Hello, I'm a little stumped with my A-10 brushless numbers. - RC Groups
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Mar 26, 2006, 11:42 AM
Fly it like you own it.
_Pattern_Man's Avatar

Hello, I'm a little stumped with my A-10 brushless numbers.

Hi everyone,

In my GWS A-10, I'm running EDF-55 300H fans with Fiegao 2035-4700kv motors and thunderbird 18's.

Now I seem to be pulling 16.5 amps at full throttle and 10 amps at 3/4 throttle.

These little motors are rated for 10amps max. And this was on a TP 3S1P 1320mAh 11.1V pack.
If I switch to a 14.8 Volt 4 cell pack, will my amps go down or go up from the increased rpm?

I thought I had heard somewhere that more volts equals less amps?? But it would also equal more RPM and I can't exactly change the prop.

Also at 4700 Kv at 11.1V I'm looking at 52,170 rpm. And at 14.8 Volts, I'd be at 69,560 rpm. Will the 4 cell pack push the fan beyond it's limit? It seems a little fast for an EDF-55.

Thanks alot.
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Mar 26, 2006, 12:50 PM
SoCal, Year Round Flying!
bmiller's Avatar
WOT w/4S will increase your ampdraw since the rpms increase.
(I believe) if you throttled down to the SAME rpm level as the WOT w/3S setup,
Your ampdraw would be lower at the same rpm.

But basically the 4700kv is too high for the load and may burn out with extended WOT running. So throttle back!
At the stated rpms the blades may rub but they'll clearance themselves after a few flights. I would add throttle on mine until they rubbed lightly, and after about 4 flights they don't rub at all anymore.
Mar 26, 2006, 04:07 PM
The best in EDF since 2005
Extreme_RC's Avatar
I'm a bit lost as to your numbers, are you pulling 16.5 amps WOT for both motors or one? Are they rated to 10amps each, or combined? I would have thought 4700Kv would be rated to at least 10 amps each, but at 20 by 35mm size would have expected more like 14-18amps rating.

And your battery at 1350mah is pretty small for this kind of current. I now have 4400Kv motors in my A10 rated at 12 amps each, they are 20 by 30mm and fit into the 55-150 housing. When I first spooled them up with my 1500mah 15c battery I hit 27 amps which quickly dropped to 24, the battery was over its limits, the voltage dropped towards 9v within 7-8 seconds. At 2/3rd throttle I was pulling around 17 amps and it fly fine like this with quick bursts to pull vertical for a loop etc. Today i am going to get a new pack, and will report on what happens, as its the same physical size and weight as my 1500mah JP, but offers 36amps max continuous and larger capacity with fancy korean cells. I am expecting to pull more amps and have this thing produce 700g plus of thrust, but time will tell!!

Hay Bill, you see my pics? I think they uploaded the second time. I have since weathered the paint a bit and done some decorating, its looking quite nice now
Mar 26, 2006, 04:12 PM
The best in EDF since 2005
Extreme_RC's Avatar
Oh and dont forget, those rpm numbers are unloaded ones, take away 25-30% from what I have been able to calculate to get loaded rpm with the EDF55 6 blade rotor.

This particular issue has been nagging me for ages, so I compiled as much data as I could from sites showing motors fitted to EDF55 and the resultant rpm with x voltage, I ended up with around 25% or so drop in rpm with the 55 fan unit on the shaft. If I am wrong, or someone has some actual measured data with a tacho please post it!

PS: this might actually be worth askin Mr GWS about, he should be able to tell us % drop in RPM with the 6 blader.
Mar 26, 2006, 04:38 PM
Go FASST or go home...
Ben_E's Avatar
Originally Posted by mocca
This particular issue has been nagging me for ages, so I compiled as much data as I could from sites showing motors fitted to EDF55 and the resultant rpm with x voltage,
Could you share your findings??
I think the issue regarding the selection of powersource for the EDF55 is very little covert by testers and producers...

Mar 26, 2006, 04:56 PM
Registered User
68Strat's Avatar
if you didnt already cut down the rotor to 3 blades this will increase rpm and pull less amperage.
Mar 26, 2006, 07:03 PM
Fly it like you own it.
_Pattern_Man's Avatar
Thanks for the input.
To clear it up The motors say 10amp max on them. So per motor. I was drawing 17 amps at WOT on 1 motor. And the lipo is 16c so it was fine. I didn't know what to expect for amps.

I would think I'd be alright if I manage my throttle properly but I wanted to drop the amps a bit.

I'm stuck with these motors and I don't want to trim blades if it means I'll loose thrust.

Plus the TB18 ESC's are only rated for up to 3S Lipo.
Mar 28, 2006, 04:24 PM
Watts your motivation
roccobro's Avatar
Originally Posted by 68STrat-DFAlpha
if you didnt already cut down the rotor to 3 blades this will increase rpm and pull less amperage.
Not by much less amps at all. The increase in rpm just compensates for the decrease in thrust for the same rpm. Not really worth the effort, just get the correct motors and be happy (your ESC's will thank you too).

Seems this urban legend has popped up (again) since HL mentioned it for one of their models they didn't have the correct components to do it right from the get-go.

Mar 29, 2006, 07:07 AM
The best in EDF since 2005
Extreme_RC's Avatar
4700Kv is too fast for the EDF55, you are pulling too many amps. Also your battery is way too undersized for the A10 with brushless, you will find after 5 seconds your battery is dropping very quickly towards 9v, and will go under it if you hold WOT for 15-20secs. You need a battery like the Hyperion I chose, cont' discharge rate is 36 amps, weight is 140 grams, its only 12 grams heavier than my JP 15c 1500mah but provides heaps more power on the bench. My setup is only pulling 16c WOT which is perfect.

Your motors are a little bigger than what I use, mine are 20-30 and weigh 43 grams, (same as original) are 4400Kv and rated at 12 amps but I am pretty sure they can stand more.

My 3400Kv motors from the same factory pulled only 8 amps WOT each yet were rated at 14A, the A10 flew nicely but could not pull vertical.

My current tests are:

4400Kv motors in the EDF55-150 housings, 6 blade fan, twin 18A ESC's and one of the new Hyperion CLX1800 20c batteries. On freshly charged battery it pulled 31 amps and 320 watts, dropping slowly to around 27 amps, 10.8 volts for 290 watts.

RPM on the fans at full throttle was around 19,000 on a hyperion meter, so that completely f#$%s my calculations of a 25% drop under load from the unloaded Kv figure!! (or the hyperion was getting bad readings)

I have yet to fly with the new battery, hopefully tommorrow will be a little more friendly wind wise, from the very basic measurements I can do right now I am looking at around 600-700 grams thrust.
Last edited by mocca; Mar 29, 2006 at 07:19 AM.
Mar 29, 2006, 07:28 AM
Fly it like you own it.
_Pattern_Man's Avatar
Thanks for the info guys. The TP 1320 is not the battery I plan to use with the A-10. I should have emntioned it was just what I had close by for testing at the moment.

I have some 20C Apogee 2100 packs that I'll be using.

I'm pretty disappointed about the motor. I was told that the 5400kV motors were to much and that the 4400 was perfect. The motor seems to handle it fine but the 10 AMP MAX printed on it kind of scares me. It seems as though it should be able to handle over 10 amps.

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