Peter Beeney

Jeff, It actually came to light quite easily, I’d reposted in 2016 in Nigel Heather’s thread about the Ruckus. My thinking is that as it’s probably the same motor powering that model it may be of some interest. Not really much detail as how I actually did this, though, I simply cut the holes at the back end by guesswork and fixed the servos in. Soldered the extension leads and made the appropriate fairly solid pushrods. Not too clear there either but I did use a BlueBird on the rudder as well. Playing safe! The rudder did get quite a lot of heavy stick, so to speak… And by way of additional information I would also remove the metal weight in the nose as a first move; I faithfully follow the advice of the gentleman that coined the succinct little adage - ‘For success, add lightness’. All this tinkering moves the CoG back a bit further even, and probably gives the elevator a bit more authority, all good and useful stuff as far as I’m concerned. Re, the theoretical speed figures I don’t know what the actual speed is but it’s certainly quick; relating to that, as I remember it weighed just over 3lb so at 33.3 amps of motive power that equates (I think..) to around 180 watts/lb, fully charged . It does show…… This is the post: I have a ‘hack’ Riot which has flown on 4 cells for quite some time now. It’s certainly been through the wars, so to speak, but still keeps tramping on, actually it’s still rather lively; and it’s also been modified a bit to cope with the extra poke. The motor is ok, but it is fairly basic, it has a plain oilite bronze bush bearing, they are not that easy to repair but I’ve vandalised mine more than once; and oddly enough, I can find every size of bush on the web except that one. Same with the rear end circlip, we have a very friendly motor accessory shop handy and they have every size of E clip bar the Riot motor! There is a compatible ‘Donkey’ motor from HK, exact same fit and very much cheaper; lower kV rating, though, 720 from memory. So a 9 x 7 might be ok here. When I changed to 4 cells I straightaway found the rudder and particularly the elevator were very iffy, so I decided that the push rods were now not up to the job and I moved the servos to the rear end and used short stout metal push rods. Much better, but the elevator could still be a bit reluctant, especially at the end of a flat out power dive very close to the ground. Interesting times! Installing a Blue Bird 380 metal geared fixed it, now total confidence in any situation. The aileron servos have never blinked, though, despite having the max travel available. Like every thing else, they often have to work hard when I go flying, I sometimes tend to get a bit carried away in the heat of the moment… I changed straight to a 9 x 7 ACP i/c prop, this was excellent until the motor started chattering loudly, on landing I found the bearing had knocked itself out and was mostly plastered around the motor on the inside of the fuz in the form of a black gunge. I replaced this with one from a motor with broken lugs, changed to a 9 x 6 ACP and it’s been fine ever since. I’m not too keen on the Century prop driver either, so I changed that too. I tend not to generally consider watts and stuff too much, I just use a tacho and check how hot it’s running. Incidentally, if the motor starts stuttering cut the throttle immediately; the power system is being subjected to a full current flow and could quickly complain by rapidly overheating. The motor is rated at 850 kV and 4 cells fully charged = 16.8V. 850 x 16.8 = 14280 rpm, which is about what I clocked for the no-load rpm. On the 9 x 6 it’s 12000 rpm, which gives a theoretical in the air speed of about 68 mph. The nominal voltage figure of 14.8 gives a speed of about 60 mph. The pack is a 2.2Ah Nano Tech, I fly for around 5 - 6 minutes if using a lot of loud pedal, but there’s always some ampere minutes left. I’d estimate a current flow of around 30 amps, perhaps, everything stays nicely cool even after a lively flight; but there is a good cooling air flow through; very important. The next move might be upping the ante to some Hyperion higher voltage 4 cell packs. A little bit more get up and go and these have a reputation for being able to hold the voltage up under load, too. Hope this useful for anyone who is looking to improve the performance a few shades! Edit. Just for interest, I’ve just checked the current, and with a fully charged pack it’s 33.3 amps. So up to about 560 watts then. Good luck.. PB

Keith, From some previous experience with a number of Riots, (Mk I) and some enthusiastic schoolboys I’d tend to agree with you that your model, as standard, may possibly be lacking in power somewhat. I think that I’d be seriously inclined to start at the beginning and do an unloaded motor revolutions check; if I were using a fully charged 3S in good nick, I’d expect to see around 10,700rpm. I’d be looking for a 10% drop to around 9, 600, your 7,600 figure is very close to 30%. In my opinion the (only) 30 amps of current flow, at these revs that is, does not really tie in with this either so I’d guess a coat of further looking at is required. If you consider 4S then you can get up to almost pylon racer style performance. I did a post on this a while back, I had to mod the ele and rudder servos and pushrods considerably to cope with the faster speed and therefore control surface loadings. I could probably dig it out if you wish… Good luck. PB

