# Radio control servo problem



## topshed (Jan 20, 2008)

Hi all,


I;m not sure which is the best forum to post this on, initially I posted on the R/C and power forum, then I thought; as it a live steamer issue, why not post it here too? Twice as many responses!


I gave my Accucraft live steam Garrett an airing today, first time for a while so new batteries and a good charge up for the R/C system. She has always been a bit trwitchy, but today I think I have worked out why. The throttle servo operates perfectly until I operate the valve gear, then the throttle servo goes back and forth like a fiddlers elbow! Is this some kind of cross-channel interference, and what can I do about it?


Puzzled.


Martin


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## weaverc (Jan 2, 2008)

When I've run into the twitching problem before, it's because the servo polarity had been reversed at some time. This usually destroys the internal logic. It is very important never to cross wire a servo. Servos are relatively inexpensive, so try changing the offending servo and see what that does.


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## Dan Pantages (Jan 2, 2008)

I know nothing about radio control but I have heard about "glitching". Is that the problem?


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## Pete Thornton (Jan 2, 2008)

then the throttle servo goes back and forth like a fiddlers elbow! Is this some kind of cross-channel interference, and what can I do about it? 
If you are not running 24Ghz digital radios, then the problem is 'metal-to-metal contact', which the guys at the r/c airplane shop gleefully told me about when I mentioned trains. For some reason I haven't explored, metal joints (valve gear, couplers, etc.,) produce interference and thus the deadly "glitching". 

As you can guess, replacing the transmitter/recvr with something like the Spectrum digital system will get rid of it. There are interference suppression systems available - if you have factory r/c then it should be included? I know my Roundhouse loco never exhibited any problems. 

My C-16 has an old FM r/c system that I installed and it has 'glitching' in spades. My solution is to set the controls where I want them and then turn the transmitter off. My receiver (obviously intended for an aircraft,) will continue what it was last told to do until the signal returns. Makes yard switching tough, but mainline running is a breeze.


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## rodblakeman (Jan 2, 2008)

I have to agree with Pete ( above) I have installed RC to a number of Accucraft Garrett's and only use the 2.4 Ghz systems. There is so much "mechanical noise" with the 2 Garrett engine's that using an old 40 Mhz RC set will almost always result in continuous "Glitching". It is fairly straight forward to swap over to a 2.4 Ghz set up, apart from the initial cost of course.[script removed]


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## topshed (Jan 20, 2008)

Hi All, 

many thanks for your hints ands suggestions, it looks as if the only real solution is to use a 2.4 GHz R/C system. 


All the best,
Martin


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## JoelB (Jan 3, 2008)

If glitching is indeed the problem, another remedy is a servo smoother. There are a few of these on the market; one which I had good luck with was made by Brian Jones in the UK. It's probably a big less expensive than a 2.4Ghz R/C set, but it has two drawbacks: it takes up space and it introduces some lag time in servo response.


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## Dave Ottney (Jan 2, 2008)

Martin, 
Be sure to check out the very inexpensive 2.4 systems -HK, Flysky, Exceed- they're all the same just relabeled . 
Check the RC forums for 2.4 info, here one thread -http://www.mylargescale.com/Community/Forums/tabid/56/aff/35/aft/112802/afv/topic/Default.aspx 

These radios are around US$30-40 and extra receivers are US$10-15. Vendors include Hobby City, Hobbypartz, SNHobbies to name a few. The receivers have a main receiver with a smaller satellite attached. You can remove the satellite receiver and still have plenty of range They indeed are less affected by the noisy model RR environment. 
Dave


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## dwegmull (Jan 2, 2008)

Hi Martin, 
You mention RC in a Garratt: do you have some pictures you could share showing how you setup your servos? I'm in the process of setting up mine: I've got a servo in each truck for the reverser and one in each truck for the drain cocks. I have not yet decided how I will mount the throttle servo... 

Bad pictures (cell phone):


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## rodblakeman (Jan 2, 2008)

David, 
There are some pictures of a Garrett RC installation I have just done here; 

http://picasaweb.google.com/wpandyr/GarrattRL# 

Hope they help.


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## Pete Thornton (Jan 2, 2008)

Bad pictures (cell phone): 

"The website declined to show this webpage 
Most likely causes: 
•This website requires you to log in" 

David - can you put the pictures somewhere else?


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## dwegmull (Jan 2, 2008)

Hi, 
Sorry about the broken links... As I am logged into that site, the pictures work for me ;-) 

You can view them by going here: http://www.twitpic.com/photos/dwegmull.


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## topshed (Jan 20, 2008)

Hi, I'm just beginning to get my head round the possibility of changing to a 2.4GHz system. If I do so, will I just have to change the transmitter/receiver, or will all the servos need to be changed as well? Thanks, Martin


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## TonyWalsham (Jan 2, 2008)

The servos will work OK.


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## topshed (Jan 20, 2008)

Thanks, Tony, I'd better get on with it then! 

Martin


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## topshed (Jan 20, 2008)

Hi alll, 

Just to let you know that I've now installed a new 2.4GHz system and on the bench, all seems to be fine; the real test will be a proper run outside. When I have a few hours free and the UK is not being deluged with rain I'll give it a go and let you know how I get on!









Martin


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## topshed (Jan 20, 2008)

Hi all, 

Managed to find an economically priced 5 channel system at a local model shop and have installed it successfully! Here is a video of the test run. Gave her a bit of a blast at first, then had a good slow run to check for glitches - which were, of course, non existent! 


http://www.youtube.com/watch?v=GmJY3oXwHs0



Thanks very much for all your help.


Martin


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