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Old 18-08-2016, 22:34   #16
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Re: Back-up autopilot

I started out with an Autohelm which was unreliable as the Darlington H bridge transistors were easy to burn out. I then upgraded to a Raymarine ST4000 head but retained the wheelpilot drive system until the little nylon gears stripped. Since they wanted in excess of $1,000 for a new one I rigged it with the motor and gearbox from a battery drill and ran that for a couple of years before throwing it away and making one from the old autohelm motor and two battery drill gearboxes in tandem driving the wheel via an auto timing belt. That lasted about seven years until the gears gave out and I replaced the motor/gear part with an electric bicycle motor with 1/2" bike chain reduction which is still in service. Because I cannot find any more of the motors I am rebuilding a backup unit using auto radiator fan motors and a two stage 1/4"/1/2" chain reduction as backup to the Simrad hydraulic unit on the new boat.


Since folks in other places herein appear to be doing well on adapting OpenCPN to cheap single board computers like the Raspberry Pi it would be nice if the coders would have a look at an autopilot control add on, fluxgate modules appear to be fairly cheap and available.
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Old 19-08-2016, 00:10   #17
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Re: Back-up autopilot

A lot of good info here, thank you folks.
Regarding to set up a parallel Raymarine autopilot, I believe it would not have helped in our case.
We had some lightning damage while at anchor and some of the electronic was fried, including the autopilot. A parallel would have been fried too.
Seems the CPT might be the way to go.


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Old 19-08-2016, 00:11   #18
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Re: Back-up autopilot

^^ nice work RaymondR, love the Frankenstein AP solutions.

One issue with two identical units is often the same issue can effect both systems, Ie one faulty motherboard may blow both motors in quick succession. Also as they get older it gets harder to get spares for both.

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Old 19-08-2016, 00:47   #19
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Re: Back-up autopilot

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Originally Posted by Sindbad View Post
We are considering to install a back-up autopilot. Our boat is a Tayana 55.
A wind vane we would not really consider, because of the davits and solar panel arc. Electric power is not a concern.
It has to be a simple, robust stand-alone system. No integration with the primary Raymarine system, no wind vane mode, just steer the choosen course.
Any ideas?



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We have a tayana 58, derived from the tayana 55. The PO installed two fully redundant autopilot systems, one a raymarine, the other a b&g.

There is a simple rotary switch in the nav station that selects between them. Each has its own ram attached to one side of the quadrant.

While I see advantage in using two identical systems, I do find them sufficiently different that I prefer having the difference. The b&g eats brushes every 10,000 miles or so, but does a better job in heavy weather/rough seas.

I don't feel strongly about which brands to get, but i am sold on having completely redundant systems.

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Old 19-08-2016, 01:19   #20
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Re: Back-up autopilot

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Originally Posted by Snowpetrel View Post
^^ nice work RaymondR, love the Frankenstein AP solutions.

One issue with two identical units is often the same issue can effect both systems, Ie one faulty motherboard may blow both motors in quick succession. Also as they get older it gets harder to get spares for both.

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When I adapted the first battery screwdriver I had to make an adapter plate and the only machine screws I had were about 2" long so it actually had the bolts through the head thing.
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Old 19-08-2016, 01:28   #21
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Re: Back-up autopilot

Quote:
Originally Posted by Sindbad View Post
We had some lightning damage while at anchor and some of the electronic was fried, including the autopilot. A parallel would have been fried too.
Seems the CPT might be the way to go.
A windvane would not have been fried... just sayin'
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Old 19-08-2016, 01:33   #22
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Re: Back-up autopilot

I was thinking about this for my original long distance cruising plans. Install the latest RM AP and a second drive unit and physically disconnect my old unit.

To save the backup from frying with a lightening strike, couldn't you have it setup so that to use it you must physically plug the seatalk, power & drive units into the course computer if you want to activate it. You could set that up to be a simple job, it just wont be a flick a switch solution. Keeping it isolated like that I assume/hope will save it from a strike?
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Old 19-08-2016, 01:35   #23
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Re: Back-up autopilot

Quote:
Originally Posted by RaymondR View Post
I started out with an Autohelm which was unreliable as the Darlington H bridge transistors were easy to burn out. I then upgraded to a Raymarine ST4000 head but retained the wheelpilot drive system until the little nylon gears stripped. Since they wanted in excess of $1,000 for a new one I rigged it with the motor and gearbox from a battery drill and ran that for a couple of years before throwing it away and making one from the old autohelm motor and two battery drill gearboxes in tandem driving the wheel via an auto timing belt. That lasted about seven years until the gears gave out and I replaced the motor/gear part with an electric bicycle motor with 1/2" bike chain reduction which is still in service. Because I cannot find any more of the motors I am rebuilding a backup unit using auto radiator fan motors and a two stage 1/4"/1/2" chain reduction as backup to the Simrad hydraulic unit on the new boat.
One really good reduction gearbox that is often available is the angle drive from an old angle grinder. Some of them have a good reduction ratio plus they are very rugged. I've bought them in the past from tool repair shops for a few $. Of course tool repair shops are becoming a bit rare these days. Used one for a motorised bike project many years ago. It coped very well, but the laws changed and the engine was too powerful for the new regulations.

Then also, if you are looking for a 12v drive system that is both very robust and very powerful, you can pick up secondhand electric wheel chair motor/gearboxes for a song. Worm drive, very very high torque, and super reliable, plus an excellent reduction ratio so often they turn slow enough for easy application to other projects. I used one for a home-made electric trailer dolly to move our two ton trailer sailor around the back garden at home. $20 for the motor, a few bits of wire and some welding. Easy. I am considering adapting one as a substitute for the much loved Milwaukee angle drill as an electric winch handle.
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Old 19-08-2016, 09:27   #24
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Re: Back-up autopilot

Quote:
Originally Posted by Sindbad View Post
A lot of good info here, thank you folks.
Regarding to set up a parallel Raymarine autopilot, I believe it would not have helped in our case.
We had some lightning damage while at anchor and some of the electronic was fried, including the autopilot. A parallel would have been fried too.
Seems the CPT might be the way to go.


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That's why our backup AP electronics is disconnected, wrapped in aluminum foil and stored below.
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Old 20-08-2016, 23:03   #25
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Re: Back-up autopilot

Quote:
Originally Posted by GILow View Post
One really good reduction gearbox that is often available is the angle drive from an old angle grinder. Some of them have a good reduction ratio plus they are very rugged. I've bought them in the past from tool repair shops for a few $. Of course tool repair shops are becoming a bit rare these days. Used one for a motorised bike project many years ago. It coped very well, but the laws changed and the engine was too powerful for the new regulations.

Then also, if you are looking for a 12v drive system that is both very robust and very powerful, you can pick up secondhand electric wheel chair motor/gearboxes for a song. Worm drive, very very high torque, and super reliable, plus an excellent reduction ratio so often they turn slow enough for easy application to other projects. I used one for a home-made electric trailer dolly to move our two ton trailer sailor around the back garden at home. $20 for the motor, a few bits of wire and some welding. Easy. I am considering adapting one as a substitute for the much loved Milwaukee angle drill as an electric winch handle.
I actually have a right angle drive from a grinder lying about in the boat somewhere. I tend to do salvage runs on stuff before I throw it out. Your right about the robust even the cheapest grinders have substantial drive gears.

Electric wheel chair drives look like another good source and maybe the mobility scooter things might have hefty DC drives. I'll check them out when I get back to civilization.

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