Just for interest there was a little quirky feature relating to the Schulze charger that actually proved to be quite useful, but I’m not entirely sure it was actually designed to be so. Whenever I was tinkering with other people’s batteries I alway wore an imaginary cap of Lincoln Green with a large feather in the band, …and probably a pair of green tights and shoes with long toes that curled up at the end to match because I always thought that far too many perfectly sound batteries were unnecessarily being thrown away, more often than not because of the presence of the dreaded black wire corrosion. Serious recycling facilities were still only a twinkle… This was back in the day when you could have your pack in any colour you wanted as long as it was nickel… So the first thing I always did on a checkover was good gaze at the wire connection and I noticed the very first rather inconspicuous indicator that it might be making an appearance was when looking at the plug under a good light the little part of the crimped socket you can see in the plastic plug the pos would appear bright and shiny and the neg would be very dull and faded by comparison. So at that point a quick re-wire with a replacement cable and all would be well again. One day a fellow handed me a Rx pack from his helicopter and asked if I might have a look because he’d noticed that the charger sometimes was reluctant to charge it properly. On examination everything was really bright and shiny and indeed he had remarked that he’d only had it a few months, bought new from LMS. So a discharge to be able to start from scratch, this was perfectly normal, then on charge. After a while I noticed the trace was progressing as it should be, but it was definitely different, slightly fuzzy as opposed to the normal clean line. Now it’s a process of elimination, just a few moments work to slice open the wrapping and a pair of jumper leads with croc clips onto the terminals to bypass the lead. Result - a perfect trace in an instant! So as usual a rewire was all that was needed. I considered this very obscure phenomenon to now be the first indication of the onslaught of the wire corrosion, but I could see nothing wrong with the wire. A cursory resistance check proved inconclusive, but there was no doubt that something was already changing within the conductors. Over the years I can remember at least two other similar cases with the fuzzy trace syndrome. So I’m also convinced that in just about any other situation the pack would have just been thrown out, probably by LMS on an exchange deal. It would have been just accepted as yet another faulty battery. Also I made myself a few flight packs for powered gliders and I used silver loaded solder for this, kidding myself that the slightly better conductivity would give me increased performance. I used this solder on the battery leads too, wondering if this might act as a preventative, but I was never really able to prove it one way or the other. All historical stuff now fortunately. I rarely see any mention of the black wire blues these days. But there again, lithium packs have certainly had their moments, and in many ways, more seriously so. Although with improving safety features on chargers etc., I’m sure this improving. I think I’ll just stick with the LiFe gang for now, the (ancient) lazy man’s power pack…. PB Edited By Peter Beeney on 06/12/2019 19:07:25

Fear not, Keith, I’m not offended in the least and never likely to be. I merely meant that we are always likely to see this in a different light. The simple reason I don’t know why the batteries weren’t charged is just that I didn’t ask the pilots at the time. It was a long time ago and not a very significant incident anyway. Sorry if I gave you the impression that I’ve said that I’ve forgotten to charge my batteries at some point, I did say “could forget’ when perhaps I really meant to say ‘IF I forgot’ to charge, simply just using this as an example. Also I do have some experience with cells as it happens. Perviously I’ve spent many years checking and testing battery packs for members of two busy clubs. I used a Schulze Chamäleon isl 8-936g Charger, this had a large screen on which you would get a perfect display of all the charge/discharge curves. I could take a photo, show the owner and explain any discrepancies. There are a few examples in my photo albums in the White Light folder and one in the Transmitter Battery Discharge. Again this was a long time ago, as I remember the owner had a problem with the low volt alarm coming up soon after he started flying. Pretty obvious when you look at it. I’ve had very little dealings with the plug in load resistor plug in type checker, I’ve had little reason to. And I’ve never seen a situation such as you describe, with folks getting confused with the readings; again I’ve seen very little use of these anyway. I personally have no problems with the onboard type faithfully following the discharge curve, though, and that’s very easy to prove with a volt meter and a variable DC voltage supply. I think I will continue to use such a checker and you will continue to just charge your batteries. Probably the story of aeromodelling clubs all over. Although within our club if anyone now crashes soon after takeoff with a flat battery there may well be some very odd looks thrown at the pilot responsible; …to say the very least… Happy flying…in both disciplines… PB

