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Old 03-05-2010, 13:51   #1
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How to Create a Shaft Brake ?

My transmission was just rebuilt (velvet drive on Formosa 51/Ford Lehmnan 120 hp) and my mechanic insists that for world cruising I want to fashion some kind of shaft brake; he suggested a "poor man's approach -- a pipewrench!!) Is there a less "poor" way to go w/o resorting to the complications of hydraulic brake systems?
I like the idea of stopping my prop from turning while sailing, and like idea of something that's not expensive or complicated, and that doesn't add another damned system that needs manintenance. Any thoughts?
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Old 03-05-2010, 14:10   #2
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One of the simplest I have ever seen consisted of a 2" diameter teak cylinder, bored for the shaft size, split and clamped around the shaft. A GM diesel fuel shut-off solenoid was attached at 90* to the shaft, to a flat stainless steel strap which looped around the shaft and was anchored back at the solenoid base. The solenoid released the tension on the teak when powered by the ignition on circuit (actually thru a relay). No ignition, no power, solenoid clamps tight on teak. Had been on the boat for 20 years.
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Old 03-05-2010, 14:10   #3
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Check out
Shaft Lok Inc:

SHAFT LOK INC.

Including:

Body
cover_photo
EasyLokMod2pic
Simple Spring Locking System by Shaft Lok Inc.
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Old 03-05-2010, 14:53   #4
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Check out
Shaft Lok Inc:

SHAFT LOK INC..
That's got to be one of the worst web sites I've ever seen!
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Old 03-05-2010, 15:18   #5
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That's got to be one of the worst web sites I've ever seen!
Straight out of the Mosaic days....
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Old 03-05-2010, 15:19   #6
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If you are looking to do it for cheap and on your own, many people have done it with pickup truck disc brake parts. How you attach the disk to the shaft depends on the application. Generally, you can have a disk turned for you out of just a solid piece of steel then heat treated. The disk is often installed between the shaft coupler and the transmission output although a stub shaft is sometimes necessary to give clearance. You can also make a disk with a hole bored in the center to slip over the shaft and bolt up to something else (or just key it and clamp it real hard).

Then, you need to make a mount off of the engine beds to hold a caliper on the disk. To actuate it, you need a hydraulic cylinder that is manually actuated (you can actually use a car break setup). It is actually relatively easy to automate this process so that when the engine is running, the shaft will be unlocked. Another thing that you can do is make the disk manually actuated but that requires climbing into the engine room whenever you start or stop the engine. Another possibility is to make it cable actuated. The components for an E brake work well for this. Basically there are lots of options.

This is the cheapest and easiest way that I know of to make a real shaft brake but there are plenty of other possibilities.
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Old 03-05-2010, 16:22   #7
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If you can easily get to the shaft, vice grips are the cheapest and best way to go. They will self release if you forget to take them off, and you will. A pipe wrench would work but I'd be afraid what it would do to the engine., shaft and/or transmission when you forget to remove the wrench.

Other than that you can buy a hydraulic shaft brake but they are about a unit, IIRC. Fabricating one out of a car disk brake is a possiblity but a real PITA to do for those of us lacking a machine shop and probably a welder.
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Old 03-05-2010, 17:29   #8
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Once again, thanks very much for all the thinking out there. Question for Roverhi: With the vice grips, if I'm lucky enough to have that shaft really turning (i.e. I'm actually sailing), what's the reality of getting the vice grip on there without scoring the shaft, or smacking them hard into the bilge fuselage? Or tearing my hands off?
I've never tried to stop a turning shaft; I'm imaging there is a lot of torque.

Meanwhile, I've looked at the Shaft Lok and though the web site isn't grand, it looks like a way to go, and there goes another chunk of change...
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Old 03-05-2010, 17:43   #9
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Seems like the teak block is what you are looking for. Cheap, simple. If it breaks, you won't cry. If it brakes, you will be happy.

No crying, just happiness.
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Old 04-05-2010, 17:24   #10
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On our W32 with an oversized 2 blade prop, it was not a problem to stop the shaft with one hand. You could easily tell when the blades were hidden behind the deadwood as there was virtually no torque. When the prop was spinning, I'd just grab it and stop it and use the other hand to clamp on the Vice Grips. The Vice Grips didn't score the shaft much though that depended on the clamping force dialed into them. I forgot to remove the vice grips a couple of times and they just fell off. Bit of a PITA fishing them out of the bilge but that's what magnets on a stick are all about. I used the Vice Grips for the 10 years we owned the boat and 2 years of 24/7/365 cruising in SoPac.
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Old 04-05-2010, 18:28   #11
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I am so new to sailing but I have to ask. What is the big deal if the prop spins while sailing?
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Old 04-05-2010, 18:42   #12
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I am so new to sailing but I have to ask. What is the big deal if the prop spins while sailing?
Some designs of transmissions will fail.

Lots of previous threads on this.

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Old 04-05-2010, 18:44   #13
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@ Captin_Kirk, I believe there would be added vibrations in the boat, wear and tear on the rotating components and the packing seal would have a higher chance of leaking.

As for the braking system why not go the route of a cable actuated motorcycle rear disk brake with the associated handle which includes a parking brake lever. You would need to get creative with the mounting method of the disk.
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Old 12-05-2010, 21:46   #14
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Scrub brake: rubber on a steel strap with a bicycle brake lever. Can't beat it for simplicity.
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Old 12-05-2010, 22:23   #15
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There is a 'Prop Lok' shaft lock for sale at a local consignment store. The Prop brake disk fits onto a collar that is for a 1" shaft. Looks like it could be bored out for a larger shaft or easily fab'd by a machine shop for a smaller shaft. Think they are asking $100. The shop is Blue Pelican Marine 510 769-4858.
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