Jump to content


Photo

Rudder indicators


  • Please log in to reply
19 replies to this topic

#1 Chrisc

Chrisc

    Advanced Member

  • Advanced Members
  • PipPipPip
  • 702 posts
  • LocationWhangamata

Posted 11 June 2018 - 08:26 PM

This new vessel of ours has two helm stations, each with identical instrumentation which includes Vetus rudder indicators. There is a lot of close quarter manouvering here on the canals so the indicators are quite useful, or would be if they worked properly.
The indicator in the wheelhouse is very precise in showing rudder angle but the one in the top helm position shows a bias to port by about 15 degrees. Both take their input from the same rudder mounted sender via the ignition switch. When the ignition switch is off both rudder indicators are at rest in the hard to starboard position. Since the wheelhouse indicator is beside the ignition switch and the top indicator has a cable run of 5 metres I assume there is some sort of voltage differential, but then the wiring is very heavy gauge so...
Any help please, and keep it simple, I find electricity difficult.
  • 0
Young at heart.
Other parts offered without warranty.

#2 Island Time

Island Time

    Advanced Member

  • Administrators
  • 5,763 posts
  • LocationHome from Cruising, Now Gulf Harbour

Posted 11 June 2018 - 09:10 PM

There must be a way to set zero on each instrument. Which model are they?


  • 0

There is nothing, absolutely nothing, half so much worth doing, as simply messing about in boats


#3 Chrisc

Chrisc

    Advanced Member

  • Advanced Members
  • PipPipPip
  • 702 posts
  • LocationWhangamata

Posted 11 June 2018 - 11:58 PM

Sorry, done a mistake. They are VDO rudder indicators and I can't see any model numbers. There is a brand new spare instrument on board so I assume that the previous owner bought it to fix the problem. I tried it but it shows the same degree of port bias. There is no adjustment anywhere on the gauge, which is why I thought it may have something to do with input voltage. The new instrument has a wiring loom in the box so may pay to try wiring up that?Attached File  20180611_134707.jpg   645.68KB   0 downloads
  • 0
Young at heart.
Other parts offered without warranty.

#4 wheels

wheels

    Advanced Member

  • Advanced Members
  • PipPipPip
  • 16,527 posts

Posted 12 June 2018 - 05:52 AM

Hi Chris. Pretty sure those units are a very simple Potentiometer that works just like a Fuel tanks sender. Basically a linear resistor with a wiper arm running along it. If you connect two gauges to the same terminals, that will likely upset the reading. Although I would have expected the error to be seen on both gauges.
Anyway, they use a Two station sender if you need two stations. That will mean that on the sender unit, (mounted on the rudder quadrant), there will be three terminals if it is twin station. If there is only two terminals, it is only single station.
SO if there are three terminals, then one will be common and the other two for each separate gauge. Try swapping the two and see if the fault then switches to the other gauge. That will determine if the fault is at the sender itself, or between the sender and gauge.
Calibration was simply setting the rudder to midships, then adjusting the sender unit till the gauge/s read midships.


  • 0

#5 mattm

mattm

    Advanced Member

  • Advanced Members
  • PipPipPip
  • 202 posts

Posted 12 June 2018 - 08:19 AM

Not necessarily correct on the dual station part wheels. All the VDO rudder pos senders I’ve seen, dual station ones that is, are two terminals. One is earthed, and the other goes to the S (signal) position in both of the gauges.

To adjust the reading you do just rotate the base of the RPS. which does not help when you have two, reading differently. I’d try swapping the gauges over and see if the issue moves or not, to tell you if it’s a gauge or the wiring. Remember, if it’s a gauge, it could be the ‘correct’ one, and the RPS has been adjusted to allow for it. Good luck.
  • 1

#6 wheels

wheels

    Advanced Member

  • Advanced Members
  • PipPipPip
  • 16,527 posts

Posted 12 June 2018 - 12:08 PM

Thanks for correcting that Matt.


  • 0

#7 Chrisc

Chrisc

    Advanced Member

  • Advanced Members
  • PipPipPip
  • 702 posts
  • LocationWhangamata

Posted 12 June 2018 - 05:44 PM

Thanks for the replies.
To recap, when the wheelhouse indicator shows straight ahead the top helm indicator shows about 15 degrees to port. The wheelhouse indicator is correct as the vessel runs straight when this indicator is in zero helm position. I have changed the top indicator with a new one found on board but it shows the same error.
Now this is where it starts to get out of my comfort zone.
Turn on the ignition and centre the rudder according to the wheelhouse indicator, the top indicator will show about a 3-5 degree bias to port. Start the engine and the top indicator will slowly increase to a 15 degree port bias whilst the wheelhouse indicator remains in midships helm position. I can imagine all sorts of scenarios going on here.
  • 0
Young at heart.
Other parts offered without warranty.

#8 ex TL systems

ex TL systems

    Advanced Member

  • Advanced Members
  • PipPipPip
  • 785 posts

Posted 12 June 2018 - 06:16 PM

Bend the needle until it shows you what you want to see !
  • 0

#9 Island Time

Island Time

    Advanced Member

  • Administrators
  • 5,763 posts
  • LocationHome from Cruising, Now Gulf Harbour

Posted 12 June 2018 - 06:21 PM

Nah Chris, Matt told you the right stuff. Swap the upper and lower units over and see if the issue remains on the upper one. If it does, the issue is resistance in the wiring to the top unit....


  • 0

There is nothing, absolutely nothing, half so much worth doing, as simply messing about in boats


#10 wheels

wheels

    Advanced Member

  • Advanced Members
  • PipPipPip
  • 16,527 posts

Posted 12 June 2018 - 07:51 PM

Two things to check. Is the cable tinned wire or plain copper. If plain copper, the copper could be corroded and need replacing. Second thing is check the terminal connectors are well crimped to the wire and make sure the terminals are clean and tight. Ypou need to do this at both ends. Also, of the gauges are engaged and disengaged by the Key, check the terminals t the Key switch also. As IT says, the fact the fault still remains when you change the gauge, shows the fault is in the wire, not the gauges.
The issue of the gauge moving with Key and then engine starting suggests a faulty connection somewhere. Possibly earth.
These things work very simply with a voltage passed down the cable and the wiping resistor in the sender unit alters that voltage. This in turn swings the dial from 0 to fullscale. The 0 will be say hard to Port and the Fullscale will be full to starboard. The centre position reads midships. So the issue is that the upstairs gauge is not getting the full voltage required to deflect it to the correct position.


  • 0




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users