Keith, I fell that we shall perhaps continue to look in different directions on this particular subject, maybe it’s just like the multiple types of Rx batteries on offer now, which ever one you choose is never really going to make much difference. The simple answer to your question is I’ve no idea why their batteries were flat. A likely cause is that the batteries weren’t charged. It was quite a while back now but in the case of the Pitts as I remember the pilot had bought the model second hand with the checker already installed; it’s possible that he’d not used one before that and so he’d not taken that much notice anyway. However, it did highlight the installation’s shortcomings and it was suggested that the unit be placed in a more prominent position, generally in the line of sight at the front. In the other case the pilot noticed it when assembling the model. My humble opinion about this situation though, is that had both these devices NOT been present at the time then the final outcome, the inevitable and quick demise of the models, could have had a far more serious result! I personally would consider that a big model on full throttle with no radio power is potentially an uncontrolled lethal weapon. The crashed model was actually a near example of this. Had this happened right out in the open country, as they usually do, fortunately, then I’m sure it would have been just one more crash and little or no attention paid to it. The fact that it happened rather closer to home quickly concentrated everyone’s thoughts. The gentleman is a very pleasant guy actually, but he is as he is. Just needs patience and some firm persuasion to mend his ways. Agree entirely with you about the ‘complacency and/or the lack of due diligence’ bit. I’d generally put it under the umbrella of pilot error. But I also have to say that I also could very easily forget to charge my Rx battery too, especially these days. However, I also like to think that when I got to to the patch and the checker, which I couldn’t forget, was indicating something was different this time then I couldn’t ignore it either. It would be my personal safety lock. I reckon a debate about the pros and cons of on load checkers could go on a bit but I can give my opinion if you wish. But the one observation I can make with some certainty is that if I switch my LiFe battery powered model on and the red led is gleaming forth then the battery is close to it’s flat voltage of 5 volts. One exception might be the fact that the checker is faulty but either way I’m most definitely not going flying until I’ve sorted it out. I’d be very interested indeed in any argument that says I should do otherwise. Keep on flyin’ Keith. PB

Keith Miles 2 @ 04/12/2019 15:14:18 Keith, If you do not wish fit an onboard battery checker on your models then I guess that is your personal choice and I certainly wouldn’t have any issues with that at all. All I can say is that I was just offering Richard my advice based on many years of observing modellers together with their sometimes little foibles and misconceptions; and that’s more often than not about things electrical. He most certainly doesn’t have to heed it in any way, shape or form. It’s not a case that that I don’t trust myself particularly, rather more in that anyone else that’s interested can instantly see the state of charge of my battery if they want. But of course if it were not in place or not working then I would certainly miss it. I certainly think that if anyone used one for a while they would not want to be without it. It’s all about safety for me. I know for certain sure that these things have prevented two models taking off with flat batteries. In one case, a large Pitts, the pretty red light was spotted in the cockpit by another pilot casually standing behind the model, the engine was already running. Quite a while back now a large warbird went in at full chat two minutes after take off due to a flat battery, much too close for comfort. Despite being advised to the contrary the pilot had decided an onboard checker was unnecessary. In the event this became a loud wake up call all round and he certainly uses one now. No harm done as it happens but I think we can all make mistakes, especially when we least expect it… Just to be pedantic for a moment, and relating specifically to the 7 led 6.6 volt LiFe checker, I have played about with these quite a bit in the past. At one stage I paralleled 4 together in a Rx and wound the voltage up and down to compare the actual visual difference between leds. There was a very slight variation between greens but all the reds came on simultaneously; that’s as in exactly together. Can’t really get better than that. Also the last one is very bright; it would be difficult not to see it, even from some distance away. You mentioned a Fluke multimeter in another thread; on another occasion to get a really firm grip on the operating range I also used a Fluke to measure accurately the millivolt rises, and falls, between leds. I related all the gory details of this stuff in a post way back in the mists of a time long ago. Just as an aside, my meter, like me, is now very old; and it’s not been calibrated for a while either. but even so I’m happy that it’s sufficient for modelling purposes. Can I also say that I think I would place just as much faith and trust in the monitors as I would in any other piece of model flying equipment. Stay safe… PB Edited By Peter Beeney on 05/12/2019 10:55:13

Perhaps some of the confusion is simply caused by the fact that we are now rather spoilt for choice these days; 4 or 5 cell NiMh or 2 cell LiFe, just take your pick because they will all do the job ok. Even a 2 cell Lipo with a £1 6V 1A voltage regulator soldered into the switch harness works perfectly well, I gave that one a bit of a bashing when lithiums first appeared on the scene; it was simply the fact that the very early batteries themselves were not too reliable, one went open circuit overnight without warning, that was of greater concern and subsequently bought those proceedings to a standstill. A standard trainer model with 4 x 148 servo types controlling it is not going to be very power hungry either, so just about any capacity size will cover it. Good luck with whatever you choose, Richard, the only piece of useful advice I may be able to offer is to invest in the appropriate onboard Rx battery checker at the same time… PB

