How powerful is it?

[Ernie]

Hi guys

 

I have sitting in front of me, my new Ray 3542/06 electric motor , along wth it's ESC and a ray li poly battery,  labelled 25C..2200mAh...3s/11.1V (why is it so complex?)

Can someone tell me what IC engine is it's equivalent? so that I can plan project 2

 

ernie 

 

 

[ken anderson.]

ernie-i'm going to stick my neck out and be the 1st to say=to a 15...20 ic...

 

 ken anderson.....=after timbo's crown---never......

[Pete B]

Hi Ernie,

I'm far from being an expert - that's why we need Timbo but if your motor, which I can't find on the net, has similar specs to this one then I suspect it is nearer a 30 size equivalent. What's the kv - 900-1000 ish? Seems 500-600 watts is the possible output.

Doing a search on the net, it seems that this size motor is popular for 2m-ish powered scale sailplanes, like the CMPro Ventus, and it's being run with 12 - 13 x 6 props, so it's definitely more than a 15-20 (sorry, Ken)

When are you going to let us know what project 2 is?

 

I'll get me coat...............

Pete

[Tim Mackey]

Its 1000 Kv and around 550 Watts. I do not like to try to give "IC equivalents" as it ddoesnt work as simply as that - it depends on too many variables such as which nbattery and what prop you use. All I would say is that if you use the 3s pack, on a 12" prop expect about 30A current draw, so therefore about 300 Watts.

I would say thats more like a decent .20 - .25 Ic engine. For more power, either go to 4s battery, or larger prop ( but then lower revs )

[PatMc]

Electric motors are so flexible in how they can be used that there is no way to directly compare them with ic. And if you think about it how some ic engines of the same capacity are no where near equivalents either.

 

What's the weight , max current & kV of your motor.

 

Actually the power you have available is governed more by the battery than the motor.

E-gliders apart, I usually consider the sensible max current draw from a lipo to be around 12-10C because that gives a theoretical 5-6 minutes at  full power & doesn't distress the battery. In practice this equates to flight times in excess of 8 to 10 minutes & batteries with a decent lifespan.

 

If you were to load your 2200mAH 3s battery at 12C you could expect a realistic average of 25A @ 10V which is 250Watts.

But 746 Watts = 1 HP so you have 250/746 HP = .33HP.

This is about the attainable power of an average 15 - 20 ic engine but note it's the input power to the electric motor & shaft output power of the ic engine. However depending on it's kV the electric motor might be swinging a prop that's much more efficient because it's both larger diameter & has thinner blades. So the true equivalent power might be nearer to a 25 or even 30.

 

IMO matching an electric motor to a model is much easier & less complex than matching an ic engine to a model.

[Peter Beeney]

    May I just to throw another couple of questions into the debate, is it worth considering this from the commercial view point? I’ve had very little experience of industrial motors but I very much suspect they come with a plate on stating the input power as the motor voltage and the full load current, and the the output (shaft) power stated in watts or HP.
The output is always going to be less than the input, and the indicators are pretty unambiguous. Also, I don’t know this, but I suspect this is part of commercial law.
    However, if we buy a domestic vacuum cleaner rated at 900W, because the manufacturer wishes to make his product appear as impressive as possible, this power input value is the only figure we get. In truth, the output figure might well be somewhere between 500-700W. For starters, these motors can get very hot, and this heat is a part of the 900W input figure. This may be a trifle misleading, to say the least.
    Can it be possible the same principle may apply to model motors? The competition in the sales market is certainly keen.

    Another angle(!?) I’ve not seen discussed very much is that of power factor. My very small amount of tinkering with brushless motors reveal that the input to the motor is AC, (alternating current). Both my voltmeter and clamp meter insist this is the case and that being so then when AC is applied to an inductive coil, i.e. the winding, power factor starts to play a part to a greater or lesser degree.
So my second question is this.
    Bearing in mind that industry views p.f. with a very perceptive eye, but our model motor manufacturer is not likely to mention this because it can only ever reduce the efficiency of his motor, and has no redress to do this anyway; in fact I’m sure that no one has any obligation at all to mention this when related to consumer issues, should we consider taking this into account? If it exists to any degree, then I think it will have an effect on any calculations we do.
    Any figures of any experiments to establish this, if it’s ever been done, might be interesting.                     PB                     

[Ernie]

Hi Guys, Thanks for all that.

