Lee Morton Posted January 28, 2021 Share Posted January 28, 2021 **LINK** Hi again all. So had a bit of a bad crash on my carbon cub. Got everything repaired, the servos were going and had to replace them. Got myself a servo tester just to be sure and have installed 2 new ones. I’ll try attach a video but whenever I power on, the plane normally moves the elevators and rudder then settles. However the rudder is being moved back and forth fully in a quick manner as if it’s almost like it cannot stabilise itself. Any ideas how I could fix this or what would be causing the issues? Thanks in advance! Quote Link to comment Share on other sites More sharing options...
Phil McCavity Posted January 28, 2021 Share Posted January 28, 2021 Is your battery fully charged? Quote Link to comment Share on other sites More sharing options...
Lee Morton Posted January 28, 2021 Author Share Posted January 28, 2021 Posted by Phil McCavity on 28/01/2021 18:49:26: Is your battery fully charged? It’s not on full charge no sitting around 3.9 Quote Link to comment Share on other sites More sharing options...
Geoff S Posted January 28, 2021 Share Posted January 28, 2021 What battery is it? I thought the Carbon Cub was electric. If your battery is a 4 cell NiMh then it's very low. Geoff Quote Link to comment Share on other sites More sharing options...
Lee Morton Posted January 28, 2021 Author Share Posted January 28, 2021 Posted by Geoff S on 28/01/2021 19:22:43: What battery is it? I thought the Carbon Cub was electric. If your battery is a 4 cell NiMh then it's very low. Geoff Hi Geoff. It’s a 3s battery that came with the plane RTF. Quote Link to comment Share on other sites More sharing options...
EarlyBird Posted January 28, 2021 Share Posted January 28, 2021 Are you sure it is 3.9v? That is 1.3v/cell. Just check to make sure. Quote Link to comment Share on other sites More sharing options...
Geoff S Posted January 28, 2021 Share Posted January 28, 2021 In that case it's had it if it's down to 3.9v. You need a new 3S battery. The voltage should never be allowed to drop below 3v/cell and higher is better so I'm afraid the minimum voltage it should ever be is 9v and storage about 3.5v/cell (10.5v for a 3S). Geoff Quote Link to comment Share on other sites More sharing options...
Lee Morton Posted January 28, 2021 Author Share Posted January 28, 2021 Sorry all. So the battery is 3.9 per cell. So it’s sitting at around 11v total. Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted January 28, 2021 Share Posted January 28, 2021 Sorry this modern electric fly is all new to me. Is there an idiot's guide to all this on here please ? Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted January 28, 2021 Share Posted January 28, 2021 Posted by Rich Griff on 28/01/2021 20:57:44: Sorry this modern electric fly is all new to me. Is there an idiot's guide to all this on here please ? Servos need a good level of voltage to maintain the centre Just to hold still at neutral. When servos jitter, it is a sign of low voltage or a poor connection. As the lads suggested at 1st post. Edited By Denis Watkins on 28/01/2021 21:07:47 Quote Link to comment Share on other sites More sharing options...
Geoff S Posted January 28, 2021 Share Posted January 28, 2021 Posted by Rich Griff on 28/01/2021 20:57:44: Sorry this modern electric fly is all new to me. Is there an idiot's guide to all this on here please ? There's a lot of information here. You can always Google (say) elelctric flight for beginners and probably find a wealth of information on the web, too. Not sure how much you need. It helps if you have some knowledge of simple elecrical DC theory like Ohm's Law. My dad explained Ohm's Law to me on a car journey one evening from Slegness home to Nottingham when I was about 12 so It's in my DNA as they say unscientifically Geoff Quote Link to comment Share on other sites More sharing options...
Lee Morton Posted January 29, 2021 Author Share Posted January 29, 2021 Ok sorry everyone so I should of added. The plane rudder movement is happening when I start the plane up without me touching anything. It’s doing it, itself and doesn’t stop I have to remove the battery for it to stop what it’s doing in the video. Quote Link to comment Share on other sites More sharing options...
Alan Hilton Posted January 29, 2021 Share Posted January 29, 2021 Try another servo in the rudder channel if it’s behaving normally the original servo is knackered so bin it if it does the same then the receiver or the rudder channel on the transmitter is duff Alan Edited By Alan Hilton on 29/01/2021 09:31:01 Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted January 29, 2021 Share Posted January 29, 2021 Lee, watched the video it's either a faulty rudder channel on the Rx or a faulty servo. Just as a test plug the elevator servo into the rx rudder port and rudder servo into elevator port. That way you'll be able to determine if it's the servo or receiver. Quote Link to comment Share on other sites More sharing options...
