tailshaft generator

[Frank Burroughs]

Ran across "tailshaft generator" in my reading. I think it creates electricity for the ship once at sea.
how close am I?

Frank

[John Arton]

Frank
Tailshaft generator or as it is more commonly known, shaft generator, is an electrical generator that is wrapped around the vessels propellor shaft between the main engine and the stern gland where the propellor shaft passes through the ships hull. Once at sea and full away on passage the ships diesel generators can be shut down and the shaft generator will then take over the task of supplying sufficient electrical power to supply the normal requirements of hotel load (galley and accommodation) along with navigation and main engine requirements (fuel transfer, cooling water,bilge pumps and fuel purifiers etc.
This means that at sea the vessel is only consuming fuel oil for the main engine and not the more expensive marine diesel fuel required to power the diesel generator's.
A number of vessels I sailed on could actually use the shaft generator as a propulsion motor, instead of generating electricity it was fed electricity from the ships generator and declutching it from the main engine can be used to propel the ship should the ships main engine fail for any reason. We called it a "take home system" and using it we could make 10knots as opposed to the 15 knots normal sea speed. The system had the added advantage that should main engine repairs, or maintenance requiring engine shut down whilst in port, we would never be classed as dead ship and could be ready to move at short notice should a situation arise where the port required us to vacate our berth.
Hope this crude explanation clears up your query.
Rgds
J.A.

[Ivan Cloherty]

If its for your novel Frank, it wasn't fitted to all vessels

[Lewis McColl]

Sailed on a few ships that had shaft generators, they were so so, as soon as you got into a bit of weather and the engine RPM was surging a bit it was back to the diesel generators going back on. Also if you were chasing an ETA the shaft generator was usually pulled so you could put another 1000kw load on the shaft and still stay within permitted engine parameters.

[Frank Burroughs]

Not so much for my novel. Just could not find an explanation for it. As always, you men have come through!
I have started my novel over for the third time. I learn so much from research that It is only fair to rewrite. The outline is almost finished, though. Should be a straight job from here. My 100 page adventure at first will probably run double that. That's a good thing.

thanks again
Frank

[John Weedon]

Walport Telmar, who supplied 16mm movie projectors and films to ships, replaced these with Sony U-Matic videocassette machines. Unfortunately, these required the supply main to be within 1 cycle of 60Hz. Greater deviation caused loss of colour, and eventually loss of picture line lock. Ships with shaft Genny's were a problem, sometimes a static inverter had to be used, as on an older ship with DC mains.

[J Gowers]

Hi Guys,
I never came across the shaft alternator described above the ones I sailed with were an alternator driven off a shaft coming the main engine gear box, not the propeller shaft, but the affect was the same. The main engines were either medium speed diesels or gas turbine.

[Lewis McColl]

Attached is a diagram of a direct drive slow speed diesel engine arrangement. Also attached is a diagram of a medium speed diesel with shaft alternatorsshaftgen_page2_slow_20170708-pto-pti-pth.jpg, med speed.jpg