Peter Beeney

Mike, Thanks for your answer but after some considerable tinkering with this stuff quite a while back I found there was little or no evidence to suggest any real issues, at least as far as I was concerned. For instance, in practise I found it actually quite difficult to charge a 4 cell nickel battery at all with a 5V regulator, as soon as the pack is at the 5 volt level (quite quickly) everything stops. The regulator is current limited and thermal protected too; I consider the thermal switch might just be the ‘destructive little gremlin’ I previously mentioned; it protects the regulator just fine but can easily destroy your model in the process! Previously the fact that I was using a battery/BEC combo for rx power saved my bacon on two occasions. Flying a ‘hot-liner’ powered glider the motor battery went open circuit, most likely due to over exuberant use of the throttle stick. I was still able to land safely but without the receiver battery this would have been a missile with no means of control, something that I personally believe to be a very dangerous (and often unnecessary!) situation. It also allowed me to do all pre-flight checks before connecting the motor battery in relative tranquility; a 16 x 13 carbon folder turning at around 10k is definitely more than just a bit intimidating when close up; I treated it with more care than I would a demented chainsaw on steroids! Yet another extremely worthwhile safety point in my opinion; taking off with the ailerons reversed is still a trick that can occasionally be observed. Of course, it would still be possible to do all this stuff with the pos. wire disconnected and no motor battery, this is just another case for having a separate rx battery supply I take the point about the switching regulator but I’ve not used one so far I know, I’ll see if I can find one to play with. With regard to inadvertently opening the throttle, for many years now I’ve assigned a transmitter switch to prevent the throttle opening. I call it ‘throttle lock’. Also helps considerably with the intimidation bit. It would also prevent an inadvertent start up relating to the BEC running the motor too. I’ve found that if I always work to a set procedure when flying it does help to prevent mistakes because actions tend to become automatic but I’d also admit that I can go well off the track on occasions. I have proved that more than once!! Nothing is ever guaranteed but I do try to take every precaution. So in my semi-conscious risk assessment mode I’ve still decided that the parallel BEC/battery set up is perhaps just the lesser of two evils, as they say. Regards. PB

As a small aside to the main question within this thread, I notice there is still a continued reference to it being of some importance to disconnect the red wire in the throttle cable from the ESC when also connecting a battery in parallel to the receiver. I think this also sometimes applies when paralleling two ESCs together. Solely in my opinion this is a bit of a wrinkled old conker that’s been knocked about a bit over many threads in the past and has taken a few hits but as far as I know has never been mortally wounded; or even particularly scratched when push comes to shove. My thinking is that this actually doesn’t matter either way, really, the ESC will function perfectly ok with the wire connected or disconnected; the internal operating conditions do change though, but that is all unseen of course. In fact it may well be that there is some sort of argument for saying that adding a battery is the answer to a problem, as in Joe’s case. He disconnected the red wire perhaps but it would not have mattered had he not done so; in my view this is rather an infrequent and unusual and situation, though, I’ve never seen this happen, and I’d be endeavouring to find the root cause in the first instance; this could perhaps be a type of fault which might eventually become a disaster… And it not be the first time that’s it’s happened, either. Long ago I related a story of how disconnecting such a battery ultimately resulted in a total matchwood type crash; and to initially confuse the issue even more so the radio was working perfectly afterwards; and that destructive little gremlin has also appeared out of the blue on more than one or three occasions in the past, too… Just an individual preference, I guess, in such circumstances I would want to keep the positive supply connected but others may well decide to remove it; and in 999 cases of a 1000 it’s always going to go entirely unnoticed either way… This is all definitely just my own personal viewpoint and not in any way meant as any form of instruction or advice etc. PB

Joe With hindsight I now think it might have been rather more straightforward (and easier!) to do a spot of backtracking and then simply ask - ‘Did you by chance happen to use the same ESC?’ If not it then seems to me it’s beginning to stretch a coincidence a little bit more than somewhat… See here PB

Joe This sounds to me as though this may possibly be an electrical supply problem from the BEC. Assuming that in the first instance you are using the BEC supply via the throttle control cable, (normal practise), when you move the servos a resulting volt drop - for whatever reason - is seen at the receiver causing the throttle channel to mis-operate and momentarily fire up the motor. If this is so it might be a fairly serious condition and perhaps needs a spot of looking at. Connecting a battery to the rx then immediately provides a robust parallel supply which won’t be affected by the sudden current pulses caused by the servo motors starting up when you operate the sticks. Thus the rx supply voltage remains stable throughout and ensures the throttle doesn’t operate. On the other hand it might also be the case that these same pulses are causing the voltage regulator (BEC) itself on the ESC to fluctuate and so affecting the components on the ESC. Connecting a battery would have the same effect as before; it would keep the voltage constant. But this is pretty unlikely I’d have thought however, that might point to the regulator being seriously under-spec. BECs are usually at least 2 - 3 amps output these days. If you don’t have any test equipment, voltmeter etc., then one answer maybe is to simply leave the flight battery connected anyway… Good luck. PB

