Craig Carr Posted May 14, 2009 Share Posted May 14, 2009 I have just completed the Tony Nijhuis A400m 4 engine multi. I have wired my motors up as effectively two twins One twin is the outboard motors and the other twin is the inboard motors. Each motor is a turnigy 250 watt and both of the "twins" are parralleled to a their own 3 cell Lipo 3200 mah capable of 20c (ie one battery pack per twin). I have tested each motor individually on the Watt Meter and with my chosen prop the watts are about 220 watts each. However when I try two motors together (ie one of the twins) I only get around 260 watts. I had expected to get about 440watts. Bizzarely though the physical thrust seems about right. I have checked each ESC is programmed the same using my programming card. Any thoughts? Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted May 14, 2009 Share Posted May 14, 2009 I've never run a multi so maybe I'm not the best person to comment but if I understand you correctly you are running 2 brushless motors off 1 ESC yes? This will cause the ESC a major headache because it uses the feedback from each motor to adjust the timing....having two motors fed back will confuse the ESC...... Quote Link to comment Share on other sites More sharing options...
Bruce Richards Posted May 14, 2009 Share Posted May 14, 2009 Craig how well does the voltage hold up on your lipo when you run both motors? You are asking it for 44A. I know it is supposed to be able to supply over 60A. However, experience tells me that not all lipos can supply the current the claim too without a large drop in voltage and hence lower wattage output. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted May 14, 2009 Share Posted May 14, 2009 Steve is correct. And as Bruce asks...what are you using to measure the power etc? Quote Link to comment Share on other sites More sharing options...
Craig Carr Posted May 14, 2009 Author Share Posted May 14, 2009 Hi Chaps, Using a seperate ESC (turnigy 40amp for 1 to 4 cell lipos) for each motor so it is the ESC to battery leads that are parralled. Im using a wattage watt meter. I think if I remember correctly the voltage shown on the watt meter was 9.(cant fully recall the figure after the decimal point). The voltage seemed to hold constant during the testing. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted May 14, 2009 Share Posted May 14, 2009 Volts should hold at least 10.5V under load as a minimum. Quote Link to comment Share on other sites More sharing options...
Craig Carr Posted July 21, 2009 Author Share Posted July 21, 2009 Hi Timbo, just to close this thread really. Sorry for the late reply to this but the model was just recently completed to "flight ready status" and maidened last week. I spoke to my local e flight shop and tried some brand new JP 4100 (30c continuous) 3s packs. Anyway with the new packs the watt meter held at a steady 10.9v when running two motors at once, and I was geting in the region of 520 watts same story for the other set of motors so am getting over 1000 watts which is what I wanted. Only conclusion I can come to is that the older cells I had been using for testing were unable to hold the current as Bruce suspected.Edited By Craig Carr on 21/07/2009 09:41:19 Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted July 21, 2009 Share Posted July 21, 2009 Thats much better...glad you got it sorted - and how was the maiden flight?..wheres the pictures and full post flight de-briefing etc Quote Link to comment Share on other sites More sharing options...
Craig Carr Posted July 21, 2009 Author Share Posted July 21, 2009 Hi TImbo, first flight was a brief 3 minute sortie to get it trimmed..... Model was way out needed full right aileron trim and full up trim. Ive accidentely built 2deg neg incidence between main wing and tail (doh)..... Could rejig/pack out the main wing to bring back to zero zero but dropped Tony an email and think the best thing to do is live with the up elevator trim (although I have reset the trims to neutral on my tx and mecahnically adjusted the trim back on the model so I have full trim adj on my tx again if I need it). Now I know if flys the plastic parts have been repainted with a much better match to the profilm (you may recall earlier thread) - thats all done now and Im just fitting some cowls over the outrunners. When rain stops am going to take some pics of the model reapinted and cowled and will post. Thanks for the help Craig Quote Link to comment Share on other sites More sharing options...
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