Propeller Speed Reduction TORQUE Increase EXPLAINED

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In this video I'll explain in simple terms (and also cover the math) how a Propeller Speed Reduction Unit / PSRU / redrive actually increases torque on an airplane engine/propeller. If it didn't make sense before, it will after watching this video.
We'll also cover the advantages and disadvantages of an engine making use of a gearbox to reduce propeller speed.
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Creative Commons image credits:
-Hirth F33-Author FlugKerl2 under license CC BY-SA 3.0 (creativecommons.org/licenses/..., no changes
-Gear cog-Author SimpleIcon www.simpleicon.com under license CC BY 3.0 (creativecommons.org/licenses/..., no changes
-LIO360-Author YSSYguy under license CC BY-SA 3.0 (creativecommons.org/licenses/..., no changes
-O200-Author FlugKerl2 under license CC BY-SA 3.0 (creativecommons.org/licenses/..., no changes
-Animated ICE-Author UtzOnBike under license CC BY-SA 3.0 (creativecommons.org/licenses/..., no changes
-Rotax 912ULS-Author Greg Goebel under license CC BY-SA 2.0 (creativecommons.org/licenses/...)
-Mustang on dyno-Author AdamNavrotny under license CC BY-SA 3.0 (creativecommons.org/licenses/...)

Опубликовано:

2 сен 2023

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Комментарии : 26

@saviormz 9 месяцев назад

This video explains in a great way a question i always had about airplanes and engine rpm/ torque! You gained a subscriber.

@gamingwatherbottle7419 9 месяцев назад

too bad this vid isn't getting the views it deserves when the quality is so similar to driving4answers

@LetsGoAviate 9 месяцев назад

Thanks! Yeah the aviation audience is much smaller than the motoring audience. It's fine. I like making videos that addresses confusing topics.

@frukwam День назад

Another two benefits of reduction drives: 1) allows for lower engine mounting & 2) reduction gearboxes with slipper clutches provide some protection to the engine in case of a shock load/prop strike.

@loranroberds308 5 месяцев назад

Did a dod gig . We used herth 2 strokes . We used a belt driven reducer. Seemed to work ok . Think they were 150 hp each . We ran two belts of which each were able to carry full load

@joseruiz-Joecool 9 месяцев назад

I like your videos like this one were you do some deep research and present the fact as you see them. Thanks for posting.

@PistonAvatarGuy 3 месяца назад

One correction: PSRUs generally increase the power to weight ratio of an engine, as they allow a smaller engine to perform the same amount of mechanical work as a larger engine. Rotax 912 iS: 100 hp; 64 kg; 1.56 hp/kg; 2,388 rpm @ propeller. ULPower 260iS: 107 hp; 72.3 kg; 1.48 hp/kg; 3,300 rpm @ propeller. Continental O-200-D: 100 hp; 89 kg; 1.12 hp/kg; 2,750 rpm @ propeller. Lycoming O-235-C1A: 100 hp; 107 kg; 0.93 hp/kg; 2,450 rpm @ propeller. Lycoming O-235-F1B: 125 hp; 113 kg; 1.1 hp/kg; 2800 rpm @ propeller. Really, improving power to weight ratio is one of the most important reasons why PSRUs are used on aircraft engines. Just imagine how big a direct-drive Merlin would have needed to be in order to make its power at 1,200 - 1,400 rpm at the propeller (probably at least 60 liters).

@georgejleonard9410 9 месяцев назад

Great video Jaco, thank you for your time and dedication

@aviator267 9 месяцев назад

Always enjoy your technical videos. Well done

@LetsGoAviate 9 месяцев назад

Thanks!

@kenmcconnell4148 7 месяцев назад

superb great explanations, trying to calculate the best reduction drive for my paramotor as I am always trying different prop dia & pitch

@ValentinMakriev 9 месяцев назад

very good video

@excellenceinanimation960 5 месяцев назад

Great video!

@LetsGoAviate 9 месяцев назад

2 Cylinder Airplane Engines Technical Deep Dive : ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-jtS9tkD3M4c.html Boxer 4 vs Inline 4 Airplane Engines Technical Deep Dive : ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-0wWpSVTHQTI.html Rotax 916 Unveiled (quick overview) : ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-z2MyOPQbaD8.html 6 Worst and 6 Best Light Sport Airplane Engines : ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-iY7fDpdsAZk.html

@user-gp4gi3vt2m 8 месяцев назад

Thanks

@andremarais2706 9 месяцев назад

Thank you again. I am building a Pietenpol and have a 2 cylinder BMW 1200 GS engine of unknown hours and came from a previous aircraft installation. It is fitted with a Rotax C gearbox. I have not started on this part of the project. This video applies directly to my project. As a matter of interest, would a C gearbox be able to handle this application? Thanks again.

@LetsGoAviate 9 месяцев назад

Let me know the reduction ratio of your C box. The Rotax C gearbox comes in different reduction ratios, between 2.62:1 and 4.0:1. My guess is 2.62:1 as that will give a max propeller rpm of 2,600 (assuming engine max is 6,800). If it's the 3.00:1 or higher ratios you will need a big propeller. I think the Pietenpol sits quite low when you lift the tail so you might be limited in prop diameter for ground clearance. What was the previous application of the 1200GS?

@andremarais2706 9 месяцев назад

@@LetsGoAviate Thanks for the response. I have not opened the gearbox yet, because I am still working on the airframe. I hope it is 2.62.1. Will the gearbox be robust enough for the engine? I have no information on the previous application. It has dual fuel pumps dual ECU's and is standard with dual sparkplugs. I am considering adding an additional injector to each cylinder for redundancy, as well as small second battery. Also centrifugal clutch. Thanks again.

@LetsGoAviate 9 месяцев назад

I'm not actually sure what the max hp rating on the Rotax C box is. Might have to check with an AP or someone with experience, to be safe.

@andremarais2706 9 месяцев назад

Thank you so much.@@LetsGoAviate

@AlienLivesMatter 8 месяцев назад

When comparing propeller size and frontal-cross-sectional-area, how large can a propeller get before adds to the drag characteristics

@LetsGoAviate 8 месяцев назад

With some caveats, bigger is better as long as the propeller tips dont go too close to the speed of sound (and the usual ground clearance problem)

@chippyjohn1 9 месяцев назад

A very complicated topic. I think we have spoken about it previously. In short a re-drive is more efficient, this is why they are pushing for them in airliners, this is why helicopters use them. Rotating a larger propeller slower is more efficient than turning a small propeller faster. How much power/torque an engine produces (on a dyno graph) means nothing compared to how much power a propeller consumes. At 8:00 you compare two engines with different propeller rpms, but don't explain the propellers will be different. Even with variable pitch propellers, if you increase the pitch to absorb the torque, this does not mean that the increase in thrust will be proportional. There is very little data that is shared with regards to power made, power utilised, what propeller is being used at what airspeed and density.

@LetsGoAviate 9 месяцев назад

Yes I think I know where you are going, thrust propels an aircraft forward, not engine hp. But I'm talking about hp, torque and rpm in this video, not thrust. I'm trying to break - as you said - a complicated topic into understandable chunks in a video that isn't hours long. This is the basic understanding on the torque and PSRU subject that can be built upon, or at least that's how I see it. I think clearly you understand the subject already and moving on to the more complicated subject of thrust.