PB Posted June 19, 2013 Share Posted June 19, 2013 I needed to sort out a power set up for a new model and decided to do some tests. I chose an XYH 50-45, 890rpm/v, 36A motor and power it through a 60A ESC from firstly two Turnigy 3s 3000 lipos in parallel and then a Turnigy 4s lipo.I clamped the motor to a test bench and using a Hobby King Power Analyser and a JP Micro tacho made up the attached chart of results using various props. It's pretty clear that I can't fly this motor with a 4s lipo and the choice seems to be between the APC 11 x 8 and 12 x 6 with the paralleled 3s batteries. They give similar results but using an on line thrust calculator the 11 x 8 gives me 1.53Kg and the 12 x 6 2.2Kg although the calculator suggests that the 11 x 8 needs 442W and the 12 x 6 474W which in both cases is greater than the test results. Howeve, the maiden flight looks like the 12 x 6 with the paralleled 3s batteries and let's see what happens. Any comments, thoughts, advice on these test results would be most welcome. Edit....Ooops typing error - left a '0' off the first three 4s rpm numbers Edited By PB on 19/06/2013 14:27:36 Quote Link to comment Share on other sites More sharing options...
IanR Posted June 19, 2013 Share Posted June 19, 2013 As a newbie only just beginning to get to grips with electric power trains, I don't quite understand your problem with the 4S 5000 lipo. It would seem the better option to me since 2 x 3S 3000 might well weigh substantially more than a single 4S 5000. Is it because you're trying to keep well below the ESC's 60 amp rating? Ian Quote Link to comment Share on other sites More sharing options...
PB Posted June 19, 2013 Author Share Posted June 19, 2013 Have another look at my first paragraph Ian, the maximum current the motor can handle is 36 Amps. Actually the two 3s batteries held together with elsastic bands are exactly the same size as the single 4s 5000 lipo and they weigh just 5g less. Both give excellent C of G in the model so I could have used either but for the 4s results. Edited By PB on 19/06/2013 15:03:35 Quote Link to comment Share on other sites More sharing options...
PatMc Posted June 19, 2013 Share Posted June 19, 2013 Depends on the model & how fast it needs to fly. If I've got the maths right the 12x6 limits it to a theoretical 50mph but the 11x8 limit is 68mph, in practise it's more likely around 45mph & 62mph. However the 12x6 should give a better climb rate than the 11x8. As I've said before the static thrust is pretty meaningless. Quote Link to comment Share on other sites More sharing options...
IanR Posted June 19, 2013 Share Posted June 19, 2013 PB Doh! Ian Quote Link to comment Share on other sites More sharing options...
PB Posted June 19, 2013 Author Share Posted June 19, 2013 Pat, thanks that's very intersting. I do realise, of course, that static thrust is a very dodgy statistic and is only good for like-with-like comparisons on the ground, but it does kind of give a feel for what's going on. I too did the arithmetic that you did and came to the same conclusion but didn't put it up here for brevety's sake, but there's just some gut feeling that in this case I should go with the 12 x 6 and the 3s set up. If it ends up as matchwood my mistake, but I'm quietly confident that in practice I'll be ok. Hello again Ian. Now this must be me but I'm afraid I didn't understand your last post. If I'm missing something then please indulge me and explain so that I can respond. However, I am 69 years old, so is it and age thing? Quote Link to comment Share on other sites More sharing options...
PatMc Posted June 19, 2013 Share Posted June 19, 2013 BTW what's the model in question, young PB ? Quote Link to comment Share on other sites More sharing options...
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