[C320-list] Linear autohelm

[Greg Arnold]

   On 8/20/2022 11:33 PM, Stephen Cox wrote:

>From the relevant Mechanical Linear Drive manual the Type 1 Linear Drive is rat
ed at 18-36 W and the Type 2 Linear Drive is rated at 48-72w.  Note the minimum
of the Type 2 is greater than the maximum of the Type 1.  What makes you think t
he ACU-200 will happily drive this without letting the magic smoke out that powe
rs all electronics?  Even assuming it manages for a while what happens when you
get into strong sea and wind conditions?  The power consumption will go up and a
gain, the magic smoke will escape the ACU-200 and it will stop working.

   Comment:  Would be a problem if you were on a Cat 470.  But on a 320
   you shouldn't be drawing much juice -- about the same as if you had an
   ACU-200 and Type 1.


Why would you go to the trouble of installing an under deck drive and not use a
hydraulic system that will take the punishment of rough seas and strong winds?
Have you ever thought what is inside the Raymarine Mechanical Linear Drives?  Ha
ve a look at [1]https://forum.raymarine.com/showthread.php?tid=1943  There is a
belt drive in there and the gears even on the Type 2 are plastic.

   Comment:  The gears used to be plastic, but now are metal.   The Ray
   Marine linear drives have a very good reputation for robustness.

  Lot of money to fit an autopilot that still relies on these components.  After
 having to rebuild my Wheelpilot more than once due to stripped plastic gears I
went to a hydraulic under deck system on my C320.  In my case I kept my SPX-30 c
ontroller but fitted an Octopus hydraulic linear drive as found in [2]https://oc
topusdrives.com/download/linear-drive-brochure/# and used a Jefa tiller arm rath
er than the Edson.  I mounted the hydraulic ram back to the transom rather than
the bulkhead.

   Comment:  Where did you mount it on the transom?  Did you have to do
   some fiberglassing?

I personally don't think the plywood bulkhead to be a structural element suffici
ent for the potential forces involved.

   Comment:  I think it may be fiberglass -- very thin fiberglass.


Stephen Cox
Tegwen #1141

References

   1. https://forum.raymarine.com/showthread.php?tid=1943
   2. https://octopusdrives.com/download/linear-drive-brochure/