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Author Topic: servo question  (Read 1693 times)

hopeitfloats

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servo question
« on: February 09, 2008, 11:46:29 pm »

hi guys.  i'm starting to build a new ship and were wondering if anyone here has heard of or managed to run 2 servos off one channel .  bit of an experimenter here and are looking at making a bow thruster with a gate to divert flow to port or starboard . i want to run it in conjunction with the rudder  and thought it would be an easy way with 2 servos rather than a remote cable or a dedicated channel. any thoughts.
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malcolmfrary

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Re: servo question
« Reply #1 on: February 09, 2008, 11:59:46 pm »

To work two servos, get a "Y" lead.
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hopeitfloats

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Re: servo question
« Reply #2 on: February 10, 2008, 12:50:42 am »

thanks malcolm. thats my first problem solved
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Bryan Young

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Re: servo question
« Reply #3 on: February 10, 2008, 05:53:11 pm »

Don,t know what happens in the model world, but using a bow thruster when under way (real life) can cause a massive failure in the bow thrust compartment. Only to be used when going VERY slowly. I think it is to do with a lack of water getting to the intake pipe.
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Notes from a simple seaman

malcolmfrary

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Re: servo question
« Reply #4 on: February 10, 2008, 07:16:37 pm »

Good point, Bryan.  Arranging an interlock to stop it working when not wanted could be more difficult than just making it work when it is wanted.  Could be a good case of more channels and instructing the staff in proper use of plant and equipment.
Didn't the QM2 lose a thruster door on trials? I seem to remember something about it but cant recall the full circumstances.
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White Ensign

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Re: servo question
« Reply #5 on: February 10, 2008, 08:33:55 pm »

Bow thrusters-effiency is just good when standing still. To use the bow thruster when under way will be not very supportive.

Using two servos on one rudder is also not recomendable, as they are never exactly adjusted in the same way- which means, you`ll loose effiency as well and sooner or later one servo will burn out (motor inside will burn out). It will lead mostly to a short-cut and could damage your receiver.
The best way is, if you are not shure to use a strong servo, better a bit stronger than too small (depending on the size of the rudder.

To give a support in turning circle, change the rudder to a  balanced rudder which i.e. the first third of the rudder-blade is standing before the rod. It`ll turn under way in the propwash and will do a better job. Or use a so-called "Becker-rudder", which turns by it´s last third the propwash for another 30 degrees (approx.) and give a better turn as well.

Hope that was out of any help.

Jörg
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roycv

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Re: servo question
« Reply #6 on: February 11, 2008, 10:30:27 am »

Hi all, when sail winches were relatively expensive (20 years back) I put 2 servos on a Y lead, one for the main sail and one for the jib.  They worked without problem.
regards to all Roy
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White Ensign

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Re: servo question
« Reply #7 on: February 11, 2008, 11:11:08 am »

Roy, had two of running for the steering on my modelcar scale 1:5- two times smashed them. Always one burnt through and the other couldn`t work correctly. So I changed to one, real Big servo and since that time no prob.

Jörg
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boatmadman

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Re: servo question
« Reply #8 on: February 11, 2008, 11:15:08 am »

I think the difference here is that if you use two servo's to drive one function - eg jorg's car, then one will 'fight' the other because they are mechanically linked and not identically matched.

Using two servo's from one channell through a Y lead to drive two separate things, - eg - Roys main and jib shouldnt cause any problem as they are not mechanically linked.

Hope that makes sense.

Ian
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tubby tomo

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Re: servo question
« Reply #9 on: February 11, 2008, 05:46:31 pm »

ive got two servos working six rudders
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hopeitfloats

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Re: servo question
« Reply #10 on: February 15, 2008, 07:10:45 am »

my original idea was to use 2 servos - 1 for rudder and one for bow thruster to improve turning  on the move and so i could operate on 2 channel radio. maybe not such a good idea. still thats what the forums are for. thanks guys you may have saved me making a big mistake.  O0
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White Ensign

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Re: servo question
« Reply #11 on: February 15, 2008, 11:03:49 am »

No prob- that`s what we are here for!
Bow thrusters are fine due to "harbour" service. Under way you may reach a better result either by changing the size of the rudder, changing the style (technically meant) of the rudder or, to use two speed-controllers (if it is powered by two engines) to support over a Y-function in a computer r/c the rudder. I.e. the inner engine goes down a bit, the outer full ahead to support the effectivity of the rudder.

Happy modeling,
Jörg
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