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Author Topic: Spreadsheet Design?  (Read 1615 times)

Offline RogerGreene

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Spreadsheet Design?
« on: August 27, 2021, 06:11:31 PM »
Hi All,

As in my previous thread entries, I am new to electric power and have had several people on Stunthanger give me great information on converting my IC planes to electric. However, with so many options of motors, sizes of batteries including mah volts amps, and ESC, timers and prop sizes to then apply to the size of the airplane's wing area and time in the air it has a learning curve.

To help lessen the learning curve could someone with spreadsheet experience plug in the necessary info mentioned above, and if I have left something out please insert it, and come up with the variables that someone could input their info in, like the size of their airplane wing area, and be able to start flying the first time without too much trouble and then fine-tune their equipment?

I hope that this spreadsheet idea is possible so that those interested in electric power stunt would be able to get flying faster with reliable electrical power.

Thanks very much.

Roger

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Offline Tim Wescott

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Re: Spreadsheet Design?
« Reply #1 on: August 27, 2021, 07:48:31 PM »
Stunt ships are all pretty much the same configuration, so the easiest thing to do is weigh it, then find a similar-weight ship on the "List your setup" thread that's pinned here, and shamelessly copy.

Some things to note:

  • Motors come in fairly standard sizes, one 3228 is pretty much the same size as another (but quality will vary, sometimes a lot)
  • You want to match the KV of the system you're copying
  • "Active" timers, like the Fioretti and Burger timers use more energy than constant-speed timers, like the Hubin or KR
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Dennis Toth

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Re: Spreadsheet Design?
« Reply #2 on: August 27, 2021, 07:54:48 PM »
Roger,
Dennis Adamisin did a lot of work for Brodak and had a good list for motor, ESC, battery and ship size. I think it might be available on the Brodak site (https://brodak.com/pub/media/pdf/BrodakPowerSystems04Feb2021.pdf).

Maybe Dennis can post it here. Other option is to look through the "List your setup" section for a ship that is close to what you are thinking of building.

Best,   DennisT

Offline RogerGreene

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Re: Spreadsheet Design?
« Reply #3 on: August 27, 2021, 08:59:19 PM »
Thanks, DennisT for the PDF that Dennis Adamisin worked on. And thanks Tim the link to 'List your Set-up'. I guess the KV is the power the motor puts out?

Thanks,

Roger
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Offline Tim Wescott

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Re: Spreadsheet Design?
« Reply #4 on: August 27, 2021, 09:33:52 PM »
Thanks, DennisT for the PDF that Dennis Adamisin worked on. And thanks Tim the link to 'List your Set-up'. I guess the KV is the power the motor puts out?

Thanks,

Roger

KV is the motor speed per volt applied.  So a 760KV motor that's driven with 10V will go 7600 RPM, more or less.

What power the motor puts out has to do with the prop and the speed that it's going (which is set by the timer & ESC).  The KV has to do with how many batteries you need to use to attain a given motor speed.

It gets very complicated -- which is why just copying something that already works is a good idea unless you really know what you're doing.

(Which, if you think about it, is what newbies are told to do with slime engines.  "What engine should I put on my Nobler?" will be answered with a short list of engines, not "any 35 will do" or "any Schnurle-ported 40 will do").
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Online Brent Williams

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Re: Spreadsheet Design?
« Reply #5 on: August 27, 2021, 09:52:55 PM »
Thanks, DennisT for the PDF that Dennis Adamisin worked on. And thanks Tim the link to 'List your Set-up'. I guess the KV is the power the motor puts out?

Thanks,

Roger

The KV rating denotes the max RPM the motor could achieve for every volt applied. 
 -  Battery voltage x Motor KV rating = max theoretical RPM of that motor. 
You select the KV of the motor for the intended battery cell count and desired RPM range of operation.

4s (14.8V) x 930Kv motor, the maximum RPM would be approximately 930KV x 14.8V = 13764 RPM max.
We generally don't run the motors at anywhere near the max RPM in control line, usually around 70% of the theoretical max rpm, which in this case would be around 9500 rpm.
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Offline CircuitFlyer

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Re: Spreadsheet Design?
« Reply #6 on: August 28, 2021, 08:03:29 AM »
If you just want to get an idea of how different components can change overall performance there are a few online calculators already out there. Try Castles version of eCalc https://www.ecalc.ch/motorcalc_mobile.php?castle&lang=en  I can’t vouch for any accuracy for real world applications in control line stunt.
Paul Emmerson
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Offline john vlna

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Re: Spreadsheet Design?
« Reply #7 on: August 28, 2021, 08:16:52 AM »
Rodger
Take a look at MotoCalc. I have been using MotoCalc for about 12 years and have found it very useful for a variety of planes for 1/2A to carrier, stunt etc.
http://www.motocalc.com/

Offline Tim Wescott

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Re: Spreadsheet Design?
« Reply #8 on: August 28, 2021, 08:25:00 AM »
If you just want to get an idea of how different components can change overall performance there are a few online calculators already out there. Try Castles version of eCalc https://www.ecalc.ch/motorcalc_mobile.php?castle&lang=en  I can’t vouch for any accuracy for real world applications in control line stunt.

