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HomeRC & Power✈️Aircraft🚁HelicopterFlybarless Rotor Head SystemsFutaba CGY › JR 8915 Servos running hot
06-05-2011 11:25 PM  8 years ago
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t-rex pedro

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UK

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JR 8915 Servos running hot
Hi guys

I've just installed a CGY750/R6203SB combo in my 700N. I'm also running a Scott Gray ReactorX powering JR8915 cyclic servos at 6.8v.

The first thing I noticed was how fast the servo response is on the bench. I mean lighning fast! Faster and more aggressive than anything I've ever seen.

The issue is that the cyclic servos are getting hot after a flight. So hot that I can barely keep my finger on the elevator servo. I can also replicate this on the bench after a couple minutes of stick stirring!

Do you guys find your servos run hot with this set up? There's no binding at all and I have the align metal elevator mount fitted.

Any idea appreciated.

Thanks

Pete
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06-06-2011 01:20 AM  8 years ago
Ben-T-Spindle

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Central Illinois

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Flybarless controllers work servos much harder so you need to use good efficient servos with lots of torque. It’s a common misconception that you need super fast servos for cyclic. While speed is important if they don’t have enough torque they will run very hot and not last long especially if you run at high voltage. Brushless motor servos would be a good upgrade.

... BTS
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06-06-2011 01:34 AM  8 years ago
t-rex pedro

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UK

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Thanks for the reply. However, I would expect the JR8915's (8717 US version) to be up to the job. I have a buddy with the same servos in a Vbar equipped 700. His get a little warm, not hot at all.

Pete
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06-06-2011 03:14 AM  8 years ago
helicraze

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Victoria - Australia

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Is there an option of HZ for swash servos in the futaba setup? They may be driven at a rate a little too high for these servos.
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06-06-2011 08:03 AM  8 years ago
Mr.Gravity

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Mena,AR

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If you haven't done so, go to your "Swash Basic" setting and set your servo type. Incorrectly set would certainly make your servos HOT!Vince
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06-06-2011 08:55 AM  8 years ago
t-rex pedro

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UK

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I have set the servo type to 1520 in the swash basic menu. Interestingly the only options seem to analogue or 1520 digital. The Hz cannot be changed as far as I can see. Could this be my issue?
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06-06-2011 10:27 AM  8 years ago
davo705

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Sydney, AUS

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YES YES YES...
I have been involved with 4 CGY750 setups on 2x TREX700's, Vibe 50 and Synergy N5.
With combos of align 610's, futaba BLS451 and JR 8915's
All have had warm to hot servo bases after a flight. (measured 45deg C on backplate of servo)

ALSO all have been upward of 800mah's consumption out of the 2S lipo setups(thunderpower 25C 3600/ 5000 packs).
With combinations of Gryphon regs and no reg's (ie direct). Also wiring combo's, ie, Higher gauge wiring harness from rec battery split into two servo connectors then into reciever and direct of TP pack with futaba lead.

Obviously its a very busy system with lots going on.
In the vibe50 it ran the 3g system previously @ roughly 350mah consumption.
The vibe50 also started with align 610's then to the BLS451's and no real difference in servo temp, flight quality, time or consumption.

High and low gains in ail and ele have not made a difference in temp either. And there is no obvious temperature in the reciever, connectors, wiring or regulators.

But still flys well...

regards,
David
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06-06-2011 10:42 AM  8 years ago
t-rex pedro

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UK

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So what do I do?
I'm obviously concerned that the cyclic servos could fail with getting so hot. Also, I know on the BeastX the frame rate is selectable (200Hz for 8915/8717). I'm a bit lost here. Maybe one of the Futaba guys can jump in?
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06-06-2011 11:59 AM  8 years ago
panzlflyer

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Goldsboro,NC,USA

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On a Beast they are driven at 200hz the exact same as Bls, mine dont even get warm and theyve been thru 2 helis and 4 different fbl controllers and are on a Vbar now.
As to them not having enough torque? youre kidding right???
Sounds like Futaba needs to address the frame rate or deadband.
T700,450Pro,Spirit Pro,Beast+, Qav 500,Futaba18SZ
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06-06-2011 12:18 PM  8 years ago
t-rex pedro

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UK

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Panzlflyer - Thanks for the reply. Im also wondering the same thing with regards to the frame rate. On the other hand I know of an Elq90 with CGY750/JR8915's and the servos only get slightly warm.

