How do ring and planet get the same speed? I do not see any fixed part. Or is it just because both propellers have to do the same work?

The latter. But I admit I don't know if this works in practice. I 3d printed a planetary set and verified that I can vary the rpm of the ring and the carrier by varying the input torque to the sun and the amount of drag on the ring... So, theoretically possible?

@bzig4929 theoretically possible, but not useful in practice. It's a power splitter, not a contra-rotating propeller drive.

Differential pitch control connected to synchrophaser feedback, or just let the blade phase wander around.

I believe that the only constraint on distance - other than mechanical requirements - was to separate the props by enough distance to make sure they wouldn't collide in operation. The usual practice was to run the aft prop at a slightly steeper pitch to obviate starving.

they do, but someone was too busy "animating" to consider "physics".

@paradiselost9946 i found the patent i suspect the animator based it on: US8876462B2. It is also light on the physics. My best geuss is resistance from inertia and aerodynamic forces, but that is being very generous

For defined output speeds it needs some constraint; the simplest is to lock one element stationary or to another rotating element.

Constant speed propellers would really make this choice...

Ohh no no I'm an idiot

yup, I did this wrong. I should have fixed the planet carrier and driven the ring gear. This would have been a better way to get them to counter rotate. Driving the sun requires an extra constraint... otherwise friction would make them rotate in the same direction. I'm not sure if this is what you were seeing, but your comment was helpful.

Thanks! I could have made it more clear... the front prop is driven by the planet carrier and the aft prop is driven by the ring gear.

Because I'm driving this through the sun gear, the props can rotate at different rpms. I made a 3d printed version to verify this... If I drive the sun and restrain the ring, all power goes to the planet carrier. Likewise, if I restrain the planet carrier then only the ring gear will rotate.

Thank you for replying, (In this configuration one propeller is attached to sun gear and the other is in ring gear and the planets are held in position right?) I want to ask whether it is possible to use planetary gears in such a way that the torque produced by the propellers are balanced. (Is such a thing possible by planetary gear?)

In my animation, one prop is driven by the planet carrier and the other by the ring gear. The sun gear is the input. Whether it's possible to balance torque this way... I assume that an aircraft could do this by varying the propeller pitch of the two propeller systems, but I'm not entirely sure how they do this. There are other ways of doing the gears such that rpm is always balanced, but that would only balance if the torque of each prop was under the same load.

@@bzig4929 you have constructed this as a variation of a planetary power splitter, although the planet carrier should be driven with the sun and ring gears being the low-torque and high-torque outputs. A planetary power splitter is a well-established mechanism, but it is not useful for a contra-rotating propeller drive. It is the basis of power-split hybrid transmissions, such as Toyota's Synergy Hybrid Drive and GM's old Two-Mode system; engine power input is split between an electric generator and a shaft drive to the wheels, with the load on the generator adjusted to control the relative speeds of the three components, acting as a continuously variable transmission.

Good observation... with the input at the sun gear, both the ring and planet carrier would rotate in the same direction... unless a load (friction) is applied to the ring. When you do this, it rotates opposite the planet carrier. I have another vid on this channel where I show this with a 3d printed planetary.

With two rotating outputs, load on the outputs will determine their speeds... which is why this is not a viable design to drive contra-rotating propellers.

what's your objective with the STL file? I could create one, but I didn't really model this for 3d printing... I can't recall if I built in the tolerances needed for that.

But those turn the planet carrier... If they were stationary, then one of the props would also be stationary. What am I missing?

They should be rotating on there own four different axis , not on the center shaft axis.

It might be the camera rotation that makes them appear like that, but the planet gears are definitely rotating on two axes... They rotate on their own axis, and, as a group, they rotate on the carrier axis.

The Red gear should be

That's not rotating on two axes,@@bzig4929, it's rotating relative to two different elements all on the same axis.

