Hydraulic Steering Experience on a Cat?

[Rohorn]

Hi people.
There's a lot of backlash (freeplay), amounting to a quarter of a turn at the wheel in the four-turn mechanical steering system on my Dean, which uses an amazing but reliable collection of two chainwheels and a chain, a long lay-shaft, a pair of mangle wheels and a rack-and -pinion, connected to the tiller-bar.
This makes life tedious for the Auto helm. A detailed plot of our course would show a perfect modified sine wave.
I've pondered for ages how to reduce the play, and have made a real hobby of designing replacement systems around heavy toothed belts and the like. I'm forced to admit that perhaps a hydraulic system e.g. Vetus, might be a better way to go. I've been through their calculations but I have...
Questions......
-- Would it leak? All hydraulic systems I've met had at least a sheen of oil all over them.
-- Will it backdrive...i.e., do you get any feed-back?
-- Vetus only show short stroke cylinders, whereas I want 60 centimetres of stroke directly driving the tiller bar, not a dangerously powerful jack down close to the pintles.
-- Can one drive a hydraulic motor instead of a jack...i.e., backdrive an identical pump like the one driven by the wheel?.
-- How reliable would it be? The existing system, though gross, works unfailingly.

I'd appreciate any experience you could offer
Cheers.....R

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[Birdseye]

I have a hydraulic system on my Prout. It works well and has been completely reliable. The answers to your questions are:
1/ leak? slightly but not enough to require topping up of the reservoir in 5 years. At the plant I ran we had hydraulic machinery and found that the only real way of never having a thin sheen of oil was to weld the pipe joints. But a tiny bit of oil goes a long way since a film is visible at literally a few atoms thick - the reason you get rainbow effects with an oil film on water.
2/ no feedback in my vetus pump, but I believe you can remove the anti feedback valve from some pumps if you wish. I dont because there are real advantages to no feedback. Like putting the helm over for a tack and simply leaving the wheel to attend the sheets whilst the boat goes through the wind.
3/ my cylinder operates a tie bar through levers. Its a standard boat fitment, and the pump is set at a low cut off pressure so even if , for some reason, you continued to try to turn the wheel when you were on full lock, you would not damage the rudders. its not tike a hydraulic jack and cant be so since you need a turn of the wheel to give a good turn of the rudders. So there is no gearing down like there is on a jack. Put another way, the force on the rudders is much nearer to the force you exert on the wheel.
4/ Why would you want to? Simplicity!!!
5/ All depends on how well you engineer it - but I would expect a hydraulic system to be more reliable than mechanical systems. When did you last have a car with mechanical brakes?

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[snowleopard]

i also have hydraulic steering though unlike your setup i have no tie-bar so have two rams in series. i have massive alloy tillers about 8" long and the ram stroke is about the same amount, i'm not aware of long-travel rams on the market.

surprisingly, there is a certain amount of feel in the steering in terms of resistance to turning though there is no kick-back.

be aware that you can't use normal wheel autopilots because the wheel has no fixed dead-centre position and you can't use a below deck ram attached to the quadrant as you can't drive hydraulics backward. you have to use an in-line pump and a rudder position sensor.

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[dickh]

The first thing I would do is try and find out exactly where the backlash is and try and eliminate it. I would expect a small amount, say an inch or so at the wheel but no more. Is the play in the rudder pintles? - if so going to hydraulic wont eliminate it.

<hr width=100% size=1>dickh
I'd rather be sailing... /forums/images/icons/smile.gif

 

[Rohorn]