I have no idea which way to go with this. I cant fly the heli for fear of the servos failing and I dont want to plunk down major $ to try different servos.

Pete
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06-06-2011 12:21 PM  8 years ago
bkervaski

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Birmingham, AL, USA

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Mine BLS351's get hot, but not hotter than my BLS251 tail servo.
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06-06-2011 12:39 PM  8 years ago
JPhillips

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Waco, TX

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I've had two elevator servos go up bc of getting too hot, one was on my R90, the other on my R50. The 90 I was able to save but the 50 was in the middle of an inverted nose down dive, I was able to pull it up but then it gave up and was aimed right at me, so I put it in, I had nothing on elevator. I was running Ace 1015 servos on both, switched to BLS351 and they still get very very warm. I'm currently using the CGY750 as a tail gyro/governor until I figure out what to do or Futaba figures it out.

I'd be interested in how it comes out, if you figure it out, let me know and I'll do the same.
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06-06-2011 12:42 PM  8 years ago
bkervaski

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Birmingham, AL, USA

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I don't know that it's actually a problem ... My BLS251 servos have always run *really* hot and they have never failed in flight ... 351's and 251's have metal cases ...
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06-06-2011 01:40 PM  8 years ago
t-rex pedro

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UK

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My JR8915's have metal cases but I'm pretty sure they shouldnt get this hot. I mean so hot I cant keep my finger on there for more than a second or two. I'm also pulling major mAh out of the lipo. In the region of 800 - 900 per flight.

Why does the BeastX have the option (and even a chart) to change the servo frame rate but the CGY does not?

Again, no binding anywhere, and set to 1520 in the Swash Basic menu.

The servos are lighning fast on the bench even on 6v. Something just doesnt add up.
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06-06-2011 01:45 PM  8 years ago
bkervaski

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Birmingham, AL, USA

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That's a lot of mah per flight, I'm getting about 4 flights between charges or battery swaps and putting 2200 back in, so roughly 550 per flight here, this is on a 90. I would expect smaller helis to use less just because the servos have to do less work.
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06-06-2011 02:16 PM  8 years ago
davo705

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Sydney, AUS

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Mr Bkervaski,

Are you on a 90e @5-7 mins per flight?
Mine and mates are 8-14 min nitro flights.

And tail/ bls 251's are on all, no temperature issues on these with gains typically around 70-80 and at regulated 5.5volts.

cheers..
Stuff.... more stuff.... stuff is good....
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06-06-2011 02:18 PM  8 years ago
bkervaski

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Birmingham, AL, USA

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Rave ENV 90 Nitro, 7-9 minute flights depending on how aggressive I feel like flying.

14 minute nitro flights! WOW! On your TREX 700???
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06-06-2011 02:26 PM  8 years ago
Ronald Thomas

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Gainesville, Fl, USA

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The servos should not run hot to the touch ever and if you are burning up the mah, it sounds like the servos are being over driven and the excess mah is lost to heat. Is there a setting the select a different HZ for the servos so they are matched? If the servos are that hot after a flight, they will fail sooner than they should for sure.Team MikadoUSA 480XXTreme, 550SX, 600SX, 700XXTreme, 800XXTreme!!
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06-06-2011 02:30 PM  8 years ago
Mike Fortin

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USA

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It's normal for the servos to be pretty warm after a good hard flight.

My servos typically get hot to the touch, this is not a 750 thing as I have seen the same with Vbar and Beastx.
Have Rotors, Will Fly!
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06-06-2011 02:48 PM  8 years ago
JPhillips

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Waco, TX

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My servos are very hot to the touch too, so much that I reached across the heli and inadvertently laid my arm across the tray of my R90 and the elevator servo burned my forearm.

I don't care how hard you fly, this isn't "normal." Warm yes, but not so hot that it burns your finger or arm if you hold it there for more than a second. It's almost like touching the pipe after a flight.
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HomeRC & Power✈️Aircraft🚁HelicopterFlybarless Rotor Head SystemsFutaba CGY › JR 8915 Servos running hot
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