Thanks for commenting. I'm far from an expert on how these operate, but I was able to replicate this on a 3d printed planetary. If I constrain the ring, only the planet carrier rotates. And if I constrain the carrier, only the ring rotates. But there's a sweet spot... Just the right amount of drag on one or the other, and the ring and carrier counter rotate as shown in the animation. Propellers can vary their rotational drag by changing blade pitch, so this would be possible without mechanical friction bands.

@@bzig4929 I'm sorry, but there is still an error. There would be no absolute control over which rotation would dominate. To induce drag on any unit would induce heat which causes more drag. to regulate this would be impossible to drive both "blades" equally. Your system is flawed. If you drive the sun gear which is connected to the outer prop, constrain the planet carrier, then the ring gear would turn counter rotation connected with the inner blade. Gear teeth would have to be sized to give correct equal rpm to both blades.

You are right! Except about blade drag generating heat... This is aerodynamic drag, so, yes it suppose it becomes heat... But not internal to the gearbox. And it is possible to control the drag, individually to each set of blades, by changing blade pitch. Control of blade pitch in airplanes is extremely precise. But the way you describe is better and would be direct drive, as you say, based on the great tooth count. FWIW, I know the TU-95 uses planetaries and there are videos online where you can see the props start turning independently during engine start. I'm not trying to prove anything with these vids... I just enjoy doing the CAD and the animations.

Yes, @@bzig4929, you have constructed a power splitter, rather than a contra-rotating propeller gearbox.

Вращение будет одинаковым. Посмотрите повнимательней. Внешний пропеллер закреплён к планетарному механизму(водиле), а внутренний к коронной шестерне. Вал привода(солнце) вращается независимо.

Yes! That would be cool. And turn at like 2000 rpm.

@@bzig4929 I like your train of thought.

I mean the tu-95 was a genius design but this technology utilising turbo props was quickly made obsolete via turbo jets and turbo fans

Да,фирма Алисон пыталась разработать такой двигатель,как НК12,но отказалась.То,что знаю ,Николай Кузнецов обратился к проф.Новикову,что бы разработать зубчатые колеса редуктора по профилю ,,Новиков".Знаю тоже,что это является ноу хау .А у этого двигателя была мощность 12000л.с,а потом 15000.А сам винт-это тоже высшее достижение.Связь между передний и задний винт-дифференциальная.Первый втречает поток воздуха,а задний работает в ускоренный поток.Так,что надо адаптироватся автоматически по оборотам.Кинематическая связ нельзя быть твердая между винтами.

It works. When the sun is driven, if you control the about of drag on the ring, then the ring and the carrier will counter rotate. increasing the drag on the ring will eventually cause it to stop and only the planet carrier will rotate. There's no magic trick in CAD that will make you see gears meshing when they really aren't. Mechanical constraints in CAD are a legit way to visualize the real world. Thanks for commenting!

@@bzig4929 im not denying gears meshing correctly, or the mechanism. what im denying is that it will spread the work evenly across both props.

Maybe. Idk how the tu-95 does this with planetaries, but I know that pitch control of propellors is extremely precise and can be used to make very fine adjustments to shaft torque, so I believe this config would work with typical blade pitch control systems. But... Idk if it's ever been used. I'm aware that the RR griffon does not use a planetary contra gearbox.

@@bzig4929 maybe possibly. i may be wrong, it may be just counter torque and sharing betwen the two, and sometimes it can get confusing what rotates and what reacts. something here just feels really wrong from my experience of gears... yes, griffon uses two gear sets with an idler gear. quite easy. take say, a M3 and M4 gear set, both of say, 4:1... the M4 will have a larger center distance, so you can make an m3 idler and sneak it onto the m3 set for the reverse, the idler tooth count being of no concern... then you start thinking about what happens if you hold a prop stationary rather than the engine and its casing... or a really interesting one... what happens if the engine was driving via a right angle/bevel drive? look at a dragster ;) and the griffon is already spinning the prop backwards to the engine. the engine itself produces a torque reaction, by simply driving a load. regardless of if its a prop, a wheel, or anything... this ones overlooked ;) you may cancel out the torque reaction to spinning a prop one way, and twisting the air one way, but theres still a torque from the engine as it reacts against its crankshaft and load.