Using a hydraulic gear pump to have a clutch

[svisara]

Hey all, so I have a marine mounts setup for a raymarine rotary drive. Not wanting to spend $2k, but also not having space for a clumsy mechanical belt clutch, I was wondering about doing a hydraulic gear method.
This would give me a native clutch via the pump, and setup as though it were a linear actuator.

Can anyone help sanity check this - especially wrt strength/durability, and speed of pump translating into necessary speed of wheel? For example, I own an octopus pump that pumps 1 liter /minute which equates to .0044 gallons or ~1 cubic inch per second.

This hydraulic gear pump spins (I believe) at .6 cubic inches per revolution. So I could turn the shaft at ~1.7 rps (edit: rounds per second, not minute)? Do you think that is a workable speed?

Thanks for any input 

example pump: 
https://www.magisterhyd.com/product/0-50...JwQAvD_BwE

[seandepagnier]

I am not sure which shaft at 1.7rpm. If the rudder shaft, then ok. If it is the wheel, maybe not.

Normally -30 to 30 degrees of rudder takes 6-10 seconds.

[svisara]

Ah yes, this would be for the wheel

edit got my units wrong. 1.7 rounds per *second*

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For me, I believe lock to lock is 2 revolutions of the wheel. So I'd need a slower gear pump or gear

[svisara]

Latest idea: a 1L/min (1 cubic inch/sec) octopus autopilot pump, a gear pump like this that rotates once per 1.42 cubic inches. Also, it's a bidirectional pump; most are unidirectional.
https://m.northerntool.com/shop/tools/pr..._200641997
...that theoretically would give me .70 rounds per second. On that gear pump, I can have a 10 tooth sprocket, with a 25 tooth on the wheel. That would give me a .28 rounds per second, or just over 7 seconds lock to lock. That's the plan! Let me know how this might fail!

[seandepagnier]

This seems right. It really depends on the boat. I have rigged my boat to do 2 seconds rather than the typical 6-8 but I am also sailing at speeds > 10 knots, but my rudder stalls beyond 20 degrees rather than 30, and I may have still overdone it.

[svisara]

Copy, well it may take a few months but I'll report back when I try it

[kniven]

This seems right.   It really depends on the boat.    I have rigged my boat to do 2 seconds rather than the typical 6-8 but I am also sailing at speeds > 10 knots, but my rudder stalls beyond 20 degrees rather than 30, and I may have still overdone it.

Sean. How do you easily check the rudder end-to-end travel time? And which parameter determines the duration. 
I have a slightly oversize hydraulic pump for my boat, with an adjustable flow rate. https://www.marinepanservice.com/en/accessorio/ls-rv2
Right now, the pump is adjusted near the minimum flow rate, and seems to be working happily (just did a Norway-Shetland passage in quite rough conditions, and the motor was working without any issues. The overall current draw for the autopilot system was ~5 A).

I assume there will be a "sweet spot" where the motor controller output amps and the pump flow rate has optimum efficiency in terms of current draw...
Maybe I should consider to adjust the flow rate somewhat up. I guess that would directly affect the rudder travel time. 

Any thoughts?