Prop Brake

[yttrill]

Originally Posted by Stumble

Take a look at a company called Shaftlok. Frankly I find shaft breaks unjustified, but if you want one i have heard ( though have no experience with) good things about them.

I would still highly recommend looking at a feathering prop instead.

Last I looked there were no feathering props for my size boat. But it's not an option anyhow, I've had a brand new prop cast specifically for the boat. Fixed props are reliable. And no "clunk" engaging them or problems with reverse. One of my friends had a feathering prop and it wrecked his gearbox. I've seen quite a few that jammed up as well. I'll check out Shaftlok, thanks for the tip!

[GILow]

First let me say that I am currently using the system recommended by grant, a loop of thin line around a coupling bolt. Very simple and cheap. A bit of a fiddle to set but not a great drama.

But I have the bits to go the same way as Lee (Banjoship) and they are very cheap and very easy to source. The brake calliper can be found at any decent trailer spares shop for $100 or less. A simple cable braking calliper. Easy. The disk likewise can be bought from the trailer spares place then dropped in to your local engineer to be matched to the coupling or if steel worries you you could get one made from stainless. Personally I don't see the need. The trailer disks live in more hostile environments than my engine bay. Most installations I have seen can soak up the extra 8 mm disk thickness at the coupling but I suppose some setups would have difficulty.

For what it is worth I put this same setup on the diff on our Toyota Coaster bus so that I could dispense with the original transmission which incorporated the hand brake. It spins at a good 3000 rpm at highway speeds and has no problem holding a 2.5 ton bus on any hill. So our1300 rpm drive shaft and a piddly little 96hp rated prop in the water won't trouble it.

Matt


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[GILow]

Originally Posted by yttrill

Last I looked there were no feathering props for my size boat. But it's not an option anyhow, I've had a brand new prop cast specifically for the boat. Fixed props are reliable. And no "clunk" engaging them or problems with reverse. One of my friends had a feathering prop and it wrecked his gearbox. I've seen quite a few that jammed up as well. I'll check out Shaftlok, thanks for the tip!

FWIW I have been considering a Kiwiprop for our boat. Not in a rush to decide but at least they do make a prop big enough for our 96 hp. Not sure how high they go and if you posted your hp I missed it. I will look again. Anyway I share your sentiment that feathering props are not all sweetness and light. There's a lot to be said for the dependability of a big fixed blade bucket.

Matt


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[iancoombe]

There's been talk of reduced drag if the prop is allowed to spin, I'm not sure about water but if the engine in a helicopter stops I want the rotors to keep turning to slow down the decent rate, known as auto rotation.

[GILow]

Ha ha. Just read this carefully. You state that you have a Nissan Patrol
Motor. Any chance you have either the SD33 or ED33? We have the latter which was rare in the Patrol but the former was quite popular. 6 cylinder instead of 4. Slightly less HP but smoother.

Matt


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[GILow]

Originally Posted by iancoombe

There's been talk of reduced drag if the prop is allowed to spin, I'm not sure about water but if the engine in a helicopter stops I want the rotors to keep turning to slow down the decent rate, known as auto rotation.

Oh no. Don't open this can of worms! Please, it's been done to death on CF. I've read the threads and all I got was a sense of confusion plus a headache. In the end I decided that I hated the noise so much that I did not care which system created more drag.

Matt


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[yttrill]

Originally Posted by GILow

But I have the bits to go the same way as Lee (Banjoship) and they are very cheap and very easy to source. The brake calliper can be found at any decent trailer spares shop for $100 or less. A simple cable braking calliper.

Trailer brake! Brilliant! Thanks!

[yttrill]

Originally Posted by GILow

Ha ha. Just read this carefully. You state that you have a Nissan Patrol
Motor. Any chance you have either the SD33 or ED33? We have the latter which was rare in the Patrol but the former was quite popular. 6 cylinder instead of 4. Slightly less HP but smoother.

