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Prop Size Selection


Kim Taylor
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Hi to all

First post in this section, so be gentle!!

I'm just completing a WOT4 XL converted to electric and would like to ask the advice of the assembled experts on prop sizing.

The motor I am using (EMax GT4020/09 470kV) is rated at 65A and 1440W using a 6S Lipo on a 16x10 prop in their spec sheet. I know that I would be better off with a larger case sized motor, but at the time (and possibly still) everything within my budget was out of stock.

I have test run my setup with a 16x10APC thin electric prop and fully charged it's pulling in excess of 87 amps and producing 1880 watts or so.

It was so far over I didn't hang around to make notes!!

So, I obviously need a lower rated prop, either in diameter, pitch or possibly both. My question - see, I got there in the end - is what do you guys with experience in these matters think. Am I better going down in size or pitch and what's your gut feeling on how much smaller I need to go?

My feeling is that my first move should be to a 16x8 but would like to get somewhere near without having to buy the shops complete stock of props.

Thanks

Kim

 

Edited By Kim Taylor on 06/09/2016 12:34:53

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Hi Kim,
In my experience you would be better off going down in diameter to reduce current draw
to the level required.
If it helps, I ran the Emax 4020-08, the 540kV version of your motor, on a 12x8 at around
950W on a 6s & if I remember correctly, around 1250W on a 13x6.
The bigger prop draws much more current.

Perhaps try a 14" prop on your setup.

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Thanks for your thoughts Richard, interesting to hear your first hand experience.

As this is my first 'real' electric setup (i.e. not one that came out of a box all built up) I haven't got any real 'feel' for whats required.

I was searching my memory from a million years ago, when I used to work with centrifugal pumps. These are governed by the same laws of physics as fans, which I reckon is what a prop is. So I looked up 'Fan Laws' and found the relationship between pressure (thrust) governed by the prop diameter, flow, governed by the pitch, power consumed and rotational speed.

So it would seem that rotational speed and flow are proportional (makes sense), the thrust increases by the square of the change in rotational speed and the power increases by the cube of the same. Which kind of contradicts your real world observations, Richard.

In which case, if I reduce the flow (pitch) to a factor of 0.8, say the power consumed will reduce to a factor of 0.8 cubed, i.e. 0.51 (assuming that the speed (kV) stays the same.

So my 88 ish amps will reduce to 45 or thereabouts - or will it? I have no easy way of measuring the prop speed, but common sense would suggest that the speed will creep up a bit, therefore increasing the power consumed, but will it go above 65A (the flc of my motor). I'll have to experiment and see.

Alternatively, if I reduce the diameter to a factor of 0.94, the power will decrease by a factor of .88 and my amps should reduce to 77amps - not enough.

Another inch down is a factor of 0.88, power factor 0.77 and amps of 68 - close enough to experiment with.

So I'm rushing down the shop to get a 16x8 and a 14x10 and see what happens, and as a curve ball I might see what a 17x8 will do.

Or am I talking complete b..... rubbish?? Anyone care to comment?

Kim

edit - just noticed a flaw in my maths - back later with corrected numbers.

edit 2 - wobble over,  the numbers were correct after all

Edited By Kim Taylor on 06/09/2016 20:51:56

Edited By Kim Taylor on 06/09/2016 20:54:10

Edited By Kim Taylor on 06/09/2016 20:56:00

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I am not very good with the theory behind all this, but I do have the software "Drive Calculator" on my computer. It contains a whole database of E-motor types, unfortunately not the one that you have chosen. But the EMAX GT4030/06 is included, with a kv of 420, which is lower than your 470. I set the voltage to 21.0 V (allowing for some voltage drop under load) and compared 3 APC-E props; a 14x10, a 16x8 and a 17x8.

The results: 14x10 : rpm=7837 I=45.6 A - Pout=734 W

16x8 : rpm=7326 I=60.2 A - Pout=922 W

17x8 : rpm=7154 I=65.3 A - Pout=980 W

Of course your motor runs more than 10% faster, so you will have to compensate for that.

Max.

Edited By Max Z on 06/09/2016 21:20:21

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Posted by Steve Hargreaves - Moderator on 06/09/2016 21:22:10:

I think the key thing is not to get too hung up on the numbers & the calculations.....the theory often doesn't work out in practise. Try a prop & measure the result....then go bigger or smaller until you get the power you want.

