Here is a list of all the postings Peter Beeney has made in our forums. Click on a thread name to jump to the thread.
|Thread: Servo voltage question|
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.
Edited By Peter Beeney on 16/11/2019 23:08:33
|Thread: Lipo for trainer|
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.
|Thread: Wattmeter Quandry?|
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.
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.
|Thread: Skyleader Clubman Super 35Mhz TX battery wiring|
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.
|Thread: Rx Voltage|
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.
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 …
Edited By Peter Beeney on 30/04/2019 16:39:58
Edited By Peter Beeney on 30/04/2019 16:49:13
|Thread: Variable resistors|
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.
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…
|Thread: How to reduce voltage?|
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…
|Thread: Motor / prop calculator?|
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.
PeterF @17/02/2019 23:36:01
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.
|Thread: Need to Change Kit Specified Prop?|
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…
Edited By Peter Beeney on 17/02/2019 13:27:59
Edited By Peter Beeney on 17/02/2019 13:30:27
|Thread: Are all watts created equal?|
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.
I have to say in general terms that I’ve never really found props to be a big issue. I’ve found that when propping electric motors the secret is to find the right size, too big and the motor is running too slowly, the current flow is increasing, as is the torque, but is unable to maintain the necessary revs. My short answer to me would be to find a more powerful motor; if I needed to actually use to that particular prop, that is.
I’ve also found that checking the revs in the first instance gives a general guide as to the performance; as with i/c. Comparing the prop revs with the unloaded revs will usually give me some idea as to what the current flow is going to be.
I would also agree that the kV is also one very important governing factor. The prop is alway going to turn slower than the unloaded revs per minute. So there is always going to a speed at which the prop, and consequently the aeroplane, can never exceed. Of course this can be altered by changing the applied voltage, more cells, but this will change everything else, too.
My take on this would be that the output power of a motor is that created by the deflecting action of two magnetic fields, an electromagnet and a permanent magnet. This is mechanical power and to be accurately measured would have to be checked on a dynamometer; the amount of turning action in a given time by the prop shaft. The wattmeter measuring the electrical power from the battery is measuring the voltage and the current flow also in a given time. However, in so doing the current flow creates heat and in the case of model aeroplanes heat is something we wish to avoid. The wattmeter is measuring the heat generated; and that’s not always the power at the prop shaft.
In extremis these two measurements can be diametrically opposite.
I’m always a little cautious when comparing input and output power; so I invariably finish up by changing props until I find the best size to suite any particular model.
I’d consider that all watts are equal in the sense that they can easily be converted from one unit name to another, for example, HP to watts; and talking of horse power, when I’ve played around with this it soon seems to be a little bit of a remarkable power unit…
|Thread: Prop size?|
When I checked the motor specs., Simon, it gave a watts figure of up to 580, a continuous current of 35A, max burst of 49A for 10 secs, cells 3 - 4S lipo and recommended props, 2 blade, of 9 x 7.5 - 12 x 7. May I respectfully suggest (in my opinion) that the smaller size, 9 x 7.5, appertains generally to the 4S pack and the 12 x 7 to the 3S.
Hence my confusion…
PS All driven by a 40A ESC…
Edited By Peter Beeney on 12/02/2019 09:06:07
Just having a little ponder on this set up, it all seems to me to be a mite confusing; I think I might want to look carefully at the three blade for a start. I’m sure it must be ok otherwise it would soon be flagged up, but could it be improved?
May I ask, Simon, why you would want to change the propeller in the first instance, please?
|Thread: How hot is hot|
I’m probably being a bit pedantic here, and maybe it really doesn’t matter much anyway, but the power at the prop is not necessarily that as seen as the reading of the watt meter. In fact, it can never be exactly equal, it’s always going to be modicum less, due to amongst other things, the power used overcoming the inertia of the motor; however, reducing the prop size might not always reduce the power/thrust.
There is a rational explanation for this, but one simple short answer might be is to be prepared to try a variety of prop sizes and see which one performs best; changing diameter and pitch, with a combination of both. Keep an eye on the current flow but the faster the prop turns the better, it will be using less amps; and as an added bonus will thus give a little more duration. I invariably use ACP i/c sport props; in general I’ve had better performance from these than the E types…
Hope this is of some use…
Very sorry indeed to read about your Acrowot, I’ve always though it’s bad enough when I plant one due to my own mistake but when it’s due to an unknown factor…
I would very much suspect that changing over completely to FrSky will eliminate this, I’m sure they do occasionally malfunction but there seems to be few reports of this.
