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Author Topic: What size electric motor for Sig Fazer?  (Read 327 times)
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Ministick7
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« on: April 07, 2018, 04:52:24 PM »

Hello, modelers, I am building a Sig Fazer for electric power. Used to have one with an OS .46 that was a blast to fly. I would like to duplicate that power but without glow fuel. What size motor would you recommend? Any brands that you particularly like? I will also need to learn what battery to use for 5-7 minute flights. And what servos to use. Futaba 148s used to be in my old Faser. Probably do not need digital or super-fast. Thanks for your input. I appreciate your help.
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Konrad
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« Reply #1 on: April 07, 2018, 09:52:39 PM »

Lets get some philosophical stuff out of the way.
First there are no electric motors that emulate a glow engine. This because by their nature they produce power very differently. You can see this in the shape of the power curves for both motor types. You will notice that they effectively have power curves that slope in opposite directions. You will need to be aware of this as you start to match the power to the air frame. With glow if you wanted more power you went down on the prop load. With an electric motor one adds to the prop load to get more power.

Today I see no reason to use analog servos, well buy any that is. Today most 20 to 30 gram servo will out perform the S148 of old. I’d like to see you use a servo that is at least as fast as 0.10 sec/60°. With today receivers having a gyro native to them the speed is often needed to keep the gyro induced oscillation in check.  Love the KST brand as they are high performance combined with great value. the Hitech 225 is a good old school servo but today its modern 5245 brother is better

Also no glow conversion will work out as well as a design initially designed for electric. An electric airframe often ends up being about 30 to 50% lighter than its comparable glow brethren.

The Sig Fazer with the OS 46 was probably running an 11 to 12 inch prop and not producing much over 1hp to 1.2 hp on that small a prop.
http://www.sigplanes.com/SIG-Fazer-Kit_p_64.html

To get an honest 6 minute run time you will need a large power system. This means a motor that is about 280 to 300 grams in weight and for the Fazer you will want about 800 to 900 watts.
You are looking at a 500kv motor on a 6 cell lipo battery pack. this will drive a large 14 inch prop. At about 1/2 throttle you will have about the same performance as the OS46 equipped Fazer.

I like to run 2 3cell packs in series with a capacity of 2200 mAh to 3300 mAh.

Now for the recommendations.
Motor:
https://hobbyking.com/en_us/turnigy-aerodrive-sk3-5045-500kv-brushless-outrunner-motor.html

ESC:
http://www.castlecreations.com/en/talon-1/talon-60-6s-25-2v-60-amp-esc-with-20-amp-bec-010-0163-00
http://www.altitudehobbies.com/flyfun-series/hobbywing-flyfun-series-100a-sbec-v4-esc
http://www.altitudehobbies.com/flyfun-series/programming-card-for-hobbywing-escs

Battery;
https://alofthobbies.com/gens-ace-3300mah-3s-25c-xt60.html

Servo:
https://alofthobbies.com/radio/servos/kst-servos.html
https://www.servocity.com/hs-225mg
https://www.servocity.com/hs-5245mg-servo

Give this a good look
https://www.precisionaerobatics.com/product/addiction-xl-arf/


To get this big a power system in the Fazer might be a problem, ground clearance with the 14 to 15” prop.
A 4 cell option would be a 700 KV motor. But this might fall short of the 6 min requirement
https://hobbyking.com/en_us/turnigy-aerodrive-sk3-3548-700kv-brushless-outrunner-motor.html
With a 3300 plus mAh battery;
https://alofthobbies.com/tattu-3700-4s-45c.html

You can drop down to a 50 amp ESC.
And 15 to 19 gram servos should still be fine.
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Re: What size electric motor for Sig Fazer?
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Ministick7
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« Reply #2 on: April 08, 2018, 01:34:49 PM »

Thank you kindly, Konrad. Your expertise will help me greatly make this airplane fly its best. I will digest all that you said. As a former Indoor freeflight builder, I can usually build light. I will use lightweight wheels, etc. wherever it makes sense. Maybe even space the ribs a little further apart. Perhaps I do not need a full 6 minute flight, and can save some battery weight there. I will take your advice on servos and other electronics. Thank you again. I will keep you posted here on the progress. I am going to print your response and go over it several times. All the best to you.
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Konrad
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« Reply #3 on: April 08, 2018, 02:37:50 PM »

Actually most of the weight in a glow model that can easily be removed, is in the front of the fuselage. Often times there is far too much structure, mass, needed to absorb the vibration of the engine. With an electric most of this vibration is gone so lighter materials and structure can be used.

What do you have for a charger?

All the best,
Konrad
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Ministick7
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« Reply #4 on: April 10, 2018, 12:59:53 PM »

Ordered the 660 watt motor suggested and the 60 amp ESC. And, battery for that motor as recommened by Konrad (thank you.) Got 4 servos KST. Now, waiting for the Fazer kit to arrive. My target weight is 3.5 pounds ready to fly. What propeller would you recommend? I do not have a multiple cell charger. What suggestion(s) do you have there. I am thrilled to get this experienced pilots' input. Thanks again.
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Konrad
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« Reply #5 on: April 10, 2018, 01:51:44 PM »

Not sure of your flying style. But if you have the ground clearance a 14x7 is good for hovering. A 13x9 or 12x11 might mimic the 46 cid.

I like the FMA brand of charger. The Hyperian is also a good brand. I think you will want 800 to 1000 watt per channel chargers. I like to see you get more charger than you need because you will grow into to it. Also taking 30minutes to an hour to charge a battery is a real pain.
http://www.usastore.revolectrix.com/Products_2/GT-Series-Battery-Chargers-US

What servo did you choose. I'm really impressed with these, more torque, way more speed, and less than half the weight of the S148 and it has metal gears.
https://alofthobbies.com/daviga-ds213-servo-3-0kg-41-7-oz-in-07-sec.html

Now I never did like Futaba servos I had far too many failures with the S126,S132, S133, S135. Had good luck with the S3002  but this servo cost me $79 in 1990 dollars!

All the best,
Konrad
« Last Edit: April 10, 2018, 02:13:00 PM by Konrad » Logged

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Ministick7
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« Reply #6 on: April 10, 2018, 03:07:21 PM »

Great minds think alike. That is exactly the servo I chose. 4 times. I will look at the chargers and see which one(s) look best, then ask for your input, if you will. Thank you.
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Ministick7
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« Reply #7 on: April 12, 2018, 04:31:02 PM »

Is there any reason to not get this one? Charge two batteries at once?
http://www.usastore.revolectrix.com/Products_2/_GT1000DUO/GT1000DUO_2

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Konrad
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« Reply #8 on: April 12, 2018, 04:51:33 PM »

None that I konw of. Other than if it is stolen you effectively loose 2 chargers.

All the best,
Konrad
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Ministick7
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« Reply #9 on: April 12, 2018, 06:14:52 PM »

Would the perpetrator be charged with two counts of larceny?
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Konrad
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« Reply #10 on: April 12, 2018, 06:31:32 PM »

Lol,

Don't know what he would be "charged" with.
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Ministick7
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« Reply #11 on: April 13, 2018, 08:02:01 AM »

Charged with "battery?"
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