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Author Topic: Twin engine ?  (Read 1914 times)

Offline John KruziK

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Twin engine ?
« on: February 27, 2012, 07:39:51 PM »
How do you set up a plane with twin electric motors? Two of everything or two motors one esc. one battery? Thanks
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Offline Wynn Robins

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Re: Twin engine ?
« Reply #1 on: February 27, 2012, 07:59:45 PM »
either way works - I think Dennis has figured the one ESC to two motors scenario - its a post on here somewhere
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Offline Tim Wescott

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Re: Twin engine ?
« Reply #2 on: February 27, 2012, 08:08:41 PM »
You definitely want one ESC, and two motors.  Whether you use one battery or two is a detail -- but the way ESCs work, you don't want the battery leads to get too long.  If I were designing from scratch I'd keep the nacelles long, and put the batteries in there.  If I were building some scale-ish thing that didn't let me do that, I'd call Castle Creations, let them know how long my battery leads were, and see if they had any suggestions (other than batteries in the nacelles and big hunks of lead in the nose).
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Offline John Cralley

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Re: Twin engine ?
« Reply #3 on: February 27, 2012, 08:15:30 PM »
Tim,

The simple solution is to make short battery leads and long ESC to motor leads. Two Castle Creations Phoenix ESCs would let you play with the RPM for each motor (maybe the inboard a bit faster). I suppose those who know will chime in here. One timer should work two ESCs.

John
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Online Dennis Adamisin

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Re: Twin engine ?
« Reply #4 on: February 27, 2012, 08:55:28 PM »
* Brushless motors require indiividual ESC's - due to the governing feedback signals.

* I think it is hopeless to use anything except Set RPM mode with the Phoenix ESC's.

* My two electric twins are set-up with a single battery and Y-harness. In the Pathfinder twin the harness is especially long and it is heavy.  However one battery is easy to handle - just like a single.  Individual batteries will put a lot of weight out in the wings - I am not comfortable with that either.

* I use a single timer with a Y-harness.  Believe it or not the motors still start slightly different, but cut-off is guaranteed simoultaneous.


Just duit folks!
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Denny Adamisin
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Offline Howard Rush

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Re: Twin engine ?
« Reply #5 on: February 28, 2012, 12:39:37 AM »
What don't you like about weight in the wings?
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Offline Igor Burger

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Re: Twin engine ?
« Reply #6 on: February 28, 2012, 03:54:54 AM »
Quote from: Tim Wescott on February 27, 2012, 08:08:41 PM
You definitely want one ESC, and two motors.

 ??? ... I think you mean TWO ESCs and two motors
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Online Dennis Adamisin

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Re: Twin engine ?
« Reply #7 on: February 28, 2012, 07:38:24 AM »
Quote from: Howard Rush on February 28, 2012, 12:39:37 AM
What don't you like about weight in the wings?

Barbells!
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Denny Adamisin
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Offline Tim Wescott

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Re: Twin engine ?
« Reply #8 on: February 28, 2012, 07:55:46 AM »
Quote from: Tim Wescott on February 27, 2012, 08:08:41 PM
You definitely want one ESC, and two motors.
D'oh!!!
You definitely want one timer and two motors.

And you always want one ESC per motor.

I shouldn't post stuff when I'm too sleepy to think -- but how will I be awake enough to stop myself?
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Offline Igor Burger

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Re: Twin engine ?
« Reply #9 on: February 28, 2012, 07:57:38 AM »
yes yes ... one ESC per one motor :- )))))
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Offline Tim Wescott

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Re: Twin engine ?
« Reply #10 on: February 28, 2012, 07:59:21 AM »
Quote from: John Cralley on February 27, 2012, 08:15:30 PM
The simple solution is to make short battery leads and long ESC to motor leads. Two Castle Creations Phoenix ESCs would let you play with the RPM for each motor (maybe the inboard a bit faster). I suppose those who know will chime in here. One timer should work two ESCs.

D'oh again.  Well, that's obvious once you whack me upside the head with it.  Of course.
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Offline John Rist

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Re: Twin engine ?
« Reply #11 on: February 28, 2012, 07:59:49 AM »
With a one battery, two ESC, two motor setup could you use the ESC's to reach back to the battery?  Locate the ESC inside the wing headed back toward the fuselage.  This gives you the combined length of battery leads, motor leads and ESC to reach the battery. This way you may not need to extend the battery leads (at least not much). The only problem may be ESC cooling.

 :!   :!     :##
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Offline Tim Wescott

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Re: Twin engine ?
« Reply #12 on: February 28, 2012, 08:08:07 AM »
Quote from: John Rist on February 28, 2012, 07:59:49 AM
With a one battery, two ESC, two motor setup could you use the ESC's to reach back to the battery?
Well, you could, but it would make all the wiring hard to get to, and you do still need to cool the ESCs somewhat.

You can make the motor leads longer (as long as they're dressed nicely so they stay close together), just not the battery leads.  And ESCs and batteries have similar cooling requirements, so it's quite reasonable to put them all in the same airflow.  You will need a cooling scoop for the batteries, but you knew that.
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Offline Dean Pappas

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Re: Twin engine ?
« Reply #13 on: February 28, 2012, 06:39:31 PM »
Hello Friends!
Castle (probably others too) make a capacitor-long lead kit that allows you to run a single battery in the middle and ESCs in each nacelle safely.
You'll need two of the capacitor widgets, one near each ESC.
http://www.castlecreations.com/products/cc-cap-pack.html

Mongo dislike barbell too!

