Downsizing hydraulic cylinder

[marinovich.91]

Hi to everyone, first I wil try to put here my current system, then what I would try to do and then couple of questions. This may be a big thread but my apopogies.

The current problem on my sailboat is that somebody before I bought it had putted hyrdaulic steering on 31 foot boat, and made couple of mistakes along the way.

So courrent setup is that i have:

• 28cc steering helm pum connected to 70cm diameter steering wheel
• 168cc steering hydraulic cylnder

This gives me 6 turns from end to end, and main problem is that I dont feel the rudder at all(no feedback). I have been googling it a lot and found that there is couple of solutions.

Before I continiue I must mention that I have raymarine EV100 Autopilot connceted to my steering wheel over Autopilot wheel attached to it(with small electromotor)


So to get any feedback from rudder I found that I need to remove checkball’s from nonreturn valve system on helm pump(80% sure). So fluid from my steering cylnder can influence steering wheel.


At current system I dont need use any effort to turn the wheel and when there is rough sea, sailboat is behaveing like local drunk, since I cant chatch the boat>>There is no feeling and 6. turns from end to end.
Manovering is story for its own.

Solution for this is downsizing hydraulic cylinder or buying bigger capacity pump. Since I dont have space, and hy. cylnder is cheaper to change I decided to change the cylnder.

The main problem arise when I contacted Seastar tech. support about it.
He told me downsizeing the cylnder effort on steering wheel incrises a lot. (a lot is the main problem).

Recently I calculated my rudder torque by calculateing area an running it in calculator and got 6kg/m. Pictures attached, Calculator web site is on this link..

Calculator gave me:
Force of 210
Rudder torque of 6kg/m

I am not sure since there isnt any units; what this should mean

Solution 1.
I would like to go for 69cm3 (2.5 turns) capacity of hydraulic cylnder but I dont know if my autopilot will be able to handle it becouse friction of fluids and pump. As well max torque of cylnder is 32 kg/m but output force is 170kg.


Solution 2.
Another option is to go for 84cm3 (3 turns) capacity of hydraulic cylnder but I dont know if my autopilot will be able to handle it becouse friction of fluids and pump. As well max torque of cylnder is 58 kg/m but output force is 387 kg.

Lady in Hydrodrive told me:
On application 28cc pump and 84cm3 cylinder, on shaft pump, to reach the max pressure, needed a torque of 42 Nm.

But I want the feedback as well.

The main question is how to calculate how much stiff my steering wheel is going to be, since I want it to be just on border so my autopilot can handle it, to have feedback, as little as possible turns and normal effort steering.

Thank you for your Help and time

[marinovich.91]

Pictures now attached.

[gabilo]

Hi Stipan
I think there is no solution for your „rudder feedback“ issue when going hydraulic. You can make it stiffer, but still no feedback.

The reduction of turns of the wheel can be solved as you described... but is it worth it? Sail out of Barnica a lot and you will get used to it.

[marinovich.91]

Haha, Thanks for advice. But I am preety sure feedback will be possible since all helm pums has 2 nonreturn valves for each hose. I am affraid maybe that my "overballanced" rudder wont make enough force to cylnder so it can transver it to helm pump and make effort on 35cm leaver which you make over 70cm wheel.

Next year hopefully will go for some local sail regatas, so I want to make my wheel as good as mechanical steering system. As well, going to open sea you want to be prepared and feel each wave.

[marinovich.91]

My whole system works at maximum of 70bar.

"Lady in Hydrodrive told me:
On application 28cc pump and 84cm3 cylinder, on shaft pump, to reach the max pressure,torque needed is 42 Nm on pump shaft.What does this mean if my max torque from rudder is 6kg/m?"

Cylnder in question has 58kg torque at max pressure of 70bar and Force of cca 387 kg.

52/6 =866% or 8.6 times
4.2kg at 1m is at(70cm radius/2 = 35cm) comes to 12kg/35cm
12kg/8.6 = 1.4kg (70cm radius/2 = 35cm) at maximum of 35 degrees and speed of 7knots

1.4kg is needed in istance* (at maximum) when you go full left or right on full speed of 7knots to turn the rudder 35degrees

Is this right way to look at this solution?

By your opinion I will get force feedback for sure if I remove nonreturn valves?

Istance / since speed drops when boat starts to stear thus lovering rudder resistance trough water.

[AmigoII]

Hi Stipan,

I have hydraulic steering my 40 steel cutter, I don't know of anyway you can set it up to get rudder feedback. Installing a rudder angle indicator is a great help with hydraulic steering and would likely be way cheaper and simpler. I really like my hydraulic steering and it has worked flawlessly for over 30 years.

[RaymondR]

When you say:

"I have raymarine EV100 Autopilot connceted to my steering wheel over Autopilot wheel attached to it(with small electromotor)"

What does it mean?

Does it mean that you have a Raymarine Wheelpilot, which is attached to the wheel in the cockpit or does it mean that there is an electrical motor driven hydraulic pump plumbed into the hydraulic steering system?

If it is a Wheelpilot mechanical drive attached to the wheel then you should not need any non return valves in the hydraulic steering system.

[marinovich.91]

I posted a thread on hydaulics forum as well and found answer. Using it it is possible to calculate any volume helm pump torque on shaft.

Dont mind for my bad math. I didnt use it from college.

https://www.eng-tips.com/viewthread.cfm?qid=462143