Gary, My take on both the timing aspect and the frequency of brushless motors is that as far as aeromodellers are concerned they are both relatively unimportant; it’s perhaps only when you are looking for the optimum performance that adjusting the timing can make the difference. However, as with just about everything else in life, it has to be at least a small compromise, so some care is needed, altering the one condition may result in other unwanted effects. As you say, you can change the ESC setting to suit but I think it’s most unlikely you will be able to change the frequency. Indeed, I’m not sure that you would ever want to change it. 5 degrees of timing is low, is your motor a low pole count high kV lump? Some ESCs have an auto timing setting, this may give you the best all round performance; no harm in trying. I suspect the 8KHz frequency figure may suggest that this is the lowest to use, or perhaps it’s to do with the resonant frequency of the motor; either way I’m sure I wouldn’t be poggering over this too much. A name/description for the combo would be very useful… The frequency is always in the background, this is the speed at which the Pulse Width Modulation, (PWM), signal is being generated within the ESC to regulate the voltage, (and thus the speed), being applied to the motor. This switches the current on and off in a series of equal length pluses, with the on/off time variable in each pulse.This pulse train can tend to raise the temperature on the ESC, though. When the motor is on full chat it’s getting all the available battery voltage so there is no modulating signal present. These oscillators are usually graded in steps of 2KHz; 4KHz; 8KHz; 16KHz and so on; 16KHz is a popular ESC figure but your’s may well be an exception to the rule. But again, all this is of little consequence anyway… Hope this is of some use and as stated, these are just my own views and ideas, they may not all be correct so I will apologise for any mistakes made in advance. PB

It’s always seemed to me that whilst great acclaim is made for all these aeroplanes, and rightly so of course, occasionally there maybe some scope for giving rather more credit to the men whose ideas led to these aeroplanes in the first instance. Clever men with long range forward vision. The Mosquito was a good case in question; Geoffrey de Havilland and his team designed it and Wilfrid Freeman ensured that ultimately it was built and went into service. Although this did require some considerable tenacity to achieve on their part however, because reading between the lines of many of the wartime history chronicles there was much infighting at times between various departments and personalities. Nothing changes much, even in wartime. To start with Geoffrey de Havilland had to fund it himself as a PV (Private Venture) right up until the first orders were placed. Wilfrid Freeman also had enough faith in the project to ignore orders from Lord Beaverbrook to cease work on the development of the Mosquito at least three times; it also seems as though some others weren’t convinced either; indeed, for a while the embryo plane was known as Freeman’s Folly… However, once they started flying in earnest they soon proved their worth. For at least the first eighteen months they were the fastest planes in the air; at least until the later variants of the Focke Wulf 190 began to play catch-up. They went on to prove that they could deliver bombs at very long range with pin point accuracy for the lowest loss rate in Bomber Command. They’ve also been credited with being the most successful photo reconnaissance vehicle ever. And that’s from more than one source, I believe. I remember reading somewhere too, a little story about Geoffrey de Havilland in the early days visiting an American Airbase to give a ‘spirited demonstration!’ in a Mossie. Unfortunately the article didn’t describe too many of the manoeuvres that he performed but it did mention vertical upward rolls from ground level on one engine… Doubtful if there’s any film record, and perhaps even the Yanks were rendered speechless for a while… Maybe Bob Hoover was watching… Today’s H&S inspectors would still be having nightmares… Much later on a 12 foot long 57mm 25 round rapid fire Molins cannon was slotted into a few Mossies and used as submarine hunters in the Bay of Biscay; which they did with great aplomb… So from starting with no armament at all right up to becoming a flying howitzer and all the time performing as a high performance bomber and aerial camera cab in between… An extremely efficient and versatile aeroplane if ever there was one! Sir Geoffrey de Havilland and Air Chief Marshall Sir Wilfrid Freeman were both giants in their own fields. The author Anthony Furse describes Wilfrid Freeman as The Genius behind Allied Survival and Air Supremacy, 1939 to 1945; …and that all sounds about right to me. Wilfrid Freeman had an interest in the development of the Merlin but the Mustang was also one of his favourites. He submitted the original spec. to North American Aviation, fortunately the president there, one J. H. ‘Dutch’ Kindelberger, also had his eye on the situation in Europe and could see what was happening; he’d had already done some ground work in anticipation and thus was able to get a prototype ready quite quickly; more forward vision again. The first Mustangs arrived at Liverpool in November 1941 and one soon found it’s way to Duxford where Wing Commander Ian Campbell-Orde, CO Air Fighting Development Unit (AFDU) immediately rang Ronald Harker giving him an opportunity to come and fly it. Ronnie Harker was a Rolls-Royce service liaison pilot at the RR Experimental Flight Test Establishment at Hucknall, he flew as a test pilot in an evaluation and troubleshooting capacity, particular on the Merlin engined planes, but with a sideline in flying all their competitors and other brands that he could get his hands on as well, including enemy types if they became available. Mr Harker was suitably impressed with the Mustang, in his subsequent report he included the paragraph - ‘The point which strikes me is that with a good and powerful engine like the Merlin 61, it’s performance should be outstanding, as it is 35 m.p.h. faster than the Spitfire V at roughly the same power.’ This quickly went up the line to reach the ear of Wilfrid Freeman and thus the rest, as they say, is history. The Mustang was originally designated the NA-73, the Americans went on to name it the Apache but the RAF decided it was a thoroughbred Mustang; the Americans then fell into line with this. I’ve no evidence of course, but I’ve always liked to have had a little suspicion that Air Chief Marshall Sir Wilfrid Rhodes Freeman, 1st Baronet, GCB, DSO, MC, FRAeS might just have had a small input in this minor but very appropriate detail too… PB

