Flywheelpropeller

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Christian Lucas

Well-Known Member
Joined
Aug 23, 2012
Messages
339
Hi,

i will start to show my newest inspiration . The real start of it begun some years ago ,when i read about the history of tethered line hydroplanes at www.onthewire.co.uk .There i found the interesting boat of Bernard Pilliner here , http://www.onthewire.co.uk/pilner.htm

http://www.onthewire.co.uk/pilner.htm. It was not the steam driven boat , it was the propeller he used and the position of the engine. This was back in 1953 . Already 6 years befor i step out of Abrahams Sausage in this wonderfull world. It make me think about this propellerflywheel and i came to the solution that with todays materials and other production methode ,we can build a much different Design of such Propeller. The main problem in my thinking was the very high pitched propellers that are used for the last record boats and the reason to use very high speed turning Motors ( 50000 rpm and higher ) and the high speed propshaft with very small bearing in the strut. Also when we talked here about tipspeed of modelboat propellers ,Andy Brown told that dragrace boat propellers rev about 12000 rpm result in tipspeed high over mach1 soundspeed up to 960 mph.

This gives me the right boost to calculate . My ever , most loved propeller was the Octura X440 .How fast do i have to rev it to reach the current records . That are realy high 88000 rpm and the tipspeed was allways low with 414 mph ,less than the halve of dragboats tipspeed .

So there is a lot of room to go higher . Lets think about 100000 rpm and that will give us the posibility of running a propeller with a high efficancy dia to pitch ratio of 1,4 and 1,2 . Normaly we could not use such propeller with such high rev ,as most motors do not run this speed and with such speed the problem begun with high speed bearing and high rev motor design . Solve the motordesing and use a gear . No not very good because of bad efficancy .,So other idea needed.

No i remember of Pilliner flywheel propeller . This was the best way to get high tip,speed without need of high rev motordesign . The long leverarm of such propeller rise the tipspeed to the highest dreams and all without a geared overdrive .All with stone age know how. A short calculation show the all the relation a clear working . Rev down of the motor does rise the torque in the same way as needed to turn the propellerblades with the same power of the high rev motor can do. But with the lower rev and the big dia of the flywheelpropeller it has a other positive effect . The dia of the motor can be high and the useable dia and design of the motorbearing can also be bigger and stronger , No need of super expensiv high class microball bearing . So i have designed a flywheel propeller using the propellerblade of a Octura X440 ,you see the bigger dia of the propeller hub . With todays manufactoring possibility of my friend Albert i could get a laser print stainless steel flywheel propeller model .And this is the result . Ass i need the same propellerblad frequenz that hit the watter ,same frequenz of a two blade propeller i need for with the lower rpm moore blades ,with the result i need a five blade design to be equal.With this propeller i have designed differnt boats that can use it. First the record breaker roket design inspirate by Lee Taylor . Second a Momohull design using a Mosquito airplane hull. And third a outborder that can hang out on tunnelboats and canard and monohull and rigger and other futuristic boats. Now i start test run and test drive the prop.

Data of the propeller are: Hub dia = 70mm(2,76") ,Propeller dia = 100mm(3,94") ,Pitch = 56mm(2,2") .

This are very good data for outrunner motor use with higher torque and lower rev of 35000 rpm .

For ic motors do the same using a smaler hub dia of 1,6" and all dia of 2,75" with 2,2" pitch . Easy motor start from back like airplane starter . Rigger design with small front and narrow sponson as low waight there . Bigger wedge ski under the motor also to get motor in very deep position vor low c.g. .

Happy Amps Christian

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Very interesting concept Chris.

The drag boat prop rpm is actually 20 to 21,000 rpm. Engine rpm 8000 to 8600. Gears 2.3 to 2.5/1.

Normal prop diameter is 10.75 inches. Tip speed from simple rotation @ 20,000 rpm becomes 640 mph. Add 260 mph

of forward speed and the actual tip speed becomes 900 mph. At 21,000 the tip speed becomes 932 mph.

That is Supersonic in air. I guess it would be considered Hyper-sonic in water.

Keep up the good work Chris!
 
Chris,

I forgot to mention. Moving the X440 out to that diameter will add a very large amount of pitch. The blade angle would have to change a good bit to arrive at the original X440 pitch.

Good boating,

Andy
 
what about a single helix around the out side diameter?

Make it more like a drum to accommodate the pitch of the helix?

Single blade prop of sorts.
 
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Hi Andy ,

thanks for your coment ,will start to see what it will do .Yes you are right only taking the angle will,result in a X4100 with 5,5" Pitch ,to much .As there is a lot of space inside this big dia hub for future prop it can made with changeable blades formdesign and angle but to much mechanic will fail ,so this one is robust .

@Dwilfong ,

yes i have thought about a single helix blade ,but i think it will have to much friction drag ,so i fugured out the five blade design is my first test wheel . I don't know how it will worke .maybe in the next week i can start testing .
 
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Excellent creativity Christian,

One challenge I see is the relative height of the prop compared to that of the tub. If this were a conventional setup it is as if the prop were exiting the transom and the hub was flush with the bottom of the tub. Depending on the design of the hull, most try to lift the hull out of the water reducing the possibility of hydrodynamic drag and optimizing the lift to aerodynamic drag.

I would fear the close proximity of your hub to the tub bottom will result in increased hydrodynamic drag as the hull is not lifted out of the water.

Are you going to have this at the Munich event in two weeks?

Tyler
 
Hi Tyler ,

the pic show not how the boat will be when ready . Motorposition is to high , no question the tube has to be clear above the water. Motor will mount deeper so the flywheelprop need a conical plastik part for stepless streaming . See the drawing ,that show the boat .It will have moore small wings and a ski in the front .Wings are in a low position to get groundeffect but have to be small in wide to ad no c.g. moving like full hull in groundeffect will have . Also during start they are full hydrofoils lifting the hull . At teh transom are two wings one on top and one close to the watersurface . Lower position of flywheelprop and maybe a ruderfin ,but i will test it first without a fin only like an outbord ,the whole motor is stearable amd the shaft where the motor hang on can be used as a ruderfin shaft with a seperate servo to control the waterflow . And maybe a small fin at the front ski .

And yes i will visite the Munich SAW but not start with a boat , to early ,i plan for next year , will also build a monohull ,see test pic of liftingbody , freeflight test are sucsessfull .

Do you vistite Munich ? Would be realy great .

Happy Amps Christian

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