Shaft couplings

[GILow]

Hi all,

I've got to fit a new prop shaft to the boat.

1.25 inch drive shaft, 50 HP engine. Shaft length is about 1.4 meters for what it is worth.

I'd like to fit a new coupling, interested in the sort that doesn't appear to need any machining of the shaft end to fit. They appear to be simply two halves that clamp to the end of the shaft.

This is different to my current coupling flange which needs a keyway and taper cut in the shaft.

Does anyone have any thoughts about these couplings they'd like to share?

Matt

[Fore and Aft]

Gilow Polyflex here in Brisbane is my go to place for couplings and engine mounts. We have one of these half couplings on our shaft. I fitted it six years ago and have forgotten if it had a key way? Either way it's worked perfectly since then.
Cheers
https://www.polyflex.com.au/half-couplings/

[GILow]

Originally Posted by Fore and Aft

Gilow Polyflex here in Brisbane is my go to place for couplings and engine mounts. We have one of these half couplings on our shaft. I fitted it six years ago and have forgotten if it had a key way? Either way it's worked perfectly since then.

Cheers

https://www.polyflex.com.au/half-couplings/

Thank you, yes, they were going to get a call on Monday. I use their stuff on the other boat.

[capt jgw]

The split couplings I've seen still had a keyway. You need something to keep the shaft from turning in the coupling and clamping force alone isn't likely to do that.

[Sailmonkey]

I added a split couple a few years ago. Still has a key though.

[PippaB]

We had keyless split couplings on our 30mm shafts driven by 40 HP inboard diesels for 5 years, never had a problem. Registration marks across shaft/coupling never shifted. Swapped out to SigmaDrive a couple of years ago (because every time we checked alignment it never was) and those, too, are keyless. Again, registration shows the shafts have not moved in the couplings.

One data point and one experience (with two engines), that’s all I can give you.

[ItDepends]

Some of the clamp on couplings (I'm thinking some of the Vetus Couplings here) dispense with the key and setscrews and instead go with a drift pin that requires drilling a hole in the shaft. It secures the coupling against both angular longitudinal displacements.

A PITA to install (drilling the shaft is a non trivial task--unless it is bronze), and even more of a PITA to take off, but REALLY secure.

Regular couplings should be a matched set with the shaft. The coupling is installed on the shaft, and then the face is turned to make it 100% perpendicular to the shaft axis. If it is not it is impossible to get a perfect alignment.

[GILow]

OK, seems Polyflex are very happy without a keyway at these sorts of horsepower.

[Uncle Bob]

Originally Posted by GILow

OK, seems Polyflex are very happy without a keyway at these sorts of horsepower.

Another for polyflex, good products and good to deal with.

[GILow]

Originally Posted by Uncle Bob

Another for polyflex, good products and good to deal with.

Yes, they were super helpful with my rather challenging installation in the Swanson.