Apologies if slightly off topic There is also the ‘semi-legitimate’ type of scam which can can exist without you actually being fully aware of it it. It seems money can extracted from your bank account without necessarily your having given your full approval……or even any conscious approval at all! Some years ago quite fortuitously I noticed a withdrawal of £15 from my account; it just happened to be the last entry on a mini-statement. I couldn’t remember doing this this and it started to irritate me so fortunately I went in a bit deeper. The online statement just showed it as being identified only by a long string of digits, when I googled that it was just a single web page which I didn’t recognise at all. Looking back at the statements it was there on the previous one again but no others. I took it to our local bank, a small rural branch because they are very helpful indeed, the young lady said “ That certainly looks suspicious”, she picked up a phone, dialled a number and said “ Have a word with the bank’s fraud squad”. The gentleman I spoke to was not quite so accommodating, he just said it wasn’t fraud because it was a legitimate company. I asked what it was about and it was apparently an outfit which gave out information, email or hard copy, about ‘monthly best buy’ bargains of all sorts of items, in the nature of the monthly mag ‘Which’, perhaps. The first three months were free and after that, if you didn’t cancel, you just continued to pay the £15 monthly subscription ad-infinitum. I stated that I’d never signed up for this and I’d certainly never received any such information. I also very much wanted to know how they’d managed to set up the direct debit without my knowledge or permission. His rely was a trifle less than reassuring: “Oh, there are various ways, but you probably bought something online and didn’t un-tick a box as an option at the checkout! All quite legal!” So I presume this must have been in the very small print somewhere. He did particularly name one country wide store, the one were you write numbers on a slip of paper and the goods follow back over the counter a few minutes later. He then gave me a number to ring to cancel and get a refund, He said if that didn’t happen to get back to him. I did this, spoke a very foreign gentleman who did the necessary after a short halfhearted discussion not to leave. The £30 was back in straightaway. After some more Google time I found this was very widespread malaise indeed, worldwide in fact. Mine was one of least worse cases, I remember one American victim said that he and his wife had a very busy joint account and this mob had been lifting $10 a month for nothing for several years before they latched on. He didn’t say if he’d got his money back, though. I also noticed that the same country wide retail store got the occasional mention as well. I very much suspect this ‘approved fraud’ is still in existence. If it weren’t untouchable I’d have thought it would have been shut down; and perhaps it might be off shore too, that might make all the difference. I wonder just how many people have one of these everlasting hidden money sinks without realising it… I have read that the perfect con is the one that you don’t know is happening; sounds about right; I guess I got lucky at the time. But even now I still pay fairly close attention to the mini-statement… and all the small print... Yo’ll be careful out there now… PB

Exactly so, Mike, but I’m still a little sceptical in parts. Multiplying the amps by the generated voltage to get the output power is surely just measuring the heat generated again, not the mechanical turning force? This may well be ok when the input and output power ratings are as close together as they are going to get, but not so accurate when they are far apart. Your 9V example in the last paragraph, as apposed to the previous 10V, would appear to show the way this is developing. You have the ability to do the calculations so you would be well aware of whats what but I might simply look at the 387 watts displayed on my watt meter and think what a nice powerful motor I’ve got; this is exactly the reason why I’m saying I would be a bit cautious when comparing figures. Also the sentence: ‘The motor is also measured to by running at 10,000 rpm,’ does that imply you’ve also clocked the rpm with a tachometer? If so, how often is this action quoted, recommended or even mentioned? I seem to have missed it. As it happens, a tacho is always right on the top tray of my toolbox together with a new CR 2025 cell, it’s bound to go flat just when I need it…I’ve found with a bit of practise this can give me a great deal of information. Frank, I think I would like to try out the bits and pieces listed in Mike Downs’s OP on the bench for myself. For instance, what (low) cell count pack would I be using to keep the amps at 50 or below on a 12 x 8 prop? Also what are the revs, this is where I start, it will give me a good indication how the model will fly amongst other things. Mike B mentioned his ‘good’ 12 volt battery, (able to sustain 12v under that sort of load!), I use a fully charged 12V car battery for bench testing motors, now that is a nice stable supply! If I had a model that required a larger slower propeller I’d want to obtain an appropriate motor that still allows me to use it at it’s optimum revolutions point. Nigel, I’m not sure a propeller is any sort of dynamometer at all, but with a bit of trial and error, or as in my case, poke and hope, it will give you a fairish visual indication of how well or not your model will perform. At the end of the day I probably don’t really need to know very much information at all, I can just tinker until I get it right. But a dynamo. will give me the point on the revolutions curve where it’s at it’s most powerful straightaway. Interestingly, I believe that model aero engines were once tested with a propeller. They needed to know the torque so that together with the rpm they could calculate the horsepower. In the first instance they bolted the engine on a torque beam which was variably weighted at one end and pivoted against the opposite torque of the propeller thrust; but there were some anomalies arising due to the prop wash etc. so they found the the dynamometer a better instrument to use. And somewhere in the distant memory banks I’m sure I’ve seen a picture of an early full size aero engine up to the same sort of caper… I simply said that I would be a bit cautious when directly comparing the output power of the battery with the output power of the motor; and also including i/c. That’s not to say you shouldn’t do it though, in fact I tend to subconsciously compare electric motors with i/c all the time, I suppose because I’ve used glow engines for so long I’ve a pretty good idea how they are going to perform. Again fine if the the electric set up is spot on but again if the watt meter gives an erroneously high reading it might be a tad misleading. However, I’m sure that as folks are using e.p. more and more the increasing knowledge and experience will lead to less confusion. I actually think the modern DC brushless motor is a real cracking lump of engineering. With it’s design features and some help from components like neodymium magnets and the very essential but equally as impressive Electronic Switching Commutator it’s a real little powerhouse; and I have noted at the patch that some are still running faultlessly after very much use, too, so in some cases at least their longevity would appear not to be questionable either. More power to your (electric) prop… PB

