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Old 10-12-2015, 08:14 AM   #1
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Generator as "Get Home" power

As an offshoot of the "Single vs Twin" thread:


What does it take to make your generator also serve as a Get-Home engine?
Seems this would be a cost effective way to add the capability but you still have a common shaft/prop.

Assume a larger genset for one.
Hydraulic pump or a belt drive of some sort on the propeller shaft?

If this is your only genset and you increase the size, how do you manage it wrt loading it properly for normal use?
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Old 10-12-2015, 08:45 AM   #2
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Originally Posted by ktdtx View Post
As an offshoot of the "Single vs Twin" thread:


What does it take to make your generator also serve as a Get-Home engine?
Seems this would be a cost effective way to add the capability but you still have a common shaft/prop.

Assume a larger genset for one.
Hydraulic pump or a belt drive of some sort on the propeller shaft?

If this is your only genset and you increase the size, how do you manage it wrt loading it properly for normal use?
Wesmar offers a system with hydraulic drive off genset connecting to either existing shaft or auxiliary get home shaft. Selenes and Northern Marine have a variety of hydraulic setups worth a look.

The best get home setup I've seen is on the Dashew FPB 64s. Boat speed is 7 to 8 knots with main shut down.

I recently noticed a Nordhavn 52 for sale that had 750 hours on the main and 110 hours on the get home.
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Old 10-12-2015, 09:16 AM   #3
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The best combination seems when the boat uses hyd for many purposes.

The main gets a hyd pump large enough to run a hyd cruise generator 4 -6KW (or two) is not a big drain.

The noisemaker is operated during docking with its high RPM running to provide power to the bow or stern thrusters.

Otherwise it too feeds the same hyd power pack as the main would for AC juice.

This gives the flexibility to use either a hyd motor on the shaft , or to power a wing prop with a hyd motor.

The wing prop needs to be for pushing , not for slimness while under sail, so the HYDE is the only feathering units built for this service.

Hyd has a bit more involved when installing , but when overloaded it has no white smoke to escape.

And when desired the bow thruster can be used for more than seconds.

Would be an expensive retrofit for a voyager.
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Old 10-12-2015, 05:04 PM   #4
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Would be an expensive retrofit for a voyager.
That's why I was focusing on driving the existing shaft/prop. Seems it would be less expensive.
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Old 10-12-2015, 05:12 PM   #5
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I know a couple of people with hydraulic drives on the main shaft as a backup propulsion system. Power is from a hydraulic pump on the gen set..
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Old 10-12-2015, 06:27 PM   #6
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That's why I was focusing on driving the existing shaft/prop. Seems it would be less expensive.
I suppose as long as you can still turn the main shaft.
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Old 10-12-2015, 06:34 PM   #7
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...I recently noticed a Nordhaven 52 for sale that had 750 hours on the main and 110 hours on the get home.
Using the auxiliary for maneuvering/docking (as I think Bay Pelican does) could account for some hours as could "exercise", but it seems disproportionate. What brand is the main?
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Old 10-12-2015, 06:36 PM   #8
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Chain Drive with clutch

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I know a couple of people with hydraulic drives on the main shaft as a backup propulsion system. Power is from a hydraulic pump on the gen set..
I worked on a small trawler with a generator driven hydraulic pump, and chain driven main shaft from a hydraulic motor. It had been abandoned at the coupling for whatever reason, the motor and pump had a forward and reverse control at the helm. With a generators constant RPM I could see some issues maneuvering. Everything worked except it was disconnected from the shaft. I was doing survey work that included aligning the engine and propshaft. At time I thought it looked like a good idea. The clutch and chain were a rusty mess, I would guess lack of maintenance is the reason the system was abandoned.
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Old 10-12-2015, 08:12 PM   #9
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I have the chain driven main shaft arrangement running off of hyd. from Gen. Set. One direction-no speed control from helm. It is a "get close to home" arrangement then ask for an assist.
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Old 10-12-2015, 10:15 PM   #10
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Using the auxiliary for maneuvering/docking (as I think Bay Pelican does) could account for some hours as could "exercise", but it seems disproportionate. What brand is the main?
Also they are used for anchoring.
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Old 10-12-2015, 10:19 PM   #11
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I have the chain driven main shaft arrangement running off of hyd. from Gen. Set. One direction-no speed control from helm. It is a "get close to home" arrangement then ask for an assist.
I'm seriously considering a hydraulic get home at some point. I have two gensets on board a 20kW and an 8kW. I was thinking I could put the hydraulic pump on the 20kW genset.