I’ve never really quite understood the frequent discussions about the voltage difference between a 5 cell NiMh and a 2 cell LiFe when the LiFe is inevitably seen to be the bad guy. The fully charged voltage of a NiMh can be as high as 1.6 volts, thus creating for five cells an 8 volt pack, whereas a fully charged LiFe is unlikely to be any higher than 3.6, thus making a 7.2 volt pack. However these soon settle back to about 1.3V for the NiMh and 3.3V for the LiFe. So that results in 6.5V versus 6.6V, not a lot in it really. For many years I used triple A 800mAh Uniross cells in homemade packs of 5, giving me a nominal and lightweight 6 volts. I never had any problems with these; and the internal resistance must have been sufficiently low too, because the voltage monitor always stayed rock steady in the top green during any multiple servo check. Also I reckon the voltage range of a modern servo labelled 6/4.8V is generally between 4 and 8 volts. If this is not so how have I, and many others also, not had any failures? And all this despite the batteries often being fast charged in a few minutes with an auto charger, usually in the back of the car on the way to the patch… I’m not that convinced by the big packs, either. For me, the old adage, probably coined by an astute modeller when model flying first started, “For success, add lightness”, always springs to mind. There is another reason that likewise is fairly unforgettable but maybe it’s just a one off. Not all modellers are electrically minded, indeed some positively? shudder at the mere mention of an on/off switch and way back in the dark ages one such gentleman had some trouble with his Rx pack which we proved to be shot so he took it along along to our LMS, remember them, for a straight replacement. However, he returned with a much bigger pack, perhaps it was sub C, which they’d manage to convince him was a much better bet. For starters he had some trouble getting it into the fuz. of his trainer, and adding perhaps another 0.5lb in weight as a very dubious bonus. One of the stronger selling points had been, “ You only have to give it a little charge occasionally.” Unfortunately he rather took this suggestion right to the limit and promptly forgot to charge it at all… Ok for a couple of outings I guess and then the inevitable happened… All in all, quite an expensive expensive battery… Halcyon days II PB

My choice would be a simple 2 cell LiFe, usually 700 or 1000 milliamp hour size; and not forgetting the mandatory (for me, anyway) on board Rx battery voltage checker to go with it.These two should be joined at the hip. Personally I think this is a superb piece of safety kit, not only is it very accurate when performing it’s main function of faithfully following the battery voltage, i.e. down among the reds where you really need it but also by default it might also give you first indications of other possible model traps too. If everything is in apple pie order when you constantly stir the sticks, on the ground of course, the second led should stay firmly lit. It’ll be the second led because a LiFe quickly falls a snifter from it’s fully charged voltage; and then just stays there. If the leds run up and down a bit then that may need a quick look, if it keeps hitting the red, as one did that I saw recently, then definitely dive in. That one was the battery plug, but the model was still flying perfectly. Also not forgetting to check the unit itself as well in the event of a mystery, a lesson learnt early in a working life a long time ago. Just for interest, again way back in the days of Futaba M kit, I was tasked with with finding a trainer that could be used constantly all day long. At first I thought that the receiver battery, a 4 cell 500mAh nicad, the one and only standard in those days, would fail so I made sure I had spares and they could be changed easily. In the event the Rx pack ran all day without even blinking but the Tx lump only managed about 3 hours. This was 2 4 cell 500mAh packs in series, hard wired in so they couldn’t be changed and no fast charging either back then; so proceedings then came came to a rather frustrating halt. I solved it by drilling a hole in the plastic side, fitting a jack and wiring it so that I could use a 9.6V 2.5Ah Makita drill battery with the requisite wander lead soldered to it and carried in a little pouch on my belt supplied by ‘er indoors. As it happened this actually worked better than I ever expected, I could just pull the plug for any ground work and plug back in when flying. This was the Master Tx for a buddy system and the first sign that the battery was getting low occurred when the model fell into a tight spin when on the buddy box. All the control surfaces went to the end stops. Full control fortunately came back on releasing the button. Looking back now, was this some result of unexpected consequences, an early form of unintended failsafe perhaps… Halcyon days… PB Edited By Peter Beeney on 02/12/2019 14:41:49

