David E Posted January 23, 2009 Share Posted January 23, 2009 Hi everyone, have been having great fun with my MCX - thanks for the recommendation! I had a little servo problem that I fixed by taking the servo off the board and cleaning the position sensing contact track that it runs on. However, after putting it all back together (stripped the heli down quite a bit to get easier access to the circuit board) and shortening the forwards/backwards pitch servo link by a turn or two (I've read this allows faster forward flight, and it does seem to do that) I now find that I need to put on quite a bit of right yaw trim, and when under full power the heli spins left quite fast. This is leading to a lot of crashes. Anyone got any suggestions what might be the problem? Many thanks! Quote Link to comment Share on other sites More sharing options...
David E Posted January 23, 2009 Author Share Posted January 23, 2009 PS yes, I have tried another, fully charged, battery, makes no difference Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted January 23, 2009 Share Posted January 23, 2009 Either you have messed something up during your fiddling, or maybe you are forgetting to let the gyro settle before moving the heli? Quote Link to comment Share on other sites More sharing options...
David E Posted January 23, 2009 Author Share Posted January 23, 2009 Yeah, think I've been letting the gyro settle. It seems as though one of the motors is producing less power or experiencing more friction than the other or something, and just below full throttle that motor runs out of available power. Maybe there's a problem with one of the motors. Running brushed motors backwards shouldn't cause a problem, should it? The first time I connected it back up, I had both motors connected the wrong way round, although I stupidly didn't spot it until I tried to take off and it didn't! I had checked that they were counter-rotating but missed that they were both wrong. Maybe I should try re-lubing things. Can anyone suggest what I should use? Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted January 23, 2009 Share Posted January 23, 2009 the brushes will have probably bedded in on the commutator for the "normal rotation" so may affect power on reverse rotation, but as you spotted and correcteed this very quickly, unlikely to be a problem. If you must lube it ( and I wouldnt personally ) then maybe a very light application of graphite based lube may do it. I cant honestly see this being the problem however. You have double checked the baldes are fitted correctly I assume. Quote Link to comment Share on other sites More sharing options...
David E Posted January 23, 2009 Author Share Posted January 23, 2009 I'll be double checking that tonight then! :D I'll see if running the motors for a bit longer in the forward direction fixes it. The original problem with the servo was that it would only give half travel - backwards but not forwards. Has anyone else come across that before? There seemed to be a fair amount of gunk on the sensor track, presumably from any lube that was originally on the leadscrew? Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted January 23, 2009 Share Posted January 23, 2009 hello david, iv'e got a couple of contra heli's--had medivac for a couple of years-experience has shown me that when one of the motors is on it's way west(sick)the other one takes over and no matter how much you ajust the yaw trim-it gets gradually worse and the only cure i find is to replace the motor-the mcx use's a different type to the twisters i believe-but might be worth looking at/trying-there appears to be spares for the heli--say goodbye to your dosh and get one. ken anderson. Quote Link to comment Share on other sites More sharing options...
David E Posted January 23, 2009 Author Share Posted January 23, 2009 Yeah, I'm coming to the conclusion it's one of the motors. I think running it backwards didn't help it much. I tried switching the motors to isolate the problem, (which makes them run backwards as they rotate opposite ways) and now it's not quite so bad. So now they're more equally knackered? I'll try to track down some replacement motors... Thanks for the thoughts all. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted January 24, 2009 Share Posted January 24, 2009 Steve Webbs Quote Link to comment Share on other sites More sharing options...
Owen Hailey Posted January 24, 2009 Share Posted January 24, 2009 Hi all I havent got a MCX yet, but this sounds like a giro problem to me on the cx heli's if you run the the motors in the rong derection. the giro stops reacting and the heli is impsible to stear so have you got the motors in the right plugs and the blades the right way round as I found this out the hard way when I got it rong on my cx and it did as you have exspaned, hope this is of some use and gets you over your problem. happy hovering Owen. Quote Link to comment Share on other sites More sharing options...
David E Posted January 26, 2009 Author Share Posted January 26, 2009 Have checked that the blades are assmbled correctly, with the angled ball bars on the top rotors to line up with the flybar, and the perpendicular ones on the lower rotors to line up with the links to the swash plate. I stripped down the heli last night to check everything was balanced, straight and freely rotating. A quick test flight shows the problem is still there, so I'll try replacing the motors. Can anyone tell me which is the correct orientation of connectors for the motors? If you can tell me the sequence of wire colours going from left to right (as if sitting in the heli's imaginary cockpit) that would help me be confident I'm putting the right motor on the right side, with the connectors the right way round. Quote Link to comment Share on other sites More sharing options...
Former Member Posted January 27, 2009 Share Posted January 27, 2009 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
David E Posted January 27, 2009 Author Share Posted January 27, 2009 Many thanks for all your help guys, have now fixed the problem! It seems the left motor was a bit knackered I changed both to be on the safe side as they'd both been subjected to backwards running. Now the yaw stays steady until perhaps the last 5% of power, which I think is similar to new and probably down to the friction in the swashplate and other bearings between the outer shaft and the chassis. (is that the right word for an a/c?) I am also able to run until the light flashes without the yaw going totally screwy. Eric - thanks for looking this up for me, it helped me be sure I had the motors connected to the right connectors. However, for anyone else's reference, both the old and new left motors rotated in the correct direction with the connections white, black, red, blue (from port/left hand side to starboard/right hand side, facing forward). It can be hard to tell which way round the wires go in to the connectors though, cos of the sleeving and the twisted wires. It seems that the brushed motors don't like being run backwards! Hopefully I'll remember this in future and make a note of connections before disassembly! Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.