getting the right system for the model !

[Geaneral Walker]

Well i over shot this one by putting a 14.8 25c 2200mah lipo with a 60amp esc and a 740w 3538/1100kv motor and got a hot esc and a hot motor! i got a 5lb 60in ws ceasna182 completely remodeled , so just were did all that heat come from on a bench test ? wooow , the power was Awesome ! TY .

[xviper]

First off, I'd guess there's no airflow on a bench test. I've flown this sort of motor/ESC set up before on 4s and yes, it can get warm, even hot, but the powertrain seems to be able to take it so long as there's good air passages to keep the motor and ESC well ventilated. On such a set up, you might not want to run full throttle for more than 15 seconds at a time if the plane comes down with hot components. Additionally, you can mitigate the heat to some extent by reducing the size and/or pitch of the prop. Did you actually measure 740 watts or is this what the motor specs say? Published watts is a max estimate based on a typical application given a specific range of props. Even if you did measure that on the bench, it won't actually do that in a flying airplane.

[Geaneral Walker]

so right , finally found a site that people know what their talking about ! Thank You ! , i was Thinking the same thing! but , i am going to put a bigger esc and , i might change the lipo to a 15c 3000mah ? what you think ! good ? smart !/? we know don't we ! i will tell you ! i did bump that throttle stick (all Hitec) pretty hard , man, i had to hold that caesna down , it just floated up in my hand ,! woow ! dangerous? brave ? i do stay my butt behind them props , and i am running two sizes under what specs call for , a 10 X 6 , it calls for 11" 12" and 13 ty

[Aspirin]

Are you aware of online programs like E-Calc? They are invaluable in selecting props and power components.

http://www.ecalc.ch

True, I don't know what 3538 means in electrical terms. The 3538 is just an identifier usually of the motor's physical size.

But to answer your question the heat comes as a function of the thermal efficiency (the blue line in the attached graph). You want to select your components such that the motor is operating a few (around 2 percentage) point after the peak efficiency.

Running before the peak usually means you have too large a motor. Running too far aft of the peak means you risk burning up the motor.

Please note that thermal runaway has a time component. That is to say that any given motor might be fine at say 300 watts for 10 minutes before it overheats. That same motor might be good for 740 watts but for only 15 seconds (such as used in high powered gliders).

When adjusting props try to keep the pitch speed (RPM X Pitch) the same. As per the lift equation it is velocity (speed) that allows the wing to make lift not thrust or watts.

All the best,
Konrad

[Geaneral Walker]

good reply , ty so much ! like i said , my hand touching the motor and esc and battery is my bottom line watt meter tester ! i will be putting a 100amp esc and drop in burst ,15c 3000+mah , i must reach this motors value , in weight of 132w per pound was 528w motor for this model , i steped it up by accident , basiclly i made a mistake that i must correct , i addmit , wooow ! but , man , thing don't play , it will snatch quick , and i checked the CG , perfect !!!! ty bro , G-Walker Here ! ♥

[Geaneral Walker]

i checked that E-Calc site out , you gotta pay for info , lol , no problem , i probably could teach them something , because some things in this hobby , you just can't explain , if you know what i mean , just saying , lol , i love it , i ain't had a system yet that i couldn't straighten out , ty G-Walker ♥

[Aspirin]

No, you don't. It is a demo version. Not all features are available in the Demo. Nor are all the components available at any one time in the Demo. But if you refresh your browser the catalog of available components rotates about every 30 seconds.

It is well worth buying as it will save you hundreds in lost equipment.

All the best,
Konrad

P.S.
"Teach them something" Did you find a problem in the math (code)?

[WintrSol]

You can't go by manufacturers recommendations, period. If you are going to combine your own parts, you should have a Wattmeter, so you know if you are under the ratings. If you are getting close to, or over, the Amps the ESC is supposed to conduct, you can use a smaller prop, and re-test. Also, airflow over the ESC and battery are necessary, if you don't want them to overheat.

[Geaneral Walker]

thank you WintrSol and Aspirin , that motor i ordered is one thirsty dog ! but man , it's got the fire ! and says in the stats that it will carry 6 cells , like i said , i run a 10X6 single ! ???? check this out for me bro, i ain't the smartest in the hobby ,lol ,, but , if we put heads together , we can rule the world , to speak ,,

• Kv (rpm / v): 1100
• Power (W): 740
• Coil : 4
• Resistance (mΩ): 28
• Invalid current (A): 1.8
• ESC (A): 70
• NiCd / NiMH Battery sessions : 9-18
• Lithium battery section number : 3-6
• Propeller : 12 * 6 / 12 * 6.5 / 13 * 8
• Weight: 170g

TY G-Walker ♥

[WintrSol]

My math tables indicate that, with that prop, you should be making in the neighborhood of 700W at about 40A with that prop and battery. That means you have an airflow problem on the bench, if the parts really got hot. Tell me, if you wet your finger and touched the motor or ESC, would it hiss, or could you touch either without yanking your hand away? Too hot is hot enough to burn skin, if you keep your skin on them for a couple seconds. Anything less is OK, more or less, given the conditions. Make sure there is plenty of propwash going through the motor and over the ESC, and that there is an exit for that hot air when the model is closed up. For example, are both openings on the bottom at least partially open when the model is ready to fly? Also, are there several large holes in the firewall around and behind the motor?

[Aspirin]

Great posts you two!

Data will set you free to explore the possibilities.

All the best,
Konrad

[WintrSol]

The tables give a range, and lower values are ~500W at ~30A, so you really need a Watt meter (and to improve the air flow).

Also, 740W is optimistic for a motor that weighs 170g; most consider the power rating should be between 3 and 4 Watts per gram, so between 510W and 680W, as long as you don't exceed the current rating, which seems to be absent.

[Geaneral Walker]

WintrSol you are 100% right ! you are a winner ! and the first ! it is 528W , so i just rounded it to 600w motor by the weight of the model ! i have a nice 580w motor picked out , ! and the air flow - I am working on that right now ! i will share when i get it done ! i just got so much going on ,, I love it ! Thank You very much , i have subscribed to you , ok? TY Again !.... G-Walker ♥

[OV10]

Wintrsol is a good one to subscribe to cause he knows his stuff on the tech front.

[WintrSol]

I can't help it, I was an electronics engineer in aerospace for over 40 years. :>D

[OV10]

And that's how I know you know your stuff cause I was a microwave RF engineer in my early aerospace corporate career before moving out of the tech world into procurement/contracts management. ;)

[Grossman56]

Hey, its also great to see Wintrsol again, it's probably me, but I haven't seen you in a bit, good to see you buddy.
General Walker, great to have you aboard as well and I'm glad to see that you're availing yourself to all our talent on the Squawk. There are always people here willing to help out, Charlie and Wintrsol are two of the best!!

Grossman56

[Geaneral Walker]

Grossman56 and Mr.WintrSol ♥ You really opened my mind to some things to check for , and , i think i got a winner ! we will find out in just a few , vid to follow ! Thank You all very much ! i wish there was a flying feild around these parts , but unfortunately , there is not , i would love to meet you all ! ty again ! ♥ G-Walker.

[OV10]

GW...........Seeing you in shorts and bare feet just reminds me why I need to sign up for the NY Snowbird club. Was 28F today with sleet being pushed by 20+ winds. Today is the first day of winter and we've already had 70 inches of snowfall so far this season. SUX to be an RC pilot in the northeast. :dodgy:

[WintrSol]

I'm always learning something new in pursuit of this hobby - they say it keeps you young. I don't know about that, but I do like to pass on what I've found out. Here's hoping all our mandatory landings are good ones!