Hi....great to get such good feedback so quickly! Many thanks.
--Sure, my concern about sheens of oil is really cosmetic. Around the Cyclades the dust accumulates everywhere like a red-brown talcum powder. It even sticks to small (damp) rust patches on stainless making it look ten times worse. Suntan lotion patches pick it up too. I don't want an eyesore!
-- Do you have an autopilot? I use mine for tacking or maintaining a course while working the winches. Feedback seems to me to be useful info about the boat's balance and handling under sail. Vetus say one can retro-fit check-valves if one so wants. Might be chic to valve some in as an operational option.
-- Brother-in-law fitted hydraulic steering to his steel monohull, using a standard Vetus lever-arm and cylinder. Watched horrified as the anchored (and pivotted) end of the cylinder distorted the steel hull as he turned. Much reinforcing was welded in... To avoid these forces on hull and pintles, my thinking was to connect a very long stroke (60 cm) cylinder to the tie bar direct, exactly as the existing rack and pinion. Such a cylinder is not available as standard, except in some huge diameter. From your description it sounds like you have achieved exactly this, by amplifying a standard cylinder stroke with a pivotted lever. I guess I could make something similar, fixed to the very solid (vertical) cockpit transom, accepting that the geometry is not in the same plane as the tiller movement. Just have an adequately long drag-link to minimise the skew. Yes, I'll sketch that out and see if there's room.
My rudders immersed areas are 50 cms wide by 80 deep each, skeg mounted, and the boat weighs five and a half tons. Which sized Vetus units did you use?
Good point about reliability of car brakes. I'd thought in case of failure I'd disconnect the cylinder, let the rudders trail and make it home steering with the engines. If single handed I couldn't steer with the tie-bar and still see over the cabin roof.
The idea of back-driving another motor was to drive the existing pinion of the famous rack and pinion, but you are right...keep it simple.
Many thanks once again.....Cheers....R

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[dickh]

If you go the route of hydraulics, you will be able to get a cylinder made up with the correct bore but longer stroke if you go to a hydraulic cylinder manufacturer - just specify Stainless Steel piston rods - all at a fraction of the cost of a 'Marine' cylinder.

<hr width=100% size=1>dickh
I'd rather be sailing... /forums/images/icons/smile.gif

 

[Rohorn]

Hi...Dickh....I've studied this amazing system for some years now!. The wheel is attached to a shaft on which is keyed a chainwheel. The chain drives another keyed pinion which lives on a short shaft which is coupled to a two metre long tubular drive shaft using ....keys. This shaft is coupled to another short shaft on which keyed a large gear wheel. This meshes with another identical wheel which is welded to a shaft which projects through the transom. (The gears move the centre line of the drive past the end of the fuel tank). This through-transom shaft turns a crude pinion which drives a massive rack which rides on nylon rollers and is flexibly linked to a tube (draglink) which is flexibly connected to one tiller, to which is attached the tie rod (tube) which drives the other tiller.
The inboard stuff is heavy stainless and almost totally inaccessible, having (I think) been installed before the two halves (top and bottom) of the craft were glassed together. I couldn't get in to weld all the keyed items to their shafts, and anyway felt it wouldn't fix all the problem.

This is an early Dean 1989-90, and they got most things right, but not the steering. Later models have Morse steering, but that would be hard to retrofit. Hydraulics is surely the way to go, I've just needed to be fully convinced !
Thanks for your comments....Cheers....R


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[Rohorn]

Hi Snowleopard....I also thought about a ram and lever arm on each rudder, linked hydraulically, but keeping the tiller bar to maintain alignment and geometry. The same problem...strong forces too near the pintles.
For simplicity, less expense, and forces no greater than I have now, a smallish diametre but long stroke ram on the tiller bar seemed good, except that isn't available as standard, as you say.
I'd thought of increasing the stroke using an elegant (to my eyes) system of pulleys and toothed belts, but the hosing the sand and pebbles out of that lot would be insane. I can adopt Birdseye's idea to use a standard ram and simply increase the stroke using a pivotting lever system, even though the forces will again be great (work is work), but by fitting it to the massive and vertical transom, that'll be ok.
I don't get the point about not being able to use the existing Autohelm. This doesn't have a fixed mechanical set point anyway...it drives through a slipping toothed belt (pinion on one side driving a belt which lies on a large diametre smooth wheel on the other--acts like a clutch) to a selected fluxgate compass heading. So slippage in a hydraulic pump or ram isn't important Sounds like yours is a very serious system, perhaps motor-pump driven as opposed to hydrostatic?
Oh by the way, reference another thread, I found a calorifier in a caravan/boating store near Lyon. 16 litres capacity, rectangular shape easily stowed, with element, 380 Euros.
Thanks once again for you comments......Cheers...R

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[timevans2000]

most Prouts seem to have used Hynautic hydraulic steering. They are now part of Teleflex Morse. Have a look at the website. They may do what you need.