Well there yer go, Caveman, I stand humbly corrected, just shows you how your memory can play tricks - especially when you get old… It was the original colour scheme that reminded me… So slightly larger than the Boomerang then; thus will be similar power requirement methinks. Your choice of a 46 size looks good, at least for proper and sensible flying at any rate; and your conversion of 750W is standing very close indeed to 125/lb; but I’m sure you already know this anyway. For an electric power plant I think I’d may be looking at a nominal 850 - 900W labelled jobby and I also like to spend time finding exactly the right sized prop to suit the installation. One other way that sometimes works of overcoming the ‘prop too long’ problem is to fit a slightly larger nose wheel. Well done on keeping the model flying so long. It must be knocking on a bit by now… Happy landings… PB

Chris, Just to get a general comparison with an i/c engine in the Seagull Boomerang I used one for quite a while with an Irvine 53 up front. I can say, though, this really does amount to plenty of power, there is definitely a little in reserve, …and then a little more after that, too! The Irvine power figures are 1.82PS, that about 1.8 hoss, at 17,000rpm. I reckon that a bit fanciful, there can’t be much of a prop on it at that speed so I’d say a rather more practical performance, from experience, would, on a good day anyway, be around 11,000rpm on a 11 x 7 APC. I’d best guess the output to now be down to around perhaps a conservative 1.3HP. That’s 970 watts on the hoof and if the ’rang weighs in at 6lb that equates to 160W/lb. …which by coincidence also gives it a fag-packet S&L speed of 70mph! So finding a motor that can turn an APC 11 x 7 i/c prop at 11,000rpm might give similar results. I can say, though, that the Irvine will run flat out for 20 minutes on nine ounces of fuel. I did measure and time it. And just dropping in some more useless information, as I related in a thread long ago just to prove a point, this engine ran normally on one occasion on standard fuel with 10% of wet water added. Most of time I was flying the Boomerang I was expecting the wings to fold but they never did. In fact the model handled it all very well indeed for a long time but at this power level I would definitely use a minimum 8 count proper wide 9” lacky band wing fixing. Of course I’m sure it will fly much more sedately, but still perfectly adequately, on much less power if you want. As I remember about flying the occasional Nova back in the day it’s a small lighter model so I’d imagine it wouldn’t need quite such pokey motor. Good luck. PB

Yes indeed, Martin, I certainly take your point. I once tried an APC electric propeller in a test for best performance, the current flow was down, therefore the revs were up so I gave it a test flight. After a short time, seemed like only a minute or so, one blade sheared. Maybe I was perhaps a bit too enthusiastic and the revs were too high but I wouldn’t have thought so. I’ve only ever used APC i/c types ever since. Having said that, the carbon fibre folders we used a good few years back now on the ‘hotliner’ powered gliders of the day were very successful, I don’t ever remember having any problems with those. PB

i12fly, sincerely hope your hand is soon ok again. One other little concern I might have about your OP though is the fact that the prop seemed to break with such relative ease in the first instance. I’d have thought that normally it would take some considerable effort to break a blade off at the boss, although if it were a wooden one that may be a bit different. Indeed you really do have to be careful; there is also yet another way a prop can bite. A modeller decided to run his model at home; the engine being a medium sized four stroke. Like me, he uses exactly the same starting procedure as he does at the field; hopefully this helps to automatically keep his actions the same every time. So the model is in it’s restraint, he’s holding the fuz behind the engine with his left hand and applying the starter with his right. It starts instantly, at a high throttle setting, he instinctively lets go of the fuz and the model moves very sharply backwards with the result that the back of the prop struck his left hand before he had time to move it out of the way. The blow injured his hand to the extent that the ambulance crew decided that rather than take him to a nearby A &E they would take him straight to a specialist hospital equipped for physical types of injuries further away. It’s all healed up now, but he’s left with no sense of feeling in his index finger and thumb; the surgeon told him at the time that some nerves were too badly damaged to repair. His immediate surmisal of the situation was that he’d reversed the starter lead 4mm banana type plug connections into his flight panel; which of course makes perfect sense because of the speed at which the engine started. As always with hindsight it’s easy to say that a polarised connection would have prevented this, but who would have considered it happening in the first instance anyway? Certainly now it’s apparent that it’s another good reason for the more recent technique of having a lipo permanently attached to the starter, though! Hopefully not too far off topic… Take care, PB

