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Old Jan 28, 2013, 05:01 PM
Tossing planes into the snow
Canada, BC, Smithers
Joined Nov 2011
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On the subject of internal BEC's vs UBEC's I would like to share the following information. The following was cut and pasted from the user manual for the EFlite 30 amp ESC that comes with many of the ParkZone planes...

---------------------------------------------------------------
Servo Ratings with BEC Enabled:
Drives up to 5 analog or 4 digital sub-micro-sized servos with the BEC on any recommended input voltage.
Some servo combinations we have tested in various models include:
• 1 analog standard servo, 1 digital sub-micro servo, 2 analog sub-micro servos—E-flite Apprentice 15e RTF
• 2 ParkZone (PKZ1081) analog sub-micro servos and 2 ParkZone (PKZ1090) digital metal gear sub-micro servos—ParkZone T-28 Trojan RTF & F4U Corsair RTF

Some other brands and models of servos may have significantly higher current draw. Digital servos and binding servos of any kind typically have higher current draw. As a general rule, micro and sub-micro servos draw less current which may affect your servo usage as shown in the examples above. We recommend the use of a Hangar 9 Servo and Receiver Current Meter (HAN172), installed between the throttle lead of the ESC and receiver, to confirm current draw of the actual servos used. Also, always
be sure to position the ESC for maximum airflow since cooling can significantly aid in the performance of the BEC.
Before first use, please refer to “Servo Ratings with BEC Enabled” notes for BEC usage guidelines. You must follow these guidelines for safe operation. If you are using more than 5 analog sub-micro-sized servos, more than 4 digital sub-micro-sized servos, or servos with higher current draw than the BEC can deliver, you will need to disable the BEC. If you wish to disable the BEC, you must remove the red receiver wire lead and connector from the receiver lead housing, and then insulate it properly to prevent shorting. When operating with the BEC disabled, E-flite recommends the use of a separate, high-power, external BEC (like the Ultimate BEC), or receiver pack and switch using the following items to ensure trouble-free operation:
--------------------------------------------------------

The obvious question is...why is that ESC being shipped with the Radian Pro, which has 6 servos, 2 of them being digital?
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Old Jan 28, 2013, 05:47 PM
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Quote:
Originally Posted by dangerdan View Post
Judging by the discussion there maybe no benefit to using an external UBEC in a Sailplane

Thanks for the info. It was very usefull. I may bring this issue up at our next meeting.
Again, it depends on the BEC that is included in your ESC. Note that not all ESC include BEC.

Read the instructions with the ESC and see if it makes any recommendations.
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Old Jan 28, 2013, 06:12 PM
Tossing planes into the snow
Canada, BC, Smithers
Joined Nov 2011
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Originally Posted by aeajr View Post
Read the instructions with the ESC and see if it makes any recommendations.
I read the instructions and they recommended that 5 servos were the maximum it could handle (as quoted in the previous post). I'm still wondering why it is the stock ESC on a plane that has 6 servos.
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Old Jan 28, 2013, 06:21 PM
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USA, CA, Chico
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Quote:
Originally Posted by Jovanx View Post
I read the instructions and they recommended that 5 servos were the maximum it could handle (as quoted in the previous post). I'm still wondering why it is the stock ESC on a plane that has 6 servos.
I've seen this point brought up many times about the radian pro,, I guess they HH feels that in a sailplane application that six servos is OK,,,,, or maybe they just figure : its a foamie,,, so why bother. :-O
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Old Jan 28, 2013, 06:31 PM
Tossing planes into the snow
Canada, BC, Smithers
Joined Nov 2011
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Quote:
Originally Posted by Airman74 View Post
I've seen this point brought up many times about the radian pro,, I guess they HH feels that in a sailplane application that six servos is OK,,,,, or maybe they just figure : its a foamie,,, so why bother. :-O
I guess you are right. Foamies are easy to fix for sure. I am surprised and not surprised that HH has never come up with an explanation for this anomaly.
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Old Jan 28, 2013, 06:33 PM
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Here's my quick and dirty take on ESC/BEC.

