PB

As a relative newcomer to the hobby I've learned a great deal from the responses to my OP. Thanks to everyone who has contributed. The only thing I can add to the prop or no prop debate is that I would never under any circumstances whatsoever attach the prop to an EP model in my house or any other confined space come to that. This is not a 'mantra' handed down from my club safety officer or instructor, it comes from my personal understanding of the massive amount of power contained in the average electric model power set up. The thought of accidentally unleashing 400 or 500 Watts of energy instantly and without warning in a living room/dining room/kitchen should be scary enough for anyone simply to remove the possibility of it happening. So no prop in the house for me.

"I do notice how few flyers really understand electric, and certainly never set up their ESC correctly for the model. Most clubs seem to have a wealth of experience about ic gained by many years of usage. However, in depth knowledge or understanding of electric is far less." How true Martin. The advent of Lithium batteries has brought a whole new tranche of people into RC model flying, including me. I have had a lingering interest in model flying for many years and did a bit of control line 40 or so years ago, but I was never enthusiastic about IC. Now, in my late 60s, I find I can come into the hobby on terms that I understand because I'm a retired electronics engineer familiar with the building blocks of EP model flight. Indeed it was back in the early 1970s that I first struggled with the torque and slip mathematics of electroncially commutated motors as they were called back then. So the power train of an EP model is no stranger to me either in theory or practice. I have been pretty surprised at the lack of knowledge of EP fligh amongst exclusively IC flyers in my own club, and the lack of knowledge of IC flight by exclusively EP flyers in the club. More alarming still are the misunderstandings, myths and misconceptions bandied about the flying field with regard to EP flight from both IC and EP flyers. I noted with interest recently that a club member who took his A test with an IC model was asked no safety questions about EP flight, and another club member who took his A test on an EP model was asked no safety questions on IC flight. Is there a case growing for an EP A test and an IC A test which restricts the candidate to that type of flight only.... ......or is that another thread? Edited By PB on 19/07/2013 17:23:51

That's sound advice Pete B thanks, I'll do that from now on. I don't really want to drag this on, but thought I'd report that I have now carried out lots of tests with a motor clamped in a vice in my garage with battery, ESC and receiver connected and I have tried every which way to get the setup into 'fail dangerous' mode 'accidentally', but haven't been able to do it . I even tried binding the Tx as normal then leaving the bind plug in while trying to get the ESC into programming mode - perhaps that's what I did - but that doesn't work because the Rx needs to bind first. If I could identify a procedure which makes this condition happen then I'd be prepared to admit that I made a mistake of some kind, but I can't and that's worrying. It's shaken my confidence a bit, and I'll be ultra cautious from now on. Thanks for all the input........it's probably run its course now. Edited By PB on 19/07/2013 08:51:23

Thanks Steve, I'll look at that. This incident has got me quite worried to be honest because somehow, it seems, I've managed to set two of my ESCs to 'fail dangerous' and I simply have no idea how that could possibly have happened. What procedure did I do to get them in that state? I have no idea. The only time I have switched my Tx on with the throttle stick fully up is when I want to put an ESC into programming mode. That seems to be the industry standard method of entering ESC programming modes. So OK, I've switched the Tx on with the throttle stick fully up and the ESC goes into it's programme mode. Fine, but there's no bind plug in the Rx at the time so how can the Rx pick up that throttle setting and reset the failsafe? It doesn't make sense. It's just a mystery I'm going to have to live with I guess but you're right BEB, I'll never trust a live EP model again after this one.

The Tx is a DX6i. Yes of course you're absolutely right, but that's so unlikely it never even occurred to me. I'm completely mystified. To the best of my knowledge I have never bound any of my EP setups with the throttle stick fully up. I mean to do so is just unthinkable, but it must be the case because I've rebound those two ESCs and they're now OK. I have no idea how that came to be, but it's a lesson learned - at a cost. Thanks for the input.

I've recently had a nasty incident in my garden with a new EP model under test. I had just tested the model with a Wattmeter and tacho and all was well, drawing 36A at full throttle from a 3s 4000 Lipo connected to a new 40A ESC driving a 35-48/55A motor. This set up gave me 7600 rpm with a 12 x 6 prop - perfect - ready for the flying field maiden tomorrow. I then went to carry out my standard disconnect routine. I put the Tx on the ground, still switched on of course, with throttle stick fully down. I went to move to the model to disconnect the battery but I stumbled and my automatic reaction was to put my hand out as I went down. My extended hand hit the Tx and switched it off. Before I could recover my stance the motor in the model powered up to full rpm and the model careered across my garden and smashed into my swing seat trashing one wing. I was shocked and astonished that this new ESC had put the motor on full power on loss of signal. When I recovered my compoure and stopped shaking I carried out some tests of some spare ESCs and motors using a spare Rx. One other ESC also put the motor on full power when I switch off the Tx, but two other ESCs did not. Also, the ESC which put the motor on full power did so whatever the position of the throttle stick, that is, if it was on say half throttle and I switched off the TX this ESC put the motor on full power. The two ESC which didn't put the motor of full power when I switched off simply cut power to the motor if it was running when I switched the Tx off. Now OK, I have never EVER switched off my Tx before disconnecting the battery from my EP models - it's my unfailing disconnect routine to leave the Txd on - so this was something completey new to me. Surely it is dangerous for an ESC to put full power to a motor on loss of signal, so are these two ESC of mine that do so faulty? Thoughs would be greatly appreciated.

I bought the E Flite J3 Piper Cub. This nice little high wing trainer went together well in a few hours and it flies as nicely as expected with a 35-48 motor, Turnigy 3s 3000 Lipo, 40A ESC, 12 x 6 prop and Orange Rx. However, I was surprised to find this loose-leaf notice in the intruction book and I just wonder if there's anything in what it's saying or whethe it's E Flight trying to sell me their receiver battery pack and switch. I'm flying all my EP models using the ESC BEC and I haven't had any trouble with any of them. So what are E flite up to here?

That's inetersting thanks. Yes, I suppose accuracy toleranaces across the various bits of kit in use could account for it, especially the battery checker. I hadn't looked at it in that way though Frank, that if 1.245Ah represents 'about' 50% of the battery capacity then it's 'about' a 2.5Ah battery, but I guess that must be right. Thanks for your thoughts on it......

I put my Watt meter between the battery charger and the battery being charged and it shows me the current flowing into the battery, the battery voltage, the Wattage the battery charger is supplying and the accumulated Ampere hours the charger is replacing in the battery. Ok, so I have a 3s 3000mAh battery which shows 50% on the battery checker and I attach it to the charger via the Watt meter. When the battery charger beeps to tell me that the battery is fully charged I would expect the accumualted Ampere hour reading on the Watt meter to be 1.500Ah which is the 50% of the full charge that needed to be replaced, but it doesn't read that it reads only 1.245Ah. The battery checks 100% charged on the battery checker after charging so where is the missing 0.255Ah? Is it just down to the battery checker and Watmeter accuracy or am I missing something?

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?

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

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

I also have lots of ESCs which auto detect which I've never had a problem with either. But this one doesn't auto detect. I couldn't believe it either, but it doesn't.