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Old 13-02-2020, 07:56   #1
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spit balling, AC gen on front of main engine..

So keep in mind I'm a dreamer still, but somewhat know what Im talking about.

On a production cat, say 38-40 ft range, hypothetically could you mount a 8-10 KW generator head onto the front of a 3GM30 with a HD electromag clutch, and interlock to only allow it to be used in neutral?

My question is more asking if anyone has seen it done. the Engineering involved is always doable, and the benefit would be worth it (in my mind). Most portable gennys in that range run on about 20 hp motors, so the engine will manage in neutral no problem. set RPM/HZ to 50hz (in my case) and clutch in.

Thoughts?
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Old 13-02-2020, 18:54   #2
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Re: spit balling, AC gen on front of main engine..

Quote:
Originally Posted by Fendell View Post
So keep in mind I'm a dreamer still, but somewhat know what Im talking about.



On a production cat, say 38-40 ft range, hypothetically could you mount a 8-10 KW generator head onto the front of a 3GM30 with a HD electromag clutch, and interlock to only allow it to be used in neutral?



My question is more asking if anyone has seen it done. the Engineering involved is always doable, and the benefit would be worth it (in my mind). Most portable gennys in that range run on about 20 hp motors, so the engine will manage in neutral no problem. set RPM/HZ to 50hz (in my case) and clutch in.



Thoughts?


Good question and yes it can be done but it ain’t easy whichever way you go. The toothed belt option requires a substantial metal frame that attaches to the 4 engine mounts and provides a metal platform for the generator and new heavy engine mounts are required.
There are 2 choices of generator, 1500 rpm and 3000 rpm but because the Yanmar has a variable speed governor and a generator requires a constant speed governor you will need to control and adjust the rpm for each change of load to maintain frequency. Yanmar also advises that the side loading on the front of the crankshaft be less than 6 hp on a 3gm (A config) at 3800
The alternative installation has the generator again mounted on a plate and frame that spans the four engine mounts but with the generator joined head to head with the crankshaft and connected by either a mechanical or electric clutch. This way you get extract more hp (12hp from memory) but are still faced with the governor dilemma UNLESS you buy and install an electronic governor as an adjunct to the Yanmar governor.
It is possible to get a type of ac generator that can run at various speeds and the output remains a steady 50 or 60Hz via electronics.
What this “Frankengen” setup means, regardless of how you do it, is an incredibly difficult engine to maintain and align and whatever space you had in that engine room is now dominated by the frame and generator.
I saw the side mount setup on a Dean cat and the front mount arrangement on a monohull.
The variable speed constant frequency setup was on a perkins 6-354 and side mounted in a large engine room.
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Old 13-02-2020, 22:40   #3
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Re: spit balling, AC gen on front of main engine..

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Originally Posted by skipperpete View Post
There are 2 choices of generator, 1500 rpm and 3000 rpm but because the Yanmar has a variable speed governor and a generator requires a constant speed governor you will need to control and adjust the rpm for each change of load to maintain frequency.
Or just configure the load so that it is a constant draw on the genset (battery charging, watermaking etc) while in use. Id agree that chasing constant revs every time a light gets turned on would be near impossible but only when the genset is turned on or off shouldn't be too onerous.

Of course if you ran a smaller genset while under power then any change in electrical load would likely be unnoticed amongst the engine's main propulsion load.

Cheers
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Old 13-02-2020, 23:29   #4
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Re: spit balling, AC gen on front of main engine..

