OK, good information. Taking Mark's estimated servo moments and converting to back to kgf-cm and going to http://www.teaser.fr/~osegouin/aeromode/servos.phtml or more easily (since I don't read French) http://www.rcgroups.com/forums/showpost.php?p=5010862&postcount=43 and getting the amp draw for a Volz MicroMax HP servo (the figures are assuming a 5v source)
Flap servo moment = 62 in-oz = 4.46 kgf-cm = 1.3 amps (servo maxed out) Ail. servo moment = 40 in-oz = 2.88 kgf-cm = .85 amps Rud. servo moment = 27 in-oz = 1.94 kgf-cm = .63 amps Each half of the wing is pulling on the order of 1.3+.85 = 2.15 amps, or 4.3 amps for the total wing. Add in the rudder and holding the elevator on launch easily could add another amp for a total draw in the battery of about 5.5 amps. I will put on my flame suit and also say I am very comfortable with single set of 24 gage power and ground wires going to each half of the wing servicing both the flap and aileron servo. This is why I use IB1200 NiMH batteries which will not blink when 5.5 amps are requested (assuming you are not flying in really cold weather). Some of the A and AA NiMH packs will not allow such a large amp draw without plummeting voltages. This is why I also wire the wing plug in the fuselage with single pair of heavy gage (20 or 22 gage) power and ground wire going to the switch (just on the other side of the battery) and not going to the rx bus. The rx bus is wired with another set of heavy gage wires directly from the switch. don -----Original Message----- From: Mark Drela [mailto:[EMAIL PROTECTED] Sent: Saturday, February 18, 2006 11:08 AM To: soaring@airage.com Cc: [EMAIL PROTECTED] Subject: Re: [RCSE] Carbon Supra #48 flies - weight < 61 oz ! Molded Supra launch hinge moments are listed below, for a 200 lb tow load (hard F3j launch). For smaller tow loads, hinge moments will be proportionally smaller. wing camber = +10 deg rudder defl = 30 deg wing CL = 1.2 lift = 200 lbs q = 0.16 psi = 1104 Pa V = 95 mph = 42.5 m/s Flap hinge moment = 4.87 in-lb = 78 in-oz = 5.62 kgf-cm Ail. hinge moment = 3.15 in-lb = 50 in-oz = 3.60 kgf-cm Rud. hinge moment = 2.12 in-lb = 34 in-oz = 2.45 kgf-cm To get the servo moment (torque), this hinge moment must be multiplied by a linkage geometry factor, which is approximately by the ratio of servo/surface horn lengths. This is between 0.7 - 0.9 for most installations. Assuming a horn length ratio of 0.8, the servo moments are: Flap servo moment = 62 in-oz Ail. servo moment = 40 in-oz Rud. servo moment = 27 in-oz RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