Regards,
 Dean P.
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Offline Fred Cronenwett

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Re: Twin engine ?
« Reply #14 on: March 03, 2012, 08:38:47 PM »
I am in the process of building a 4 engine CL profile scale project with electric power, so I have double trouble compared to a twin. 

I have been running the motors on the test bench and basically I have a separate speed control, battery for each location. I am using electronic controls for throttle so I have one reciever that feeds the same signal to the all four speed controls. The 4 way harness splits off the reciever signal to all four speed controls. Each motor is a stand alone unit each having a motor, battery and speed control.

You might be able to get by with one timer with a 2 way Y-harness, just make sure both speed controls are programmed to respond to the timer the same way. I am using e-RC speed controls from Hobby Lobby and I have to program them so that they all are matched and respond the same to the electronic control system I am using. When I move the throttle stick from motor off to idle all four motors start up and idle the same, I then can bring up the throttle on all four electric motors.

It might be worth a try to hook up two stand alone motor, speed control and battery combinations being controlled by one timer. That way it will be the same timer and RPM setting for both motors.

Good luck,
Fred Cronenwett
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Offline Jim Fruit

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Re: Twin engine ?
« Reply #15 on: March 03, 2012, 09:54:00 PM »
John:

I am doing a Beech D-18 twin for scale. My set up is two outrunner motors with an ESC for each motor and a single battery. I have been advised that it is most important that the the length of wire between the battery and the ESC not be extended too much, more important than the set of wires between the ESC and the motor. Consequently my plane is set up with the two ESC's in the fuselage with about a 2" long Y-connection to the battery that I fabricated. The longer runs of wire are between the ESC's and the motors, they are about 6" long.

I am controlling the whole mess (plus landing gear and flaps) with one of Clancy Arnold's control systems. I can control the motor speed by two slide pots at the control handle. I will start the motors to idle independently. Then I will use the slide pots side by side, similar to the throttle quadrant in the real plane. It will be possible to run the motors at different speeds, but I don't envision doing that. I intend to run the two motors contrarotating. I could run the two motors on a single slide pot by using a Y-harness at the control into the ESC's. Clancy tried to convince me of this method due to a bad experience that he had with IC engines turning in on him when one side of the system failed. I like the thought of starting the engines individually, however.

I could have installed one battery for each motor system, but I would rather have the power for each motor be the same. That way, we won't have the possibility of one side sagging off due to the depletion of it's power source. That could be a disaster for a multi-engine.

Jim Fruit
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Offline Fred Cronenwett

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Re: Twin engine ?
« Reply #16 on: March 04, 2012, 10:38:18 AM »
The Grumman Tigercat I fly with two OS-15FP engines has been flying for over 14 years now has had every type of engine run problem, not very often thankfully. I have had the right and left engine quit at some point during the flight. While this model is not electric powered it would behave the same way with electric with an engine out problem

When the left engine quits I have to make very small changes to the throttle and come in and land immediately. If I was to increase the throttle quickly the model will turn in and result in a crash. This model has never turned in on me even with the left engine dead and the right engine running since I never throttle up the running engine.

When the right engine quits the line tension increases, but still have to land because one engine is not enough to fly the model with authority.

I have noticed with the twins and tri-motors I have flown that the RPM differences between the engine is not as critical as you might think.

One of my friends flew a Cessna 310 electric powered with separate motor, speed control and battery all controlled with one throttle stick without any problems.

I would be temped to run both motors clockwise on a twin so that they force the model to the outside of the circle.

Fred Cronenwett
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Offline Tim Wescott

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Re: Twin engine ?
« Reply #17 on: March 04, 2012, 12:24:03 PM »
If you've got throttle control then it's different.  With throttle control on a scale model, I'd want to find a speed control with braking, and be able to intentionally fly with one engine out.  I don't fly scale in competition so I don't know if it still counts, but as far as I'm concerned, demonstrating level flight with one prop stopped (or one engine throttled down) is a scale maneuver.
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Offline Jim Fruit

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Re: Twin engine ?
« Reply #18 on: March 04, 2012, 03:12:48 PM »
Quote from: Tim Wescott on March 04, 2012, 12:24:03 PM
If you've got throttle control then it's different.  With throttle control on a scale model, I'd want to find a speed control with braking, and be able to intentionally fly with one engine out.  I don't fly scale in competition so I don't know if it still counts, but as far as I'm concerned, demonstrating level flight with one prop stopped (or one engine throttled down) is a scale maneuver.

Tim:

There may be some problem with that approach. Current rules require that for optimum points for the multi-engine option, all motors must run throughout the demonstration. That rule has been on the books forever and was obviously written with the difficulty of keeping multiple IC engines all running in mind. Electrics somewhat negate the intent of that rule as they can be started and stopped at will (poor Will!). However, I would not want to be the first to list shut down and restart as an option because it might be challenged as violating that rule. I have way more than the required 6 options available to me anyway, so I really would not need another.

Jim Fruit
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