crashwrench

Hello To all,

I am looking for the Mother of All Conversion Charts FOR ,,, Two sroke Glow , Four Stroke Glow , Two stroke Gasoline , Four Stroke Gasoline , Electric Motors , Air Plane
Wheight / Size .......

I have seen a chart like this , But Dummy Me Did Not downLoad it.....

The chart had it Broken Down from A .049 CI. up to 200cc to Wattage ( KV 's ) to the Air Plane's Wheight.

Any HELP .

Thanks ,
Mark K.

mainegold

My Feedback: (1)

A chart like this would be handy, especially for this forum!

edpare

I sure could use one right now!

Mr Cox

I don't understand what such a chart would do or help with?
Is there any specific problem or issue?

edpare

I am new to electric power and don't know how to choose an electric power system that would exactly match the performance of a nitro engine such as, say, an O.S. .46 AX ABN.

Mr Cox

When "converting" a plane from electric to glow, which this forum is all about, just look at the wingarea, total weight and what performance you are after etc. Then it is usually fairly easy to pick a glow engine that will do the job.

edpare

I want to go the other way: convert an EP L-4 to glow. The problem is the instructions for the EP L-4 are vague in Chinese and only specify a "36 size". My ignorance doesn't allow me to translate that to x motor, y ESC, and zz battery. Since I already have 3 2100 LiPo 3s batteries, it would also be convenient to have a motor and ESC that could use them.
I have MotoCalc and find it to be overly complex and slanted toward expensive products available in the EU.

That's why a simple chart would be better for me.

Mr Cox

A .36 glow engine? What's unclear about that?

edpare

In this case, "EP" is defined by the manufacturer as Electric Power.
Thus, my question is: what the heck is a "36 EP"? (notice no decimal point).



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A .36 glow engine? What's unclear about that?
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Mr Cox

Several manufactures use numbers to denote the approximate glow size, quite often use see things like 30E etc. denoting .30 glow size.
Regardless of that just look at the wingspan, wingarea and the total weight, and you can quite easily estimate the required glow engine from that. Glow also comes out a little lighter, so that's another bonus with using glow.

Which L4 are you thinking of?

edpare

Is this something like we are looking for?

http://www.electrifly.com/powersyste...brushless.html

Mr Cox

I don't know what the OP is after, the electric motor numbers doesn't mean anything to me.

opjose

A small bit of math is all you need.

745watts = 1HP

The OS .46 AX is rated to produce about 1.7HP, realistically it probably produces about 1.5 HP

1.5 x 745 = 1117.5 watts

Now choose a voltage to get you there.

1117.5 / 18.5v = 60A

So to get that level of performance you'll want to use a motor capable of 60A 18.5v or put another way 1118 watts or better.

According to ThrustHP a 12x6 prop spinning at 12000 RPM produces about 1.56 HP.

12000 RPM / 18.5v = 650KV

A 20C 3000mAh 18.5v battery pack can just keep up with all of this, but you'll be driving it very hard.
A 20C-25c 4000mAh 18.5v battery pack will fair much better and a 20C 5000mAh 18.5v pack will give you good long flight times.

So there you have all the motor, ESC and battery specs you need!

It really is that simple, just not often clearly spelled out.

edpare

Thanks opjose! I understand what you wrote and can use the information if I want to convert from glow to electric.
My current problem, however, is finding what the manufacturer meant when he called for a "36 electric power".
How much horsepower is "36 EP"?

Ed

opjose

It's hard to tell from "36 electric power".

However assume that what you read is a poor translation from Chinese or some other language.

Since most glow motors come in .32, .40, .46 sizes in that range it is unlikely that 36 refers to motor power and is most likely indicative of motor diameter.
However the actual intended motor is unknown.

So you are best off looking at the estimated weight of the plane all ready to fly ( all up weight AUW ).

Take the given weight and multiply by a factor, I use 1.3 to get a good estimate.

Assuming the manufacturer says that the plane weights 3.6lbs...

3.6 x 1.3 = 4.68lbs

Then apply the watts per pound "rules"...

e.g. to get good aerobatic performance you want approximately 130 watts per pound...

So 4.68lbs x 130watts = 608 watts

A target wattage range of 610 watts will do.

Again we use the desired battery voltage ( in this range I'll go with either 11.1v or 14.8v... )

610 / 14.8v = 42A

610 watts = .82 HP

ThrustHP says that an 11x7 prop spinning at 10400 RPM produces .82 HP.

10400 x 14.8v = 700KV

So again we have a good working configuration given the weight...


- A 620 watt+ motor 700KV motor

- An ESC capable of 42A continuous ( get at least a 50A ESC or better ) @ 14.8v

( Note remember that an ESC's AMP rating may be given at different voltages so if you need a 50A 14.8v ESC and the advertisements are primarily dealing with 11.1v you'll need to INCREASE the AMP rating accordingly... thus to get something that can handle 50A @ 14.8v you'll want to look for a 60A+ ESC given for 11.1v.... although I'm not being precise on the math on this... it's easy to work out... )

- A pack capable of 42A continuous @ 14.8v, say a 2600mAh 14.8v 20C LiPo or larger...

And a prop that puts you in the right wattage/AMP draw range.

Since the prop has such a dramatic effect on the power draw, you really always want to test your configuration out with a watt meter just to be sure you have things dialed in correctly.

A watt meter will also tell you if your pack is suitable ( e.g. if the voltage does not drop too much under load, you're fine ) and how much power your prop is pulling from your electronics.

nbawannab

hello gang i have a specific problem...i have an "FD4-1 Skyray" it calls 4 a 91 ducted fanglow engine but i would lke 2 goelectric....any info would b a great help indeed....thanks a bunch in advance....
stu

iron eagel

A .91 glow for for DF use produces a bit over 2.2 hp if it is set up right, that would put you in the 1800 watt range for an electric...

airraptor

My Feedback: (66)

iron eagle wrong in hp on those engines. closer to 5hp.

For the guy wanting to convert your .91 size DF to EF should go visit the EDF section in here or even better yet goto RC groups forum under edf Jets.

Edpare give us a ling to your plane or give us the dimensions of it. Dont get hung up on the 36ep thing.

also you cant compare direct watts of a glow engine to an electric power.

That 1.5 hp in the 46 is way off. closer to 1.1 hp in that engine. that 46 will not spin a 12x6 at 12,000.

900 watts is close to most 40-55 size engines. the electric motors turn bigger props so they make more thrust.
also it will take more KV than 650 to spin that 12x6 at 12,000 rpm. most electric motors are around 80%

iron eagel

Thanks Airraptor! I have a OS .91 VR DF with the tuned pipe with the Dyna MAX DF unit to go with it, I should have checked the manual to be sure ! Your right it was the rear exhaust .40's for DF's that were in the 2 hp range. So for a .91 vs electric your talking more on the order of 4Kw power system either lots of amps or volts to equal a .91 for example at 14.8 volts (4 cell) your talking 270 amps.

As to the OP's question I think AXI used to publish a chart for their electric motors, compared to glow engines, your best bet is to go for the weight of the finished airframe to determine what your power requirements are with either a IC engine or electric motor.
Keeping in mind that as raptor pointed out, an electrics motor's power is actually not the the wattage that it will take as input, keeping in mind that the power to the prop is anywhere from 75-95% of that figure due to losses in heat and alike.

airraptor

My Feedback: (66)

Edpare can you post some specs of the plane so we can help best chose a motor for you?

nbawannab

thanks airraptor..nd i tried the edf link no responce yet