 

It is all so complicated..I just want to go and fly  Anyway, It's a good discussion

 

ernie 

[Peter Miller]

THis is a recurring theme through out the threads.

 

Now you know why I like ic engines

[Tim Mackey]

No it isnt - its just that some people like to make a simple thing complicated

[Peter Miller]

"No it isn't" What?

 

"No it isn't a recurring theme" or "no it isn't the reason that I prefer  i.c".

[Tim Mackey]

Well far be it for me to suggest that you dont prefer IC Peter - - I meant of course, that it is not a recurring theme

Some people come on here asking for advice about a particular powertrain for a particular model, and we can simply and quickly give them several possibilities.... just as there can be several options for IC.

2 stroke, four stroke, glow, petrol, diesel, long stroke, short stroke, single, twin, radial and so on.....

Edited By Timbo - Moderator on 06/08/2009 21:11:25

[PatMc]

Posted by Peter Beeney on 06/08/2009 17:55:05:
 

 

 

 "May I just to throw another couple of questions into the debate, is it worth considering this from the commercial view point? I’ve had very little experience of industrial motors but I very much suspect they come with a plate on stating the input power as the motor voltage and the full load current, and the the output (shaft) power stated in watts or HP."

 

All industrial motors have already been installed in the machine they’re powering or are replacements for specific machines & haven’t given much info beyond rpm & HP. I’d imagine the full motor spec would have been available if requested but that would normally only be by the designer(s).

 

"The output is always going to be less than the input, and the indicators are pretty unambiguous. Also, I don’t know this, but I suspect this is part of commercial law.
    However, if we buy a domestic vacuum cleaner rated at 900W, because the manufacturer wishes to make his product appear as impressive as possible, this power input value is the only figure we get. In truth, the output figure might well be somewhere between 500-700W. For starters, these motors can get very hot, and this heat is a part of the 900W input figure. This may be a trifle misleading, to say the least. "
 

When I bought a new vac (early this year) as well as the gross power demand there was a figure stated giving a measure of the suction power. 

 

"Can it be possible the same principle may apply to model motors? The competition in the sales market is certainly keen."

 

The power figures given with model electric motors are indeed simply marketing hype. Our motors don’t actually have a defined maximum Watts input.

"Another angle(!?) I’ve not seen discussed very much is that of power factor. My very small amount of tinkering with brushless motors reveal that the input to the motor is AC, (alternating current). Both my voltmeter and clamp meter insist this is the case and that being so then when AC is applied to an inductive coil, i.e. the winding, power factor starts to play a part to a greater or lesser degree."

 

The input isn’t AC. It’s switched DC. Your meters are indicating what they measure at whatever scale they are set at.

There will be a phase difference between voltage & current due to the inductance of the coils but only at the rise & fall of the applied pulse. This must cause some “wattless” component to the power input power but less than if the supply was AC. The same would apply to brushed, commutated motors.

So my second question is this.
    Bearing in mind that industry views p.f. with a very perceptive eye, but our model motor manufacturer is not likely to mention this because it can only ever reduce the efficiency of his motor, and has no redress to do this anyway; in fact I’m sure that no one has any obligation at all to mention this when related to consumer issues, should we consider taking this into account? If it exists to any degree, then I think it will have an effect on any calculations we do.
    Any figures of any experiments to establish this, if it’s ever been done, might be interesting.                     PB    

 

I think the industrial considerations of PF & corrective measures are too complex for a discussion in a model aeroplane forum. However in industry many small motors are used without any attempt to improve PF simply because any likely improved efficiency would not be significantly reduce the running costs.

