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Author Topic: jittery rudders  (Read 2089 times)

Wasyl

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jittery rudders
« on: November 30, 2009, 08:20:31 PM »

I,m sure i saw somewhre on here, a topic concerning rudders, well jittery rudders,but i can,t find it,
anyway,here goes,I recently bought a Tsekoa11,its got two 500 motors fitted and a Graupner speed controller,the problem i have is,when i switch on,everything is as it should be,My problem starts when i try to start off slowly,the motors turn but the rudders jerk,if i push the stick hard forward,the boat takes off,and the rudders take up their correct position,its only at slow speeds that the rudders are jittery,..The motors do not look as if they have suppressors fitted,although they might be internal,..slow speed manouvering is out of the question,the boat does not have a bow thruster fitted,

No hair left,Wullie
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boater12

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Re: jittery rudders
« Reply #1 on: November 30, 2009, 08:27:27 PM »

Internal suppressors in 500 motors ? is it possible ?

Jim
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DickyD

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Re: jittery rudders
« Reply #2 on: November 30, 2009, 08:35:35 PM »

You need suppressors Wasyl
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boater12

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Re: jittery rudders
« Reply #3 on: November 30, 2009, 09:00:33 PM »

The motors do not look as if they have suppressors fitted,although they might be internal

How would you fit suppressors internally - is your real name Paul Daniels ?  {-)

Jim
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FullLeatherJacket

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Re: jittery rudders
« Reply #4 on: December 01, 2009, 09:06:50 AM »

I think the thread referred to was from Ian Beattie about his wayward Puffer, and that problem was narrowed down to the hull shape.

This sounds like a classic case of RF interference. 0.1uF suppressor caps across the brush terminals is the first remedy to try. If that doesn't fix it, then twist the wires from the motors to the ESCs together along their length and/or fit a ferrite ring to the wires. Also make sure these wires are as short as possible (i.e. less than around 6"). The last possible solution would be to earth the motor cases to the prop shafts.

I normally would hesitate to educate an elderly relative in the art of extracting the life-essence from an oblate spheroid but also make sure the Rx aerial is well away from any power wiring and preferably has as much of its end as possible sticking up vertically out of the model somewhere e.g. a functioning HF whip antenna. If you're using 2.4Gigglehurts then this last suggestion does not apply.

FLJ
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Wasyl

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Re: jittery rudders
« Reply #5 on: December 01, 2009, 10:42:22 AM »

Thanks for the replies,first of all let me clarify,..."internal suppressors".a few months ago i contacted a modeller ,who told me he had a 20year reputation in building boats,..to cut a long story, I supplied him with all the materials and model to build for me, when i supplied 2 x graupner 400 motors,i asked should i have them suppressed,..he told me they were suppressed intenally,who was i to dis-believe,

as for fitting suppressors,on a scale of 1 to 10  how hard, ..remembering i,ve got 10 banana,s masquerading as fingers,

Wullie
btw, i,m using 27mhz
 
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FullLeatherJacket

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Re: jittery rudders
« Reply #6 on: December 01, 2009, 11:32:06 AM »

i supplied 2 x graupner 400 motors,i asked should i have them suppressed,..he told me they were suppressed intenally,who was i to dis-believe,
as for fitting suppressors,on a scale of 1 to 10  how hard, ..remembering i,ve got 10 banana,s masquerading as fingers,
Wullie
btw, i,m using 27mhz 

Speed 400 motors are fitted with internal suppressors. If you take one that hasn't had its terminals soldered then you'll see a very thin wire emerging from the plastic insulator around the base of each terminal and alongside said terminal. Those wires are the ends of the internal capacitor. Other Graupner Speed motors may or may not have these fitted - you have to RTFM.
As for fitting a capacitor across the brush terminals, if you can't manage this then you really ought to think about bird-watching instead of modelling. On a scale of 1 to 10 it ranks about minus three..............
FLJ
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Wasyl

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Re: jittery rudders
« Reply #7 on: December 01, 2009, 03:57:56 PM »

-3...mm,so i can assume its quite easy,...as some of you will have already guessed,i,m not really a modeller,i am a buyer of models,..so when a seller tells me its RTR,then i take his word for it,if as whats happened here,i now find that this boat needs some minor repairs,then first i,ll ask, to ascertain how to fix it then i,ll get it fixed,
I thank you all for your input, and can say i,m a little wiser,

Wullie
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malcolmfrary

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Re: jittery rudders
« Reply #8 on: December 02, 2009, 11:14:56 AM »

Assuming that you can do electrical soldering, and you can get at the terminals, fitting a capacitor across the brush terminals is one of the easiest of jobs.
If you are using an AM radio, any interference will probably result in rudder twitching because of the way they work.  The transmitter sends a short pulse for channel 1,, anther for channel two and so on for however many channels.  Then it sends nothing for (in electronic terms) a long time.  The receiver notices the long period of nothing, and determines that the next information is the start of the sequence, and anything that turns up that can be resolved as a signal is duly passed to channel 1.  This is commonly the rudder, hence rudder twitching.
Servos are also sensitive to supply voltage fluctuation.
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Wasyl

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Re: jittery rudders
« Reply #9 on: December 02, 2009, 01:04:41 PM »

To make my life easier i have taken the motors out of the boat,as access to them to do an in situe solder job was out of the question,I,ll get the capacitor,s fitted asap, then i,ll let you all know if my prob has been fixed,

Wullie
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johno 52-11

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Re: jittery rudders
« Reply #10 on: December 02, 2009, 08:27:07 PM »

I have come across a issue like this in a friends narrow boat. When I looked inside the wire from the speed controller to the receiver and the fire from the servo to the receiver where side by side for almost the whole length and it was causing some sort of cross channel interference all we did was re route one of the cables and it stopped. Sometimes being neat and tidy is not always a good thing.
 
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Nordsee

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Re: jittery rudders
« Reply #11 on: April 26, 2010, 11:41:48 AM »

How would you fit suppressors internally - is your real name Paul Daniels ?  {-)

Jim
I have a 400 size and a 540 car motor with internal suppresion.
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