hydraulic steering system LM 32

[marcos]

Hi,

I've replaced the original cable steering system from my LM 32 and have installed a VETUS hydraulic instead ( model HTP 2010 + MTC 3008).

The overall outcome is fine but however I'm not entirely happy  when using the wheel as it's become slower with respect to the cable system and it now  takes much longer before the rudder  starts to respond.

Any advice on the above will be much appreciated.

Many thanks.

Attachments:

[pengwyn]

hi marcos,

you might need to check, if the reservoir for the hydraulic fluid is full and there is no air trapped in the hydraulic system. there should be little nozzles at the hydraulic cylinder to get rid of air. If there is air in the system, it feels as if steering wheel and rudder are connected by a rubber band.

you also might want to adjust the response and the number of turns required from full stbd to full port by changing the position, where the hydraulic cylinder is attached to the rudder.

(if it gets too close to the axle of the helm, very high (and too high)forces might be introduced into the system - if the lever is too long, it will take more revolutions at the steeringwheel to produce the desired effect. before making any changes, check at least twice, if changing the position allows free movement of the hydraulic cylinder and if the piston of the cylinder extends long enough and it should also be +- symmetrical

if that does not help (unlikely, but not completely improbable), the size of the pump at the steering wheel might be to small and/or the hydraulic cylinder at the rudder might be too big. the size of the two pumps have to match the force to be transmitted (too small will probably break) and they have to provide the correct transmission to result in appropriate rudder angel according to a certain number of turns at the steering wheel. thats not only a matter of the manufacturer of the hydraulic system but involves the whole geometry at the rudder / helm and the options to place the hydraulic cylinder.

btw... if you ever plan to stop the rudder from moving manually - e.g. for a windpilot having its own rudder, it not a good idea, to do that by introducing a valve in the hydraulic system, as there will alway a (slow) drift in the hydraulic cylinder under constant pressure from the rudder. also in most hydraulic steering systems its of little user to mark a certain position at the steering wheel, as the neutral position for the rudder, as the position of the steering wheel might change. This might also result in some issues with autopilots, attached to the steering wheel and rudder indicators attached to the steering wheel.

good luck!
& happy sailing

Pen Gwyn

[penggwyn]

Hi Pen Gwyn,

Many thanks for your quick and complete reply.

I'll share your information with the Vetus delaer/supplier and let's hope the problema might be resolved!

Kind regards and happy sailing!

[marcos]

Hi Pen Gwyn,

Many thanks for your quick and complete reply.

I'll share your information with the Vetus delaer/supplier and let's hope the problem gets resolved!

Kind regards and happy sailing!

Marcos Freire

[marcos]

Dec 12, 2016 22:49:33 GMT pengwyn said:

hi marcos,

you might need to check, if the reservoir for the hydraulic fluid is full and there is no air trapped in the hydraulic system. there should be little nozzles at the hydraulic cylinder to get rid of air. If there is air in the system, it feels as if steering wheel and rudder are connected by a rubber band.

you also might want to adjust the response and the number of turns required from full stbd to full port by changing the position, where the hydraulic cylinder is attached to the rudder.

(if it gets too close to the axle of the helm, very high (and too high)forces might be introduced into the system - if the lever is too long, it will take more revolutions at the steeringwheel to produce the desired effect. before making any changes, check at least twice, if changing the position allows free movement of the hydraulic cylinder and if the piston of the cylinder extends long enough and it should also be +- symmetrical

if that does not help (unlikely, but not completely improbable), the size of the pump at the steering wheel might be to small and/or the hydraulic cylinder at the rudder might be too big. the size of the two pumps have to match the force to be transmitted (too small will probably break) and they have to provide the correct transmission to result in appropriate rudder angel according to a certain number of turns at the steering wheel. thats not only a matter of the manufacturer of the hydraulic system but involves the whole geometry at the rudder / helm and the options to place the hydraulic cylinder.

btw... if you ever plan to stop the rudder from moving manually - e.g. for a windpilot having its own rudder, it not a good idea, to do that by introducing a valve in the hydraulic system, as there will alway a (slow) drift in the hydraulic cylinder under constant pressure from the rudder. also in most hydraulic steering systems its of little user to mark a certain position at the steering wheel, as the neutral position for the rudder, as the position of the steering wheel might change. This might also result in some issues with autopilots, attached to the steering wheel and rudder indicators attached to the steering wheel.

good luck!
& happy sailing

Pen Gwyn

[marcos]

Hi Pen Gwyn,

I've discussed the tips of your post with the local installer of the vetus system.

