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HELP, with the motor pusher thrust angle

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Old 09-03-2007, 11:03 AM
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arck
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Default HELP, with the motor pusher thrust angle

Hi Guys, I need help to install the motor to my challenger II pusher plane, the plane was build in left thrust, I think is too much, pusher motor needs thrust angle as the tractor planes?, here are some pics to explane what I'm requesting,,,
Thanks in advance
wm
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Old 09-03-2007, 12:50 PM
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Default RE: HELP, with the motor pusher thrust angle

Is that the top or bottom we are looking at ??

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Old 09-03-2007, 01:17 PM
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Default RE: HELP, with the motor pusher thrust angle

Is the top, here more pictures,
Thanks for your quick response
wm
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Old 09-03-2007, 02:45 PM
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Default RE: HELP, with the motor pusher thrust angle

First, let's think of the thrust angles in terms of orientation related to the fuselage, as if you were sitting in the cockpit. Forward is the direction of flight, left is the left wing, etc.
On a conventional airframe, the motor is in front of the CG, and sitting in the cockpit the propeller appears to be spinning clockwise. The torque effect of spinning that prop is to roll the airframe's nose upward and to the left (toward 10:30), so the motor is offset downward and to the right to compensate (toward 4:30). (The motor is also, typically, 1/3 of the fuselage length away from the CG.) This is caused by the direction of rotation in relation to the CG.
I'm going to presume your motor (at least the propeller) is sitting aft of the CG on that model, but you are going to use a motor with normal rotation and a pusher prop. So, sighting from aft to forward along the fuselage, the propeller will appear to be spinning counter-clockwise. That means the torque effect is now up and to the right (toward 1:30), but it is AFT of the CG, so the effect to the nose of the airframe is down and to the left (toward 7:30). To compensate for that, the motor thrust line must be compensated up and to the right of the nose (again, when viewed from aft to forward along the fuselage). The vertical component of your motor's thrust-line (up or down) is not mentioned or visible in the photos, but the horizontal aspect (left or right) looks to be in the correct direction.
I believe the amount of angle is needed because the motor is very close to the CG, and the greater angle is needed to rotate the (much longer) entire airframe. BTW, the angle appears to be about 3 1/2 degrees, or less than double the typical 2 degree offset angle. Probably the model-makers experience says this much is needed.
Just put it together and fly it as is. If you are good enough to tell, and need to adjust the angle later, you can always add or subtract more washers behind the mount.
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Old 09-03-2007, 03:30 PM
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Default RE: HELP, with the motor pusher thrust angle

Yeah, it looks okay the way it is (great explanation BTW...) ...that came up in the pusher bobcat thread as well...in the end, no thrust off set, but a lot of down thrust...mind you, it is a totally different configuration...
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Old 09-03-2007, 03:40 PM
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Default RE: HELP, with the motor pusher thrust angle

Quote:
ORIGINAL: Bad_Daddy

First, let's think of the thrust angles in terms of orientation related to the fuselage, as if you were sitting in the cockpit. Forward is the direction of flight, left is the left wing, etc.
On a conventional airframe, the motor is in front of the CG, and sitting in the cockpit the propeller appears to be spinning clockwise. The torque effect of spinning that prop is to roll the airframe's nose upward and to the left (toward 10:30), so the motor is offset downward and to the right to compensate (toward 4:30). (The motor is also, typically, 1/3 of the fuselage length away from the CG.) This is caused by the direction of rotation in relation to the CG.........
Wow, thanks thats what I want to here, good explanation, the motor is seated aft of the CG as you can see in my next pics, What do you think, I will pull out all the washers I installed to tried to correct to zero or let some to only 2 1/2 degrees left from the center of the plane and try for the maiden,,,,how much, all the 10 degrees per designers? or less,,how much up thrust do you recomend......
Thanks
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Old 09-03-2007, 03:53 PM
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Default RE: HELP, with the motor pusher thrust angle

Quote:
ORIGINAL: Wayne22

Yeah, it looks okay the way it is (great explanation BTW...) ...that came up in the pusher bobcat thread as well...in the end, no thrust off set, but a lot of down thrust...mind you, it is a totally different configuration...
Sweet,,,,and now,,,,back to the beginning ,,,,,
I think I will ask those people, maybe they have the answer, hehe
[link=http://www.youtube.com/watch?v=c6ny5ts2lVk&eurl=http%3A%2F%2Fwww.rcgroups.com%2Fforums%2Fshow thread.php%3Fs%3D237dba23eb9ae75148c5bad186301250% 26t%3D662668%26page%3D6]full scale challenger[/link]
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Old 09-04-2007, 08:53 AM
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Default RE: HELP, with the motor pusher thrust angle

Guys if you look at the video, it seems that the motor of the full scale has down thrust, what do you think, weekend is coming and I need to resolve this issue,,,,,
Any comments?
thanks
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