What size genset do you have and how powerful is your hydraulic motor? What size is your boat and what speed can you make with it?

Thanks

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Old 10-13-2015, 02:56 AM   #12
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Richard: The boat is about 52' steel hulled 47 ton. The gen set that can provide the get home is a 20KW. I have yet to have to hook up the chain drive but I would imagine it would make about 3 knots. I will check the next time I am on the boat as to the specs of the Hyd. motor.
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Old 10-13-2015, 04:17 AM   #13
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What about the electric saildrive options? MasterVolt and several others offer that option and are quite small footprint. I am curious about the losses compared to hydraulics but my best source was my late father but he's gone now. I know lots of larger ships do generators to electric drives (and locomotives too). Why not an electric get home engine? With a folding prop, it should be minimal maintenance and drag.
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Old 10-13-2015, 08:20 AM   #14
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What about GenSet size. If you size your GenSet for get home power and the main use is to provide electricity for the boat are there any long term problems with chronically underloading the generator engine?

Any way to manage this?
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Old 10-13-2015, 08:30 AM   #15
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Ktdtx: I have a 5 KW gen set that I typically use a couple hours a day to run the batt chargers, refrig. and normal lighting requirements. My 20 KW I run to handle those same loads and Air Conditioning when necessary. The 20 KW is the get home engine. Therefore, I do not chronically under-load the 20 KW.
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Old 10-13-2015, 09:49 AM   #16
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Richard: The boat is about 52' steel hulled 47 ton. The gen set that can provide the get home is a 20KW. I have yet to have to hook up the chain drive but I would imagine it would make about 3 knots. I will check the next time I am on the boat as to the specs of the Hyd. motor.
Sounds familiar. Stillwater is 54' and about 35 tons. I have two NL gensets - a 20kW and 8kW. So why haven't you tried the get home yet? Was it installed by a PO?

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Old 10-13-2015, 09:51 AM   #17
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What about the electric saildrive options? MasterVolt and several others offer that option and are quite small footprint. I am curious about the losses compared to hydraulics but my best source was my late father but he's gone now. I know lots of larger ships do generators to electric drives (and locomotives too). Why not an electric get home engine? With a folding prop, it should be minimal maintenance and drag.
One of my concerns would be duty cycle. If I really need a get home motor it'll be because I'm out of tow range. If I'm half way to Hawaii then I could need to run it for 1000 miles. I'm not sure if want to do that with an electric motor.

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Old 10-13-2015, 10:23 AM   #18
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Richard: Well, I guess that I misstated a comment above. I have hooked up the chain and made sure all worked as designed. I only ran it a minute or so at dock. I meant to say I have never HAD to run it due to loss of main engine. I am not sure as to which PO installed it but it has been there awhile. With a 52 year old boat it is sometimes difficult to get the history of what all has been done and what might have been original, I am pretty sure the get home is not original. I might ask Delfin if he had one on his Romsdal.
As to hooking it up: I would think it would be somewhat of a challenge in heavy seas of course I find a lot of things more challenging these days.
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Old 10-13-2015, 10:27 AM   #19
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Richard: Well, I guess that I misstated a comment above. I have hooked up the chain and made sure all worked as designed. I only ran it a minute or so at dock. I meant to say I have never HAD to run it due to loss of main engine. I am not sure as to which PO installed it but it has been there awhile. With a 52 year old boat it is sometimes difficult to get the history of what all has been done and what might have been original, I am pretty sure the get home is not original. I might ask Delfin if he had one on his Romsdal.
As to hooking it up: I would think it would be somewhat of a challenge in heavy seas of course I find a lot of things more challenging these days.
Ah ok. That makes sense. How to hook up the drive is one of the areas of interest. Ideally it would be quick and easy.

Thanks

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Old 10-13-2015, 11:19 AM   #20
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"I suppose as long as you can still turn the main shaft."

And the transmission does not mind freewheeling with a load on its thrust bearing.

An extra tranny oiling setup might be required.
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