Yet another successful way to design a motor system for stunt is to weigh your plane, then use the guidance from the motor manufacturer for 3D flying.  We don't fly 3D, but it seems to work out.  The same should work for eCalc (assuming they don't have control line stunt as an option).

If you're going from 3D recommendations, you'll often want to add an extra cell from what is called out.  In an RC plane where you can nail full throttle and get it, even if the motor and ESC would go up in smoke, this would be a bad idea.  For us, the motor speed is controlled by the ESC and the timer.  That means that the motor will effectively be at part throttle the whole flight -- that extra cell makes sure that toward the end of the flight, when the batteries are sagging and you're doing overhead eights and the cloverleaf, that you have plenty of overhead for the motor to stay at the proper speed.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline John Rist

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Re: Spreadsheet Design?
« Reply #9 on: August 28, 2021, 09:15:38 AM »
If you are coming from the wet engine world you have a pretty good ideal of prop size and RPMs it takes to fly your stunt ship.  Pick an E-motor that will swing that size prop at the required RPNs.  Keep in mind that that you need head room on the RPMs to allow for constant speed control.   If you are wanting to turn 9500 RPMs you need around 12K  to allow for RPM regulation.  Lots of motor vs prop vs RPM info on Innov8tive web sight for both Cobra and BadAss motors.   For a given motor click on Propeller data chart.   Speed controller size and cell count can be also be determined by looking at the chart.  If you have no ideal on size of battery lots of info available in the list your setup section.  Even if you use other methods to select a motor size this is good check to make sure you are in the ball park.  D>K
John Rist
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Offline RogerGreene

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Re: Spreadsheet Design?
« Reply #10 on: August 28, 2021, 02:01:54 PM »
Thanks ALL,

Here is my first try at electric. I purchase the motor, battery, and ESC at Amazon. The motor is a D3548 1100KV Flash Hobby with a 10x5w APC prop, 40A ESC, 4C 2200mAh, 35C, 451P battery, and the timer is CircuitFlyer Adafruit Trinket MO with a run time of 6 min. and RPM 7000.

WOW. It took off and the laps were much faster than I expected ~4-second laps. Lots of pull on the lines even overhead. The lines are 60ft center to center. It did not make the full 6 mins flight time, the motor slowed down and stopped at about 4 minutes flight time. I think the motor was a little too warm during the flight because all the labels on it are gone.

What should I do to remedy the fast flight, I prefer a 5 to 6-second lap time?

Thanks,

Roger
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Offline Tim Wescott

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Re: Spreadsheet Design?
« Reply #11 on: August 28, 2021, 03:28:09 PM »
Here is my first try at electric.

Tell us the airplane weight.  The first crucial factor is whether it's generally a stunt plane (it is).  The next crucial factor is how much does it weigh.

You've got to be spinning that prop at way more than 7000 RPM, or I'm cracked.  Did you tach the prop, or is that 7000 number what the program is set to?  You didn't say if the system is speed regulated -- does the timer regulate the speed?  (Edit -- no it doesn't -- there'd be an extra wire in there if it did)  If not, then you need to use an ESC that has a helicopter mode, and set it up to use it.

A 4-cell 2200mAh pack should be enough to finish a six minute flight at normal speeds for a 36-ounce stunter.  A 46-ounce stunter should be right at zero battery after a normal flight.  You're going way faster, so the thing is going to use power quicker -- this'll both heat up the motor and drain the battery faster.

If your stunter is heavier than 36 ounces, you just need more battery.  So, tell us how much it weighs, and we'll give you some guidance.

In the mean time, I'd cut the speed setting to 2/3 the current value, then fly again and time the laps.  You may want to "short tank" the thing (set it up for one or two minutes of flight time) until you have the speed sorted out.  I'd go for lap times a bit over 5 seconds at first (between 5.2 and 5.3, at a guess).  Once you get there, then if the plane is no more than 42 ounces, you can try full-length flights.  You'll be beating up the batteries (for long battery life you don't want to use the full rated capacity), but you'll at least be flying. 

After you get the speed correct, see how much charge you're taking from the batteries for a full-length flight, and use that to determine the batteries you should get next.  Take the mAh that your charger puts into the batteries, multiply it by 1.25, and buy a 4S pack with at least that much capacity.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline RogerGreene

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Re: Spreadsheet Design?
« Reply #12 on: August 28, 2021, 04:11:48 PM »
Thanks for the reply.