I'm sure you're right, so I'll try and get over to my lms today and pick up some sensible alternative sizes.

The trouble (apart from the cost) is that the shop is a two hour round trip once you've found what you want (and often something you didn't even know you needed!!)

Kim

Edited By Kim Taylor on 07/09/2016 08:00:09

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Posted by Steve Hargreaves - Moderator on 06/09/2016 21:22:10:

I think the key thing is not to get too hung up on the numbers & the calculations.....the theory often doesn't work out in practise. Try a prop & measure the result....then go bigger or smaller until you get the power you want.

Very good advice.
Battery age & condition will also be significant - eg. power readings taken using a tired
old LiPo will be less than those using a new battery. 'C' discharge ratings will also
play a part.

 

Edited By Richard Wood on 07/09/2016 09:36:11

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Posted by Andy G. on 07/09/2016 08:08:31:

Prop speed will always be a product of the motor's Kv rating versus applied voltage,

Under no load conditions, yes. But when loaded the rpm drops considerably. Look at my example for the 17x8 prop, the no-load rpm calculates as 420*21=8820, while the loaded rpm drops to 7154, which is almost 20%.

Max.

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Kim.

With the greatest respect of of course, and I’m only trying to be a little helpful here, but I think your possible tiny flaw @20:28:03 is in your statement: ‘but common sense would suggest that the speed will creep up a bit, therefore increasing the power consumed,’. I have to say that I think that if the prop speeds up the current flow will reduce, but the power output, at the motor drive shaft, will stay the same. But because the current flow has reduced the power supply from the battery will decrease by the same amount. It’s all to do with how the motor functions. The short explanation is that the power output from the battery is not always the same as the power output at the prop drive shaft.

I reckon Steve has the best solution, poke and hope until you get the right result.

Playing with Max’s nicely succinct figures for a moment, the 14 x 10 prop will result in a speed of 74mph. The 16 x 8 = 55mph and the 17x 8 equals 54mph. So between the first and second two props we appear to have something like a 26% decrease in speed for a 25% increase in power consumption. I’m not quite sure this is what we really want. This is all up in the air fag packet stuff, so to speak, the motor will unload in the air and reduce the current flow further for a start, but this is mostly the gist of it.

We are operating permanent magnet motors and the torque, current flow and revs are all inexorably linked together, when one changes they all change. If we change the applied voltage or the load value this will also change the running conditions. It also now becomes clear from the figures that as the revs decrease the current flow goes up.

Also it depends to some extent on the flying characteristics of the model, but I’d expect the Wot4 to be fairly agile, thus it would require a good forward speed. I think I’d start with the 14 x 10 and then maybe try a 13 x 10; it’s possible that the increased prop speed may give you around the same sort of urge but with a slightly increased flying time per battery. Or, in other words, the motor is operating more efficiently.

Hope this is of some use…

PB

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Posted by Peter Beeney on 07/09/2016 10:26:50:

It also now becomes clear from the figures that as the revs decrease the current flow goes up.

I think that needs a bit more background information. In my examples (which are all static figures), the revs decrease because the load is increased due to the larger prop, and so the current increases also. When flying, the prop unloads because the relative flow through the prop is reduced since the plane (and thus the prop) itself is moving through the air. And because the load decreases, the current decreases.

I agree with the other posters that selecting the right prop depends on what you hang behind it.

Max.

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Yes, very sorry about that Max, it just seemed rather obvious to me at the time that a larger prop would naturally be an increased load. I think that perhaps what I was trying to say, too, was that a bigger prop, or a heavier load, was not always necessarily the best way to go. Perhaps another way of phrasing it would be to say that the current flow is exactly proportional to the revs per minute; if the rpm’s are reduced by increasing the load the current flow will rise by the exact same proportional amount.

I did mention the prop unloading in the air as well, but I guess that unless you have a telemetry function this is going to be a bit of an unknown quantity; also there could be some prop slip to take into account as well, although this might rather affect the model’s airspeed. My post was overall just a general guesstimate anyway; no more than my own view and might not always be that accurate; but as Steve says, ‘.....the theory often doesn't work out in practise.’

I also referred briefly to the flying characteristics of the model, but coupled to that possibly the pilot may also want the model to fly in a certain manner or style too. So if the motor was excessively loaded to enable it to fly very slowly say, then some duration of flight time might have to be sacrificed.

PB

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Thanks to everyone for adding their thoughts to the discussion.

