Looks good on the surface but beware, there are aerodynamic losses at wing tips and propeller tips. Each of your props could certainly “absorb 15kW” as you put it, but much more will be lost to tip drag since your system has six tips to the traditional propeller’s two.A Hummel size plane will perfprm well with a 1360mm prop driven by 30kW.
It will perform just as well with two 1012mm props placed 700 mm apart ,counterrotating and each absorbing 15 kW.
Swept areas are the same and that is somehow important
Yes I can see a few going around the pylons hoping for a payday. If a belly fuel tank is added then that may be a good area for the radiators on each side much like a P-51 belly scoop and low vibration on firewall from the Rotary.A Taylor Monoplane with a rotary would be a real performer.
A Hummel Type Aircraft, Gross Weight: 850 lbs = 385.5535 kg / 10 kg = 38.55535 kw needed = 51.70358 hp needed. 51.7hp at 75% Power = 38.7hp.
Used for Powerplant: 1 × Volkswagen air-cooled engine four cylinder, air-cooled, four stroke automotive conversion, 85 hp (63 kW). 85hp at 75% Power = 63.75hp!
Stall Speed: 46 mph! How much hp needed to stay above that Stall Speed?
A 1/2 VW weighs like 95 lbs, so what does a Four Cylinder VW Weigh? You still need to stay in that 4 Cylinder Weight Envelope.
A Twin Engine setup also still needs to be able to Fly if (1) Engine Fails, so probably minimum 38hp Engines.
- Gross weight: 850 lbs (386 kg)
- Empty weight: 457 lbs (207 kg)
- Useful Load: 393 lbs.
- Fuel capacity: 20 U.S. gallons x 6 lbs = 120 lbs. 393 - 120 = 273 lbs.
Ok my question.The comments guide me to where more explanation is needed so let them flow.
Ok my question.
The Junkers 3 post talks about not needing gears to keep pistons in sync.
Use permanent magnet generators to do that.
I can see how at cranking speeds to start, it could work.
But at full power - If the magnets are strong enough overcome combustion forces and keep pistons in sync - how does the engine generate enough excess torque to turn the props?
Another wise guy.Thank YouWhere to begin. As Billski already pointed out, single cylinder opposed piston engine would have HUGE crankcase airflow issues, thus why they need to be in at least two cylinder layout. Then, to even think of 4 cycle is preposterous - and something given up on 100 years ago. The whole point of such an engine is to NOT have cylinder heads, valves and all of the unnecessary junk associated with wasting half of the engine's time, effort, space and weight with double excess of powerless strokes. The real magic is in exploiting not only 2 cycle tech, but realizing this is a UNIFLOW engine that doesn't pee away a bunch of energy turning the cylinder airflow around to puke it out the same way it came in. Now, in the weigh thing: the gensets simply add massive amounts of weight that don't make any sense. The crank synchronizing gear train is much lighter, simpler and more reliable that another ton of electrical garbage. Also: the synchronization of the cranks is extremely critical - the "exhaust" piston leading the "intake" side by about 14 degrees (and CRITICAL to be very accurately maintained). Finally: spark ignition? Why in the name of anything logical would one put such a silly fuel into an engine that is ideal for heavier distillates and compression ignition (EXACTLY as Prof Junkers figured out once again 100 years ago (he had flyable engines at end of WW1).
Oh...forgot: the angular velocity/momentum variations from a big single OP engine would result in HUGE issues for prop drive(s). It is difficult enough with 2 cylinders thus why the sweet spot for such engines is 3. Also: when you talk about 120mm strokes, the engine becomes extremely wide (when horizontal) - good for your dual prop concept, but IMHO you are going down a road of incredible wasted weight and complexity to do something that has long ago been established as the simple, workable and highly proven way to go about it. Also: very large OP engines really need to be mounted on a vertical cylinder axis (once again, as per the Junkers 205 example).
If you really want to exploit the unique properties of OP engines, take a look at the Napier Deltic, Junkers 223 and much later "barrel" layout engines (the latter really interesting for aviation layouts).
Oh: on the "vibrationless" count? Having one massive piston on one side and a tiny one of the other will make for an extremely vibrating prime mover.
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