I think I would always be a bit cautious when it comes to directly comparing the output power of the battery with the output power of the motor; or indeed the output power of an i.c. engine, too. To my mind we are measuring two different types of movement here. I’ve probably got all this wrong again, I usually seem so to do, but as I see it the battery power measurement is electrical whilst the motor power measurement is a mechanical one. They are always going to equal each other in total, but the two different effects are not always what we really want. Generally speaking,* when a current passes through a conductor it has to overcome the resistance, an action which produces heat, and it at the same time it creates a magnetic field surrounding the conductor. Again, rightly or wrongly, I figure that the magnetic field comes for free; the cost, in our case here anyway, is that it always requires it’s accompanying current and that in turn is causing heat which we don’t want, at least in this case. The circular motion of our permanent magnet DC brushless motor relies solely on the reaction, or rather a deflecting action, of two magnetic fields, one established by the flow of current. The mechanical movement, or power, of the prop shaft is derived by multiplying the torque by the rpm and here we seem to be measuring the strength of the inter-action between the magnetic fields; to get an accurate measurement of the power we would need a dynamometer to read the torque and rpm to calculate the power; whereas placing a watt meter between the battery and ESC measures the amps and volts to give the watts. Unfortunately this is just measuring the heat generated, rather than the turning motion! To illustrate this let’s consider two points on the motor’s power curve. At the instant of start up the motor is stationary therefore the current flow will be at a maximum. If we were able to read our meters in slow motion the watt meter would read max amps, therefore max watts input (all heating effect) but although the dynamometer would read max torque there are no revolutions which equals zero power output; but of course this situation doesn’t last very long; the motor very quickly starts to turn, the current flow diminishes and the speed and current flow equalise at whatever values they ultimately reach. Right at the other end of the curve let’s consider the motor in a stalled state after running. Exactly the same situation, max watt meter reading into the ESC and motor windings but no power indicated by the dynamometer, again because there are no rpm’s. As before we are just seeing the heating effect, this time possibly indicated by the distress signals given by the power train in the form of an arising column of white smoke or worse. In my view these are the two extreme points and somewhere in between there is one point where the motor will run at it’s ‘best case’ compromise speed, where the two measurements are closest together. I suspect, in very general terms, this is most likely to be not too far away from the unloaded speed, but there are many different cases. For me this is an indicator of the importance of the resistance, or rather lack of it, of the total power train. Looking at a fictitious case of 3 circuits, with 3 different total resistances but the same 10 amps flowing in each, a) 1ohm, b) 0.1ohm and c) 0.01ohm; Then in circuit a) there would be 100 watts dissipated as heat, circuit b) 10W dissipated and circuit c) 1W. All hypothetical of course, to maintain 100 amps three different voltages would have to be applied, from a) 10V, b) 1V and down to c) 0.1V. But the magnetic field strength would be the same in each case so the mechanical power output would not change. I’d judge the quality a power train by the value of it’s (low) resistance and by the same token I’d always try and keep the rpm as high as possible, within the required performance envelope of course. * When some conductors are ‘super cooled’, that’s frozen down to near absolute zero, they tend to lose their resistance. In this state a vast amount of electricity could flow unimpeded, there is no heat generated by this but a very strong magnetic field could be created. This can be used to an advantage, indeed I believe I’ve read somewhere that the Large Hadron Collider at Cern uses super cooled electro magnets in the particle accelerator. I know nothing about it, though, does it also make it cheap(er)? to run, too? But I reckon one prevailing caveat at least must be the fountain-like eye watering cost of maintaining the low low low temperature… Just my idea on the subject and of course it does not take into consideration the other principles that enable the motor to function…and no assurances that any of this is correct, either… PB