The following pictures  explain how the whole  hydraulic set was fitted in my LM 32.

By the way, during the setting up of the system the model of the cylinder had to be replaced by a  suitable one due the constraints of the space available onboard.  As you are aware the space available underneath the tiller is rather limited.

I suppose your LM t has a hydraulic system too, is that correct?

Any comments on the above will help out.

Thanks for your time.

Kind regards!

[pengwyn]

Hi Marcos,

the hydraulic setup in your boat looks quite similar to the hydraulics in my LM27 (exept for a valve switchblock and additional hydraulic tubes for my autopilot). In my LM there seems to be more space, as there are no nice shiny white structures - behind the hatch of my LM27 it's just open space, shared by rudder, hydraulics exhaust tube, bilge tubing etc.. From your photos I deduce (I did not find out how to upload pictures), on your boat there is also a mechanism (a bolt with that spring on it and I would guess its remote controlled) to decouple the hydraulics from the tiller (without a shortcut-valve in the hydraulic system, or a mechanical option for disconneting hydraulics from the rudder,the tiller would become quite useless an a frustrating fitness-tool). While sailing I personally prefer to decouple the hydraulics from the rudder machanically, resulting in a more direct, more sensitive feeling at the tiller. The hydraulic shortcut-valve I only use if switching has to go fast and to reduce the risk of damaging my fingers (seems mechanical decoupling is much better on your boat and less dangerous for fingers ;-) ).

But the valves to get rid of air in the hydraulic system are not on top. it looks, as if they might be on the side of the hydraulic cylinder, probably allowing still lots of air to be trapped in the upper part of the cylinder, resulting in a "rubberband-rudder" effect. Getting rid of the air in that hydraulic system is the same procedure as in brakes of a car ( a little rubber tube from the nozzle introduced in hydraulic fluid to avoid air re-entering the system from that side, before closing the valve). I would recommend to get rid of the air in the system, while the valves are in top position.

to adjust the transmission ratio there are three differnet holes in that little tiller, where the hydraulic piston is attached to. this allows to attach the piston of the hydraulic cylinder closer to axle of the rudder, resulting in increased turn of the rudder per turn of the steering wheel - but also in much higher forces (higher risk of failiure). If the endpoints of the piston match the endpoints of the rudder everything seems to be fine. If you would want to change the transmission, you would have to change the size of the pump at the steering wheel (or the hydraulic cylinder).

Be aware, that we are dealing with enormous forces in such a hydraulic system. If vigourously powered by turnung the steering wheel, the piston of the hydraulic cylinder might push with (several) tons towards that little tiller.


happy sailing 2017


Pen Gwyn

[marcos]

Hi pengwyn,

Many thanks for your wise and helpful advice.

Kind regards

[marcos]

Hi Pen Gwyn,

On top of the picture enclosed you will notice the changes applied to the hydraulic system which is working much better now! Basically it's  been relocated as well as readjusted.

Also the reservoir has been refilled and now it's full of fluid so it all looks to be in good order.

thanks for your advice

kind regards!

[pengwyn]

Hi Marcos,

as mentioned before, the volume-ratio of hydraulic pump attached to the wheel and hydraulic cylinder at the rudder will determine the transmission ratio. Increasing the pump volume per turn of the wheel at the Wheel side of the hydraulic system, will require less turns to move the rudder from full starbord to full port (vice versa). Decreasing the volume of the hydraulic cylinder at the rudder will have the same effect.
More turns per movement of the rudder will improve the sensitivity of rudder adjustements that can be made. Less turns per rudder movement might result in some sort of go-cart steering wheel performance, but will decrease the sensibility of the steering - also more force at the steering wheel will be required.
(you could also decrease the amount of turns required by attaching the hydralic cylinder closer to the rudder shaft - this I would not recommend, as the forces in the hydraulic system, Cylinder, lever at the rudder shaft might exeed the specifications and the whole mess might break).

On my LM27 it takes 6 turns from hard to hard - so it's three turns for sufficiently fine adjustements from neutral to hard port /starboard. If you find the amount of turns required somewhat cumbersome while maneuvering in a harbour or similar conditions, I would recommend to attach a knob to the steering wheel (as seen on many tractors and trucks for the same reason), which allows very fast turns of the steering wheel when needed - whithout loosing the ability for very fine adjustements of the rudder.

hope this helps


Pen Gwyn