When the very first lithium polymer cells appeared on the scene a good few years ago they came as single units in an ali foil case and the two output tags; also fairly low capacity, as I remember. At first we couldn’t even get a charger for them, I used my bench supply and a voltmeter. It immediately occurred to me then that 2 cells in series might be very suitable for use as receiver packs. So I just cobbled a 6V 1A output regulator in the wiring, purposely left hanging free for max cooling, and lobbed it into a plastic drainpipe hack model. About 50 inch span and 5lb weight; Irvine 46 as motive power. 5 Futaba standard servos. After some heavy ground testing I flew it as hard as I could many times - the regulator never ever even got warm! Although in all fairness I have to say this was due to the very low input/output voltage differential, max 8.4 to 6V. Thus at best the reg. would only ever have to dissipate 2.4 watts of heat, (in theory anyway), definitely a not impossible task. However, I did abandon this idea sharpish when one of the cells went open circuit overnight; and indeed there were vague rumours this was happening occasionally at the time. Nowadays though, I’m certain this setup would be absolutely reliable, but I would use LiFe’s anyway now. 6V 1A regulators are as cheap as chips, so to speak, so it’s not an expensive mod to do. Please don’t consider this to be any form of advice or instruction, it’s simply what I found when I was tinkering with it. PB Edited By Peter Beeney on 16/11/2019 23:08:33

andy, Looking at this from a slightly different angle, if I started from the other way round and was changing upwards from a 3S to 4S then with all other things being equal I’d reduce the prop size down a couple of notches to keep the current flow remaining within permissible limits. For instance: a particular motor on 3S and a 12 x 6 windmill performs in an perfectly adequate manner; changing to 4S and a 9 x 7 tug keeps the current flow in the same sort of area but the performance is now being remarked about… Such as “ How do I get some of that?” So all you have to do now is just reverse this; however, the action is bound to slow down somewhat - all other things being equal. I would be inclined to raise the pitch size for starters, this might improve the speed a bit more on 3S. A case of trial and error perhaps - or as in my case, poke and hope… It looks as if the 3S will be lighter than the 4S, every little helps…CoG back a smidgen at the same time - floats my boat! It’s always useful if you have some means of checking the various points of interest, current flow, motor revs etc., too. As you remarked that it fly’s well on half throttle this implies (to me that is) that this is at half battery voltage and half current flow and thus half revs. So maybe a bit more more wellie may be required on 3S but still very flyable. Well worth a try. Good luck. PB

I’ve always tried to figure out this stuff using my own brand of KISS, Keeping It Strictly Simple, so I then have to generally judge these result by what I actually see in the air. I’ve never used a wattmeter but I do have some useful kit, mostly which is now like me, getting very old; although unlike me it still seems to be quite reliable… These are respectively a voltmeter, a clip on power meter and a contact thermometer. Plus a slightly more recent micro tacho. I always check the unloaded speed first, this gives me a true known datum point, the rpm per volt; mostly the figure is as stated but not always, one motor recently in a ARTF with no information printed on it at all, had a kV of 600. The model’s specification sheet gave it as 850. Then bolt on a prop, that might be one that I just think is suitable or perhaps more likely one that’s recommended in the manufacture’s spec., (but it will be an ACP i/c prop), and check the revs again. As a starting point the figure would want to be at least within 20% or better of the unloaded revs. At the same time I’m definitely checking the current flow, and if I’m really pedantic about it the battery voltage as well; but really I’m only concerned about the current, I know roughly what the voltage will be and I’m not particularly interested in the watts anyway. Then maybe some experiments with other props, generally until I get the motor turning as close to the original unloaded revs per minute as practically possible. I’d also want to give it a fairly long flat out run too, and check that nothing is getting overly hot; although the current passing through should now be well within limits; the ESC temp check at around seven eighths/three quarters throttle. Finally an eyeball flying test to see how the model performs compared with what I’m expecting. Of course, much of this is going to depend on the model and how it’s expected to perform, such as the comparison between a Cub and Corsair for instance. But I’m always up for a bit of wellie and I’m sure that a reserve of power is never going to be a bad thing, there must have been times when pilots of both models and full size had been very appreciative of a few extra hosses… Probably a bit of a basic and primitive method by modern standards but I’ve personally never had any problems. And, indeed, because of the increasing popularity of electric models over the last few years I think the electrical knowledge generally gained by aeromodellers has increased by leaps and bounds; which can only ever be a good thing. PB

