Ed

I have a Turnigy G46, 420kv motor that I plan to use on 4s, 4000 mah. How well can I expect it to fly a Sig Kadet Senior kit that I plan to build ? It will be weighing about 6 1/2 pounds. I'll be using a 15 x 8 prop, and what kind of flight times can I expect ?.

Thank you.

Eduardo

aeajr

My Feedback: (2)

A link to the specs for the motor would help.

Ed

Will this help ?



Spec.
Battery: 4~5 Cell /14.4~18.5V
RPM: 420kv
Max current: 55A
No load current: 11V/1.5A
Internal resistance: 0.032 ohm
Weight: 300g (not including connectors)
Diameter of shaft: 6mm
Dimensions: 76x50m
Test Data:
18.5v - 14x10 Prop - 40A - 2650g Thrust
18.5v - 15x8 prop - 44A - 3150g Thrust

aeajr

My Feedback: (2)

Your test data is only on a 5S, 18.5V pack for that motor. I would estimate on a 4S pack it will pull about 36 amps or about 520 watts. That would be about 80 watts per pound which is fine for sport flying and mild aerobatics.

I would estimate about 6 minutes at full throttle and about 8 to 10 minutes of mixed throttle flying.

Ed

Mr. Aeajr, I can't thank you enough for coming back with that estimate. I have been getting conflicting opinions of how well, or poorly this plane will fly. Most opinions that I have been receiving are, that it will fly poorly. My goal is slow precision flight. Burning holes in the sky ? Been there, done that, and it leaves me cold.

Your statement " I would estimate about 6 minutes at full throttle and about 8 to 10 minutes of mixed throttle flying. ", has made my day.

Thank you Sir.

Ed

Ed

[TABLE]
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[TD]
For what it is worth, here are some additional Specs that I found on the same motor.

Thank you folks, for any and all comments.

Ed[TABLE]
[TR]
[TD]
[TABLE="class: defaultLineHeight"]
[TR]
[TD]Kv(rpm/v)
[/TD]
[TD]420
[/TD]
[/TR]
[TR]
[TD]Weight (g)
[/TD]
[TD]300
[/TD]
[/TR]
[TR]
[TD]Max Current(A)
[/TD]
[TD="width: 50, bgcolor: #E3E3E3"]55
[/TD]
[/TR]
[TR]
[TD="width: 140, bgcolor: #E3E3E3"]Resistance(mh)
[/TD]
[TD="width: 50, bgcolor: #E3E3E3"][/TD]
[/TR]
[TR]
[TD="width: 140, bgcolor: #E3E3E3"]Max Voltage(V)
[/TD]
[TD="width: 50, bgcolor: #E3E3E3"]19
[/TD]
[/TR]
[TR]
[TD="width: 140, bgcolor: #E3E3E3"]Power(W)
[/TD]
[TD="width: 50, bgcolor: #E3E3E3"]925
[/TD]
[/TR]
[TR]
[TD="width: 140, bgcolor: #E3E3E3"]Shaft A (mm)
[/TD]
[TD="width: 50, bgcolor: #E3E3E3"]6
[/TD]
[/TR]
[TR]
[TD="width: 140, bgcolor: #E3E3E3"]Length B (mm)
[/TD]
[TD="width: 50, bgcolor: #E3E3E3"]55
[/TD]
[/TR]
[TR]
[TD="width: 140, bgcolor: #E3E3E3"]Diameter C (mm)
[/TD]
[TD="width: 50, bgcolor: #E3E3E3"]50
[/TD]
[/TR]
[TR]
[TD="width: 140, bgcolor: #E3E3E3"]Can Length (mm)
[/TD]
[TD="width: 50, bgcolor: #E3E3E3"]27
[/TD]
[/TR]
[TR]
[TD="width: 140, bgcolor: #E3E3E3"]Total Length E (mm)
[/TD]
[TD="width: 50, bgcolor: #E3E3E3"]76
[/TD]
[/TR]
[/TABLE]


Again, I will be using it together with a 4s, 4000 mah LiPo, and a 6 1/2 pound airplane on a 15 x 8 prop.

My goal is slow precision flight, but there are people here and elsewhere, who are telling me that my Sig Kadet Senior ( kit not ARF ), is going to be a very poor flyer. Why are they doing this ?