Whether it's a separate component or built in one needs to differentiate between "linear" and "switching" BECs. A linear BEC is basically just a resistor and it converts excess voltage into heat. A switching BEC actually turns the current on and off really fast to arrive at an "average voltage". The general consensus seems to be that a quality, name brand, ESC with a built in switching BEC is great for most applications.

A stand alone BEC provides a measure of insurance if one's setup fries the main power circuit of the ESC. In this case one will retain radio power even though the motor is dead as long as the battery doesn't fail too. On the other hand, a stand alone BEC is another electronic component that can fail. For a truly "fail safe" setup one would probably be better served by running a separate receiver battery.

The biggest possible drawback with a switching BEC is that it does create more "noise" than a linear BEC. Though I have not tested it myself I have read that linear BECs are better with older radios that are not 2.4ghz. Most 2.4ghz radios can handle the noise and one can add a little more insurance with a ferrite ring on the wires.

It seems like separate circuits are more important with aerobatic planes than with gliders. Neither the motor circuit nor the radio are as likely to be running near their maximum capacity in most gliders. Assuming that the ESC is sufficient for your motor and the BEC is sufficient for your radio you should be O.K. with a combined unit. Just to pick arbitrary numbers; one can get into trouble using a 40amp ESC with a 40amp motor and the BEC is built to handle 2 amps and one's servos draw 2 amps. That's a recipe for disaster.

I have seen no compelling reason to run separate ESCs and BECs as long as one uses good components that have some excess capacity.
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Old Jan 28, 2013, 06:36 PM
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Quote:
Originally Posted by Jovanx View Post
I read the instructions and they recommended that 5 servos were the maximum it could handle (as quoted in the previous post). I'm still wondering why it is the stock ESC on a plane that has 6 servos.
I think that they are using the "stall current" of the servos as a guide to give themselves an out on liability. A BEC that can survive 5 stalled servos should be more than sufficient for normal use with 6 servos.
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Old Jan 28, 2013, 06:41 PM
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Quote:
Originally Posted by Airman74 View Post
I've seen this point brought up many times about the radian pro,, I guess they HH feels that in a sailplane application that six servos is OK,,,,, or maybe they just figure : its a foamie,,, so why bother. :-O
I had numerous brownouts with the stock RadianPro ESC, so on one of the replacement airframes I substituted an ice lite 50 for the original ESC and on another airframe I have added a castle 10 amp UBEC. No more brownouts. I will use the castle UBEC on the mystique when the time comes.

--Jason
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Old Jan 28, 2013, 07:51 PM
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Red Bluff CA
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I will use stock setup. Just saying
Randall
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Old Jan 28, 2013, 08:16 PM
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United States, WA, Bellevue
Joined Oct 2010
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I just bought the ARF today...gearing up to build it now

Question: I'm considering using the Gforce G25 motor on this bird (link below). Anybody have any thoughts on that? Also any experience in general with that motor guys?
http://www.valuehobby.com/power-syst...ner-motor.html

Also, does anybody have any slim wing servos they might want to sell?
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Old Jan 28, 2013, 10:54 PM
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Quote:
Originally Posted by Jovanx View Post
I read the instructions and they recommended that 5 servos were the maximum it could handle (as quoted in the previous post). I'm still wondering why it is the stock ESC on a plane that has 6 servos.
Quote:
Originally Posted by Airman74 View Post
I've seen this point brought up many times about the radian pro,, I guess they HH feels that in a sailplane application that six servos is OK,,,,, or maybe they just figure : its a foamie,,, so why bother. :-O
If I am correct, the recommended ESC is the e-flight 60 amps
http://www.horizonhobby.com/products...s-esc-EFLA1060

Key Features
Up to 60-amp continuous current with proper airflow, 75-amp peak
5-volt switch-mode BEC circuit capable of 2.5-amp continuous current on any recommended input voltage
Drives up to 7 analog or 6 digital standard-size servos, with the BEC on any recommended input voltage

Now, we are not using standard size servos we are using micro or mini-servos which draw less than a fully loaded standard servo so I think the internal BEC should be just fine.

