Power steering all cars. Log Out | Topics | Search
Moderators | Register | Edit Profile

Australian RR Forums » General Discussion » Threads to 2015 » Power steering all cars. « Previous Next »

Author Message
Top of pagePrevious messageNext messageBottom of page Link to this message

bob uk
Unregistered guest
Posted From: brig-cache-4.server.ntli.net
Posted on Sunday, 13 August, 2006 - 04:15:   Edit PostDelete PostView Post/Check IP

I was recently talking to young lad at work about power steering.
And like the youngen in Bill Coburns Tee One Topics did not fully understand power assited steering.

On the boats I work on some have what we call an assited link in the steering system which works the same as power steering in cars.
Power assited not power because the steering still works in the advent of hydraulic failure - the pump belt breaks or what ever.

On boats when they are stationary the rudder can be moved with ease but when under way the passage of water tends to weight them up and on some of the faster stuff quite a lot, add the water being pushed back by the prop and you can see that there could be a problem.

So we fit a strut that is a hydraulic ram with one end allowed a bit of free play in the joint,inside the joint is a spool valve held central by springs. When the helm is moved the joint moves a bit before the linkage causing the spool valve to open which allows fluid to enter one side of the ram and the sttering moves under power assitance. These units are self contianed and can be disconnected entirely and the steering will still work but be heavy.

What he did not understand is that because when the boat is stationary the helm is light that there is not enough load on the springs to cause the spool valve to open and therefore the assitance is nil or very low -- if you move the helm very fast the power will cut in. This is the opposite of cars. This means that when a car is at speed the steering loads which are lighter give less assitance to the steering. Rolls-Royces are the same the steering assitance gets less as the car speeds up. This gives the same weight regardless of speed ( with in limits ).

More importantly on both boats and vehicles because the spool valve is load sensitive it works in reverse. It a car hits something in the road -like a house brick- then the sudden reverse load opens the spool valve and the hydraulics hold the steering steady. This is a great saftey feature.

This particular boat had a very senstitive rudder fitted and with out power steeering would get knocked about by the current causing the helmsman to have to make constant corrections which is tiring and therefore could be dangerous. The power strut continaleys steady the rudder like a damper.

To test the power steering stationary I simpley push on the rudder with a lump of wood while someone holds the steering if they can feel my efforts then make a judgement of how well it is working. To adjust I add or subtract shims under the springs.

Then we take the boat for a spin which why I work on boats--- I get to drive them. Nothing like a boat on the plane in open water with a couple of 10 litre diesels on full chat. I have had a few airbourne which usually sorts out which of the passengers is nervous. Never had any problems because the boats we build are strong. Plus I know that the strut will hold the rudder steady when I land agian. A rudder going hard over when the boats hits the water will probably capsize the boat. No speed limits outside the harbour.

Power assited steering is very clever because is works in reverse and saves broken fingers.



(Message approved by david_gore)