Leopard Red Series vs. Turnigy XK Series (comparison)
03-15-2012, 06:00 AM
#26
Thread Starter
RE: Leopard Red Series vs. Turnigy XK Series (comparison)
To go further off topic on the piston engine matter (just for good measure), guys that knows a lot more about engines than any of us, namely Rolls Royce, the undisputed world leader of civil aviation propulsion, used to build single cylinder models to prototype their new WW2 fighter motors.
Rolls Royce Merlin, Rolls Royce Griffon, Rolls Royce Crecy were all prototyped and bench tested as single cylinders before they got their final airworthyness tests performed as a full scale, all cylinder engine in an actual airframe.
If Rolls Royce can trade away 11 of the Merlins 12 cylinders and still have a test engine comparable to the 12 cylinder, so can you.
The reasoning behind is that power is torque multiplied by revolutions.
Torque is the pressure (BMEP) in the cylinder, multiplied by cylinder crown surface area, multiplied by half stroke length. (The length torque arm which the piston has on the crankshaft).
Thats all there is to it, that is horsepower produced on the crankshaft.
nowhere in that equation is number of cylinders mentioned.
Rolls Royce Merlin, Rolls Royce Griffon, Rolls Royce Crecy were all prototyped and bench tested as single cylinders before they got their final airworthyness tests performed as a full scale, all cylinder engine in an actual airframe.
If Rolls Royce can trade away 11 of the Merlins 12 cylinders and still have a test engine comparable to the 12 cylinder, so can you.
The reasoning behind is that power is torque multiplied by revolutions.
Torque is the pressure (BMEP) in the cylinder, multiplied by cylinder crown surface area, multiplied by half stroke length. (The length torque arm which the piston has on the crankshaft).
Thats all there is to it, that is horsepower produced on the crankshaft.
nowhere in that equation is number of cylinders mentioned.
03-15-2012, 06:12 AM
#27
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RE: Leopard Red Series vs. Turnigy XK Series (comparison)
And how many cubic inches was the single piston engine? probably bigger than most V6 engines, size does matter.
03-15-2012, 06:24 AM
#28
Thread Starter
RE: Leopard Red Series vs. Turnigy XK Series (comparison)
Indeed it was a lot bigger than most V6 engines. It was supposed to model a 12 cylinder, 27 litre!
As I said myself further up this tread, there are reasons to why big displacement engines tend to end up in the ball park of straight six, or V8 to V12.
Balance to counter vibrations is one of them, and compactness to fit in the engine bay is another.
If you look closer on my equation, displacement IS taken into account.
Stroke length multiplied by piston crown surface area is...... Yep, right
Displacement.
As I said myself further up this tread, there are reasons to why big displacement engines tend to end up in the ball park of straight six, or V8 to V12.
Balance to counter vibrations is one of them, and compactness to fit in the engine bay is another.
If you look closer on my equation, displacement IS taken into account.
Stroke length multiplied by piston crown surface area is...... Yep, right
Displacement.
06-02-2012, 03:59 AM
#29
Thread Starter
RE: Leopard Red Series vs. Turnigy XK Series (comparison)
To further follow up the question on Turnigy XK vs. XK "B" series, I have gotten my hand on one of each and pulled them apart.
The case lies in the belief that the XK series is different from XK-B series, where the "B" indicates that the motor is 4 pole, has slotted stator construction and is otherwise more similar to a Leopard.
As I have pointed out previously in this thread, there is slotted stator, 4 pole Turnigys out there without the B in its name, so this belief that B is distinguishing between 2 different series seems to be incorrect.
This is confirmed by my findings this time again, showing that both the XK and XK-B has the same slotted stator construction, and same 4 pole rotor construction.
This further implies that wether or not you get a "good" Turnigy XK or not is totally random.
Motors side by site, one is B series, the other is not:
Identical stator construction:
Identical rotor construction:
The case lies in the belief that the XK series is different from XK-B series, where the "B" indicates that the motor is 4 pole, has slotted stator construction and is otherwise more similar to a Leopard.
As I have pointed out previously in this thread, there is slotted stator, 4 pole Turnigys out there without the B in its name, so this belief that B is distinguishing between 2 different series seems to be incorrect.
This is confirmed by my findings this time again, showing that both the XK and XK-B has the same slotted stator construction, and same 4 pole rotor construction.
This further implies that wether or not you get a "good" Turnigy XK or not is totally random.
Motors side by site, one is B series, the other is not:
Identical stator construction:
Identical rotor construction:
