steering gear

[richardm]

I sail a Roberts 34 built in steel about 5.5 tonnes. The steering has always been quite heavy and while it was OK for short voyages I now need to do something about making it more friendly. The boat is quite well balanced so I don't think that is the problem. I have a 600mm diameter wheel. a 70mm cog with 11 teeth and a 250 mm quadrant (measured from the centre of the rudder stock to the outside edge of the quadrant). Is there a formula that ties in the variables or where would the best starting point be. Just found the edit button! I have cable steering and it takes only just over 3/4 of a turn to take the rudder from full starboard to full port. Feels like trying to steer using a very small tiller!



<P ID="edit"><FONT SIZE=-1>Edited by richardm on Sun Jan 13 09:08:40 2002 (server time).</FONT></P>

 

[Guest]

I would start by elimnating the gear step by step .
Lift the chain off the wheel to see it turns ok .
Take the quadrant off then turn the wheel to see if it's the cable run.
while you have that off see how the rudder turns
If your cable is sticking then it usualy means that at some point in it's travel there's a bend which is too tight.
The rudder is normaly the cause ,the lower bush and or where the rudder stock housing goes through the hull .
When did you last grease this !!.
Finaly it could be the ratio between the chain gear and quadrant ,it does sound like there's not much turning before your side to side.
Mick

 

[Guest]

Whilst there may be scope for reducing friction within your existing system you have really answered your own question by saying that at present it is like steering with a very short tiller. Your "tiller" is your quadrant, and at 250mm it sounds rather "short." You need to increase your mechanical advantage either by fitting a larger quadrant or by other means, e.g. reducing the diameter of the wire rope drum. You seem to refer to a sprocket within the system: perhaps if you have a roller chain linkage in the system then there may be scope to increase the ratio by changing sprockets.

 

[hlb]

Its hard to say without knowing how much spare room you have round the boat But. Think of it like a bike. Big cog on the pedals, small one on wheel. Now the pedals are your steering wheel, so you want a smaller cog on there, or a bigger one on rudder, or both. Or if you can find a little gearbox somewhere that would be ideal. Try Fenners.


Haydn

 

[LadyInBed]

Only 3/4 turn hard over to hard over, doesn’t seem that much to me. On my CC33 it is 2 1/2 turns and I have about a 1/3 larger wheel. When I got the boat, the steering felt stiff, so I dribbled engine oil from the wheel chain down the cables. That made things much better.

 

[ParaHandy]

NigelB's diagnosis sounds right (not enough turns). She must feel very heavy. With that size of cog and quadrant, the maths just about give a 120 degree movement of the rudder with 3/4 wheel movement? Why not reduce the 70mm cog (11 teeth) to something a lot smaller but still can get shaft thro' it?