IMO the efficiency gains for model motors probably wouldn’t justify much effort to improve PF. Simply connecting suitable size & matched capacitors across each coil would theoretically be the answer but I’m not sure whether this would upset the timing &/or the feedback from motor to ESC & start up current might be unacceptably high unless measures were

[Ernie]

Hi Guys, and especially Timbo,

 

When you do understand something, it may seem simple, but isn't necessarily so.

I find cooking a souffle you could that could float out of the kitchen simple, but it seems like a black art to my partner.

 

It is reasonably easy to understand the workings of most internal combustion engines, even the RCV range. Whether they are glow, diesel, petrol, four or two stroke, the system can be readily visualised. bang/blow/suck etc

 

Re electics, It is difficult to visualise the flow of electricity through wires, and exactly what happens inside the wee anodised shell, and as for what the magic smoke is, I've yet to find out.

As for Ohms, watts, volts, mAh. I cant see them, so find them difficult. Ok, I can repeat what I read, but I don't really understand

 

All this is not helped by the terminology that surrounds all this, What does T2212/13 1000KV(120w+) mean? or X55SB pro brushless ESC, or XM2826CA-15 etc (all from my current RCM&E)

 

mills 75 or OS 40 is easy (maker, capacity)

 

ernie

[Peter Beeney]

       PatMc   Thank you for your interesting reply. It’s certainly more food for thought. But, perhaps I ought to try and qualify a couple of things.
    With regard to the electrical machines that I’ve seen, such as industrial rectifiers and emergency standby equipment etc., at the very minimum the name-plate would state the input and output values. I’m still not convinced that industrial motors would not be the same; I’m not counting things like fridge or washing machine motors, that’s the consumer market again. I will endeavour to find the type I have in mind, but it might not be easy.
    Re. the vac.  At least you have some sort of output value, if only to compare it with another cleaner. Perhaps you need to convert the suction power to watts, and then compare the output to the input? The little point I’m trying to make is that it’s generally quite difficult to actually get a comparison between the input and the output. 
    As you say, regarding our model motors, there is not generally an input figure but I notice that we do tend to frequently measure this, usually in terms of watts, and then assume that this is what we are getting out. I feel this might not always be quite correct. And, let’s face it, really what we are mostly interested in is what is driving the prop!
    The meters and AC. Like you, I assumed the current would be switched DC, but now it certainly seems debatable. My voltmeter, a Fluke 8060A, will not give a reading unless it is switched to the correct scale. And I had to switch it to AC to get a reading. The clamp meter, a HEME  AC/DC Powermeter clip-on, is self-ranging, just clip it on and read off what you see. This also indicated it was looking at AC. It also reads Hertz, Volts, phase angle, VAs and ac/dc watts. Both these clocks were within the strict specifications set for test instruments by the telecoms outfit that I worked for. The HEME also has provision for connection to a ‘scope, something I’m no longer able to do, being long retired. But I do keep threatening to buy a USB oscilloscope, for this computer. Maybe I shall have another fiddle around, to see what I can discover.
    I certainly agree that a power factor debate is not the way to go, and it was a very long time ago indeed when I was puzzling over this fascinating?! (that’s infernal!) subject. But my point is that if there is a power factor element to consider then this may be affecting any power calculations that we do. I wasn’t really considering any correction measures.
    Also am I not correct in assuming that if you wanted to connect a reactive load, however small, to the public mains supply it had to be within certain limits. I know that the supply companies take a bit of a dim view of anyone who doesn’t keep up to the mark. Or, at least, they used to.   
    As always this is subjective and mostly guesswork. After working with the same small gang of (very friendly) smart-alecks for a very long time I soon learnt that if you were going to make a bald statement you needed to do your homework first. At least three times. And so far I haven’t really done this.
    So maybe, but that's only maybe, now I think I might spend a modicum of time and energy trying to fathom this out, at least to my own satisfaction.
    With humble apologies to Ernie, this is indeed a goodly discussion. Powerful, but perhaps largely devoid of facts!
 
