Inside a Planetary Reduction Drive

[@Vrishnak]

Not sure how I ended up here, but I could watch you build/dismantle things all day.

[@AgentJayZ]

+Mike Taylor Thanks!

[@Vrishnak]

What was this used in?

[@monkeyboom6753]

Idk why i just watched a guy grease some gears for 16 mins, but cool and very nice job :)

[@AgentJayZ]

Monkey Boom I should maybe rename this video " are you a gearhead pt.2 ".... you passed the test!

[@pi7137]

Same

[@Chuck59ish]

We used those on the Pratt& Whitney J-57 on the CF-101 Voo Doos. When we tested them we had a 1-ton weight as a flywheel. When we ran the motor up to cut off speed it took an hour for the flywheel to stop. Our starters used 1,500 psi air tanks on a 3,00 pound compressor to start the engines.

[@confuseatronica]

Today I learned that when jet engine starters are opened for service, there is a tiny amount of reggae released into the atmosphere!

[@OhTeeee]

Hi AJZ. I rarely comment on YT videos but I felt I needed to today after watching this video. I've just recently discovered your channel. I don't know how I missed it, but better late than never I guess. I've been flying turbines as a pilot for almost 25 years now. I started on PT-6s,Garrett's and am currently flying CFM-56. I really just wanted to say thank you for sharing your knowledge with us. I can honestly say I've learned more about turbine engines in the short time I've been watching you videos than I've learned from many hours of reading aircraft flight manuals. You have an amazing ability to explain things in easy to comprehend "layman" terms. I truly thank you for your efforts, it's such a pleasure to watch videos made by a true professional who has mastered his trade. Merry Christmas

[@AgentJayZ]

Thanks! Always good to hear from people with experiences using these engines.

[@doubledaddy2006]

Just how small can this thing actually make a planet ? I may have an interesting application for this device.

[@sighpocket5]

Ah Ha... That is what happened Pluto!!!

[@Outland9000]

Ha! This comment made me laugh.

[@Dra741]

Yeah make a planet full of women

[@brucemcgeehan2847]

Love the bured centre nut

[@youtert]

It doesn't make a planet, it takes an existing planet and makes it smaller. That's why they call it a Planetary Reduction Drive.

[@AgentJayZ]

Automatic transmissions contain actuators, which push and pull and do things. They are very similar to hydraulic rams, and they work by pressure differential accross a piston in a tube. Especially when the trans fluid gets old and gooey, it takes a while to warm up and build enough pressure to make the actuators work at full strength.

[@heligeorge]

I'm the guy from Cyprus.Yes Cyprus is the kind of place to settle down...but it's nice to see the world too.It definitely does not get near as cold here as it does where you are but AgentJZ...you are a global hero...I watch all your videos ...just as I used to watch aviation videos on the Wright Brothers back in the mid 70's.

[@AgentJayZ]

It is connected by cable to the start cart. Once the starter has reached its maximum speed, the switch is energized, the start cart air bleed is closed, and no more air is supplied to power the starter.

[@heligeorge]

Hey AgentJayZ, greetings from Cyprus,the tiny Mediterranean island.You cannot imagine how glad I am to really know all about turbines.Thank you for your videos and please try to keep some good stuff coming over during the cold winter.

[@UnauthorizedExpression]

A demographic that is overlooked by machinists is 3d designers. The better we understand how actual machines work and how the physics works in our world the better we are at mimicing that in our creations. Very cool videos.