The plane weight is 55oz ready to fly. Span is 56 inches wing area 540 sq. in. I did not check the rpm at the field. I just now checked it and it's 12,200.  Well now I know why it went fast y1 y1

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Offline Tim Wescott

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Re: Spreadsheet Design?
« Reply #13 on: August 28, 2021, 04:46:07 PM »
Thanks for the reply.

The plane weight is 55oz ready to fly. Span is 56 inches wing area 540 sq. in. I did not check the rpm at the field. I just now checked it and it's 12,200.  Well now I know why it went fast y1 y1

Rule of thumb for constant-speed timers (i.e, Hubin, KR, yours) -- 7 watts per ounce average, 11 watts per ounce peak.

7 * 55 = 385 watts.

385 watts for 1/10th of an hour (six minutes) = 38.5 Watt-hours.

You're running four cells, at 3.7 volts/cell.  That works out to 14.8V.  (38.5 Watt-hours) / (14.8 V) = 2.6 amp hours.  So if you flew for six minutes, with that plane properly adjusted, you'd expect to suck 2600mAh out of your pack (1 amp-hour = 1000 mA-hour).

You want to suck no more than about 80% out of your pack, so multiply 2600mA-h by 1.25 (that's 1/0.8), and you get 3250.

So -- expect to need a 3300mA-h pack (and that your plane will get a bit heavier).  If the motor has a peak power rating at all, make sure that it's at least 600 watts (11 W/oz * 55oz = 605; I rounded).  If not -- just fly, and see if it overheats when you've got the speed dialed down a bit.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline RogerGreene

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Re: Spreadsheet Design?
« Reply #14 on: August 28, 2021, 05:20:55 PM »
Thanks, Tim,

For your input on my problem. So gotta get the RPMs down to a good lap time with a short run time. Then not use more than 80% of the battery.

Looking over the motor specs: the KV (rpm/v) = 790 with Max Power 717w and it says to use a 70A ESC. I used a 40A.

Will getting a 70A ESC help?


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Offline Dennis Toth

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Re: Spreadsheet Design?
« Reply #15 on: August 28, 2021, 07:35:36 PM »
See simple. Just like running a FOX 35. Really, just look in List Your Set-up" find something close and go. Don't over think it.

Best,   DennisT

Offline Tim Wescott

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Re: Spreadsheet Design?
« Reply #16 on: August 28, 2021, 08:03:12 PM »
The motor is a D3548 1100KV ...

Looking over the motor specs: the KV (rpm/v) = 790

Eh?  How does 1100 = 790?  I'm now confused.  What motor do you actually have?  I'm assuming that it's the 1100 KV one, because I don't see how you could get to four second laps on sixty foot lines with four cells and KV = 790.

with Max Power 717w and it says to use a 70A ESC. I used a 40A.

Will getting a 70A ESC help?

Your peak power is 605W, which pencils out to a hair over 40A with four cells.  So -- yes.  But I wouldn't hurry, because it's survived so far, and if it's stuck on the side of a profile it's getting exceptionally good cooling.  The hot motor, short battery life, and too-fast laps don't have anything to do with the ESC.  If you ask for too much current from your ESC it'll overheat and either shut down or die -- it won't cause those other symptoms

See simple. Just like running a FOX 35. Really, just look in List Your Set-up" find something close and go. Don't over think it.

That's not bad advise.  If you can spend the $$, just follow it.

If you're on a budget, just get some 3300mAh 4-cell batteries and give them a whirl.  Otherwise do what Dennis says.  Your current ESC is marginal, but should work.  The motor should be fine for that plane.  With a 3300mAh pack, you're probably fine; with an ESC that's good for 50A or more (and has helicopter mode), you're definitely fine.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline RogerGreene

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Re: Spreadsheet Design?
« Reply #17 on: August 28, 2021, 08:16:44 PM »
OOPS,

I looked at the wrong line on the chart it's KV (rpm/v) 1100 with Max Power at 911W chart attached. This is the title on Amazon: D3548 1100KV Brushless Motor Outrunner for RC Models.
Fly Stunt <><
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Online Brent Williams

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Re: Spreadsheet Design?
« Reply #18 on: August 29, 2021, 08:40:43 AM »
Hi Roger,  that's a huge motor for a plane this size a 2826 would be much better, that doesn't mean this motor won't work but I would recommend going to a 11X5.5 apc and set the rpm at around 9600 to start, good luck.  y1

This 3548 motor is the equivalent of a 2826.  It is just using the other method of motor sizing.  This version uses the outside diameter of the motor can, which in this case is 35mm.
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Offline Dwayne Donnelly

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Re: Spreadsheet Design?
« Reply #19 on: August 29, 2021, 01:14:44 PM »
This 3548 motor is the equivalent of a 2826.  It is just using the other method of motor sizing.  This version uses the outside diameter of the motor can, which in this case is 35mm.

Jeeze and I know that to, my bad.  n~
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