Colin Carpenter Posted January 29, 2021 Share Posted January 29, 2021 Is this an AS3X receiver ? If so , I have seen this occuring on two Parkzone Visionaries. On one the hunting disappeared in the air after a few circuits. Lockdown stopped any further investigation on the other. Colin Quote Link to comment Share on other sites More sharing options...
Romeo Whisky Posted January 29, 2021 Share Posted January 29, 2021 I find this is not uncommon with digital servos, especially if the transmitter is too close to the model, or indoors where the signal can bounce around a room. Suggest you try restraining the model outside if possible, and then move the transmitter several feet away from the model. If the jittering doesn't stop, you may have to replace the rudder servo. Quote Link to comment Share on other sites More sharing options...
Nik Harrison Posted February 1, 2021 Share Posted February 1, 2021 Lee, I've had trouble with servos going mad/not working before. My problem was that the Rx I used (Spektrum AR8000) was not able to supply sufficient current to drive said servo. I installed a simple current amplifier and problem solved. Spektrum do a similar amp in a lead. **LINK** Don't know if it's still available but I've attached the circuit that I used to make my own amp. Hope this is of some help. I did find a website that offered a range of such devices so it seems to be a problem that many people have. Unfortunately, I can't remember its name!! Cheers, Nik Quote Link to comment Share on other sites More sharing options...
Nik Harrison Posted February 1, 2021 Share Posted February 1, 2021 Lee, Found the website. https://modelradioworkshop.co.uk/shop/specialised-items/mrw82-signal-booster/ Cheers. Quote Link to comment Share on other sites More sharing options...
Lee Morton Posted February 1, 2021 Author Share Posted February 1, 2021 Thanks so much will check all this information out once finished work today. I did try to install a new servo thinking that was the issue but same thing unfortunately. Thanks again for advice will let you know if this solves my issues. Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted February 1, 2021 Share Posted February 1, 2021 Posted by Alan Hilton on 29/01/2021 09:29:07: Try another servo in the rudder channel if it’s behaving normally the original servo is knackered so bin it if it does the same then the receiver or the rudder channel on the transmitter is duff Alan Edited By Alan Hilton on 29/01/2021 09:31:01 As Alan says Plug your aileron servo into the rudder channel to see if they do the same Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted February 1, 2021 Share Posted February 1, 2021 Just a thought - I don't know your model or its radio but have you replaced the servos like for like? Could they be analogue where the originals were digital? A faster frame rate than the new servos can handle might well explain the behaviour. Supply voltage shouldn't be an issue with a part discharged flight battery but there is the possibility that the voltage regulator (BEC) built in to the ESC has gone faulty. Do you have access to a multimeter to check the supply voltage (normally 5v but maybe 6v) - usually the red and brown or red and black wires, depending on the wire used by the manufacturer, from the ESC? Quote Link to comment Share on other sites More sharing options...
Cuban8 Posted February 1, 2021 Share Posted February 1, 2021 Looks to me that the servo in question is actually being commanded to move in the way it is - can't be certain but duff servos I've had in the past have oscillated very violently over a much smaller angle and buzzed loudly. - much more so that what we see here. Odd that the other servos are OK. As has been said, substitute the servo for another to eliminate it (try it on a servo tester as a double check) and if the problem still persists I wonder if the problem could be with the stabilization system? A crash was mentioned so maybe a nasty has occurred to the flight controller that I believe these models are equipped with. Try a bog standard RX without all the clever SAFE stuff and see what happens. BTW don't even think of flying it again until a definite cause that is repeatable has been found. If the fault 'just goes away on its own' that's even worse. Anyway, good luck, I'm sure you'll get to the bottom of the mystery. Edited By Cuban8 on 01/02/2021 15:00:54 Quote Link to comment Share on other sites More sharing options...
Colin Carpenter Posted February 1, 2021 Share Posted February 1, 2021 See my post on 29 January! Club mate eventually changed servo on rudder but it persisted! Plane flew ok. Change Rx out. U can try adjusting rudder gain too. Quote Link to comment Share on other sites More sharing options...
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