I didn't get time to get over to the model shop today, so still no further forward in my particular quest.

Am I wrong in thinking that a pop's efficiency decreases as the pitch and diameter get close together e.g. a 12x10 will, by definition, be less efficient than a 14x8. I understand that you may prefer the characteristics of the 12x10 but you take a hit on efficiency and therefore duration.

For my application, I am using the WOT4 XL as a second stage aeroplane and therefore don't want to tear up the sky, but do want enough thrust to get me out of trouble if (when) I find myself a bit low and slow. I'm led to believe that the speed envelope of this airframe is very wide and I am willing to trade off speed against thrust, knowing that it won't drop out of the sky in the lower speed ranges.

I am therefore keen to stay with a 15" or 16" diameter to hopefully achieve this and once I get a chance to try some alternatives, I'll know where I'm going (I think).

Peter, I think I know what you're getting at, but I'm pretty sure that if you reduce the prop speed by half, you'll reduce the absorbed power by much much more. Unfortunately I've got no means of checking revs, so I can't give any figures to back this up, perhaps someone could tell me if half throttle is (approximately) half revs on an esc?

KIm

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Kim,

I’m sure it's quite in order to use any prop you choose, but it might be a plan to stay within the specifications……as per your OP. Actually, there would appear to be something of a little anomaly in there, too, why the significant discrepancy when using the recommended size propeller? I think that warrants a second coat of looking at; although a 16 x 10 does seem to me to be a trifle on the tall side anyway for that motor anyway, it would definitely not be my choice to start with.

The max watts at 1440 equates to around 1.9 BHP, roughly the same as a 60 i/c engine. The engine develops this power, at the crankshaft, on a 11 x 7 or 12 x 6 prop at maybe 12000rpm plus. It really does seem to be asking a bit much for an electric motor to do the same on a 16 x 10…

I’ve always thought that prop efficiency is generally fairly linear across the range, but it does improve as they get bigger up toward full size, I believe, and dropping off very rapidly as they get very small. Certainly, though, if any inefficiency results in a greater current flow the duration may suffer.

You may well be right regarding the prop power and speed, but in my view the correlation between the power output at the prop shaft and the wattmeter measuring the battery output is not always that straightforward; so it may be difficult to gauge. To reduce the speed the ESC reduces the voltage, therefore if half throttle equates to half revs on your ESC, which is highly likely, then that’s half voltage, equivalent to a 3S pack. As it so happens, here the power output would be reduced by a factor of four, if, say, on 6S the current flow was 50 amps and the voltage 20 volts then 50 x 20 = 1000 watts. At half speed the current flow would be 25 amps and the voltage 10 volts, 25 x 10 = 250 watts, thus the power is reduced to one quarter.

I’ve never owned a wattmeter; in the past I used a clamp meter and a contact thermometer plus a tachometer, but nowadays I seem to getaway ok with just using the tacho. I can estimate from the difference in revs how a particular model is going to perform on any one particular prop, and as I’m invariably going for the fastest turning prop anyway it soon becomes a one prop choice; and if using the same set up on a different model I’d know which prop to use from experience.

As always, just my view…

PB

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Posted by Peter Beeney on 09/09/2016 11:01:02:

Kim,

I’m sure it's quite in order to use any prop you choose, but it might be a plan to stay within the specifications……as per your OP. Actually, there would appear to be something of a little anomaly in there, too, why the significant discrepancy when using the recommended size propeller? I think that warrants a second coat of looking at; although a 16 x 10 does seem to me to be a trifle on the tall side anyway for that motor anyway, it would definitely not be my choice to start with.

The max watts at 1440 equates to around 1.9 BHP, roughly the same as a 60 i/c engine. The engine develops this power, at the crankshaft, on a 11 x 7 or 12 x 6 prop at maybe 12000rpm plus. It really does seem to be asking a bit much for an electric motor to do the same on a 16 x 10…

I’ve always thought that prop efficiency is generally fairly linear across the range, but it does improve as they get bigger up toward full size, I believe, and dropping off very rapidly as they get very small. Certainly, though, if any inefficiency results in a greater current flow the duration may suffer.