Thank you for your help.
Eduardo

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aeajr

My Feedback: (2)

Context and goals are always the critical elements and you have not provided either until now. Also, a link to the web site for the motor is far more useful than you providing selected bits of information that may not be what I want to know. And you have not told me what ESC you are using so I don't know if your ESC will be able to handle that motor.

What sort of performance are you expecting?

What is your intended purpose for the aircraft?

Without that information the only answer I could give you is what the power to weight ratio would be and my opinion of what that would mean in terms of performance. Whether that would meet your goals was unknown to me.


Most glow pilots who are converting from glow to electric won't be happy at less than 100 watts/pound.

If you intend is to fly in a scale like fashion and fly mild aerobatics, 75 watts per pound should be plenty.

If you want to go pylon racing, 3D flight or pattern flying, then you will need 150 watts per pound or more. If you want to use this as a tow plane for gliders then you might need 200 watts/pound as you will be pulling two aircraft.
So, the opinion you get about how the plane will fly is based on the assumed goals of the writer.

The good thing is that your motor can handle that prop on a 5S pack so if you find the plane underpowered, just drop in a 5 S pack and you will get a big bump in performance. A 15X8 on a 5S pack will produce about (18.5V X 44 amps) 814 watts of power. Now you are at 125 watts/pound, a much higher power to weigh ratio.

Another path to more power, if you feel you need it, is to use a bigger or deeper prop. You are using a 15X8. You could go to a 16X8 if you have the ground clearance. Or you could go to a 15X10. Both would produce additional power on a the 4S pack and likely still be within the amp range of that motor. I have done this myself where I change the prop according to my intended use. For sport flying I might use one prop. For competition flying I might use a different prop.



So the move to more power is just a matter of changing the battery pack or the prop. Whether your ESC can handle that is unknown to me.

Ed

Mr. Aeajr, thank you so very, very much for having the patience to deal with this Newbie, I will try to supply you with the best information that I can. Here is the link to my motor. http://www.hobbyking.com/hobbyking/s...arehouse_.html

My goal is to putter around with a 6.5 pound Sig Kadet Senior, and do some touch & goes. No wild and crazy 3D stuff. Here is the link to my ESC. http://www.hobbyking.com/hobbyking/s...arehouse_.html

I will be using these along with a 4s, 4000 mah LiPo. How long do you feel my flight times might be ?

Eduardo

aeajr

My Feedback: (2)

Glad to help.

That ESC looks fine. Motor looks fine and the user comments seem to be very positive.

My original statements about performance and duration still apply. Your current battery and prop will have you in the Trainier, mild sport flying range.

I am a HUGE advocate of using Wattmeters to confirm that the motor/battery/prop combo is giving the results I expect. If you do not have a wattmeter I would recommend you get one. Based on the kind of plane you are building I would recommend you get one that can handle at least 30 volts and at least 80 amps.

here is the one I have used for years:
http://www3.towerhobbies.com/cgi-bin...&I=LXLMV2&P=ML

I recently purchased this one from HobbyKing to try it out. It also has a servo meter though I have not tried that feature yet. Have not used it much but the wattmeter seems to give similar results to my Watts-up Wattmeter.
http://www.hobbyking.com/hobbyking/s...r_1_5_TFT.html


Something to consider

A build thread is always appreciated by people so if you feel like posting your progress and photos and then flight reports I am sure many would be interested. And your experience will help other to be confident to proceed with a similar project. And don't be afraid to report mistakes and what you learned. We learn far more from our mistakes than our successes.

Best of luck with the project. I look forward to your updates.

Ed

Thank you Sir, I really do appreciate your help and advise. I will obtain a wattmeter. And also, is it reasonable to believe that smaller KV motors, like a 400 KV, will draw less current, and achieve longer flight times then a 600 KV motor ?

Thanks again.

Eduardo

aeajr

My Feedback: (2)

.


You might find this on-line book helpful in understanding more about electric power systems. I am the author.


EVERYTHING YOU WANTED TO KNOW ABOUT ELECTRIC POWERED FLIGHT
http://www.rcuniverse.com/forum/m_7100376/tm.htm

Chapter 45 talks about understanding kV. In fact, based on our conversation I actually updated that article to provide more clarification. You will recognize a few links from our conversation here.

Ed

I have saved your book, and I am going to read it cover to cover. Thanks a million !

Ed