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I want to add a UBEC

Old 01-30-2015, 08:59 AM
  #1  
Ed
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Default I want to add a UBEC

I was concerned that the 3 amp BEC onboard my ESC was not going to be large enough to support the aircraft that I was building, so I added this UBEC> http://www.hobbyking.com/hobbycity/s...dProduct=50437 , for insurance.
At 5A, (7 1/2 A Burst) , It was the largest that Hobby King had. Do you think that this will now be big enough to power my Rx, 1 digital, and 3 regular size analog servo's ? My plane is a Kadet Senior, powered by a Turnigy G-46. This is my first large electric, and I need your assurance that I am doing it right. I don't plan any 3D, just some relaxed flying.

Thank you.

Ed

Last edited by Ed; 01-30-2015 at 10:27 AM.
Old 01-31-2015, 01:47 AM
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chuckk2
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There is more than one G 46 variant. What is the KV rating of the one you have? When you say standard servos, what is the torque rating?
With normal servos, the BEC you selected seems to have the current capability (by spec) that you want.
If your speed control has three leads, you should likely disconnect the red wire. Otherwise, the ESC's internal BEC and the external one can "fight".
I also use http://www.castlecreations.com/produ...-cap-pack.html as a filter, and connect an SBEC to it.
Old 01-31-2015, 02:27 PM
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Ed
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The plane will be a Kadet Senior, I want to do some slow precision flying for a change. And so, I choose the 420 KV motor, because it will be turning a 15 X 8 prop. Will it pull more or less current then the higher KV motors ?

The servos will be 3 standard 48oz Futaba analogs, with one digital 72oz on elevator.

OK on the red wire, already done did it.

Thanks for your help.


ED
Old 01-31-2015, 03:29 PM
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chuckk2
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In general, at the same voltage and with the same prop, the 420kv motor will provide less rpm and less power than the higher kv versions.
The secrets are based upon such things as e-calc's approximation and rules of thumb.
In Short, knowing the motor power battery number of cells, the prop size, the motor specs, the ESC specs, you can establish how much
power and RPM are available. The aircraft weight and wing loading are also factors. From E-Calc, the motor may be producing less power than it can.
using the 15x8 prop at ~18 v
I see about 44-50A current

Really, the weight and wing loading is needed to get a more accurate picture.

I have the ARF version of what was referred to a a P-51 RTS that is electric powered.
Total weight is about 10-1/2 Lb. As a result, I chose to use an E-Flight 52 instead of the E-flight 46
and a 6cell 5000mah lipo. The higher rpm calls for about a 12x8x3 prop.

Lets start
Turnigy G60 Brushless Outrunner 420kv
Kv(rpm/v) 420
Weight (g) 300
Max Current(A) 55
Resistance(mh) 0
Max Voltage(V) 19
Power(W) 925
Shaft A (mm) 6
Length B (mm) 55
Diameter C (mm) 50
Can Length (mm) 27
Total Length E (mm) 76

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
Old 01-31-2015, 03:53 PM
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Ed
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Chuck, it's a Turnigy G-46, not a G-60.

Being a newbie, I don't know anything about E-Calc, but here is what I do know. The Kadet Senior should come to about 6.5 pounds, span 78", has 1150 sq in wing area. Maybe about 13.oz per sq foot ? ? ? Using a 4s, 4000 mah pack ( 14.8v ), together with the G-46, 420 KV motor, swinging a 15 X 8 prop. Spekie AR 7000 Rx, 3 standard 48oz servos, one 72 oz digital servo, 70 A ESC, and a 10 A UBEC. I have been told that a big prop is more efficient for a slow flier, and needs a low KV motor ? ? ? I don't know how true this is ? ? ? No 3D Planned here, just slow precision flight.

Do you have any idea on what my flight time might be ? Does your E-Calc tell you that ?

Thanks Chuck.


Ed

Last edited by Ed; 01-31-2015 at 08:18 PM.

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