You may well be right regarding the prop power and speed, but in my view the correlation between the power output at the prop shaft and the wattmeter measuring the battery output is not always that straightforward; so it may be difficult to gauge. To reduce the speed the ESC reduces the voltage, therefore if half throttle equates to half revs on your ESC, which is highly likely, then that’s half voltage, equivalent to a 3S pack. As it so happens, here the power output would be reduced by a factor of four, if, say, on 6S the current flow was 50 amps and the voltage 20 volts then 50 x 20 = 1000 watts. At half speed the current flow would be 25 amps and the voltage 10 volts, 25 x 10 = 250 watts, thus the power is reduced to one quarter.

I’ve never owned a wattmeter; in the past I used a clamp meter and a contact thermometer plus a tachometer, but nowadays I seem to getaway ok with just using the tacho. I can estimate from the difference in revs how a particular model is going to perform on any one particular prop, and as I’m invariably going for the fastest turning prop anyway it soon becomes a one prop choice; and if using the same set up on a different model I’d know which prop to use from experience.

As always, just my view…

PB

All good points.

As far as manufacturers recommendation, The 16x10 was for a 6S pack. The speed at 470kV is likely to be considerably less than your typical 2stroke motor, I seem to remember the spec rpm was around 7000 fully loaded on a 6S, although that in itself suggests that the motor is well and truly 'loaded up' on this prop.

I've briefly run it with a 16x8 and the amps are down to around 70, although I haven't had time to do a proper run yet. I've also got a 15x8 and a 15x10 to try. I'm thinking that one of these will do the job, but need the time to test them back to back. I'm going on holiday for a week from today, so nothings going to get done 'till I get back.

All of my readings are, of course, on the input side of the esc. My (vague) recollection of ac inverter drives was that any meaningful measurement of current, voltage had to be done on the input side, as the frequency 'chopping' caused all kinds of transient spikes on the output - may be different on these simple dc devices though.

I really must invest in a tacho, if only for my own curiosity I'd like to know what rpm I'm actually getting. My mk.1 ear device is telling me that the speed on the 16x8 is quite a bit higher than on the x10, but that's understandable I guess. I used to have a nice mechanical chronometric tacho, but somewhere along the way I've misplaced it. It was just as accurate as an electronic one, and the batteries never wore out!

And I agree that experience is the best tool in the box when it comes to some things.

Kim

Edited By Kim Taylor on 11/09/2016 17:20:13

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Posted by Kim Taylor on 11/09/2016 17:18:34:may be different on these simple dc devices though.

Simple devices they are not, in fact they are dc/ac converters. They have to be to create the rotating field that gets your brushless motor going, and to keep it going as triggered by the rotating magnets and the coils in the stator. Admittedly, this happens at the relatively low frequency of the rotational speed. The actual power control is done by chopping the current (Pulse Width Modulation or PWT) at a much higher frequency. So each pulse at say 100 Hz required to activate a group of coils in your stator is subdivided into a lot of smaller pulses for which the on/off ratio is controlled as a function of the setting of your throttle stick.

So yes, you should measure your current at the input to the esc where the adverse effect of this pulse-melange is less.

Max.

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Kim, I have a very similar set up and I'm running a 14x7 - getting 1400W off a 6s 3000mAh. Seems a good combination and flys well with decent duration.

BTW - in my view its a biy dodgy to compare prop-sizes off IC and electric which have similar power outputs. The torque characteristics of the two power sources are so different.

BEB

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Posted by Max Z on 06/09/2016 21:18:28:

I am not very good with the theory behind all this, but I do have the software "Drive Calculator" on my computer. It contains a whole database of E-motor types, unfortunately not the one that you have chosen. But the EMAX GT4030/06 is included, with a kv of 420, which is lower than your 470. I set the voltage to 21.0 V (allowing for some voltage drop under load) and compared 3 APC-E props; a 14x10, a 16x8 and a 17x8.

The results: 14x10 : rpm=7837 I=45.6 A - Pout=734 W

16x8 : rpm=7326 I=60.2 A - Pout=922 W

17x8 : rpm=7154 I=65.3 A - Pout=980 W

Of course your motor runs more than 10% faster, so you will have to compensate for that.

Max.

Edited By Max Z on 06/09/2016 21:20:21

That's very useful for me, Max, because I have exactly that motor to fit in my quarter scale Mew Gull and it's unrun so far. I have a heavy Master Airscrew Classic16x6 in my collection I intend to try just to see where I am and what I need for the test flight (still a good few months away).