ED33, 4 cylinder. Not really enough grunt for my boat, but I can't replace it. Marinised by Diecon in Brisbane. Keel cooling. 80hp. Big boat, and doesn't glide through the water like the Swannie ..

[Stumble]

Originally Posted by yttrill

Last I looked there were no feathering props for my size boat. But it's not an option anyhow, I've had a brand new prop cast specifically for the boat. Fixed props are reliable. And no "clunk" engaging them or problems with reverse. One of my friends had a feathering prop and it wrecked his gearbox. I've seen quite a few that jammed up as well. I'll check out Shaftlok, thanks for the tip!

MaxProp makes off the shelf models up to 50" and larger ones by request. I cant imagine you would need one much bigger than this. Other feathering prop companies tent to top out a little smaller, but up to 24" is pretty common.

Good luck.

[GILow]

Originally Posted by yttrill

ED33, 4 cylinder. Not really enough grunt for my boat, but I can't replace it. Marinised by Diecon in Brisbane. Keel cooling. 80hp. Big boat, and doesn't glide through the water like the Swannie ..

Yep, that's exactly the same engine and trans we have. It is probably a bit undernourished for your boat, about right for ours, you don't want to lose any performance to less than perfectly matched prop, that's for sure.

Anyhow, I double checked those prices I stated, and it turned out I was hopelessly wrong. Brake callipers are not under AU$100 each, they are under AU$50 each. I must have been thinking of a pair.

Thinking more about the disk, I remembered that for the bus I got the local engineering outfit to make the disk from scratch, as they said it would be cheaper than buying one and adapting it. I can't remember what I paid, but it was very cheap, so I believed them.

Matt

[NahanniV]

Originally Posted by iancoombe

Mount an alternator and enjoy the spin

The alternator will also slow it down quite a bit, reducing the noise and wear.

And of course some extra power is always good.

Cheers,
JM.

[rwidman]

Originally Posted by iancoombe

Mount an alternator and enjoy the spin

Yep. And then feed the output of the alternator to an electric motor to power the boat!

Locking the shaft will introduce some drag, no doubt but if you need to lock it to protect the transmission or other equipment, you have to lock it somehow.

[Nicholson58]

Originally Posted by yttrill

Sure but that's not suitable for me. i have a fixed prop. I need a "cheap" solution, replacing a brand new prop isn't cheap, even if there was one available for my size boat (which there wasn't when I investigated it).

I specifically chose a non-feathering prop anyhow, I don't like the complication, maintenance burden, unreliability, and stress factors involved with feathering designs. Great for race boats .. but I'm a cruiser.

You are right about the co$t. Not necessarily on the 'race boat' point. Adjustable pitch from the cockpit; 24 inch; 0-90 degree blade rotation; reversing transmission (also hydraulic). This prop is a working bruit. We adjust pitch based on sea state, speed & wind to optimize the exhaust temperature. With shallow pitch we have huge thrust at low speed. Making distance on motor alone, we make 7-9 knots at 550 rpm prop speed on flat water. If there is enough breeze to add sail we can stretch out the pitch even more.

Can you lock up the shaft through the coupling with perhaps a wood dowel? That way, if you forget it or need prop in a hurry you just shatter it.

We buy brakes from a company called HORTON. They and others make pneumatic and hand applied brakes - also no cheap. If you have space, you might fit a wheel drum with an intact emergency hand brake from a light truck. There are also a few suppliers who sell mechanical, hand-set calipers. This search will show you quite a few. https://www.google.com/search?q=pneu...Q&ved=0CCAQsAQ

One of the other posts asked why bother since there are prop shaft generators in use. I doubt they are a big assist but they rely on auto-rotation.

[vinayfm]

Actually a revolving prop applies more brake than one that is locked and capitate. In my humble opinion



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[GILow]

Originally Posted by vinayfm

Actually a revolving prop applies more brake than one that is locked and capitate. In my humble opinion

And here we go again...