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From-scratch build for wheel steering (hardware)
#1
Hi all,

I'm currently in the (very long) process of building my auto-pilot, and while I have the software & electronics part pretty much figured out, I'm stumped on the hardware side. For context, I have wheel steering.

It looks like most everyone here has started from an existing autopilot (at least in part), but I currently have nothing of the sort, and I'd like to figure out the best / cheapest way to get a functioning autopilot.

The easiest way would probably be to buy just the drive unit for a wheel pilot, but it's ~500$ on Ebay which seems a bit excessive for just a motor & some plastic bits.

I'd actually prefer to mount the whole thing directly on the rudder quadrant belowdecks, so I've looked at linear actuators, but my main question here is how do you "disconnect" them when you want to steer manually? I've tried searching for ones with clutches, but they mostly seem to be geared towards overload protection, not straight-up disconnect. Can anyone recommend some products here?

The other avenue I've thought of is a hydraulic cylinder with a "bypass" solenoid valve that just lets the fluid circulate between the two parts of a piston until it's turned "on", then it goes to a pump.

So, to sum it up, the current options I'm thinking of are:
- Buying the drive unit for a commercial wheel pilot
- Finding a linear actuator that can "free-wheel"
- Assembling a hydraulic system

Any other options?
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#2
I started from scratch as well but my boat had a hydraulic helm pump (manual) I just purchased at inline electric hydraulic pump, and two short hoses to connect it and I use that. Still not cheap, I think it ended up costing around $500 as well.
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#3
(2020-08-07, 11:07 PM)rastam4n Wrote: I started from scratch as well but my boat had a hydraulic helm pump (manual) I just purchased at inline electric hydraulic pump, and two short hoses to connect it and I use that. Still not cheap, I think it ended up costing around $500 as well.

Yeah, that seems like the obvious choice for hydraulic steering. I have cables on my boat, unfortunately.
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#4
Okay. So how to you plan to use AP? Are you sailing? Cruising? Fishing?
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#5
(2020-08-08, 04:20 AM)rastam4n Wrote: Okay. So how to you plan to use AP? Are you sailing? Cruising? Fishing?

Cruising.
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#6
I also started from scratch and got the motor of my autohelm 4000 for steering wheel (with drive belt).
I'm still in the testing, but my last test was very encouraging, especially in compass mode, and after a few adjustments the boat followed the starting course perfectly.
Whether you have cables or a manual hydraulic pump to control your rudder doesn't have to change much with this system.
cordially
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#7
another possibility is to mount a windshield wiper motor to your pedestal and use 3d printed toothed pulleys of 8:1 reduction belt to the wheel. This would end up costing about $20 (if you get wiper motor from junkyard and have a 3d printer) You would need to remove the belt each time. I want to make kits for this eventually... Any ideas for disengage ?

The wheel pilots on ebay for $500 is too high. That's basically what it costs new, and the motor is weaker than a wiper motor. These also wear out, and if you look at how the clutch works in them, there is a lot of friction so they can't be the best efficiency.
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#8
(2020-08-08, 06:52 AM)kinefou Wrote: I also started from scratch and got the motor of my autohelm 4000 for steering wheel (with drive belt).

That's not really "from scratch"  Wink

Starting from an existing pilot hardware seems to be the easiest option for wheel steering; I'm strongly considering it if I can find the hardware for cheap.

(2020-08-08, 02:30 PM)seandepagnier Wrote: another possibility is to mount a windshield wiper motor to your pedestal and use 3d printed toothed pulleys of 8:1 reduction belt to the wheel.   This would end up costing about $20 (if you get wiper motor from junkyard and have a 3d printer)    You would need to remove the belt each time.   I want to make kits for this eventually...     Any ideas for disengage ?

The wheel pilots on ebay for $500 is too high.  That's basically what it costs new, and the motor is weaker than a wiper motor.   These also wear out, and if you look at how the clutch works in them, there is a lot of friction so they can't be the best efficiency.
Yeah, windshield wiper motors are probably a better idea than RC-style motors (too fast and too weak).

For disengage, I think a system of idler pulleys with a lever that takes the belt off the motor pulley would probably work pretty well. That was my original plan with RC-style motors.

I've also played with another boat's autopilot (actually the first time I've touched a commercial unit), and I was really surprised at the amount of friction when disengaged. I definitely want a better system than that.
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#9
wiper motors already have a large gear reduction. an RC style motor with a planetary gear could be a little more efficient, but you need to use a brushless controller with sensors.

do you mean the typical wheel drive system of raymarine? It has a huge amount of friction. I don't think the people who design it are sailing much.

I managed to 3d print a lot of toothed pulleys.

Lets hear about your idler pulleys if you get them working. Another way is to hinge the motor or to have a pin that locks the large pulley to the wheel shaft.
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#10
(2020-08-17, 07:26 PM)seandepagnier Wrote: do you mean the typical wheel drive system of raymarine?  It has a huge amount of friction.  I don't think the people who design it are sailing much.

Yeah, exactly.

Quote:but you need to use a brushless controller with sensors.
 
Why does it need sensors? It seemed to work with a regular "boat" ESC (that has reverse). Is it for over-current detection? I can easily add those on the power input side.

I really like the idea of 3d printing pulleys, but I'm afraid my 3d printer isn't large enough to print the big one. Might have to build it out of wood or something.
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