Quadrant

[Mrleft8]

Re: Quadrant

It's not schizophrenia...... It's bloody Quadraphenia!!!!!

[Canoeyawl]

Re: Quadrant

There is another way to do it
Threads are easier to machine than gears

[Ian McColgin]

Re: Quadrant

Worm gears are most powerful for turning on the rudder post. Goblin had a single screw, single arm Edson but you sometimes see doubles like this even on moderate (under 20 T) yachts. There is no such post on an outboard hung catboat rudder.

The under-tiller that can be rigged in an emergency to relieving tackle is a nice feature. We had such above deck on a tug that had hydraulic ram steering under the deck. When the ram ruptured one stormy night I essentially swam under the grate over the tiller, breathing with nose up against the underside of the grate between waves that came aboard, to hook up a tackle on each side so we could steer back to Statin Island. Everything cool on a tug requires suitable weather - night, sleet, Force 5 or more. Anyway, this rig is certainly more accessable.

[Mrleft8]

Re: Quadrant

There is another way to do it
Threads are easier to machine than gears

OMG! Can you imagine a billowy pirate shirt sleeve, or buxsome lass's blouse getting caught in that screw?!

OK.... Forget the billowy pirate shirt.

[Jim Ledger]

Re: Quadrant

I've had a pattern for the tiller kicking around ever since I made the rudder a few years back. Say's "tiller pattern" right on it. Ive moved it at least once a week. I can't seem to lay my hands on it now that it's needed.

Is it me?


Canoey'all, that's some nice steering gear. You see more of the worm gear steerers on the used market than the rack and pinion. As Ian said though, they are suited to counter-stern boats with metal rudder stocks coming up through a rudder port.

As for machining a gear, that would be completely beyond my capabilites. The gear I intend making will be cast and cleaned up a bit with a file, as are the Port Townsend and Edson units. All the fussing will take place on the wooden plug. The bore hole will need to be machined to size on a lathe. To this end some kind of boss will need to be incorporated on the casting in order that it may be chucked in the lathe. After boring the boss will be machined off.

[Peerie Maa]

Re: Quadrant

There is another way to do it
Threads are easier to machine than gears

Thames Barges used that system

[andrewpatrol]

Re: Quadrant

Jim you mention mounting the steering shaft in another pillow block on transom to account for flex I imagine, is there any potential flex in the tiller and quadrant?

[Ian McColgin]

Re: Quadrant

There is flex but it all works out because the rack quadrent is not rigidely attached to the tiller. With the rudder centered you can push one end of the rack town and pull the other end up for almost an inch total movement - +/- 1/2" each way. The rack is held under the beveled gear at the end of the steering wheel shaft by set screw from below. So any flexing in the system won't cause a binding strain.

[debenriver]

Re: Quadrant

Seems awfully complicated to me. We built sailboats – traditional carvel, wood epoxy, and aluminum alloy from 35' to 100' – and we most always fabricated our own quadrants from either mild steel (galvanised) or aluminium alloy, for wire steering. A roller chain sprocket (or in earlier days a chain gypsy) on the steering wheel shaft; then good diameter wire rope sheaves (which we also fabricated); and wire rope cables to turnbuckles on to quadrant. Never had any problems. Never had a vessel where the geometry was not possible. Easy to calculate the power ratio. Easy to fix if something does break in some out of the way place; easy to carry a set of spare wires. Hundreds of thousands of sea miles and seldom any problem.

[Ian McColgin]

Re: Quadrant

Yes. I have built and repaired many cable quadrent/disc systems and they are quite wonderful where the helm is light. For catboats, cables are suitable for smaller boats, under three tons. Marmalade (the type Jim is building) is an actual 7 tons and the helm strains are at times enormous. The helm needs to be engineered for serious strain. Given the enormous strains, the constant 90 degree turn at each end will work harden and cable and will fray out any fibre in short order, unless it pulls the turning blocks right out.

[outofthenorm]

Re: Quadrant

OMG! Can you imagine a billowy pirate shirt sleeve, or buxsome lass's blouse getting caught in that screw?!
OK.... Forget the billowy pirate shirt.

The big unit with 1886 worked in the end is the cover, methinks.

[Jim Ledger]

Re: Quadrant

All right then, enough looking at pretty pictures...lets make some sawdust.

I'll confess right here that I've never made a quadrant or gear, have seen few and have none available to refer to, so there might be a certain amount of wheel reinvention to put up with.

My starting point, after the very basic diagram, is a set of teeth for our mock-up quadrant. They will be isoceles triangles in cross section, partly because this is easy to make and partly because I have a hunch it might work...having seen a photograph that looked like that tooth form. You have to start somewhere.

To that end a few strips of Poplar have been ripped out, slightly oversize...

[Jim Ledger]

Re: Quadrant

Chopping out some two inch pieces starts to give out something that looks like teeth.

A couple of problems present themselves.

Firstly, the teeth are slightly bigger than the diagram calls for...

...and secondly, the teeth want to lay in a straight line, instead or the nice radius arc of the quadrant.

[Canoeyawl]

Re: Quadrant

The third problem...
solved,

[Jim Ledger]

Re: Quadrant

Thanks, CY, that's an interesting site, to be sure, especially if you're an engineer, which I sure ain't.

It might well turn out that this tooth form might not be workable. What is being worked out here is a method to be able to try another tooth form without much trouble. This is a very low-tech application and it's important not to overthink it. I would imagine that a lot of what was known about simple gearing was worked out by patternmakers long before the mathematics were understood. This is not a high speed overhead camshaft an doesn't require that level of engineering.

One of the difficulties understood by patternmakers, but given little thought by engineers, is how to accurtely reproduce a gear tooth pattern in wood. The pieces are small and difficult to hold and shape, and yet they must conform to each other in size and shape to a high degree.

Here is the begining of a shooting box, which is a jig which holds the tooth while it is planed to it's final shape and size. In this case it is simply a flat piece of Poplar with a V-groove sawn in. Initially the groove is too cut too deep.