[@timgriffith8748]

Just recently, I have found your videos. I enjoy watching. I have been an automotive mechanic for years, own a repair facility and we do a large amount of performance work. I rebuild automatic/manual transmission, transfer cases, differentials, turbochargers and the like. The components from the starter you are rebuilding are very familiar, pretty much the same as what we see in automatic transmission. From the planetary gears to the sprag, I deal with similar parts. Do you have problems with the sprag "flipping" or failing in the units? In a performance automatic transmission, it is a constant battle to find a sprag that will hold the power. Depending on the application, we may use a sprag similar to the one in the video. Other units use a mechanical diode sprag, which I think you referred to as a "ratchet". Much older models utilize a simple roller and spring clutch, however they tend to be very weak. Do you perform "end play" checks on the units? If so, it there a "selective" washer somewhere in the unit to allow for adjustment? I have become a bit bored on the automotive stuff and I am really interested in aircraft. I enjoyed your videos on the nuts and bolts of how a turbofan engine operates. I had viewed many animated videos claiming to demonstrate how a unit functions. However, I was looking for a real life explanation. You provided such with clear information on the power flow, what drives what, how the air is compressed, where the fuel is added, how it is ignited and what the combustion actually drives. I wish you were closer to where I live and I would come work for you for free, simply for the knowledge. Thank you for taking the time and sharing your knowledge and perspectives.

[@edwarddejong8025]

thank you for making these videos. i am a computer programmer, and never get to see any industrial type of work, but it is fascinating, and jet engines are such clever things.

[@Jangle2007]

This was great. What a gift to see inside these great pieces of equipment. Learned something new as well...had to look up "sprag clutch". Many thanks, Jay.

[@BikiniDuckCreations]

One of the reasons left hand screws were used in non-critical locations was for counterintelligence. By looking at the copies the OEM could figure out how smart the copier was. The story goes that with the Sidewinder missiles, a lot of the screws were leftys. When the Soviets copied them, they figured out they werent needed, and replaced them with easier to machine righties. But the Chinese copies were still using lefties, showing that they had no idea how to "fix" the missile design.

[@mxcollin95]

Just curious, do you remember (cuz this video is a couple years old) what type of grease you used on the gearing and what you packed the bearings with? I’m slowly working through all your videos and have enjoyed every single one of them! A huge thank you for taking the time to do them!! 👍

[@AgentJayZ]

It's a special grease that you mix with graphite powder. It was for the bearings and for the gears meshing. Since it was specified in the early 1960s, I'm sure any high quality modern grease would be more than up to the job.

[@K1w1scot]

AgentJayZ: graphite grease is used because thin film oil lube would add an extra level of complication to the design in that it would need its own lube system. Way to complex for something that's only engaged for 1/2 a minute or so each engine use.

[@AgentJayZ]

The electric switch cuts off power to the starter once the jet engine reaches sufficient rpm. The screw... "I hate to start sounding repetitive... but the screw is totally unnecessary, and is only used to keep the spline adapter in place during assembly. The adapter is totally captive, and has no room to move in any direction when the starter is installed on the engine."

[@disregardingsanity2890]

Again, an excellent rebuild vid. and mentioned which type of grease and why. Also gave insight as to why different components function as they do. Great job man and much appreciated!

[@AgentJayZ]

@mytmousemalibu A couple of the sparking tests were due to bad bearings, and they were replaced. A couple were more serious, and sadly they had to be put down. These starters are not as powerful as the radial inflow Garrett model that we use for our test engines. They put out 285 lb-ft of torque at 0 rpm, and by the time they get to cutout, it's under 20 lb-ft. And they don't like air hotter than 350 degrees.

[@kengreenwood7583]

I do wonder how positive information being given for free could ever get a thumbs down! It must be none thinkers a suppose, great vids thanks for your efforts sir.

[@joachimsingh2929]

I always thought it was people who think planes pollute to much.

[@videolabguy]

WORK. The "I can watch it all day" channel. Thanks! I would have never seen the inside of that in my life. Very good job.

[@AgentJayZ]

This is a video showing all the parts and how they go together. The torque wrench is not used in order to speed up the process. This is not an instructional video on how to perform the procedure...

[@AgentJayZ]

Two reasons this would probably not work: 1) the reduction drive is lubricated by grease, which means it has a duty cycle of about 3 minutes on, followed by 15 minutes of rest. Otherwise it will overheat. 2) The turbine is not designed for high temperatures, and would be damaged by the gases coming out of a combustion gas generator. What you want to do is expand the oil capacity, and put an oil cooler on a JFS100. Google and Ebay are your friends !