Sam, Just a thought but usually solenoids have a mechanism to return the plunger to the off position when it’s not operated, very often a spring loaded arrangement. The version you are using would appear not to have this facility and because it’s a ‘pull in for on’ type I think it’s already in it’s operated state; and from the spec. it’s now held in this position by a permanent magnet which is cancelled by a reversed current pulse which reverses the magnetic circuit and just releases the plunger. Unfortunately, though, it doesn’t move the plunger to it’s extended open ‘off’ position, so perhaps if you lightly pull on the plunger whilst momentary giving it a short reversed current pulse you might find it will slide out. All a bit of guesswork and speculation here on my part but I’m sure you won’t do any harm by trying… if it works come back here and you might be able to use gangster’s M.O. with the servo; but with apologies to him, in a slightly different configuration. Good luck… PB

Yes indeed, Bruce, I do have to hold my hands again up to this one. Certainly had I picked up a lipo pack and taken just a glance it would have straighten out my thinking; …and I had one just a few metres away… In this case I’d merely transposed the cell one slot along the 2S balance plug, so the charger would have probably read the balance lead as a 2 cell pack with one cell missing and would not have started charging anyway. I put it down to an advanced OAP condition with a memory state that needs a spot of re-formatting… A very long time ago, back in a distant working life, I spent a great deal of time swanning around with a small bunch of other reprobates. I very quickly learnt that if you made the correct comment about a particular perplexing situation no one said anything very much at all; but if you got it a bit wrong the sky would instantly fall in… so it was a case of doing the proof reading first and making sure the homework was always up to speed. Unfortunately in this balance plug case I forgot about my own memo! But others have also made small mistakes, too, on one space mission to Mars I believe, one half of the team used the yard as a yardstick whilst the other half used the metre as a yardstick for their landing instructions! Later on one very confused capsule! And wasn’t the Hubble Space Telescope also launched with a bit of a fuzzy lens which later had to be rectified… There have been common positive connection systems in use, cars in a bygone age had 6 volt batteries with a positive earth/chassis connection. I can remember seeing those. Also some industrial systems using large storage batteries used a common/earth positive connection, the battery voltage thus always being considered negative with respect to earth. This meant some care had to be taken when connecting equipment designed for the standard industrial common neg connection, but with practise you do get use to sorting it out. Particularly so when using mains driven test or other ancillary kit, if not double insulated it would have a green/yellow safety earth which is commonly joined up with just about everything else. This could lead to some very odd looking conditions, we always got out of it by disconnecting the earth wire and anything else that prevented the circuits from being fully isolated from each other; something I guess would not fit very well, if at all, with today’s H&S lot, but this was a fair time ago. I think I really must try and get out a bit more to the patch for some model flying and spend less poking about at these computer keys; then that would leave me less scope for thinking errors and more time for proof reading. But it’s jolly nice to know that someone out there is always getting it right, all of the time… PB Edited By Peter Beeney on 05/02/2017 15:45:57

Yes indeed, humble apologies here to Dick, he’s absolutely right, of course. I didn’t verify this to start with and I’d assumed that the battery started from the positive end when in effect it starts from the negative end. I should have looked before I spoke, it would have only taken a moment, my memory is definitely now showing it’s age... Sorry again, I’ll just keep quiet on such matters… PB

Yes, I afraid I wasn’t absolutely clear on this, either. With the greatest respect to Dick, I would place the red pos balance wire from your 1 cell in the first positive end of your balance plug (whether 2, 3 or 4 cell is unimportant) and the black neg next to it. The black wire acts only as the neg for a one cell, but both neg and pos for a two cell; in this case it would usually be a different colour. You need to tell the charger it’s only a single cell; and any other connection position will simply tell it little porkies… But in the unlikely event that you do get wrong it will just say mute anyway. It has to be connected correctly to start up. Which of course does complicate the issue if you are trying to make the charger start if a battery only gets slightly out of it’s normal operating limits… PB

Jonathan, it very much seems to me that the charger won’t fire up until it sees a voltage on the balance port, but I’d suspect that any number from 1 to 4 will be ok. This is to absolutely ensure the charger has automatically set the right number of cells, because you are unable to do this manually. So what I would do is to make up a intermediate connector in the main lead with a ‘balance’ pair attached to the main neg and pos and then using a redundant 2s (three pin) balance lead but leaving off the black neg at the end. In fact such a lead would be ideal as the 2 wires into the connector to save a little bit of knitting. If you are a bit adept at tinkering with these little bits and pieces just bodge up a temporary lead to give it a quick whizz; and then when it works ok (I’m convinced!) you can make it a bit more permanent. Not much of a plan to try and kid the balance port that it has 2 fictitious cells connected, I’d say that it’s very highly unlikely to accept this anyway but if it did it might give your cell a bit of a headache, to say the very least… The balance port is the only way the charger knows what is connected to it… Good luck! PB

Belated post 1 edit. No such thing as a PPM/PCM receiver, it’s just one or the other; in this case PCM… I should proof read my own ramblings better! Sorry for any confusion… PB

Post 2 Regarding the aerial blanking and poor installation stories, I’ve again spent considerable time trying to actually create such a kettle of fish for real but I’ve never managed it yet; but I suppose I could now say I’ve just been unlucky in this respect. I’ve also related in a thread before the story of our stringent full range test (long!) including attempts at interference and aerial orientation. This again has been a total success every time, and that also includes a DX5e with it’s AR500 rx. So I just continue to fly on rewardless regardless… When I did a low voltage test on the AR500 receiver on two separate occasions I found it went down to 2.7 volts before it locked out; but at this point the servos were also seriously complaining of the cold too, so I arranged to keep them up to 5 volts and just reduced the receiver. Exactly the same result. Oddly enough, when I’d previously done a similar check on a 35 meg set, at the time I was interested in range distance combined with low voltage, I found the receiver still had range at 2.9 volts but ceased working completely at 2.8 volts; so in this case anyway a fail at 0.1V higher than the 2.4! We live and learn… PB