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Originally Posted by skipperpete View Post
Good question and yes it can be done but it ain’t easy whichever way you go. The toothed belt option requires a substantial metal frame that attaches to the 4 engine mounts and provides a metal platform for the generator and new heavy engine mounts are required.
There are 2 choices of generator, 1500 rpm and 3000 rpm but because the Yanmar has a variable speed governor and a generator requires a constant speed governor you will need to control and adjust the rpm for each change of load to maintain frequency. Yanmar also advises that the side loading on the front of the crankshaft be less than 6 hp on a 3gm (A config) at 3800
The alternative installation has the generator again mounted on a plate and frame that spans the four engine mounts but with the generator joined head to head with the crankshaft and connected by either a mechanical or electric clutch. This way you get extract more hp (12hp from memory) but are still faced with the governor dilemma UNLESS you buy and install an electronic governor as an adjunct to the Yanmar governor.
It is possible to get a type of ac generator that can run at various speeds and the output remains a steady 50 or 60Hz via electronics.
What this “Frankengen” setup means, regardless of how you do it, is an incredibly difficult engine to maintain and align and whatever space you had in that engine room is now dominated by the frame and generator.
I saw the side mount setup on a Dean cat and the front mount arrangement on a monohull.
The variable speed constant frequency setup was on a perkins 6-354 and side mounted in a large engine room.
Cheers for your input. You can pick up a 8-10KW genny head for about $1000, or even a petrol genny in that size (on sell the motor for beer!) and mount the alternator. I agree that if this was done by an amateur it definitely would resemble a frankengen! I couldn't find on the web Yanmars specs for side loading, but I guess this could be overcome with correct flange mounted clutch units... all comes at a cost to the wallet and weight on board. real estate in the engine rooms of most boats will dictate what you can/cant do.

Quote:
Originally Posted by GoneDiving View Post
Or just configure the load so that it is a constant draw on the genset (battery charging, watermaking etc) while in use. Id agree that chasing constant revs every time a light gets turned on would be near impossible but only when the genset is turned on or off shouldn't be too onerous.

Of course if you ran a smaller genset while under power then any change in electrical load would likely be unnoticed amongst the engine's main propulsion load.

Cheers

Thanks for your thoughts. That's what I was thinking, big battery chargers so constant load, and by only running when in neutral so load shouldn't change much, and then theres no chance of snapping your crank in-half from overloading! This would be an alternative to a portable gen in my mind.

Thought provoking...
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Old 13-02-2020, 23:33   #5
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Re: spit balling, AC gen on front of main engine..

Still quite hard to maintain frequency because even a battery charger isn’t a fixed load as it goes through the charge cycle. Also there is a risk of the engine control getting bumped and either a dramatic increase or decrease in volts and frequency with potentially damaging results. An aircraft type throttle cable might be a better option than the shift control. On some ships we used a 750 rpm cruise alternator driven by a set of vee belts off the prop shaft but I think thats a thing of the past now. It worked well.
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Old 14-02-2020, 01:29   #6
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Re: spit balling, AC gen on front of main engine..

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Originally Posted by skipperpete View Post
Still quite hard to maintain frequency because even a battery charger isn’t a fixed load as it goes through the charge cycle. Also there is a risk of the engine control getting bumped and either a dramatic increase or decrease in volts and frequency with potentially damaging results. An aircraft type throttle cable might be a better option than the shift control. On some ships we used a 750 rpm cruise alternator driven by a set of vee belts off the prop shaft but I think thats a thing of the past now. It worked well.
An under/over voltage/frequency relays, with outputs to the clutch on/off could negate damage to sensitive equipment maybe?

I'm unsure of how plane throttles work, but assume push pull cable with some sort of twist lock? looking past the engineering involved, has anyone seen a dual rack lever on a fuel pump? so engine controlled via normal morse controls, or via an electric speed control module. Think 2 fork like rack levers spring loaded, with both control cables only attached via a cable end stop. cable pulls raising the RPM, spring pressure pulls back against the cable stop to follow cable input.

End of the day this is all hypothetical, as with everything anything is possible if you throw enough money at it cheers.
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Old 14-02-2020, 02:01   #7
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Re: spit balling, AC gen on front of main engine..

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Originally Posted by Fendell View Post
End of the day this is all hypothetical, as with everything anything is possible if you throw enough money at it cheers.
Or recognize it's a ghetto DIY solution and only use the generator to power/charge items that have some capacity to accept dirty power supplies. Inverter chargers or multi voltage acessories jump to mind. The latest high end e-gadgets dont.

Cheers
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Old 14-02-2020, 02:18   #8
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Re: spit balling, AC gen on front of main engine..

There are 2 choices of generator, 1500 rpm and 3000 rpm.


I asked generator repair companies which 1500 rpm generator they had to repair least, the concensus was Northern Lights with Westerbeke a close second. I had to replace our 2500 rpm genertor and went with Westerrbeke.
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Old 14-02-2020, 02:27   #9
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Re: spit balling, AC gen on front of main engine..