[@JETZcorp]

"... so we turn it counter-clockwise to tighten it." "Why?" "And before anybody asks, I'll give you the answer." "But I already asked!" "I don't know why." *falls out of chair laughing*

[@AgentJayZ]

Well, they are called wire twisting pliers... or you can call them safety wire pliers. The ones we use are sold by the guys in the tool trucks, and cost a little over a hundred. The more commonly available ones are a bit larger, and I've seen them go for about 20 in the mail order ads in car and motorcycle magazines.

[@XxXYoUrNaMeXXXXx4456]

I love this. I myself am going to school to be a computer engineer, and also love all things mechanical. The physics, and absolute genius designs behind something like is is astonishing. I hope you do more videos like this in the future. You go into so much depth into how this simple piece of the overall motor works and how you should disassemble and reassemble it properly.

[@AgentJayZ]

We were sent a shipment of 40 of these to test and repair. The engine manuals don't list the starters, and the starter manuals don't list the engines they are used on. I suppose the aircraft manual would list the starter... if we know which aircraft the starter was used on. All I can tell you is they are not used on the J79, and that they are American made.

[@Darwinpasta]

The casting for the planetary setup is beautiful... probably just structural considering the application but still, very well finished.

[@mercerconsulting9728]

This is an excellent learning experience for people like me, who only have an amateur level of understanding.

[@74HC138]

@heligeorge One-way bearings is a synonym for sprag clutch. The one way bearing in my T-Rex 600 is greased and works fine! (The kit actually ships with a tube of one-way bearing grease, and if you buy a spare, they often come with some grease already in them)

[@IDontRollMyRs]

This is a mechanical one. VOITH brand has an hydraulic one for big 6.3kV pump motors. There's a "working oil" between two shafts and no direct mechanical contact. Working oil is in a chamber between NDE side of motor shaft and pump shaft. In fact, the motor spins at the same frequency at all times because you cannot start and stop a 6.3kV motor more than a few times in a row. Level of the oil is the key factor to determine the speed of the pump. Of course this working oil takes out some percentage of the useful power and tends to heat up. But the concept is smart.

[@Ceberus3232]

The original machine had a base plate of prefabulated aluminite, surmounted by a malleable logarithmic casing in such a way that the two main spurving bearings were in a direct line with the pentametric fan. The latter consisted simply of six hydrocoptic marzlevanes, so fitted to the ambifacient lunar waneshaft that side fumbling was effectively prevented. The main winding was of the normal lotus-o-delta type placed in panendermic semi-bovoid slots in the stator, every seventh conductor being connected by a nonreversible tremie pipe to the differential girdlespring on the "up" end of the grammeters.

[@dustinlore8048]

I'm a mechanical engineering student and stuff like this is sorely lacking in formalized education. I'm glad I stumbled across your channel!

[@golferlady123]

Absolutely love your attention to detail (right down to the way you hold the screws safely in place). Very nice video, thanks!

[@AgentJayZ]

@Fierobsessed This is an earlier design, and it seems simplicity of operation in the field was a priority. Nothing to drain and nothing to add, so it was impossible to run dry and have an "incident".

[@CompositesNG]

Love the video.. and your safety wire explanation was better said then all my A&P Instructors.

[@AgentJayZ]

Thanks! You might enjoy my videos titled "Lockwire".

[@charliehubbard4073]

AgentJayZ, another outstanding video, man! The detailed subsystem assembly/disassembly videos, like this one, are fascinating. Really well done. Please keep it up!

[@parsecpres]

you must be having a blast! Fantastic presentation! thank you for letting us see the intricacies of the components

[@AgentJayZ]

@heligeorge Interesting. The Bell 206 we crawled all over in training used a sprag between the engine and main gearbox in order to allow instant transition to autorotation in the event of power loss.

