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Hydraulic controller and LS drive unit
#1
Hello,

I have a Raymarine autopilot system I believe from 2003 with S3 course computer and Lecomble & Schmitt hydraulic drive unit (Linear drive ST 40 DE BP 12 v + Power pack RV2 ST 12 V) fitted to a quadrant on First 40.7. Now it looks like that when I managed to blow a fuse while doing rewirings to Seatalk systems, I may have caused permanent damage to the course computer. So I would like to replace it with Tinypilot setup.  It seems that the drive unit cannot be run with pypilot motor controller but would the hydraulic controller work? LS recommends 25A fuse for this power pack on a 12 V system while the hydraulic controller description says up to 20 A.

A link to the LS drive unit manuals:  [Power Packs and Linear Drives for Autopilots : Instruction Manuals, Catalogues - Lecomble & Schmitt](https://www.ls-france.com/en/instruction...atalogues/

EDIT:

In addition, there is a Raymarine rudder position sensor + clutch but I assume neither of these should be an issue

Best, Jani
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#2
can you connect the hydraulic pump directly to the battery and measure the current while it is moving the rudder?

The hydraulic controller can also use a 30 amp fuse but I put 20 amp fuses. The idea is the controller never gets more than 5 degrees above ambient with currents 20 amps and less.
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#3
(2020-06-24, 03:51 PM)seandepagnier Wrote: can you connect the hydraulic pump directly to the battery and measure the current while it is moving the rudder?

The hydraulic controller can also use a 30 amp fuse but I put 20 amp fuses.   The idea is the controller never gets more than 5 degrees above ambient with currents 20 amps and less.

Thanks for the suggestion! Unfortunately I was not able to get the measurements so I got into touch with LS directly and they were kind to provide a power consumption curves (attached) plus further info: "Although the average power consumption is around 6 – 7 Amp, it can reach 25 Amp peaks by rough sea conditions when the cylinder has to push hard and the pressure rises." Pretty hard to say how likely that is to happen...


Attached Files
.pdf   COURBE 40 ST 16 12V.pdf (Size: 550.74 KB / Downloads: 5)
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#4
So just wondering if the best compromise would be to switch a 25A fuse to the hydraulic controller. Peaking over 20A should happen rarely and in most occasions the current draw would remain in 6-7A, keeping things cool
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#5
It sounds like it would be very unlikely you will ever get anywhere near 25 amps except maybe in extreme conditions (sailing hard in rip currents) etc..

takes about 2 minutes for this 20 amp fuse to actually blow at 25 amps continuous. Since autopilot is intermittent it would be unlikely it would ever actually blow, but you could use a 30 amp fuse instead.
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#6
(2020-07-02, 05:44 PM)seandepagnier Wrote: It sounds like it would be very unlikely you will ever get anywhere near 25 amps except maybe in extreme conditions (sailing hard in rip currents) etc..

takes about 2 minutes for this 20 amp fuse to actually blow at 25 amps continuous.   Since autopilot is intermittent it would be unlikely it would ever actually blow, but you could use a 30 amp fuse instead.

Excellent, thanks! We are mostly in Finnish archipelago, I do not think we get to such conditions.
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