Post 1 I think I’ve always considered the term ‘failsafe’ in this context to be a bit of a misnomer anyway, any self respecting failsafe system will automatically go to a preset safe condition in the event of anything in the system failing; and how often can the user ‘adjust’ or perhaps better ‘tamper with’ the various ‘fail’ settings as a matter of course? Using a lift in a building as an example, I suspect that if the power fails when in use there is more than one condition applied which ensures that the lift car stops and remains at a standstill; and no one can interfere with this state, either. If the power fails on a model aircraft the control conditions will stay as they are, it will instantly be totally out out of control and if it just should happen to be a 10lb warbird with a 120 FS going at full chat and it impacts close enough to the pits such some debris finally finishes up there it certainly grabs everyone’s attention a bit smartish… I know this from experience…. All the way through my model flying times and tribulations I’ve never seen a case of genuine outside interference, but I’ve seen a fair few number of power failures, that situation may be (hopefully) improving now, but it still occasionally happens. A long while ago there was a very serious incident which led to quite a lot of comments and instructions, much of which related to failsafes, at the time this was the latest radio development. We didn’t fully understand much of this because some of it appeared to be contradictory or even impossible to implement anyway. So we decided to do our own experiments and try and decide exactly what the real live effects would be in the field. As it happens, I’d bought a fun fly model second hand with a Futaba PPM/PCM receiver all ready on board, and I also had a FF7 PPM/PCM tx, which I often used as a buddy. I spent time kicking this around until I was conversant with the PCM failsafe procedures and we then tried it with the model up in the air using a second tx on the same frequency. It was a bit windy that day, but with practise I eventually found I could tolerate the interfering signal for up to a few minutes at the time, from well up wind to well down wind although it was always going to finally come down, fortunately it was never ever going to get very far away. We even switched on a second tx at one point, also on the same channel, but that made not an iota of difference. However this little episode did inspire one of my long time friends and inspired modeller that was involved to drily remark “PCM radio sure don’t behave like wot it’s supposed to”. We never did pursue this any further, though, because it seemed a bit pointless. Every case of interference would be different. I did discover one interesting little snippet on the way though. In the beginning, whilst I was tinkering with this on the ground, sometimes the settings would function ok and occasionally they wouldn’t. At first I thought it was a fault but on really getting into the system I found it was a natural quirk of the FF7 tx/rx. The servo positions were set by holding the sticks in the required positions like as now, this memory was stored in the tx and the info. was sent to the rx as a short pulse, once on switch on and thereafter about every minute. When the combo was switched off and then switched back on again the rx had no settings until it received the first pulse. Usually this was ok, but if I switched the tx on first, (as normal) and then slightly delayed the rx turn on it was possible it had no settings for up to a minute… Which is exactly what my problem was… I considered that this might not be too much of a problem with ic models, from tx on to take off is invariably greater than a minute I would think; but an electric hot liner which is carried to the strip the battery connect up there and launch can be quite swift. So in theory I thought it was possible here to have a short period of flight with no failsafe settings. In those days the PCM radio sent the last good signal to the servo…and the ESC…so full throttle with no control… I never saw this flagged up or even mentioned anywhere so I don’t think this was ever common knowledge and I’m sure this was all very insignificant at the time anyway, but my personal point is - If there is ever a serious incident for which there appears to be no explanation, could it be down to some arcane and mysterious set of circumstances of which no one is aware, such as this one? And if this situation did happen I suspect it never would be investigated, either…

Tom, If I remember correctly the Fox plugs that I favoured way back were 1.5V, I still used the 2 volt cell though, I just adjusted the length of the lead until they were nice and hot! I think most of todays plugs most be about 2V, I’ve never had any problems with them, at least not as far as the power supply being too fierce. My cell in those days was exactly as onetenor says, a small 2V wet lead acid… I’ve done a fair bit of tinkering with plugs in the past anyway, such as checking power consumption etc. and in general they are quite hardy creatures, although they do tend to rather take the hump a bit when my colleague has plugged his glow lead into the 12 volt starter outlet on the power panel. I’ve suggested that he should change the connectors on the leads in order to polarise them but so far there’s been little progress. There might just be a tiny point here. When I attach my glow lead to a loose plug the only form of heat sinking the element has is the body of the plug; and if this is left connected and lit up for a fair period of time it can all get finger blistering hot. But when it’s screwed into the cylinder head that must act like an efficient heat sink, at least under cold starting conditions. So I’m wondering if this might make any difference to the brightness of the glow. When the supply cell is in good nick I suspect most likely not, but when the voltage is beginning to sag a bit and the element is only just about a weak glimmer anyway… The next time I’ve taken a cyl. head off for any reason I’ll do a bit of tinkering with this theory and see if I can establish exactly what, or if indeed anything, does occur. Certainly a soaking with raw cold wet fuel will dampen things down a bit, too, but fortunately electrical principles being what they are, the element’s resistance now goes down and the current flow therefore goes up and thus quickly brings the element back to all it’s illuminated glory… indeed, I’d now consider the same thing probably applies with the plug normally installed, the heat sinking effect just flattens the glow battery a bit quicker… As I remember too, the first new glow motor I owned was a Veco 19, circa 1959/60, this had a throttle coupled to an exhaust baffle which moved across the open exhaust port as the throttle arm moved. No silencers back then! This covered the port when the throttle was shut, I believe in an effort to try and make the slow running more reliable. This was for R/C use. This also had a 1.5V plug too, because I can remember having to buy one of the large 1.5 volt dry cells of the times; I think those batteries were also used for powering radio sets. PB