Chris, I think you’ll find that the Skyleader battery charging system was necessary due to Skyleader’s unique charger. This had a mains input but could also be driven by a 12V DC source as well. 12 volts are not really sufficiently high enough to properly fully charge 2 x 4.8V nickel packs in series so when the Tx switch is OFF the packs are connected in parallel (4.8V each) for charging and when it’s ON the packs are connected in series (9.6V) to provide the requisite volts for operation.. At least I could only ever think this was the reason for using this complicated system anyway. If your Skyleader charger is ok, (please be careful with the first mains power connection!!), then I’d say you should be able to get this all working as per again. The original packs would have been 500 mAh AA sized nicad’s but NiMh’s should slot in nicely as replacements. They will be of higher capacity but you can just adjust the time for a full charge accordingly. Good luck! PB

Looks as though you might need some fair test kit to check this out, Dwain. Although those servos are quite substantial as it happens and at the instant point of startup the motors will be causing a spike, enough to perhaps worry the SBEC. Waggling the sticks, motors constantly starting and stopping, spikes in quick succession perhaps… confused SEC… difficult to tell. Just a thought, if you have an onboard led receiver battery voltage indicator you might try plugging that into the receiver and if that runs up and down and into the red as you waggle the sticks then that surely is indicating a serious voltage drop somewhere; most likely the SBEC. A battery with reasonable capacity of your choice might be the easy answer. Generally speaking I’ve have thought that the servos are unlikely to be as active in the air anyway so I think I’d be happy with that. Good luck. PB

The SBEC is probably not supplying enough current, Dwain, What is it’s current rating? It’s a regulated supply source and when it tries to exceed it’s predetermined current flow cut off level it just shuts down. This is to protect the SBEC rather than the radio. The battery, on the other hand, is an unregulated supply source and is capable of supplying an instantaneous heavy current flow without the voltage dropping too far. That would explain the ability of the battery to drive the servos ok. Not a good idea to use 2 cell lipo to power that flight pack. The servos may be a bit quick for a short while perhaps but then might just come to a permanent standstill! A 2 cell LiFe rx pack would be just the job though, they are used quite a lot nowadays. For the above reasons I’ve always considered the battery to be the best option if possible … PB Edited By Peter Beeney on 30/04/2019 16:39:58 Edited By Peter Beeney on 30/04/2019 16:49:13

I just happened to choose the 2V lead acid cell route for energising glow plugs, simply because in the beginning, circa early nineteen seventies, they were easily available. I simply use a slightly longer supply cable and I’d do this anyway, it’s a very necessary safety point with me so it’s ideal situation. I use an 8Ah Cyclon these days so if for any reason I wanted to reduce the distance from battery to plug I’d probably wrap the cable around the battery and then hold it in place with a turn or two of insulation tape. This little system has always served me very well, to be honest I can’t think that I’ve ever blown a plug but it’s certainly rescued a few fellow aviators with reluctant engines over the years. A long time ago I was wasting time as usual and I collected 5 assorted unknown plugs from the squirrel stock (bits and pieces box) and tested the current flow value of each one. They were all still working, quite remarkable really, and the current requirement varied from 2 and a little bit amps up to 5 as I remember; but certainly they were all different. I have to stay firmly within the KISS (Keep It Strictly Simple) principle otherwise I quickly get somewhat confused… As with just about everything else there are often a number of ways of doing something; driving a glow plug is no exception I guess. Some folks use slightly more involved systems with power panels, ammeters and variable current devices, down to a remote cell and a glow clip or the all-in-one nickel cell and plug clip. All types certainly start the engines ok, although over the years the power panel has been know to occasionally malfunction, to say the least. I’d never bother with an ammeter in this circuit, for one thing it’s just adding a bit more impedance. I would consider the terminals of a battery to be an unregulated supply, depending on the resistance of any component connected to the terminals a given amount of current will flow, if the resistance is very low indeed a large current will flow. If however we connect a voltage regulator across the terminals this device will regulate it’s voltage output to a given value, which is on the spec; it’s also a current regulator, again on the spec. This would then be say 5V at 200mA, 500mA, 1A and so on. If you have a particular piece of equipment you wish to power with a known maximum predicable power requirement you might use one of these. It maintains a constant 5 volt supply until a variable load becomes too great (resistance gets too low) then it just shuts down. But it will reset itself. A constant voltage is used for some situations whereas a constant current is a requirement for others… PB

