RCU Forums - What Eflite Power motor/esc combo for a 13 diameter prop and 10-11 lb plane

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What Eflite Power motor/esc combo for a 13 diameter prop and 10-11 lb plane

Hello,

I am semi new to the electric build arena. Previously I would just buy what was suggested. I just picked up a plane and want to convert it to electric and there are no real suggestions for the prop I want to use. I had a 15cc gas motor in it and weight was around 12lbs. After taking out all the Gas stuff I am thinking it will be about 10 lbs. I read about the 100w/lb calculations. So I figured a Power 46/52/60 would be best, really the 52/60. still clueless on the ESC needed. I can not have a prop bigger than a 13 diameter. The current prop I have from the Gas motor is a 13x8 MAS and I would like to just reuse that one. I also read I need a watt meter but I am totally in the clouds on what setup I would need. It will be a sport flyer flying off of water and land.

Thanks in advance

Decided to go with a Power 60 with a castle creation phoenix edge 100

Quote:

Originally Posted by rowdog_14 (Post 12720999)

... I also read I need a watt meter ...

A very long clearance sale, originally 200+$, high quality, now literally peanuts:
Hyperion Emeter II wattmeter with local&remote logging, optical&electrical tach, servo tester - RCG

Without a watt/volt/current/multi-meter you are in the dark.
Until something starts to glow :( ;)

To trust is good :)
To calculate is better :):)
Will get you to say within 10%, if input ok.
e-flight calculators & propdata (compilation)
To measure is a must :):):)
A watt-meter will more than pay for itself, several times over, your battery, ESC and motor will love you for it.
After calculating, always check/measure current when you have a new/changed setup.
Will also help you find optimal setup.
And it's a great tool for debugging your power train.
About watt-meters and how (not) to use them, by RCG user vollrathd:
www.wattflyer.com/forums/attachment.php?attachmentid=117297
A very long clearance sale, originally 200+$, high quality, now literally peanuts:
Hyperion Emeter II wattmeter with local&remote logging, optical&electrical tach, servo tester - RCG
Contents
- Closing out at
- Reviews by Bernard Cawley and Ken Myers
- Tech info & help threads
- Increasing max.current, double, triple, simple and cheap
- Software and manuals downloads
Careful!
(Always!) keep battery-/watt-/multi-meter wires short:
Too long wires batteryside will kill ESC over time: precautions, solutions & workarounds - RCG

Prettig weekend ;) Ron
• Without a watt-meter you're in the dark ... until something starts to glow •
• E-flight calculators • watt-meters • diy motor tips&tricks • Cumulus MFC •

Quote:

Originally Posted by rowdog_14 (Post 12720999)

... still clueless on the ESC needed ...

When you know power needed, and have decided upon system voltage, you can calculate max.current

current (in ampère) = power (in watt) / voltage (in volt)

.
.
It is a good practice to have some headroom built in. Motor runs cooler, slightly more efficient too, and you have some leeway should things go south a bit.
About derating motors, controllers, batteries, electronics in general:

Derating, starting at ... Then there is the 75% rule of thumb ...
Questions and Answers.... - Page 928 - RCG
About de-rating controllers and motors, starting at for everyone else:
Questions and Answers.... - Page 290 - RCG
Motorcurrent is proportional to voltage squared, and proportional to Kv cubed.
A 10% change in battery voltage will give a 20% change in current, a 10% change in Kv will give a 30% increase. Not quite, because battery voltage will sag more due to higher current, but you'll get the idea.
extra current with one or two cells added, simple table
A.k.a. "Why did my motor and/or controller and/or battery go up in smoke Attachment 2271622 ??? ¨.
In depth discussion
www.theampeer.org/ampeer/ampnov15/ampnov15.htm#ADD

Prettig weekend https://www.rcuniverse.com/forum/ima...ilies/wink.gif Ron
• Without a watt-meter you're in the dark ... until something starts to glow •
• E-flight calculators • watt-meters • diy motor tips&tricks • Cumulus MFC •

I know nothing about good plane/prop/rpm combinations, therefore cannot give you advice about powersystems.

Below an excellent quote about motor selection and powersystem misconceptions
From
brushless motors Kv?.

Quote:

Originally Posted by scirocco (Post 27290157)

While an absolutely critical part of the system ...
... Kv is actually the item one should choose last.

Decide your peak power requirement based on the weight of the model and how you want to fly it:
Magic numbers for modellers.
Pick a preferred cell count (voltage) and pack capacity for how to deliver the power.
Pick a prop that will a) fit on the model and b) fly the model how you want - often as big as will fit is a good choice, but if high speed is the goal, a smaller diameter higher pitch prop will be more appropriate.
Look for a size class of motors that will handle the peak power - a very conservative guide is to allow 1 gram motor weight for every 3 watts peak power.
Then, look for a motor in that weight range that has the Kv to achieve the power desired with the props you can use - a calculator such as eCalc allows very quick trial and error zooming in on a decent choice. For a desired power and prop, you'd need higher Kv if using a 3 cell pack compared to a 4 cell pack. Or for a desired power and cell count, you'd need higher Kv if driving a smaller diameter high speed prop compared to a larger prop for a slow model.

The reason I suggest picking Kv last, is that prop choices have bounds - the diameter that will physically fit and the minimum size that can absorb the power you want. On the other hand, combinations of voltage and Kv are much less constrained - at least before you purchase the components.

So Kv is not a figure of merit, in that higher or lower is better, it is simply a motor characteristic that you exploit to make your power system do what you want, within the constraints you have, e.g. limited prop diameter, if it's a pusher configuration, or if you already have a bunch of 3S packs and don't want to buy more, and so on.

Minor lay-out changes by RvS

Quote:

Originally Posted by ron_van_sommeren (Post 12721234)

Thanks for the info. I will go through it. Definitely sensory overload learning about electrics.

Don't hesitate to ask questions.

Vriendelijke groeten ;) Ron
• Without a watt-meter you're in the dark ... until something starts to glow •
• E-flight calculators • watt-meters • diy motor tips&tricks • Cumulus MFC •

Quote:

Originally Posted by ron_van_sommeren (Post 12721794)

Just wanted to say thanks. I picked up an Emeter V2. I will dig in a little more if I have any other questions.

Quote:

Originally Posted by rowdog_14 (Post 12734591)

Just wanted to say thanks. I picked up an Emeter V2. I will dig in a little more if I have any other questions.

You really splashed out there :-)

About measuring current, link opens a .pdf document
www.wattflyer.com/forums/attachment.php?attachmentid=117297

Users in these threads, include the very helpful Randy from www.rcdude.com, he knows about software versions and updates
close-out-Hyperion-watt-meter-II-(optical-tach-servo-tester-local-remote-logging)
&
Hyperion-s-New-Emeter-II-RDU

Vriendelijke groeten ;) Ron
• Without a watt-meter you're in the dark ... until something starts to glow •
• E-flight calculators • watt-meters • diy motor tips&tricks • Cumulus MFC •