One trick that’s been tried many times when winding up a reluctant motor is to just place a finger momentarily over the silencer outlet to increase the tank pressure and force more fuel into the spray bar; however, this needs plenty of caution at the same time because it could result in the crankcase quickly becoming over flooded; generally it’s a very brief affair, say for only up to a second, at least initially; an overly flooded crankcase and a energetic starter motor might not really be the ideal combination with which to start the day… Having now said all that, this simple little strategy more often than not results in an instantly reassuring burbling exhaust… I like to see a nice bright glowing orange plug, I’ve always thought this does help with starting so I’ve always used a 2V lead acid cell as the power driver. For some time now my source has been an 8Ah Cyclon cell, this is very portable but it will maintain it’s 2V output for a long time and in dire conditions. Mine is often borrowed to help out when items such as power panels are suffering from voltage drop and other ailments, particularly in the winter. Which bring me to the next point, I always tend to try to impress on beginners the importance of keeping all their batteries fully charged, especially during the cold weather because this will soon expose the laggards; it’s very discouraging to spend a long time trying to start an engine and then finding the plug is rather dimmer than yesteryears proverbial Toc H lamp… …and I suspect that it helps to be of a certain advanced age to fully appreciate that remark, too… I’ve found that a short time spent giving the engine a little bit of help in the starting blocks usually pays dividends, then it mostly becomes a first or second flick jobby.. but there are exceptions, such as the Moki, (a few posts above). One or two modellers I’ve noticed seem to be quite content to just connect the glow and then continue to crank it on the starter until it eventually fires…or doesn’t… This is a bit too much like hard work for me… In a case like David’s I think I’d be tempted to concoct a little priming bottle with an extra dollop of castor oil added. This might at least help the piston seal when it’s cold and consequently the compression and the induction; and if it doesn’t do the trick there is no harm done, either. I’ve not used castor fuel for years but I always have a small bottle handy because I add a modicum to the first tank when running in; but even then that’s only really for a bit of insurance perhaps… PB

David, Once upon a time I flew a Chippahawk with a Moki 61 two stroke up front. This was a super engine, very much suited to the equally super Skyways model. The only problem with it was that through the autumn and winter months it simply just would not start under any circumstances. I tried every trick that I knew, including priming with a drop of Keil Kraft diesel fuel but always to no avail; the best it would ever do was an infrequent pop in the silencer. I soon concluded that there was little wrong with it because it normally ran so well; and having read the stories about the difficulties starting full size in the extreme cold and also previously watched my colleagues starting their diesel lorries early in the morning in the depths of winter during the late fifties and early sixties, they would get the gas blow torch going and warm the inlet manifold up I eventually had a rethink. Part of my work kit was a small Primus gas bottle/torch so as a very last ditch attempt I lit this up and warmed the very reluctant beast up. Lo and behold, one flick and it was away!! So this instantly became the order of the day and it was always a total success, I soon discovered that a few moments concentrating on the crankcase was sufficient, I could only surmise that it possibly helped any neat fuel to vaporise sufficiently to get that first firing stoke in. In those days I was a member of a popular busy club so you can imagine the ribald and fairly derogatory type of remarks that frequently accompanied this procedure; but I usually got my own back because it always started straight away… I even got proficient in doing ‘hot’ refuels, i.e. without stopping the engine; although I have to say this was probably just really just a bit of unnecessary bravado… Whether this was a one-off Moki or whether they are all the same I do not know… The model met it’s end in a midair with a small biplane on it’s maiden flight. His prop cut right though one wing near the root and it crashed heavily on a tarmac runway which broke just about everything. The runway was fairly big, but when you consider it as a percentage of all the surrounding acres and acres of grassland… Typically his model was undamaged which was at least one consolation and as with the other two midairs I’ve had there were only two of us on site at the time. Like many other modellers I’ve owned a number of Irvines over the years, from the first 0.40 with the Dykes ring, but from memory they’ve never been significantly difficult to start… Hope you manage to fix it without any more delay… PB

