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ken
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Hi I am helping someone with the aerodynamics to program a model aircraft flight simulator however my aero study has been aimed at radio controlled gliders so I'm a bit lacking on the power side of things.
We need to relate power and thrust for various model aero engines.
I did a static thrust test on a 2.5cc Taipan glow plug racing motor. This is a 2 stroke motor running on 80% methanol, 20% castor oil.
The prop is an 8 * 4 which is a dia of 203.2mm and pitch 101.6mm
Static thrust measured at 9.5 Newtons.
Now I found a statement that power = force * distance in unit time.
The test was made with the plane on a level surface, a string attached to the plane, round a pulley and attached to a small bucket.
I pored water in the bucket until the system a ballanced. I moved things about a bit the see if friction was affecting the outcome and found it insignificant. The mass of bucket and water was found to be .97 Kg.
Reasoning that thrust of 9.5 ballanced the weight of a .97 Kg mass, it could also accelerate that same mass at 9.81 m/s/s on a level surface therefore I could find distance from :
S = U * T + 1/2 A * T^2
Asssuming acceleration from rest and unit time 1 sec, I get:
S = A / 2
Now if power is force * distance in unit time I get :
P = 9.5 * 9.81 /2
P = 46.6 Watts
Is this correct?
If I knew bhp, can I use the reverse the above to find static thrust?
Is prop efficency a factor in the above and if so, are there good estimates we can adopt?
Would I be better off just scaleing thrust based on engine capacity?
The motor I used is a racing motor, designed to produce enough thrust for a racing model at well over 20,000 rpm. Would that mean less static thrust than a standed or stunt motor usually rated at 15,000 rpm.
Is there any way to relate turust to rpm as piston motor thrust reduces with rpm?
We need to relate power and thrust for various model aero engines.
I did a static thrust test on a 2.5cc Taipan glow plug racing motor. This is a 2 stroke motor running on 80% methanol, 20% castor oil.
The prop is an 8 * 4 which is a dia of 203.2mm and pitch 101.6mm
Static thrust measured at 9.5 Newtons.
Now I found a statement that power = force * distance in unit time.
The test was made with the plane on a level surface, a string attached to the plane, round a pulley and attached to a small bucket.
I pored water in the bucket until the system a ballanced. I moved things about a bit the see if friction was affecting the outcome and found it insignificant. The mass of bucket and water was found to be .97 Kg.
Reasoning that thrust of 9.5 ballanced the weight of a .97 Kg mass, it could also accelerate that same mass at 9.81 m/s/s on a level surface therefore I could find distance from :
S = U * T + 1/2 A * T^2
Asssuming acceleration from rest and unit time 1 sec, I get:
S = A / 2
Now if power is force * distance in unit time I get :
P = 9.5 * 9.81 /2
P = 46.6 Watts
Is this correct?
If I knew bhp, can I use the reverse the above to find static thrust?
Is prop efficency a factor in the above and if so, are there good estimates we can adopt?
Would I be better off just scaleing thrust based on engine capacity?
The motor I used is a racing motor, designed to produce enough thrust for a racing model at well over 20,000 rpm. Would that mean less static thrust than a standed or stunt motor usually rated at 15,000 rpm.
Is there any way to relate turust to rpm as piston motor thrust reduces with rpm?