[@awkerper]

That clutch really IS ingenious! Very cool...

[@brandonmulford5524]

It is amazing to see how much of this is incorporated into aircraft aviation. Every single element on this video is a mechanical principle I have worked on down to the lube which looks like molybdenum disulphide.

[@AgentJayZ]

Yes, of the three sets, one is fixed and two are free to move. 1) sun 2) planet 3) ring ... I'm sure they have real names, and I'm sure someone will straighten us out on that.

[@mytmousemalibu]

@AgentJayZ They have some grunt down low! That Garrett is a beast! I wouldn't have guessed it has an inclination to tempature, somthing to do with thermal expansion/interferance? Since starters is the subject, I happened to be in our turbine shop this eve, and we have a bunch of Garrett turbine engines that look identical to the unit in your start cart! Just for kicks we also have: 2 PT6's , Allison 250, JT8D, Boeing T50, Westinghouse J30,

[@heligeorge]

In all Rc Helicopters, there is a disengaging mechanism which let's the rotor spin free to autorotate.I would therefore assume with most certainty that real helicopters definitely have that too,so when the engine is brought to idle the rotor spins free.The more economic version is the one way bearing and the better choice is the sprag wheel...which comes in one unit and has a normal bearing in parallel.One way bearings jam if greased or use very thin oil.

[@matube73]

That was one of your best yet. Well edited and very good commentary. Cheers.

[@MichaelTomey]

I would pay money to work for this guy, best teacher evar.

[@AgentJayZ]

@saxonlight Answer:the same way you clean off any slimy, greasy part... you use solvent, brushes, rags... and elbow grease :) I could show the entire procedure, but it would be 90 minutes of tediosity.... this is exciting as I could make it, really!

[@gernblenstein1541]

Never seen a spiral split ring retainer before. Cool video!

[@MrChaos39073]

Thanks for taking the time to make your videos. I love aviation and have a curiosity on how it all works but until your videos I was sure turbine engines were powered by magic. Keep them coming.

[@NecroGoldevil]

Thank you for the effort you put into making these videos. They are very informative! I know I told you a few months ago that I would "elaborate" about mechanical seals in centrifugal pumps (in response to your video on seals). I haven't forgotten, just can't seem to find the time and energy to do it. I promise to do it soon though, since I got some nice new tungsten carbide seals waiting to be shown to the world!

[@Scorpioflyer]

Starting at 15:05...Love the music, love the work that you do! Just got my A&P Cert and excited! Thanks for your vids. Helped me get through the oral part of the test!

[@CassinoG]

That was an incredibly fascinating Video. I know zilch about aircraft, and still enjoyed this. It was precise and easy to understand. I wish I could get videos like this for the DIY Auto Projects I work on.....

[@slimksibi3587]

impressive patience , high knowledge degree , very experienced teacher, congrats et merci

[@katelikesrectangles]

In watching this video, I paused about five times to go and read about a few of the things you mentioned. What a great way to learn things. Thank you very much!

[@AgentJayZ]

This gearset is not designed for continuous operation. You would need to change the lube system from grease to circulating oil. Otherwise you could try it...

[@AgentJayZ]

@saxonlight We've got a couple of those, but the heavy stuff is removed by hand.

[@AgentJayZ]

These ones are out of Bendix aircraft jet engine air turbine starters. I would expect to pay about 5K on Ebay for one if you can find any. Or... there are a couple of these inside eny automatic transmission... and in a multi-speed cordless drill... or a sailboat winch... but those ones are really expensive...

[@AgentJayZ]

The C-130 has an onboard APU, which is probably a Garrett GTC-85... the same engine that is in out start cart. So it is a very self-sufficient aircraft.

[@PastryBandit4life]

Don't ever stop making these videos man.

[@AgentJayZ]

OK... what's a pastry bandit?

[@jimmcdonald9244]

Thanks Jay, since I started watching you, I always wanted to see how you lock wire.

[@brucemcgeehan2847]

Left hand to prevent undoing in operation

[@AgentJayZ]

It's a left handed thread. A "normal" screw or bolt is a right hand thread.

[@Fierobsessed]

I was a bit surprised at the use of grease in that unit. Especially the sealed bearings. Most bearings are rated for a lower speed with grease as opposed to oil, and 42K RPM's is pretty high for bearings that size. I'm sure duty cycle plays a big part in it though. I re-watched the Garrett radial inflow starter video, I see that one uses standard MIL-L-7808 oil. Thanks again Jay!

[@K1w1scot]

Thanks for the informative video. This sort of thing inspires young minds into engineering...well, this, and maybe watching an old school combine harvester (both of which I was fortunate enough to be exposed to as a nipper). My one concern would be the use of a recessed blank in the inlet port. I know of at least 2 incidents in my time as an a/c maintenance engineer where recessed blanks, although brightly coloured, were missed in a per installation check and were duly fitted...with rather embarrassing results. Other than that, thanks for the informative vid.

[@AgentJayZ]

The little switch turns off the fuel pump in the start cart when it indicates that the engine being started reaches self-sustaining rpm.

[@harendrasingh7173]

You r great sir, your knowledge is helpful for us.i work in line maintenance, I have never seen these engine parts so closely

[@Agouti]

I highly doubt an turbine originating gear set would be easy or cheap to get, but planetary gearsets like that are widely used in a lot of applications. Depending on the size of your project, a cheap car transmission can work - I've used an old differential (with the 2 pinions welded together) as a step-down and direction change.

[@AgentJayZ]

@joelvh1 The cutoff is electrical. It is a small generator that makes just enough power at cutout rpm to trip a relay that is connected to the start cart and causes it to close the valve that is supplying air to the starter. Sponsors ? Send me bacon money !

[@AgentJayZ]

This gear train is from an engine starter. It is meant for short, intense duty cycles, while spending more than 99% of its life either cooling down or doing nothing. So it is not suited to the continuous duty of power generation. Yes, if you can find them, they will be very cheap when in non-functional condition. Ranging to the price of a nice car if new.

[@jb813]

Pretty good clip in my opinion. Always good to pre-rehearse so you don't surprise yourself while filming. I like short, concise, efficient videos (under 10).

[@AgentJayZ]

I like to not rehearse, so I can share the process of working through a job. That also makes the inevitable surprises more authentic.

[@AlexanderEddy]

Pretty remarkable piece of engineering, thanks for sharing Jay

[@Tech_Planet]

11:20 I need one of those tools!

[@AgentJayZ]

J.D. Rock The guys in the trucks have them. If you watch my lockwire video, you'll see an assortment of tools you can use.

[@Tech_Planet]

ok thanks!

[@robertglenn5398]

+AgentJayZ As I watched you grease the reduction drive, I wondered...Is it possible to over-lube or grease engine or other moving parts? When I was a kid greasing wheel bearings and such, I never really gave this topic much thought.

[@oisiaa]

I question the function of that grease after more than a couple starts. Based on the one you took apart it looks almost dry where it counts.

[@SOU6900]

That planetary reminds me of the inside of an old fashioned mechanical pocket watch minus all the grease. Kinda artist looking actually.

[@michaelmillson112]

dude your channel is awesome

[@trombone901]

nice video, im currently in school for my A&P and we are currently studying starters. your videos help me out alot.

[@AgentJayZ]

Yes it is. What engine, we are not sure.

[@KetoMelange]

I was hoping this had something to do with inverting the photon polarity in the matter/antimatter warp core injector buffer conduit, but oh well.

[@Bichoicho]

I find myself clicking "like" several times during the whole video. (That's how much I like them)

[@6Twisted]

Beautiful piece of kit

[@heligeorge]

Difference between a sprag clutch and a one one way bearing which we have on our rc Helis ?I run the one way bearings with absolutely no grease otherwise the one way bearings don't work...