Peter, Just to jump in here for a moment, don’t worry, the parallel charge rate is always fully self controlling, it’s all to do with the voltage. In your example, charging all these packs at 7.2 amps, (that’s the 1 hour rate, or 1C), will allow the 2,3000 mAh packs to charge at 2.3 amps each and the 1.3 mAh at 1.3 amps each. This is because when packs are connected in a parallel configuration all the batteries must remain at the same voltage, it’s impossible for it to be otherwise. I just bung my exhausted packs of different capacities but all the same cell count on a multiple parallel board, set a fairly low charging rate and leave them on overnight in the back of the car; not to be recommended though, this is definitely not advice to do this I hasten to add, but I’ve personally never had any difficulty charging batteries and I personally don’t have any particular worries with lithium batteries either. If I did I wouldn’t use them anyway. I’ve done this for many many years now and it’s always worked well for me. Exactly the same situation applies during discharge too, if a 20A and a 1A battery were connected in parallel and then set to discharge the same voltage must appear across both right throughout the total time, whether that time be fast or slow. Or, of course, any number of packs in parallel… Hope this is of some help… PB

Daniel, Firstly many apologies for a lengthy and rather dusty chronicle here………. Regarding your thoughts on what to do regarding your power train for the Edge 540, with the greatest respect I think if it were me in the same circumstances I’d abandon this one for now and maybe replace it with a known and proven combination; something using a 3S battery might be nice and simple, I’m sure there are plenty of examples around. You’ll probably have time to do this as well, when you join your local club for some training it can take a while to really get going; and you’ll undoubtably see some models with similar power requirements that work properly… I’m sure you’ll find most folk are very willing to help… I do have to admit that this one is a little confusing. The designer seems have taken a specific quad motor and married it to a Castle Creations heli ESC; and although you’ve changed this for yet another dedicated heli type I’m sure these will operate together ok but it might unduly complicate matters. The motor is interesting, I’ve only checked the HobbyKing site but even here it has some slightly conflicting info. The general overview gives the power as 1000W @ 18.5V, (5S) and 800W @ 14.8V (4S); however, the specification panel tells a slightly different story, it gives the power as 555 watts with the max current being 30A and the max voltage being 19V. Significantly the overview gives the cell count as only 4 - 5S Lipoly, not 6S, - the spec’s max 19 volt level also limits the count to 5S. So it would seem that a 6S battery is definitely in unknown territory here… I’ve said for many years that aeromodellers can sometimes be rather good at taking a piece of equipment and straightaway trying to make it do something it’s not designed to do… Let’s just use the overview quote above for guidance as an example, say. 1000W @ 18.5V, and 800W @ 14.8V; dividing the volts into the watts gives a a max current flow of 54A; that’s a little bit removed from the spec. max current of 30A, and also this 30A figure divided into the 555 watts of power here very neatly gives us 18.5V, the nominal voltage of a 5S Lipoly! 6S takes us over the top and connecting a fully charged pack at 25.2V, (as you may well have unknowingly done!), takes us up to 6.2 volts over limit. Not the best of ideas, perhaps, it’s advisable if you are getting into this sort of caper you really really need to know exactly what is going on. So it would seem on the face of it someone seems to have generated some rather conflicting info and you only followed the instructions?. I’d have thought this to be a very unusual line of thinking, particularly when there are many power trains around that are far more appropriate. Having said all the above though, maybe I’m still not totally convinced. I’ve always been a bit of a poke ’n’ hope sort of a bloke and I’ve often deliberately tried to get various items to malfunction but with very little success. Of course if you cross battery leads or some such the effect is entirely predicable, (and visible!) but I’m simply talking about standard setting up procedures etc. So it’s difficult to understand quite why your motor failed in the way that it did. Certainly I’d say to be most unlikely to be an error on your part, this stuff should be bullet proof. Did your motor attempt to move at all? Was it in fact free to turn? Did you hear any beeps? Once you have the motor connected and if it doesn’t start and run up to speed when you expect it to, it’s very important to disconnect it instantly because if the ESC has for whatever reason fired up maximum current will be flowing into the motor; and you may not realise this until it sends out extreme distress signals; as you’ve now already noted. Incidentally, the beeps are always from the motor, not the ESC as is sometimes thought. As I see it, the ESC sends a quick squirt of audio range AC to the motor coils, this acts in the permanent magnet field to vibrate the magnets and motor can to create the beeping sound. Maybe a bit like a very primitive speaker cone. I’d say that if the beeps are correct all is well with the windings in the very first instance, I’d have thought any shorts for instance would result in very weak or no beeps. The substitution method is a very quick and convenient way of isolating faults, but of course you do need some spares kicking around. But this does come over time. I think that’s more than enough for now, all good luck with your adventures at the model club… PB

Touché, Ron, but I really wouldn’t want to be winding you up, either… PB

Elastic? PB

Thank you for your very kind thoughts and considerations, Ray, but perusing this from my usual sort of upside down/sideways angle I feel that my ‘permeance’ regarding my ‘conductance’ may well be of an adequate sufficiency… However, I do agree that my ‘susceptance’ is now certainly showing signs of flagging (as it often does nowadays!) but fortunately the hour is fast approaching when I’ll have some pleasure in taking a small ‘measure’ to ‘rectify’ that situation… I’ve now read the link at last and I’m rather of the same opinion as yourself regarding the amount of information; but by the same token I’d tend to think that some areas at least are worthy of some sensible discussion, if only to make a token point; but nevertheless motors will continue to turn props and models will continue to fly regardless… PB