On the box it suggests props from 16x10 to 18x10 but the data on the web is more in line with your figures and a 16x8 draws 60 amps and 8100 rpm on a 6S LiPo. I'll see, but motor performance/prop size/current draw information seems to be very unreliable for most (all?) manufacturers and only actual testing and measurement by the user (ie us) gives accurate, usable results.

I think some testing of a representative selection of motors would make a useful magazine article. After all liquid fuelled engines get proper testing in the mag so why not electric motors? Until then we rely on trial and intelligent guesswork based on past experience.

Geoff

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  • 3 weeks later...

Just to 'put this to bed', I have just had time to run a couple of different sized props, with results as follows:

Using a freshly charged 6s LiPo in each case, on the previously tested 16x8, 86A , 1840w. 21.5v

Then fitted a 15x8 and recharged the battery and got 70A, 1550w, 22.1v.

All of the above are measured between LiPo and esc.

Unfortunately, still no means of checking revs.

I think what this is telling me is

1) The manufacturers recommended 16x10 on a 6s isn't just inaccurate, it's totally wrong!!angry 2

2) As I'm propping down, the motor is unloading and speeding up, so the current when measured static isn't dropping as fast as I'd hoped. (As previously stated, I can't measure the revs, but subjectively, the sound is a higher pitch, suggesting more revs).

From here, I've decided to use the 15x8 initially, based on the assumption that it'll unload a little in the air. Also, I've noted that coming only two 'clicks' back from W.O.T. reduces the current draw to 45A. If I get the magic smoke so be it, at least I'll know not to push things so far in the future!!crying 2

Test flight as soon as the weather breaks and the wind drops on a day when I'm not working and my instructor is available - should be about a week next Michaelmas.angry

Kim

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As you've found, manufacturer's figures are often way off.
Often wonder how accurate the Wattmeters we use are though...
Sounds like the motor is at its max rating with the 15x8 but you won't 
be using full throttle all the time.

Good luck when you get it flying - any pics of your Wot4 XL e-conversion?

 

Edited By Richard Wood on 27/09/2016 16:35:58

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Hi Richard,

Yes, the accuracy of the wattmeter is obviously an unknown - hey ho we'll find out in due course.dont know

I've put a bit of a write up and some pictures in cymaz' Wot4xl thread (link below)

**LINK**

This is my first attempt at either an electric conversion or power system selection, so I'm bound to have made mistakes along the way. Those noisy, smelly glow things I used when I last flew 30 or so years ago didn't give me these headaches - well only when they refused to run!!

Kim

 

 

Edited By Kim Taylor on 27/09/2016 16:58:37

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Kim,

With respect and for what it’s worth, I try to separate the watts into the ESC from the watts actually turning the propeller, in my opinion at least they can sometimes be two different things; and again, as said before, I tend to use the tacho in the first instance, as far as I’m concerned it’s a bit essential.

As an example I can quote a really well worn Riot which runs on 4 cells. The standard model runs on 3 cells using a supplied 12 x 6 black plastic prop. I lobbed in a 4S and experimented with smaller props, it now runs on a 9 x 6 APC i/c prop. The increased performance instantly rendered the ele and rudder control snakes useless, they started giving way under pressure so I moved the servos to the rear and used short heavy duty pushrods. Even then the ele plastic servo gears still didn’t appreciate the overtime rates and decided to pack it all in so I changed to a 17g BlueBird metal geared worker bee and this did the trick. Although I’ve just recently had to repair this too, I noticed the top half of the case had cracked right down where the drive shaft protrudes through. I’m quite happy to accept all this stuff, however, because I do consider that my flying style does get a bit eccentric at times, to say the very least!

The motor is a 850kV, on 16.8 volts that’s theoretically around 14.280 rpm, and when I first checked it was very close to the 850 figure; I use a 12V car batt as a testing power source, very stable and doesn’t sag at all under load. I always do that first for a reliable benchmark. The 9 x 6 yields 12,000 static on the lipo, that’s an implied speed of 68 mph, which I should think from visual observation is somewhere near the mark. In a flat out power dive, with the prop fully unloaded, it may be somewhat faster, even. Checking the current flow to be about around 32 amps and guessing the voltage to be around 14 I make that about 450 watts so I consider that’s not bad, but to it’s advantage the Riot is quite a relatively light model.

As it happens, remarkably the smaller aileron servos have been faultless through all of this.