Another alternative trick might be to use say a 20A diode in a through hole mounting TO- 220 package. If necessary this could then be bolted onto small piece of ali plate for a bit of extra heat sinking although with a max junction temperature of up to around 200 degrees C I think that it’s never really going to get hot enough to be a visible problem anyway. I’d have thought one of these would carry up to say 5 amps ok without getting overly excited and a heatsink just makes it more bulky. A typical forward voltage is 0.84V at 5A; 0.96V at 20A. Probably the most difficult exercise is actually buying a single unit, these types of components usually come in a minimum of 5; ebay may do singles perhaps? But even in a bunch they are not expensive, postage could still be the highest cost. One advantage of having more than one, if the volts drop across one diode was still insufficient it would be a very simple matter to place another in series with it, total drop then about 1.2V, that must surely be enough. One disadvantage of putting a bulb in the line is that when the PSU output lead is not connected to anything, (no load), there is still a standing15 volts at it’s end connection point; therefore when the charger is connected it may well detect this and shutdown before any load can be started to drop the volts; whereas a silicon diode is a constant 0.6V drop or more in all situations. For anyone dabbling in a bit of electric flying I’d have thought that a DMM, (Digital MultiMeter) would be another rather a useful accessory, at least it’s then maybe possible to get some sort of handle as to what is going on when the predicament gets a bit mystifying. Again, doesn’t always need to be very expensive, from £3 upwards and with free postage and nectar points into the bargain… Happy electrickyting… PB

I think I’d be a bit reluctant to try propping, or loading, a motor to run at 50% of it’s unloaded rpm, not least because the performance might be pretty underwhelming; for me anyway. Also I might be a trifle concerned about the wisps of smoke emanating from around the nose area too, it’s most likely the paint blistering on the motor casing. I think I’ll stick to the tried and trusted method of finding the best prop by simple checks before I get airborne and then making any necessary small adjustments after. I aim to get as close to the unloaded revs as possible whilst still having the max performance I’d want to see from that particular model. For me this would still apply to whatever sort of model I’m flying, not making full use of the available energy all the time is perhaps a bit of a waste; and as another forumite recently remarked, “Wasted Watts are akin to carrying a lead weight around for nothing”, …I’d certainly have an affinity with that! In fact, I suspect that motors when correctly propped do run fairly close to their unloaded speed. Depends to some extent on their resistance I think, but if they don’t the current flow might soon become a bit of a torrent… I’m sure the various apps used for calculating prop size etc. are very good; but if some incorrect information is unintentionally fed in then that may change everything. All of our toys are really only consumer items I guess, and as such I suspect the testing and specification labelling might not always quite be up to scratch; but now having said that I still think today’s motors, ESCs and ancillary bits are remarkable examples of engineering. Now all we want is a battery boasting the same exacting standards. Unfortunately I reckon batteries must probably be one of the ultimate consumer items therefore a continuing turnover has to be continually maintained… Just my ancient cynical view again. PB

PeterF @17/02/2019 23:36:01 Peter, Just jumping in here out of interest, can I say that I simply check any rpm figures with a tacho. In the first instance this would be the unloaded speed the motor achieves. This is the starting point; in most cases the figures are fairly accurate, but sometimes they can be a bit adrift. Recently I checked an unlabelled motor, the model’s spec sheet gave it’s kV as 750, whereas the actual revs per volt was 600. Had I not known this it might have caused some head scratching later on. Then checking out the motor’s specification sheet will invariable give me a clue on propeller size, I can then find the exact revolutions at full throttle again. If I compare this figure with the unloaded revs and also knowing the resistance I can make a very rough estimate of the current flow. But as I’m usually not that not sure anyway I simply check using a clip on power meter. I’ve never used any of the online calculators, but I have no problems with these whatsoever. Anything to make life a bit easier. I have to say that I’m not quite sure by the ‘as motor power is proportional to rpm cubed,’ statement. I’ve always though that the the mechanical power is the product of multiplying the rpm by the torque. The torque is at a max at the instant of start up and deceases down to a min at the unloaded revs per minute. Thus the power curve rises to a peak from zero at start up and back down to zero at the unloaded revs. My aim would generally be to get as close to the peak power output as possible. Interesting stuff……maybe… PB

The motor’s kV figure is the unloaded speed at which it turns, Chris, as soon as you load it, put a prop on, it slows down proportionally to match that load; but the current flow also increases proportionally too. That’s what you are seeing. A heavier load, bigger prop, will further decrease the revs and increase the current. I always check the unloaded rpm in the very first instance to get a benchmark starting point, it’s not always what it says on the label, and go from there. All other things being equal, and in little or no wind conditions, your model will fly at around at up to about 40mph. Hope this makes sense… PB Edited By Peter Beeney on 17/02/2019 13:27:59 Edited By Peter Beeney on 17/02/2019 13:30:27

Exactly so David, but my more regular rule of thumb is when I’m getting hot performance combined with expected battery capacity flight times I know I’m on the right track. PB