If that is the recommended ESC, and no recommendation for a separate receiver pack or BEC, one would expect the built in BEC is sufficent especially for the thermal duration glider.

However, if you are concerned, then get an external BEC. The Castle Creations 7 amp/ 10 amp BEC is $21
http://www.horizonhobby.com/products...c-CSE010000400

On an overall investment of over $700 to get the glider into the air, that is a very small incremental price to pay for some peace of mind. I would probably use the BEC in the ESC, but if I were getting and external BEC the Castle would be the one I would get. 2.5 amps is probably more than enough so anything over that should be fine.
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Last edited by aeajr; Jan 28, 2013 at 11:10 PM.
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Old Jan 28, 2013, 11:20 PM
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On a separate note, the recommendation for a 60 amp ESC is excessive considering the recommended motor has a peak current rating of 44 amps. Any ESC over 50 amps should be fine. And any switching BEC of 2.5 amps or higher should be fine, based on the specs for the e-flite 60 amp ESC.
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Old Jan 28, 2013, 11:47 PM
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United States, WA, Bellevue
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Quote:
Originally Posted by coolgg View Post
I just bought the ARF today...gearing up to build it now

Question: I'm considering using the Gforce G25 motor on this bird (link below). Anybody have any thoughts on that? Also any experience in general with that motor guys?
http://www.valuehobby.com/power-syst...ner-motor.html

Also, does anybody have any slim wing servos they might want to sell?
Another question for the folks who've already built this thing: Slim wing servos are relatively hard to find and expensive. The width of the recommended servo A7020 is 0.39 inches (10mm). If I use another servo instead with equal or better torque, what is the widest/thickest width that I can go with and still have the servo fit in the wing? Will a 0.66" thick servo work?

Also, what is the minimum torque you'd recommend for a wing servo? The A7020 has a torque of 47 oz-in (3.4kg-cm) @ 4.8V.

Thanks!
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Old Jan 29, 2013, 02:13 AM
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Australia, WA, Perth
Joined Feb 2012
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Quote:
Originally Posted by aeajr View Post
On a separate note, the recommendation for a 60 amp ESC is excessive considering the recommended motor has a peak current rating of 44 amps. Any ESC over 50 amps should be fine. And any switching BEC of 2.5 amps or higher should be fine, based on the specs for the e-flite 60 amp ESC.
My 2c's on the BEC question/doubts... All manufacturers, not just E-Flite, are conservative when talking about tolerances and how much or how few servo's a BEC is capable of running - mostly because us aeromodellers have a habit of pushing the envelope and souping up our toy aeroplanes that we all like to fly

I think the golden rule here is common sense prevails - hopefully - and be mindful of the rating that your BEC can handle and the max peak current required by your speed controller and go from there when it comes to choosing the right speedy/BEC for you. When in doubt, go by the manufacturers (whoever that may be) recommended products; or at least something that will handle exactly the same current and voltage requirement for the BEC and speedy. Don't wanna use E-Flite? Got a spare CC speedy laying around - awesome! Just ensure the critical specs match.

Finally, as to the doubts about the diminutive size of the Radian Pro BEC? Well, just remember in a 3D plane, all servos are working all the time, and usually at close to maximum throws. E-gliders don't - they don't even come close (as a rule lol) so therefore in theory a much lower (and lighter) BEC may be an option; as is proven with the Radian Pro. I've had over 200 hours on the 3 RP's I have owned over the last 18 months and never had a brownout or BEC failure. I have found trees, fences and angry eagles more of a glider killer than a BEC could ever be lol

Just sayin'...
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Old Jan 29, 2013, 07:17 AM
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Good points Timography.
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