Lots of fishermen added a generator to the main. Some belt drive and some off the front of the crank with a clutch. Since a diesel either has a governor in the injector pump or a standalone governor, the engine maintains a set rpm with load changes. But probably not as well as a governor designed to run at a single speed.
Most generator ends are built for 1800 or 3600 rpm for 60 cycles.
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Old 14-02-2020, 02:31   #10
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Re: spit balling, AC gen on front of main engine..

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Originally Posted by GoneDiving View Post
Or recognize it's a ghetto DIY solution and only use the generator to power/charge items that have some capacity to accept dirty power supplies. Inverter chargers or multi voltage acessories jump to mind. The latest high end e-gadgets dont.

Cheers
Haha 'Ghetto' is a bit harsh bud, but I guess pulling your suitcase genny out and plugging into your shore power is living in luxury...

Quote:
Originally Posted by Michael Cobbe View Post
There are 2 choices of generator, 1500 rpm and 3000 rpm.


I asked generator repair companies which 1500 rpm generator they had to repair least, the concensus was Northern Lights with Westerbeke a close second. I had to replace our 2500 rpm genertor and went with Westerrbeke.
Cheers MC, at this stage my plan is the 38-40 ft cat size, so the less weight the better, hence pondering other avenues. I figure if your running the engine anyway to generate DC power (that is if solar isn't keeping up in said imaginary boat), why cant you put a AC alternator on.
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Old 14-02-2020, 06:31   #11
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Re: spit balling, AC gen on front of main engine..

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Haha 'Ghetto' is a bit harsh bud, but I guess pulling your suitcase genny out and plugging into your shore power is living in luxury....
Hahaha. No offence intended. I guess I should have said 'jury rigged'. My intention was that with a home build, its likely to work but not have all the niceties of a commercial unit. That's ok, just allow for wider tolerances in what is delivered.

Cheers
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Old 14-02-2020, 09:10   #12
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Re: spit balling, AC gen on front of main engine..

My cat had two 30 hp Yanmar engines.

To deal with the under volt and frequency problems I decided to generate direct current an inverted to run my air conditioner and washer dryer.

I put a total of 510 A on the two engines into a total of 1100 amp hours of 12 volt AGM battery.

Set up easily ran the air conditioning or the washer dryer and the water maker under way.

Both engines failed at 5000 hours from constantly running at high load. In both cases the Pistons cracked from a parent internal overheat even though the heat exchanger was always well within spec.

Under sail, running this set up We could run the washer dryer and the water maker underway.

Both engines failed at 5000 hours from constantly running at high load. In both cases the Pistons cracked from apparent internal overheat even though the heat exchanger was always well within spec.

running this set up was cheaper and quieter than running a GEN set. I had controls on the alternator that shut off the field exciter when maneuvering under my motor. Including cost of rebuilding the two engines, about $5000.

I think the problem was my inability to get rid of the combined heat of the engine and the alternator in the engine room compartment.

I would do it again if I had another bout of that size. I would also put a significantly larger fan to get rid of the heat and locate it directly over the alternator.

I did not have a tooth belt driving the alternators And even with twin V belts they were frequently.
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Old 14-02-2020, 09:28   #13
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Re: spit balling, AC gen on front of main engine..

One issue not mentioned is the power takeoff limit in the front pulley. I have never seen an engine that rated the front pulley higher than a a good sized alternator and even some large frame alternators exceed the allowable side loading. I think the loads imposed could cause problems with wear on the from engine bearings. If you look at commercial engines designed for high output secondary loads this is always through a secondary power take off. Not sure if you can get one small enough for your boat. Iff not I would be more inclined to look at ways of taking power off the prop-shaft using interim shaft bearings to take the load.
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Old 14-02-2020, 09:34   #14
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Re: spit balling, AC gen on front of main engine..

Winco and Northstar make 120/240 volt 7200-watt generators with a power take-off. PTO/Pulley
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Old 14-02-2020, 09:46   #15
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Re: spit balling, AC gen on front of main engine..

Check out integrelsolutions.com its a system designed by Nigel Calder. Sold in the USA by Ocean Planet Energy.
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