Autopilot linear drives???

[swanny]

Can anyone tell me how a linear drive works? I have one that when disconnected i.e. switched off, is so stiff it affects the steering considerably. I want to understand how the thing works? Its a Navico Oceanpilot - not in production anymore! Of course.

 

[castaway]

The only daft purchase I ever made from Ebay was an Autohelm 5000 (I think) and this was a linear drive. I spent the winter fitting the thing, but when I tried it on the water it made the steering unreasonably stiff and notchy. Clearly the thing was knackered. One has to ask who sells a perfectly good autohelm?? I only used it the once and went back to using my venerable Pinta.

These things are similar to modern steering racks ( not rack n pinion) and I think are called 'recirculating lead screw'. I took mine appart to take a look and loads of ballbearings fell out. These (normally!) sit in the thread of the screw,and are containd by an enclosure which as the screw rotates moves up and down. This carries the ram which attaches to your steering quadrant.

Anyone want an Autohelm with loose balls???

Hope that helps

All best Nick

 

[pvb]

Electric ones...

Electric linear drives use a "recirculating ball lead screw" to generate the linear motion. There are lots of resources on the internet which tell you how these work. However, autopilot linear drives have a declutchable system which allows free movement of the ram when the autopilot is disengaged, and I've never been able to find anything on the internet which explains how this works.

Your Navico Ocean Pilot drive could probably be serviced (maybe lubrication is needed), but it's probably not a DIY job!

 

[swanny]

Re: Electric ones...

Thanks PVB, I now have a whole new reason to surf the web.....not that I need much of a reason! I haven't taken up on your last advice cos I'm in Denmark for a while, but thanks anyway.