Questions on building my new flying wing and on the J250... - RC Groups
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Jun 13, 2004, 07:02 PM
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Picoflyer's Avatar
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Questions on building my new flying wing and on the J250...


I just bought one of Jsteven's flying wings and have a few building questions and J250 questions:
In the instructions for this wing, it reccomends mounting the battery with velcro on the wing, would it be best to mount it on the top?
Should all of the radio equipment be enclosed in the wing and the covering material put over it, or is it ok if the equipment sticks up from the wing?
On the Johnson 250 motor, how do you know what connector thing is positive and which is negative and do you just need to solder the motor directly to the esc?
Thanks
Dan
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Jun 13, 2004, 08:17 PM
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jimsky's Avatar
I can only advise on what has worked for me.

1) I mount my batteries on top with Industrial Strenght Velco, never had a problem. If you are making the wing for the 1st time, this allows easy shifting of the battery to adjust the CG balance of the plane. Also makes swapping batteries very easy. Mounting the battery in the wing has its merrits (aerodynamics, battery protection) but I haven't done this yet.

2) Receiver, ESC and servos I always dig bays and bury them in the wing, then cover over them. Hopefully you will not need any access to these parts, I haven't.

3) I aways mount the prop on the motor the proper way (if GWS numbers/letters face towards front of plane), then connect up a battery/power supply and determine which way exhausts the air behind the motor. Once you got that, mark which terminal is Positive.

4) I always solder the ESC wires to the motor. Remember to install a noise suppression capacitor across the motor terminals.

Jimsky
Jun 14, 2004, 01:45 PM
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Remember to install a noise suppression capacitor across the motor terminals
What are noise suppression capaciators and where can you get them?
Thanks
Dan
Jun 14, 2004, 01:58 PM
Trying to defy gravity...
jimsky's Avatar
The carbon brushes on a brushed motor do tend to "arc" during operation. This electrical noise is basically a spark gap transmitter, much like the one Marconi used for the first transalantic radio communication link. An arc creates a noise pulse of amazing frequency content. You don't want noise getting into the control electronics on your plane.

A ceramic capacitor (typical value: 0.1 microfarad, 50 volt rating) is soldered right across the two motor terminals. A ceramic capacitor is not polarized, so there is no right or wrong orientation. This capacitor appears as a low impedance path for the high frequency nosie created by the arcing brushes, shunting it to ground locally, instead of letting it radiate and/or conduct into your flight electronics.

The actual value is not that critical, 0.047uF would work. These type of capacitors can be purchased at Radio Shack, or at All Electronics the next time you purchase some J250 motors.

Jimsky