great educator. Thanks.
back in the 70's i used to drive a IH 656 Hydro tractor and always wondered how that worked... now i know... Thanks
I really enjoyed your explanation.
Swatch plate action is powerful, especially in hydraulic applications, and this an ingenious invention.
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:)
Thank you very much and it was very informative and easy to understand and believe me helpful very helpful just what I needed to repair my lawnmower
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.
Cool, this uses a wobble plate like the aircraft hydraulic pumps. Thanks, I never knew that about my lawn tractor transmission.
Very well explained, thank you. I'm wondering, do the bearings eventually wear out and need to be replaced?
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.
You would be an amazing teacher
Actually, I used to be a college teacher in the robotics / automation world. These days, I just work on the farm and constantly annoy my kids with fun facts about 'how things work' :)
interesting, wanted to understand as i never heard before and was planning to buy a tractor with HST, well done
Thank you, that was very helpful.
Excellent video - thank you! Top shelf!
Thanks, glad you liked it! And your name is interesting. Nobody calls themself "Captain Over-Tighten' without at least a couple of expensive stories!
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?
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!
One intresting thing about this type of hydrostatic transmission is that the driver is pushing the whole vehicle forward physically when pushing down on the cylinders in the transmission.... You can actually feel this under hard acceleration. But there is quite a significant mechanical advantage.
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 explanation
A discussion about the torque of input vs output of the hydrostatic unit would be interesting too. I need to think about it a bit to see if it is a function of the angles or not. Also, is there a relieve valve somewhere in that unit? Maybe belt slip is the implied limit but would also be interesting to know. Great job showing though!
Awesome video. You are sooooo articulate. 😀
Great video! Thanks for sharing!
I've even driven tractors with hydrostatic transmissions. It's a weird feeling when you're used to old school manual transmissions on them
I was just working on an old army 4k with a hydrostatic transmission and was so confused why there was no clutch pedal on something with 6 speeds (3 forward, 3 reverse) this was super helpful.
Nice to see the inside of one of these without desecrating my own mower (Electric converted Cub Cadet :) )
Cub Cadet 95
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.
Awesome video man, keep it up !
Thank you!