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Chicago, USA
Joined Dec 2010
16 Posts
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rudder servo fail hs-81; why?
Hello all,
So I got about 15 hoursof flying time on my recently built easystar, and today the rudder servo failed . Luckily, I got the plane down without any damage, but I don't know why the servo failed. plane specs: stock 400 brushed motor greatplanes electrify C-25 ESC 2cell 2450 mah lipo 30C servos Hitec HS-81 The servo is basically frozen, and does not move at all or react in any manner when the control stick is moved. I opened the servo casing, and noticed a strong 'electrical' smell (not necessarily burnt but 'electrical smell '(sorry, I don't know how to explain this odor) from the servo. The internal wires seem to be connected and not damaged. I have not had any rough landings or crashes to date(not including todays fail), so the servos have not been abused from crashes. I am not happy with the control rods for both the rudder and elevator on this plane, as I feel the design puts more stress on the servos than is necessary. (ie the foam itself being the hinge) But I showed my plane to other pilots at the field today and they felt that the rudder did not seem to bind enough to cause problems with the servo. BTW, the servo does not appear to be stripped, as other pilots have advised me that the plastic geared hs-81 has that problem sometimes These are cheap servos (costing $13-18) and I don't mind replacing it, but I really don't want a servo to fail again. I got lucky today that the plane was not lost or damaged badly . I need to find out why the servo failed. I bought the servos and esc from rcplanet.com My questions are: 1. Has anyone had a HS-81 servo fail like this (only 15-20 hours of use)? 2. Can the ESC be at fault here? It is a quality ESC, but who knows? 3. Any thoughts on why it failed? 4. Should I consider other servos for this plane? BTW, my plane flies beautifully. I got the CG per manual just right, and have been hunting thermals for the last few weeks. The plane has enough power with this stock motor, and I've been getting 45min-60min flying time on my battery pack (lots of time with the motor shut off). Prior to todays mishap, I have been very, very happy with my EZ(1). thanks in advance for any advice you can offer on my servo problem |
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Hi Travellinjack,
I wouldn't think it would be anything to do with the ESC unless the other servo and/or the receiver were blown as well. It sounds to me like you just got a bad one in the pair. Perhaps the gears bound up and caused the motor to fry, or something blew on the controller board inside the servo. I'm pretty sure that the Hitec HS-81s have a good reputation, but not every servo out of a mass production mound of them is going to be a good performer and long lived. Sometimes you just get unlucky. I would test the outputs of the receiver by switching the remaining good servo onto the other channels and seeing if it still works properly. If that test goes well, then you know: 1) Your ESC is fine, because if it wasn't, you'd have a lot more trouble than one dead servo. 2) Your receiver is fine, because it works... 3) Your remaining servo is fine, also because it still works... and... 4) You got a bad servo, because it's the only part that failed. Finally, replace it with your servo of choice, and be glad that you got the random part failure out of the way for who knows how long, and also be glad that your plane and other parts are fine. Do be sure to check your linkages, especially the rudder linkage, for any binding, and fix it if needed, and then just move on and fly your plane knowing you dodged a bit of a bullet. I crashed my very first EasyStar after only a couple of weeks because I forgot the horn screw in the rudder servo, and talk about a mess... It worked its way apart and she spiraled 50' down to nose into hard packed sandy dirt and took a lot of damage. I was very new back then and didn't really know what to do in those last seconds, so I probably made it way worse than it needed to be. You got off easy! ;-) Oh, and about other servos. I've used both HXT900s and 939MGs on my EZ*s and have had exactly one of each fail on me, though with the HXT900 it stripped due to a crash and with the 939MG it stripped because I was experimenting with it on an application way too harsh for it. I think they are both great servos for EasyStar control surfaces, plus they are insanely cheap. I am presently using an HXT900 for the rudder, and 939MGs for the elevator and ailerons. I'd be going 939s all the way around but I was one short, lol. Rick NR417 |
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Travelinjack. It is just one of these things that happen with these things. You were lucky that your EZ* survived.
I have my EZ*s (got 3 all1s) that are trimmed to go into circles if anything fails. So they should not fly off too far. You mention the 'foam hinge'. Is it stiff? Then work it up and down a bit to loosen the foam. The control rods are normaly good and run smooth. Again check them for free running. I must admit that most of my servos are cheap ones and had very few problems. |
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Wanna get this in before Gene does anything bizarre to the thread...
Yes, very long... almost 40 minutes in total so this is kind of my "grand finale" for the year, you could say. I wanted to capture the nuances of the extensive testing for the day, and also wanted to have some fun with a well flying plane, so there it is. I neglected to mention in the video that I was also testing the idea of placing the entire VRX and its antenna up on my usual PVC pipe mast, so actually there was more testing going on than just the changes to the plane. She flew just SO well, I was really thrilled. Wind wasn't as strong as I wanted for the testing, but I still had basically a few mph worth with a little ground turbulence. Next time out, I want it to be wild and crazy so I can see how my changes pay off in rough conditions. Based on what I got from these two flights, however, I am already impressed. Anyway, off we go. Watch for the digger! ;-)
Stats: 1st Flight: 15 mins, max ground speed 95kph / 59mph, max LOS distance 919m / 3015', max altitude 112m / 367'. Estimated average current consumption: 10.8A based on flight time vs. pack recharging results. 2nd Flight: 18 mins, max ground speed 107kph / 67mph, max LOS distance 547m / 1794', max altitude 214m / 702'. Estimated average current current consumption: 9A based on flight time vs. pack recharging results. The lower amount of average current consumption is due to extra time spent gently climbing and then soaring back down unpowered. I'm a bit surprised that my power runs didn't overwhelm this factor. No data this time regarding round trip distances because of the OSD being reverted to factory settings. In defaults, it doesn't log the GPS points! Also: Just a general shout out to anyone with videos going that they'd like to see in post #6 of this thread. Shoot me a PM and give me your link, and I'll add you to the pile. Please restrict yourselves to videos shot within 2012, or if you have a time machine, 2013 is ok too. Rick NR417 |
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I had the panning on a switch, but will move it to a dial I think to it's smoother. Let me know if you come to York so we can meet up if you like.Quote:
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I got to do it again- sorry- but I like you guys and so want to share with you-
OFF TOPIC- but great flight by our Eckace...
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I don't own an EZ* and only watch this thread so that I can harass Gene. That said, he deserves/should be sentenced to another year as the thread starter just for general principals. After all, he hasn't done diddly this year. No videos of him flying his EZ*, no build reports, no new mods that he invented...nuttin' as they say in Joisey! Just pictures of him and his dogs swillin' brew at the pool in his new home in Flahridah. Time to get back to work ole buddy and make the new year special!
Ted |
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USA, TX, Katy
Joined Nov 2006
976 Posts
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We are flying 2 separate Eagle tree altimeters - awesome device for under 40 bucks- are pretty darn accurate- we have one on each plane and they almost always agree - they zero to ground level barometric pressure and start recording as soon as you get 60 feet AGL- just plug into any unused rx channel... here is a link- we love them http://www.eagletreesystems.com/Stan...standalone.htm |
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http://www.hexpertsystems.com/zlog/ |
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