Assuming you’ve spun the Acrowot before with no ill effects, then now the common factor must be the transmitter. I suspect you won’t be using this any more so it probably doesn’t matter too much.
Having spent much time over many years in the past tinkering about with model aeroplanes trying to get all things flying to actually fail, and not really having a lot of success, as it happens, I tend to discount much of the obvious stuff in the first instance and try to find something a little more obscure; but at the same time I’d still be thinking that if I do get a glitch and I don’t make every every effort to sort it it will eventually come back to haunt me…
All the very best of luck with the Taranis, a complete tx at a good price, as with all the necessary other bits and pieces to go with it. I’m sure you will enjoy this… …but I like the Horus although I haven’t got one…yet!
Just for interest, for some years we’ve always done a full power range check at 700 metres point to point. I’ve related previously in other posts our procedure on this, but so far we’ve never had a failure. At a push we could probably get another 200 metres but as we consider a normal sized model is disappearing fast anyway at 700m, 2,300ft, it’s seems rather a moot point. This is ground range too, air range is said to increase by up to 10 times.
I believe telephone signal transmitting masts are tested regularly for the transmitted signal strength; this is to make sure it’s none hazardous; that’s for the effect it might have on people. I think this is done quite close to the mast so I would would also tend to discount this as well.
Certainly an excellent test report on the errant ESC, Jon, very thorough and concise indeed! It really does point to this as being the hobgoblin that gave you the grief. I’d say you are not really too much of a stranger to this electrikity stuff in general anyway.
I’d guess that when the throttle stick is it’s top position the speed control pulse width signal is cut off completely. The same may also apply when the cut-off switch is operated. It seems the ESC does’t properly recognise a change from this for some reason; but you did say that it had been ok previously so now the other little factor in play is that you'd reprogrammed it immediately beforehand. So is it worth going back and having another look at this to see if you can spot any abnormalities that have now crept in here. Difficult to think what, but you never know… …otherwise it’s very coincidental again.
Overall though, it might really be a dodgy unit, If it does prove to be hope you can get some compensation. I think if you payed with a credit card that may be one avenue to look at if necessary. It’s certainly been done before.
|Thread: FlyFly DG-1000 set up|
It seems this model has been around for a number of years, and the tip stalling manoeuvre seems to have stayed with it. This from someone who admits to many hours of airtime with one, but that was back in 2009!
His advice to someone else that was in the same quandary…
Rudder throw once again what ever you can get.
Mix rudder with aileron by around 55 to 60 %.
Elevator throw 1/4" up and down even a little less as the elevator is very effective and most the pilots I’ve seen haul back on the stick and the DG will be on its back quicker than you can blink.
Forget spoilerons or flapperons as they only provide aerodynamic tuck of the wing on the DG1000 and don’t slow it down anyway.
The DG1000 likes to fly fast but as long as you have air speed will land pretty easy (fast but pretty easy) long flat approaches work best.
hope that helps.
I take it the T-tail is all moving? I know what he means…
The disastrous tip stalling characteristic definitely seems to remained with the model, many have experienced it, invariably to the left but at least on one occasion to the right.
Another gentleman said this:
I bought this plane, the EP version. It was a beautiful plane. My objective is to make light as possible.
I electrify it with a 3530 1100kv Turnigy and a 3s 2200mah Polyquest. With a 10x6, it draw 20A and gives 250w far enought.
My final flight weight is 1235gr. For this i use 4 four HXT 900, i replace all the servos cover with a piece of covering. i use 2 plastic screws instead of the steel one to attach the elevator, to gain weight. I replace the steel wing rod for a 6mm carbon one.
I put all the weight forward to attain the cg point without a gram of lead.
To increase it flight domain, specially at low speed and delay the tip stall, i put some turbulators at 30% of the wing upper surface and at 50% (on the upper and lower surface) on the elevator.
For the flight, it flies as trainer, fast but very nice. To land the spoileron system is effective.
PS Having looked again after a visit to Specsavers I can see it’s a standard elevator. So I guess it must be quite powerful.
Edited By Peter Beeney on 26/01/2019 16:35:36
Want the latest issue of RCM&E? Use our magazine locator link to find your nearest stockist!