12k is about 84% of 14k and I wouldn’t want to reduce the revs any further because I believe that the current flow would rise but the performance would fall; i.e. the watts output at the prop shaft are becoming less, but the watts input into the ESC are rising….

With regard to the 16 x 10 prop, this immediately seems to be too big just by Mk 1 eyeball standards. Roughly equating the rated electric motor’s 1440 watts to an i/c engine, around 1.8 HP, such as an OS 90 Surpass ll perhaps, at a complete guess the prop size would be around 14 x 7 to 15 x 6 at around 9k rpm, say. So I’m not sure the electric motor would ever turn a 16 x 10 successfully.

Tachometer here.

Good luck.

PB

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Posted by Peter Beeney on 27/09/2016 22:06:22:

Kim,

With respect and for what it’s worth, I try to separate the watts into the ESC from the watts actually turning the propeller, in my opinion at least they can sometimes be two different things; and again, as said before, I tend to use the tacho in the first instance, as far as I’m concerned it’s a bit essential................

 

..................12k is about 84% of 14k and I wouldn’t want to reduce the revs any further because I believe that the current flow would rise but the performance would fall; i.e. the watts output at the prop shaft are becoming less, but the watts input into the ESC are rising….

With regard to the 16 x 10 prop, this immediately seems to be too big just by Mk 1 eyeball standards. Roughly equating the rated electric motor’s 1440 watts to an i/c engine, around 1.8 HP, such as an OS 90 Surpass ll perhaps, at a complete guess the prop size would be around 14 x 7 to 15 x 6 at around 9k rpm, say. So I’m not sure the electric motor would ever turn a 16 x 10 successfully.

Tachometer here.

Good luck.

PB

Hi Peter,

Yes, even without any other factors interfering, input watts x motor efficiency = output (shaft) watts. If the load we apply to the shaft is greater than the rating of the motor, the speed will drop off rapidly and the amps will rise even more rapidly as the windings become saturated, until either the esc or the motor (or both) burn out.

I've noted that my figures are incomplete without rpm's, so next time I'm ordering from H-K I'll get the one you've linked to. I have looked at it in the past but I was hoping to find my old mechanical tacho which I must have lost when my garage was demolished by a storm about 10 years ago. I think that I will then confirm my gut feeling that the 'smaller' props are allowing the motor to run much closer to its design speed - i.e. the 16x10 was overloading the motor as described above.

With hindsight, it is now obvious that the 16x10 was too much prop, but it was (is) what the manufacturer recommends - now we know different. However we are always told by those who know much more than I do that we can't compare props between i/c and electric motors due to their differing torque characteristics, so in my naivety and inexperience assumed that they knew what they (the manufacturers) were talking about - lesson learned there then!!

The proof of the pudding will be in the eating, as they say, so I'm going to try the 15x8 and probably get a 14x10 and compare the flight performance and duration between these two props before deciding what's the best way forward for my particular 'plane. The availability of props in these sizes is a bit of a pain though, massive jumps between sizes don't help when you're trying to optimise the setup.

Kim

Edited By Kim Taylor on 27/09/2016 23:38:37

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  • 1 month later...
Posted by Kim Taylor on 27/09/2016 16:07:08:

From here, I've decided to use the 15x8 initially, based on the assumption that it'll unload a little in the air. Also, I've noted that coming only two 'clicks' back from W.O.T. reduces the current draw to 45A. If I get the magic smoke so be it, at least I'll know not to push things so far in the future!!crying 2

Test flight as soon as the weather breaks and the wind drops on a day when I'm not working and my instructor is available - should be about a week next Michaelmas.angry

Kim

Just to round this thread off, the long awaited maiden flight took place last weekend.

As I said above, I used the 15x8, hoping that it would unload in flight.

The first flight was 5 minutes, flight performance was fine and the flight consisted of me stooging around trying to get a feel for the aeroplane. After landing, the battery (6s 5800Ah Zippy) was found to still have 75% remaining, and the motor, esc and battery were just warm to the touch.thumbs up

Second flight was 8 minutes duration and was a slightly more spirited affair during which the vertical performance was tested and found to be more than adequate, on a fresh battery at least. At the end of the flight there was just under 50% remaining and again, everything was nicely warm.smile d

On this basis, I reckon my target of 10 minutes of general flying is easily achievable and safe with this setup, so I see no reason to change it.

Further flights were prevented by an issue with my charger, now sorted ready for this weekend hopefully.

Kim

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