I have a Prout with this set up. It has been on 23 years and is still going strong. We have a very minor leak on the back of the steering pump. It has not needed topping up for the last 3000 miles. All it needs is a seal kit installing. They cost £60 but haveny done it cos leak is small.

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[snowleopard]

Re: tie barExperience on a Cat?

if you can tie the 2 rudders with a solid bar, you have the benefit of only needing one ram which simplifies the pipework. because the back of the bridgedeck is a long way ahead of my rudder stocks, a tie isn't practical, hence use of twin rams in series. the big snag is the section of pipe between the rans which has no oil feed.

inevitably there will be a little 'creep' of oil past the ram seals resulting in the rudders becoming misaligned. to counter that i have a pair of spring-loaded bypass valves that let me force oil past the ram into the middle section of pipe. when the rudders get out of sync i turn the wheel to full lock then force it round another half turn, then repeat the other way. this forces each ram to full extension or compression and excess oil goes through the bypass. result is that both rudders are now at full lock and in sync again. the system takes half a day to fill and bleed!

i guess the simpler wheel autopilots can work without rudder position feedback but the smart ones (st5000 and up) must have it.

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[dickh]

B*****y H*LL!! that sounds a horrendous setup - go hydraulic as soon as possible! I bet one or two of the keys have worked loose over the years(or were never right initially) but as you can't access the bits I can see your dilemma.
Have you seen any one else with the same setup and compared notes?
Good luck anyway.


<hr width=100% size=1>dickh
I'd rather be sailing... /forums/images/icons/smile.gif

 

[Birdseye]

the only problem I have had using a normal wheel autopilot (autohelm 3000) was with the gearing of the system as supplied by prout. They use teleflex pumps and rams giving 4 turns lock to lock - which meant that the off course alarm was sounding because the boat was slower to respond to autohelm steering than the autohelm could cope with. so I upped the gearing using a vetus pump. now works fine - which is as well because the one downside of a hydraulic system with no feedback is that the boat isnt great fun to helm. so autohelm is used maybe 80% of sailing time.

on the prout each rudder has a square steel shaft at the top. this has a 6 inch or thereabouts lever bolted to it. the two rudders are connected by a tie bar using automotive track rod ends. in the middle of the tie bar ie inside the crossbeam at the stern is the ram, again fastened to the tie bar by a track rod end to a welded flange. the other end is bolted to the boat. the ram pivots come with the ram from teleflex.

final thing. the piping is nylon because the system is low pressure. but this means a thicker wall pipe and smaller id. so when I went to a decent output pump I was getting heavy steering simply forcing the sae 40 hydraulic oil (the standard stuff) through the pipes. changed to sae 10 and no probs. finger light steering.

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[Rohorn]

Hi Dickh....Now I've got myself finally convinced, its just a question of time and money, then I'll do it.
I'll keep the old system in situ for future generations of industrial archeologists to marvel at. I can't get it out anyway, without seriously scarring the boat!
Cheers.....and thanks....R

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[timevans2000]

My steering uses ATF. It is not viscous at all. Steering is quite light. The hydraulic equipment is Hynautic.

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[Rohorn]

Hi Birdseye.....Thanks for the info....I guess you have check-valves in your system, so there's no feedback? I was sort of hoping that a hydraulic system without the optional check-valves might feed something back. My incredible mechanical system doesn't feedback much, but what one feels is still useful.
I tend to use the autohelm a lot anyway, but when on manual, I'd like to feel something. Usually the noise of the Autohelm tells me if the trim is grossly wrong.
I note the message about tube diameters and oil viscosity. Guess there might tend to be an increase in oil loss if it gets too thin?.
I'll suss the Morse/teleflex website for info to spplement the Vetus stuff.
Thanks again.....R

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