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?

ktdtx said:

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?

Click to expand...

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.

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.

Would be an expensive retrofit for a voyager.

Click to expand...

That's why I was focusing on driving the existing shaft/prop. Seems it would be less expensive.

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..

ktdtx said:

That's why I was focusing on driving the existing shaft/prop. Seems it would be less expensive.

Click to expand...

I suppose as long as you can still turn the main shaft.

sunchaser said:

...I recently noticed a Nordhaven 52 for sale that had 750 hours on the main and 110 hours on the get home.

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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?

Chain Drive with clutch

twistedtree said:

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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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.

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.

BruceK said:

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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Also they are used for anchoring.

ulysses said:

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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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

Richard

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.

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.

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?

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.

ulysses said:

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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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?

Richard

stubones99 said:

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.

Click to expand...

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.

Richard

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.

ulysses said:

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.

Click to expand...

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

Richard

"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.

My own thoughts, from the "single vs. twin" thread and from the "twin diesels on one screw" thread:

Fewer engines should be less expensive than more.

A single often gives better access for maintenance and service. (At least ours did.)

I'd like to go back to a single-engine boat. (Not likely to happened anytime soon, but I can dream).

Having said that, since we're inshore with towboats everywhere, I'd likely be happy enough with that, as is.

Having said THAT, if I were going offshore more often, longer distances from the towboats... a get-home (or at least get-within-tow-range) sounds prudent.

An option that uses the same shaft/prop as the main seems OK at first, but there's also risk that "the problem" (that may arise) isn't the engine at all, but rather the gear, the shaft, the prop... Still, a "small" diesel ought to be much less expensive than a larger "twin" would be. Could potentially be located so as to not lose all the improved access space?

An option that includes a whole 'nother gear/shaft/prop seems OK at first, although that also means exercising that system periodically. (Not difficult.) And the time and expense of yet another system to maintain.

Using the genset diesel seems OK at first, but then there's the potential problem of underloading under normal circumstances, or else the genset diesel might not be large enough to be particularly useful. (Might be some balancing act that's possible, there.)

The option of two different size gensets is intriguing. I assume that means fixed-rate RPMs (e.g., 1800) for both, even when the larger is being used as a get-home? In any case, I'd guess the larger could drive either the main shaft, or a separate shaft, depending on the specific installation...

I'm of three minds.



But doubt I'll have to "solve" this one any time soon for our own purposes. Just examining the ideas...

-Chris

Richard: It is a fairly simple procedure. Just a sprocket that is attached to the main shaft. The chain is placed around both the hyd. motor and the shaft sprocket and connected. Open a valve to keep the dripless seal cooled and you are back underway. In heavy seas though things start flying around and heads are bumped, etc....

I have a Dickson hydraulic stern thruster with the get home option that runs off the generator. It's rated at 5hp so won't push it very fast but will push it. Haven't tried it yet since the boat is relatively new to us. The stern thruster works fine and I prefer it over the bow thruster in tight situations.

Chris: I think your "three minds" put it all in the proper perspective. In most any marine system back up and redundancy only go so far. You have looked at the problem in one direction- having a common shaft. It goes the other way too, both the main and the gen sets use fuel that originally came from a common tank. So it is possible that the main goes down from a fuel related problem and the gen set running the get home only works while its own day tank is used (about 10 hrs or so). You can plan and create redundancy and you still have to hope for the best.

Horse Power wise I have a 210 HP Main turning a 46" Prop the Gen Set/Get Home is off a 20 KW so that is about 28 HP or so- enough to move it in the right direction.

Britannia said:

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.

Richard

Click to expand...

You can. We converted our original sailboat to purely electric power (ok, serial hybrid with a Honda 2000 that we've never needed) and the duty cycle on the motor is rated for full throttle 24/7/365.

We just put in offer on a trawler that has a farymann "genset" with a chain sprocket to the shaft as a get home. Basically, it's a get home engine with a giant alternator. One of my project thoughts was to use that electric drive system (still have it) to replace the get home engine. Then sell the farymann and either get a quieter generator or use the Honda and a bunch of solar.

Electric power is absolutely the cats meow in every category EXCEPT energy density. Batteries keep getting better, but it's going to be a real long time before they're in the same league as diesel.

questionmark said:

You can. We converted our original sailboat to purely electric power (ok, serial hybrid with a Honda 2000 that we've never needed) and the duty cycle on the motor is rated for full throttle 24/7/365.

We just put in offer on a trawler that has a farymann "genset" with a chain sprocket to the shaft as a get home. Basically, it's a get home engine with a giant alternator. One of my project thoughts was to use that electric drive system (still have it) to replace the get home engine. Then sell the farymann and either get a quieter generator or use the Honda and a bunch of solar.

Electric power is absolutely the cats meow in every category EXCEPT energy density. Batteries keep getting better, but it's going to be a real long time before they're in the same league as diesel.

Click to expand...

Interesting. Is anyone selling an electric get home system?

Britannia said:

Interesting. Is anyone selling an electric get home system?

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I believe James over at Electroprop has something. I'm not sure if it's necessarily badged as a "get home" because most of the larger-than-launch sized electric boats are all sailboats. It's much easier to stomach a 20 mile range under power when you have sails. Check out his site.

For the best noisemaker efficiency simply copymyhe newest Honda units.

The engine is run at variable speed to create DC that is inverted to AC for 120 or 240 use.

Simple to do , but the main cost becomes the inverter about 4KW each.

Britannia said:

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.

Richard

Click to expand...

questionmark said:

You can. We converted our original sailboat to purely electric power (ok, serial hybrid with a Honda 2000 that we've never needed) and the duty cycle on the motor is rated for full throttle 24/7/365.

Click to expand...

questionmark said:

I believe James over at Electroprop has something. I'm not sure if it's necessarily badged as a "get home" because most of the larger-than-launch sized electric boats are all sailboats. It's much easier to stomach a 20 mile range under power when you have sails. Check out his site.

Click to expand...

??

Big difference between 1000 miles out and a 20 mile range...

This must be about some nifty combination of genset, batteries, maybe solar too?

-Chris

ranger42c said:

??

Big difference between 1000 miles out and a 20 mile range...

This must be about some nifty combination of genset, batteries, maybe solar too?

-Chris

Click to expand...

20 miles is the battery range of the Catalina 30 at 4kn. More if you go even slower. That's battery only. If you size the generator or genset properly, range is limited only by fuel.

The idea is to run the "get home" from the generator. I wouldn't bother with a large battery bank for that mission, just a small one to smooth power draw and handle torque bursts (like stopping.)

The displacement electric guys figure a KW per ton of displacement will get you about "hull speed." That's generally for easily driven sailboat hulls. Easy to do if you have a bigger generator.