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Author Topic: What size motor for a Topflite Tutor  (Read 2145 times)

Offline Geoff Newborn

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What size motor for a Topflite Tutor
« on: June 25, 2017, 05:09:28 AM »
Hi all, just getting back into control line after a long time, I have been flying RC for many years so have got motors and lipos available to use but I have no idea what sort of power an electric control line needs.
I have been given an old Topflite Tutor kit and would like to build it with electric power, in the RC world people talk about watts/lbs (100 watts/lbs for trainers, 200 watts/lbs for aerobatics) and most of my aerobatic RC models are running at 150-200+ watts/lbs. which gives good vertical performance.

Is there a similar guide for control line models?

Thanks in advance
Geoff

Offline Rogerio Fiorotti

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Re: What size motor for a Topflite Tutor
« Reply #1 on: June 25, 2017, 04:47:08 PM »
Geoff,

First let me convert Lbs into grams I'm more accustomed to.

1lb = 453.59gr if my calculations are correct.

In some "datalogger" charts drawn from Castle's ESCs peak power reached close to 800W in F2B maneuvers for an aircraft of 1900gr = 4.19lb, his thinking seems to be correct.

But I use an 1150W (Hyperion 3025 - 775kV) motor with a working temperature of 75ºC. I prefer to use engines with power greater than 30%.

I hope helped.


Rogerio Fiorotti

Offline Tim Wescott

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Re: What size motor for a Topflite Tutor
« Reply #2 on: June 25, 2017, 06:56:16 PM »
With a constant-speed timer, 7W per ounce average (to size the battery), 11W/ounce peak (to size the motor and ESC).  More for "reactive" timers like the Burger or Fiorotti, but I dunno how much.

At the top of the forum is a sticky thread called List Your Set-up that has a bunch of setups listed.  There should be at least one Tutor in there, as well as a lot of similar-sized planes.
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: What size motor for a Topflite Tutor
« Reply #3 on: June 25, 2017, 09:26:44 PM »
A back door way to get to a electric motor conversion from a nitro set up is to look at the recommended gas motor for the plane.  Look at the prop size and RPM for this motor.  I use Cobra motors from http://innov8tivedesigns.com/   They have prop charts for the various motors.  Find a motor that swings the right size prop at the required RPMs.  I use KR timers that allow me to set RPMs at 8K to 9K rpm or so.  So I look for a motor that will swing the prop at around 11K rpm giving the governor room to work.  For an example I am using a Cobra C2826-10.  Per the prop chart it will turn an APC 11 x 5.5E at 10310 RPM on a 4 cell LiPo battery.  It also states that it requires about 37 amps, info needed to pick the right size speed controller.  I have the KR controller set to 8500 RPM and this motor pulls my 576 square inch Ringmaster with ease.  Wattage ratting per lb is a good way to get into the right ball park then fine tune with the prop vs RPM chart.
John Rist
AMA 56277

Offline Tim Wescott

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Re: What size motor for a Topflite Tutor
« Reply #4 on: June 26, 2017, 08:50:45 AM »
A back door way to get to a electric motor conversion from a nitro set up is ...

Another, that I've heard about but have not used, is to just look at the recommendations for motor, ESC & battery for a 3D plane the same weight as yours.  The prop selection will be off, but at least you'll have the expensive parts chosen.
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 Tate

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Re: What size motor for a Topflite Tutor
« Reply #5 on: June 26, 2017, 09:22:02 AM »
You can not go wrong with any of the statements above. Years ago the Norfolk Aeromodelers inherited  an old beat up Twister (not lucky enough to get a Tutor). We went the cheap way by converting the twister to electric power so everyone in the club could try it. We used an Arrowind 2815-09 motor. The final prop was an 11 X 5.5 cut down to 10". A 4 cell, 2200MAH battery and an inexpensive 40 AMP ESC (several ESCs have been experimented with). Several timers have been used with some success. If you keep the weight down on the Tutor, you should have a nice stunter.

Offline Geoff Newborn

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Re: What size motor for a Topflite Tutor
« Reply #6 on: June 27, 2017, 05:12:35 AM »
Many many thanks for all your advice, I have an idea now of where I want to go, at 410sq inches it's not a big model and I have two motors which I think will fit the Tutor both are Turnigy 3536 one is 1250kv and the other 1100 kv depending on the prop and battery they give me a range of around 200 - 500 watts.

These kv ratings may be a little high but I am flying on grass and will need to keep to a max 10" prop (maybe could just get away with 11" but that would be a little big for these motors) my target weight for the Tutor is 32oz and to do that I will probably need to replace some of the wood as most of it is quite heavy grade.

Time now to start building will keep you posted on the outcome.

Thanks again for the help

Geoff

Offline Horby

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Re: What size motor for a Topflite Tutor
« Reply #7 on: September 17, 2017, 10:58:55 PM »
I used an Eflight  Power 15 with 4s 2200 batteries. I am at high altitude and the set up worked great. You don't need  the high KV motors.


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