Offset prop shaft

[MtB]

3 minutes ago, WotEver said:

It was mentioned as potentially being too inefficient but that's been questioned and OP said they would consider it again. 

 

Efficiency is in the order of 80% IIRC from when I researched getting one. A solid propshaft is 100% of course. Less a few % in the gearbox.

 

[WotEver]

Just now, Mike the Boilerman said:

Efficiency is in the order of 80% IIRC from when I researched getting one. A solid propshaft is 100% of course. Less a few % in the gearbox.

I think someone mentioned 90-95% but I could be wrong and can't be arsed to go looking

[Tony Brooks]

I said I though modern piston pumps and motors may be close to whatever figure the OP quoted for a belt system.

Hydraulic drives are NOT complicated compared with the proposed mechanical systems. Different, yes, but not complicated. The only complication on a narrowboat may be the cool water supply for the heat exchanger but the return from the skin tank shoudl do as long as the hull builder has fitted a tank that has enough area.

Reservoir, PRV, filter, oil cooler, three position control valve, pump, motor with inbuilt thrust bearing (many do not), and pipes. For diagram see: http://www.tb-training.co.uk/8dlines.htm#bmn24

Make sure the hydraulic hoses between pump and motor sizes are calculated to allow for their length. Just keep half an eye on the high pressure hoses because if one chaffs through of breaks you tend to get oil everywhere.

[Ampen Spekersohn]

16 minutes ago, Tony Brooks said:

Hydraulic drives are NOT complicated compared with the proposed mechanical systems. Different, yes, but not complicated. The only complication on a narrowboat may be the cool water supply for the heat exchanger but the return from the skin tank shoudl do as long as the hull builder has fitted a tank that has enough area.

Thanks Tony. I'm looking forward to seeing what ARS come back with. As regards the skin tank, it would be possible to get the builder to put in an additional one for the oil cooling. I guess this would then need a header tank and circulating pump though. However, I think I'm right in saying that a JP3 only runs at about 50C, so the whole system will be running at a lower temp than a modern engine.

Having said that, it could have a 'Winter' setting which would divert the hot water to a series of pipes welded to the underside of the counter: underfloor heating for the steerer!  

Edited September 11, 2017 by Ampen Spekersohn

[Tony Brooks]

29 minutes ago, Ampen Spekersohn said:

Thanks Tony. I'm looking forward to seeing what ARS come back with. As regards the skin tank, it would be possible to get the builder to put in an additional one for the oil cooling. I guess this would then need a header tank and circulating pump though. However, I think I'm right in saying that a JP3 only runs at about 50C, so the whole system will be running at a lower temp than a modern engine.

Having said that, it could have a 'Winter' setting which would divert the hot water to a series of pipes welded to the underside of the counter: underfloor heating for the steerer!  

Why complicate things with an extra tank, pump and header tank? The engine  temperature is controlled by a thermostat or a manual flow adjustment but temperature is not the possible problem. Its the amount of heat you need to get rid of and broadly across a range of engines the same HP will require the dumping of the same amount of heat as in BTU, CHU, or whatever the SI unit of heat is. It would not be a winter setting you need. The cut will probably be cold enough to draw more heat from the tank. Its a summer setting and I do not see it being pleasant on a hot day with underfloor heating.

I am sure ARS use piston  pumps but also price the parts I listed at your local hydraulic equipment suppliers. Although less efficient we ended up using gear pumps and vane motors because they proved more robust and reliable then the sine pumps and motors originally specified. About 5 years ago I met a hydraulic boat we had built in the early 1970s just north of Brentford and it was till going strong and from the engine noise the  drive was still efficient enough.

[Ampen Spekersohn]

I've just heard back from Wilsons Drive Shafts. The price for two shafts plus two UJ's, flanges, etc, was pretty reasonable at £5-600. BUT... the shaft would be 3" diameter and it would need a support bearing halfway along to support it. So I would be losing nearly half of the possible headroom gain. So it would be a fairly low cost and simple system, but doesn't entirely solve the problem.

It will be interesting to see how the hydraulic option matches up. A side benefit of course, is that the pump could also run other hydraulically-powered equipment.

More when I have it!

[WotEver]

Joystick rudder control, bow and stern thrusters, anchor winch... oh what fun. 

[Ampen Spekersohn]

6 minutes ago, WotEver said:

Joystick rudder control, bow and stern thrusters, anchor winch... oh what fun. 

Did you notice, I deliberately avoided mentioning B** T*******s to avoid invoking a massive debate? I was of course referring to things like hydraulic cutting equipment, like the things the fire brigade use to chop you out of a car. Imagine how handy that would be, when there's a tree across the cut and the chainsaw won't start! Not forgetting a hydraulically-powered windlass. The lift bridges on the Mon & Brec would be a breeze! Might need some long hoses though...

[cuthound]

Hydraulically powered legs, like some of the working flat boats.

Never need to use a mooring pin or chain again. 

[Ampen Spekersohn]

2 minutes ago, cuthound said:

Hydraulically powered legs, like some of the working flat boats.

Never need to use a mooring pin or chain again

That would flummox the yobbos who try to untie you in the middle of the night! Would also be unaffected by passing craft...

[dmr]

40 minutes ago, Ampen Spekersohn said:

I've just heard back from Wilsons Drive Shafts. The price for two shafts plus two UJ's, flanges, etc, was pretty reasonable at £5-600. BUT... the shaft would be 3" diameter and it would need a support bearing halfway along to support it. So I would be losing nearly half of the possible headroom gain. So it would be a fairly low cost and simple system, but doesn't entirely solve the problem.

It will be interesting to see how the hydraulic option matches up. A side benefit of course, is that the pump could also run other hydraulically-powered equipment.

More when I have it!

We have a single shaft running from the gearbox to the back of the boat, the full length of the back cabin. Its about 4 inch diameter (hollow) with a UJ at each end, no sliding splines, and has no central support. A few people have looked at it and declared it to be not the most elegant engineering but its done 12,000 hours now so must be a sound approach.  Another advantage of the raised back cabin floor and propshaft just below this floor is that you can then fit a large (integral) fuel tank below the prop so freeing up more space in the engine room for batteries etc.

................Dave

[MoominPapa]

2 hours ago, Ampen Spekersohn said:

I've just heard back from Wilsons Drive Shafts. The price for two shafts plus two UJ's, flanges, etc, was pretty reasonable at £5-600. BUT... the shaft would be 3" diameter and it would need a support bearing halfway along to support it. So I would be losing nearly half of the possible headroom gain. So it would be a fairly low cost and simple system, but doesn't entirely solve the problem.

It will be interesting to see how the hydraulic option matches up. A side benefit of course, is that the pump could also run other hydraulically-powered equipment.

More when I have it!

Melaleuca's is 3" diameter. It's supported by the gearbox bearing at the forward end, where there's a UJ. It then runs 9 feet back to a rubber mounted support bearing under the step with no intermediate support. To the rear of that bearing is a second UJ, then about 3 feet of inclined shaft and then a sliding joint, third UJ and the support/thrust bearing you've seen a photo of.

 

MP.