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GWS A4 Skyhawk

Old 03-16-2009, 01:14 PM
  #226  
Lieutenant Loughead
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Great video! However, I'm a little confused -- how are you belly landing her with the landing gear, fuel pods, missiles, etcetera?
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Old 03-16-2009, 04:50 PM
  #227  
Crash Test Dummy
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My scooter/A-4 has been sitting in the hanger all winter long. It has been too cold and windy to bring her out. However the weather is improving and I hope to get her back in the air soon. I put a receiver back in her last night and made sure the model was set up in my radio. After a range check it should be ready to go!!!

CTD
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Old 03-16-2009, 07:07 PM
  #228  
Kiwikid
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Originally Posted by Lieutenant Loughead View Post
Great video! However, I'm a little confused -- how are you belly landing her with the landing gear, fuel pods, missiles, etcetera?
Thanks. I have only flown the Scooter once with all the gear on (Except the refeuling probe - its made of No. 8 fencing wire) and it was not pretty - never again. All the attachments were only ever intended for static purposes as the model was built as a hand launced belly lander - the opening flying scene is straight off a hand launch. Build blog is here: http://www.rcgroups.com/forums/showthread.php?t=966521


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Last edited by Kiwikid; 03-16-2009 at 07:32 PM.
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Old 10-02-2009, 12:39 AM
  #229  
clive45
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The esc is happiest running at 100% cutting back on the throttle just makes the ESC have to dissipate more heat, that's why we try in electric helis to get the head speed we want at as close to 100%. If at 100% you exceed the ESC max ratings then you have to get a bigger ESC or cut the voltage ie 4S to 3S etc. Also linear becs have a greater problem as the voltage goes up as the amount of heat to be dissipated goes up substantially. A switch mode bec does away with that problem and a separate bec is also a good idea, if the esc fries or shuts down (over heat) there is a good chance you will still have control of the rx and aircraft.
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Old 10-02-2009, 05:30 AM
  #230  
babylon5
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Originally Posted by clive45 View Post
The esc is happiest running at 100% cutting back on the throttle just makes the ESC have to dissipate more heat, that's why we try in electric helis to get the head speed we want at as close to 100%. If at 100% you exceed the ESC max ratings then you have to get a bigger ESC or cut the voltage ie 4S to 3S etc. Also linear becs have a greater problem as the voltage goes up as the amount of heat to be dissipated goes up substantially. A switch mode bec does away with that problem and a separate bec is also a good idea, if the esc fries or shuts down (over heat) there is a good chance you will still have control of the rx and aircraft.

Hi , another thing I like to add on the ESC behavour is max. heat do not occur at max power but rather at around 30 to 60 % throttle setting.

That is because the ESC although is a switching device does have an average resistance and this average resistance vary from very low (max throttle to very high(almost infinity) at min. throttle.
When the average resistance of the ESC matches the load resistance of the running motor at somewhere 30% to 60 % throttle , max. heat occur at the ESC, and there is where the ESC gets really hot.

This in electrical engineering is known as " maximum power transfer".


In another words, a 40 amps rated ESC with a badly design heat sink can be cooked and damage at around 20 amps. It gets hotter if you increase the cells count and when one operate the throttle at 30 to 60 % power for a prolong period in time.

I have come across some badly design the heat sink base on max. power situation, which is incorrect. The correct way is to determine the heat by varying the voltage and current to device where the heat sink is attached.

Here is a simple test ,try to run between 30 and 60% throttle setting for over 1 or 2 minutes and feel if the ESC is hot, especially the China made ESC.


Cheers
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Old 10-02-2009, 09:53 AM
  #231  
Fugitive_Bill
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Hang on, I think I've lost plot...

So in OTHER WORDS, when I fly around at about 1/2 stick (be it a plane or 'sport' mode on on a Heli), thinking I'm going easy on the motor,ESC and battery, I am actually doing more damage than good and actually over heating the ESC by runnng it at 40-60%???

In reference to helis (don't why that is mentioned in the EDF Skyhawk thread, but anyway), when I switch to '3d' or 'idle-up 1', I run at 90% power, depending on throttle curve, pitch curve, motor Kv, battery and pinion used, it gets very complicated, and how the heli is behaving on those combined settings/setup.

My question now becomes, what percentage is the ESC happest at? 30%, 50%, 70%, 90%, 100%? !!!

-Bill!
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Old 10-02-2009, 05:01 PM
  #232  
FresnoJay
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Hey guys been hanging out on RCG mostly as my old comps took forever to load WF. Starting to come around and hang out on here again.

Kiwi, Nice to see you on here too.

LT, Mine has belly landed many times after being bugnee launched. I have ply skids to protect the aileron servo's and a centerline skid to protect the belly. When the time comes that she get retracts they can become stores Pylons as they are in scale locations.

CTD, She looks sweet. dust her off and get her going.

On a side note my scooter is down due to having a rough summer testing large power setups for my F-35. Plus made the switch to 2.4 and am kinda lagging on Rx's.

Jason
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