    Hope some of this is of interest.     PB           

[kc]

If " matching an electric motor to a model is much easier & less complex than matching an ic engine to a model."  is correct as stated above then perhaps some one can tell me what electric gear  I need to put in a model like a Wot 4 at 4.5 pounds weight which flies well on a 40 2 stroke with 11x 7 prop?

Thats the sort of question we want answered!  

 

[PatMc]

So a Mills 75 is nearly twice the capacity of an OS 40 then ?

Never realised that.

[Myron Beaumont]

PatMc

Get you !  All I know is that if you fit a Mills 75 with a 7 by 4 prop it'll power anything up to about 40 " span built of balsa wood .I'm with Peter on this one ! & if you have an OS 40 You can go up to about 55" more OR less" All depends on wing loading and what you want your model to do. Regarding wattages etc -Isn't it really a matter of making sure you don't exceed the limits (with a watt meter giving you the figure used by your battery) -& measure the "pull" with a spring balance ?

[Myron Beaumont]

PS

If you launch it by hand you can tell whether its going to fly by "feel"

I'll get mi coat !

[kc]

It's the correct engine number in each case.  Most modellers know that some engines were in cc and now they are in cubic inches, so it is .75cc Mills and .40 cubic inches OS, but thats not important. 

Whats important is that if someone says this will fly well on an OS 40 and that will fly OK on a Mills.75 all you need do is put the right engine in and it works!

 

You made a 'clever' remark about engine sizes, but failed to answer the question.  What electric setup will fly a Wot4?

 

Edited By kc on 07/08/2009 19:03:57

[Ernie]

Hi PatMc

nice one

ernie 

[PatMc]

KC,

the "clever" remark is merely pointing out that if anyone is walking into the hobby as a complete newcomer the labels used in ic are equally as alien as that of electric.

I don't think that most modellers actually do know that some ic engines are/were classified in cc as well as cu ins. In fact I think that many modellers don't know what the numbers mean at all.

 

How has a person gained the knowledge of what will fly on an OS 40 or a Mills .75 ?

Obviously from experience. 

Electric power for some is a new concept but that's not a reason to simply assume that there's a direct comparison between the two power sources. Both have their strengths & weaknesses. IMO saying one is more complex than the other because it's not understood isn't a good way forward.

 

Wot 4 electric setup from the horses mouth.

 

 

 

 

 

 

 

 

Edited By PatMc on 07/08/2009 19:54:45

[Former Member]

[This posting has been removed]

[PatMc]

Peter Beeney,

The LRK site this page in particular might answer some of your questions. I'm surprised that the 'scope traces of the pulses are fairly linear as they increase & decrease. Actually I'd have expected them to look more like a reverse saw tooth trace. As it is they are clearly DC pulses & of course they only vary upwards WRT zero.

Like you I'm retired having worked in telecom. I'm very familiar with seeing the classic saw tooth distortion caused by dialled pulses being transmitted down a capacitive line. Working on the pulse regenerating equipment was the bane of my life for a couple of years.

 

With apologies to Ernie for wandering so far off topic.

[Peter Miller]

The point is this, an i.c. model will have the words "for .40 to.52 size engines"  or what ever size needed on the kit box or plan. Go into any model shop and buy an engine in that range and it will fly the model.

 

If the same to could be said for electric powered models and electric motors  we wouldn't have threads like this one.

 

On cc vs cu.in, these days ccs are only used on vintage engines. Back when ccs were a common size denominator ccs were normally used on diesels and cu.in. for glows and spark ignition engines, this was in the late 40s and early 50s, Before that ccs were used in this country for all engines, e.i. Nordec 10cc, and cu.in were used in the USA.

[kc]

Thanks for the ref to the Wot4 site.  But why couldn't you tell us directly what motor and ESC is suitable?  Why not answer the original question simply?  Why make 'clever' comments that can only confuse the newcomer?     ( I posted my comments to clarify for beginners and cancel out the false info that Mills is equal to OS40 )

 

Peter Miller is right, just put the engine size or number on the box.   I wonder if the new Wot4 ARTF has the electric motor and ESC etc shown on the outside of the box like glow motors are shown.