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Old 03-02-2020, 03:11   #1
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use hydraulic motor instead of rams to control rudders

Looking at options to redo my steering on my cat. Currently have hydrive hydraulic rams controlling the rudders. Trouble is my rudders kickup and there is a lot of play.

Ideally if I could get a rotary hydraulic drive(like a hydraulic motor) mount it on top of the rudder post, there would be noplay and it could pivot up with the rudder. My rudders are in cassettes which pivot up but I havn't got the room for the rams in there.
Still trying to work out sizing.

Workable? Doable?


example of a motor
https://www.ebay.com.au/i/2530844371...saAraLEALw_wcB
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Old 03-02-2020, 03:59   #2
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Re: use hydraulic motor instead of rams to control rudders

Perhaps you could use a hydraulic servo motor

How would you coordinate and modulate the motor pulses ?

Sounds like a complicated science project to me

Also hydraulics tend to be energy intensive
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Old 03-02-2020, 04:40   #3
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Re: use hydraulic motor instead of rams to control rudders

It's a complete nightmare.

I have struggled with the same issue forever.

The only way to get this to work is to expand the size of your kickup to include the ram. What I'm doing is including the top face of a nearby step. My ram sits in the step now and does NOT kick up with the rudder. Best I could think of for a while. What I'm doing is cutting the top tread face of the step off and making it part of the kickup.

This allows the entire face of the step, which houses the hydraulic ram, to kick up with the rudder.

It will be a lot easier to do something like this than to experiment with costly custom hydraulics.
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Old 03-02-2020, 04:43   #4
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Re: use hydraulic motor instead of rams to control rudders

Quote:
Originally Posted by slug View Post
Perhaps you could use a hydraulic servo motor

How would you coordinate and modulate the motor pulses ?

Sounds like a complicated science project to me

Also hydraulics tend to be energy intensive
He's talking about hydraulic steering. That's a passive system. The only energy expended to run it is whatever he ate for lunch. Lol
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Old 03-02-2020, 11:02   #5
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Re: use hydraulic motor instead of rams to control rudders

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Originally Posted by Chotu View Post
It's a complete nightmare.

I have struggled with the same issue forever.

The only way to get this to work is to expand the size of your kickup to include the ram. What I'm doing is including the top face of a nearby step. My ram sits in the step now and does NOT kick up with the rudder. Best I could think of for a while. What I'm doing is cutting the top tread face of the step off and making it part of the kickup.

This allows the entire face of the step, which houses the hydraulic ram, to kick up with the rudder.

It will be a lot easier to do something like this than to experiment with costly custom hydraulics.

My rudders kick up with the rams. It was quite difficult to find rams that were small enough physically and still powerful enough to do the job. protecting them from the elements was also challenging but doable.


Nothing is perfect but it does work. I also have a remote bypass valve and 2 rudder indicators that allows realignment from the cockpit.
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Old 03-02-2020, 11:55   #6
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Re: use hydraulic motor instead of rams to control rudders

If you are trying to drive only the 60-90deg of rudder swing with a motor designed to spin, I think you will find the motor torque way too low to directly drive your shaft, unless you get a huge motor! You would likely need to gear the motor output.


Anyway.. to size the motor: you need to know the volume of oil the helm pumps out lock to lock. then you need to match that to the motor. So, If you want to direct drive the rudder shaft, say 1/4 (90 deg) motor turn, and your helm output is, say, 1L lock to lock, then you need a motor with a 4L displacement per rev. Pressure is the next key parameter. You need to find the spec on the helm pump and see what the rated output pressure is (or better, put a gauge in-line while loading the helm by hand and see what you get). The motor spec's will allow you to convert pressure to torque. You need to check that against the output force of your current ram times the perpendicular distance of the ram to the rudder shaft and verify the motor torque is equal or greater.... good luck!
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Old 03-02-2020, 12:36   #7
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Re: use hydraulic motor instead of rams to control rudders

The snow blower on my tractor uses a hydraulic motor to rotate the chute. These are readily available at farm supply stores like Tractor Supply. You will need a reduction drive. Mounting the motor just forward of the rudder shaft and using a chain drive should work. They drive both directions so your regular hydraulic auto pilot motor or your manual steering pumps should work. I would mount the motor without the sprockets and check the speed of rotation with your pumps then decide on the ratio of the sprockets. SS chain is readily available as they are often used on snow blowers. I don't know about SS sprockets but steel ones are available and not expensive.
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Old 03-02-2020, 13:06   #8
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Re: use hydraulic motor instead of rams to control rudders

There are hydraulic devices specifically designed to do what you are contemplating. They are used to remotely actuate things like ball valves which only need turning 90 degrees to open or close. Google "Hydraulic rotary actuators". Usually fairly hefty pieces of gear though.
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Old 03-02-2020, 15:13   #9
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Re: use hydraulic motor instead of rams to control rudders

Could be done with a standard hydraulic steering ram, keeping the ram parallel to the rudder shaft, if you used a rack and pinion in combination with a pair of 90 degree spiral bevel gears.

Might also be possible with just a rack and pinion, but I'm not so sure that a rack can be made to drive a pinion rather than vice versa as seems to be normally the case...

Wouldn't be cheap though, unless you have your own machine shop...one could always rob the gears from an old outdrive or outboard lower unit and the rack and pinion from a standard in or outboard steering system, if one were so inclined...

Below is a schematic illustration of how it could be done.
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Old 03-02-2020, 16:37   #10
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Re: use hydraulic motor instead of rams to control rudders

Thanks for all the feedback and info. Rotary Actuators sounded like exactly what I was after however rough costing from Parkers was $7000 each apparently. Pity.
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Old 03-02-2020, 23:12   #11
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Re: use hydraulic motor instead of rams to control rudders

There are a number of different mechanisms used. Some of them use pistons in cylinders which drive a rack with the pinion on the shaft to be turned, others a vane arrangement rotating in a semi circular housing. There are others using pistons acting against swash plates.

If I was going to try to build them myself as a DIY project I'd go the vane route with a longish vane working inside the rudder stock itself. Since the forces required on a balanced rudder are not very high one might be able to use mostly alloy. It would be a very interesting project.
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Old 04-02-2020, 03:37   #12
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Re: use hydraulic motor instead of rams to control rudders

Quote:
Originally Posted by jimbunyard View Post
Could be done with a standard hydraulic steering ram, keeping the ram parallel to the rudder shaft, if you used a rack and pinion in combination with a pair of 90 degree spiral bevel gears.

Might also be possible with just a rack and pinion, but I'm not so sure that a rack can be made to drive a pinion rather than vice versa as seems to be normally the case...

Wouldn't be cheap though, unless you have your own machine shop...one could always rob the gears from an old outdrive or outboard lower unit and the rack and pinion from a standard in or outboard steering system, if one were so inclined...

Below is a schematic illustration of how it could be done.

Wow, Jim.

Genius solution to the problem.
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