[@mytmousemalibu]

I have those same safety wire pliers! Love'em! I remember you testing these starters, what was the deal with sparks coming out of them? Bad bearings? Neat unit, looks pretty powerful. Let's mount one to drive a go kart and for input air, fab up a LOX/Methnol combustor!

[@Pete856]

That was very interesting. I love doing repair work on bits of machinery, usually stuff we have on the farm. What I was interested in was the "sprag" clutch, I've never come across one of those before and would love to see how it works. I'm guessing that it uses friction to grip and wedge the teeth tight when turned one way and then loosen when turned the other.

[@joeKisonue]

They are utilizing sprag clutches in mountain bike free wheels now and they are really amazing. Zero lash and a much quicker response to pedal input. I believe these ones are roller bearing assembly and they bind inner and outer race assembly in one direction only. Its as simple as the order rack at a diner the paper slides up in easily past a ball bearing but energizes against itself in the other direction.

[@egn83b]

What does the electric switch do for the starter? To me this thing looks and works just like an automatic transmission but with an air type torque converter instead of oil driven turbine torque converter. Also the reverse threads are just meshed with with direction of turn like the other poster said to keep it in place when the thing is turning.

[@MrAureli224]

that is so simple to put together that it's missleading. maybe I can do the work, but experience really makes the difference.

[@mekman]

Fascinating stuff. I find myself thinking that if you were making these videos 20 years ago, I may have had a very different career path.

[@ArnoldsDesign]

I would find that a very interesting way to make a living. Too bad there's no places around here that do that kind of work. Good explanation too on the the safety wire. Now, is the shaft that is hooked to the planetary also hooked to a compressor shaft? I would assume, but didn't see it.

[@kenjohan]

Nice guy, speaks clearly and explains well. He could be a good teacher.

[@papadelta9197]

An excellent presentation agent jz.wish more pilots view your videos , they may have a little more respect for these marvelous appliances. Do continue to post you did an out standing job.

[@IlluminatedWhiteGuy]

That 2 stage planetary reduction gear is exactly what I am looking for. I'm working on a wood burning boiler/Tesla steam turbine generator system project. Can these be purchased reasonably from an aircraft bone yard? The original turbine housing could be cut away and a coupler connected to the input shaft or better yet a through shaft machined in then port the reduced pressure steam output from the Tesla turbine right into this units original turbine to scavenge a little extra power.

[@scott-rt6hl]

Ok, not another word. Excellent videos. Very well explained details.

[@AgentJayZ]

Thank you for the cool stuff ! I hope to see you next summer !

[@gordonmccoy4537]

You could have been in the PSA Engine Shop back in the heyday of Pacific Southwest Airlines...!!! We had the BEST mechanics!!! That would be a pneumatic starter for a Pratt and Whitney perhaps????? The air would come from the aircrafts APU or ground air.... Am I guessing wrong..? Gordon in Maui

[@jesusgamboa8574]

where can you get a pair of those pliers that twist the wire to lock the bolts???

[@AgentJayZ]

This one is the best explanation, actually !

[@matthewmillar3804]

Where does the aircraft get the air supply to start the engine? Does the ground crew attach a hose or does the plane have an on-board supply?

[@AgentJayZ]

These starters are of military fighters of the 1960s. With most of those planes, either the ground crew did attach a big air hose to start the engine, or there may have been the option to use a cartridge full of slow-burning mixture, like solid rocket fuel, to generate the gas to run the starter.

[@AgentJayZ]

I thought they were nitrile. They are called Ravens and they are commonly available

[@ricostylz74]

You watched because it’s just riveting to look inside all this stuff.

[@AgentJayZ]

@heligeorge Cyprus... When do I get to come for a visit?

[@bob505470]

Is there any specific reason/benifit they went with an axial turbine over a centrifugal turbine? I would think that a centrifugal turbine would work in a system like this as it does not seem too large.