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Old 15-08-2015, 13:23   #1
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Hydraulic Operated Alternators?

Anybody out there with experience using hydraulics (instead of belts) to run multiple alternators. One is 12V (house batteries), the other 24V (starting batteries) and then a 4.5Kw dynamo for 110V on the boat. This is an older boat and we're trying to re-organize/simplify the engine room and get rid of the big, dangerous, flapping belts that are there presently.

Caveat: We're on a budget so can't invest many thousands in new stuff (our 2 alternators are brand new though).

Anyone with practical experience in this area - advice greatly appreciated.

Thanks!
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Old 15-08-2015, 20:28   #2
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Re: Hydraulic Operated Alternators????

Yup, been on a boat with a lay shaft driven by hydraulics with multiple things hanging off it.

Could be just as easily belt driven or even right angle axle i guess.


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Old 16-08-2015, 12:08   #3
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Re: Hydraulic Operated Alternators?

I'm a former commercial fisherman and we used hydraulics to run many auxiliaries. Some boats have a diesel just for running hydraulic pumps. There was a generator sold a few years ago that came with a hydraulic motor designed for fishermen that were already making hydraulic power.
It probably won't be cheap. You need someone knowledgeable to size your pump and motor. Running full time you'll need an oil cooler. Also some sort of governing controller that maintains the correct rpm for your 110v. The main engine will have to run at speed, not idle. Probably the hoses, valves and motors will make as much of a mess as the belts you have now.
What some people do is have an small diesel to run those items. That allows you to charge w/o running the main engine. Or a small diesel generator could make 110v and supply your chargers. Probably less fuel that way.
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Old 16-08-2015, 12:41   #4
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Re: Hydraulic Operated Alternators?

I work on Nordhavns and have considerable experience with Hydraulic Alternators. I can tell you that the smart thing to do, is stick to belts for multiple reasons.
The biggest being that hydraulic alternators are much less efficient.
They can be problematic if driving from a main engine that varies in RPM's also. Some of our alternators had overheating problems when run at low RPM's inadvertantly.
Belts are good !
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Old 16-08-2015, 12:43   #5
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Re: Hydraulic Operated Alternators?

"We're on a budget"
Then forget about it, just buy better belts.
You'll need to turn a hydraulic pressure pump instead of an alternator. And fabricate the new assembly. And run hydraulic hoses of good quality, and carry spare$ as well. And replace the fluid and hoses (all of them) as routine maintenance, same as you'd replace belts. And if all of that is just being used to turn an alternator?
You get efficiency losses turning the hydraulic pump, and then again turning the alternator assembly.
Hydraulics are great at snaking from "here" to "there" but I don't think anyone has ever tried to claim they were simpler, cheaper, or more efficient for small systems.
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Old 16-08-2015, 12:55   #6
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Re: Hydraulic Operated Alternators?

james, I had heard from a number of Nordhavn owners that the hydraulic alternators did not work out very well. Many had just given up on using them.
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Old 16-08-2015, 13:39   #7
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Re: Hydraulic Operated Alternators?

There is no question that you can make them work, but at what cost.
They are generally not idiot proof....
We have spent considerable time and money adding digital tachometers to try and control low speed operation to avoid overheats.
I have several alternators and their associated components on the shelf in my shop for good reason.
Anyone want to buy them ?




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Old 16-08-2015, 13:52   #8
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Re: Hydraulic Operated Alternators?

Quote:
Originally Posted by hellosailor View Post
"We're on a budget"
Then forget about it, just buy better belts.
You'll need to turn a hydraulic pressure pump instead of an alternator. And fabricate the new assembly. And run hydraulic hoses of good quality, and carry spare$ as well. And replace the fluid and hoses (all of them) as routine maintenance, same as you'd replace belts. And if all of that is just being used to turn an alternator?
You get efficiency losses turning the hydraulic pump, and then again turning the alternator assembly.
Hydraulics are great at snaking from "here" to "there" but I don't think anyone has ever tried to claim they were simpler, cheaper, or more efficient for small systems.
I would say this is the answer in a nutshell.
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Old 16-08-2015, 15:21   #9
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Re: Hydraulic Operated Alternators?

Not to mention that to generate 110vac 60Hz you (generally) have to run at a constant 1800 or 3600 rpm...
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Old 17-08-2015, 06:16   #10
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Re: Hydraulic Operated Alternators?

Greetings and welcome aboard the CF, jamesknight.
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Old 17-08-2015, 06:27   #11
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Re: Hydraulic Operated Alternators?

Quote:
Originally Posted by jimbunyard View Post
Not to mention that to generate 110vac 60Hz you (generally) have to run at a constant 1800 or 3600 rpm...

Not so with a hydraulic generator. So long as the prime mover is turning fast enough to supply a volume of oil needed to maintain 1800 rpm on the speed governed generator all will be well.
That said, in my place of work we have a lot of equipment with hydraulic generators and I can tell you from personal experience, while the generator is spinning at the correct speed with the prime mover at idle, the oil gets hot and the generator response to load changes is sluggish to downright erratic.


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Old 17-08-2015, 09:34   #12
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Re: Hydraulic Operated Alternators?

You mean something like this?



That's a 5 kw hyd generator (which spins at 3600) package driven be a constant speed hyd motor. Bet you can buy a lot of belts for the price of that baby...

The point was that, if the op was hoping to cobble something together, using off the shelf hydraulic motors, a dc alternator and an AC generator would be hard to operate off the same pump... and the pump would pull about 20 hp to boot.
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Old 17-08-2015, 09:49   #13
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Re: Hydraulic Operated Alternators?

Quote:
Originally Posted by jimbunyard View Post
You mean something like this?



That's a 5 kw hyd generator (which spins at 3600) package driven be a constant speed hyd motor. Bet you can buy a lot of belts for the price of that baby...

The point was that, if the op was hoping to cobble something together, using off the shelf hydraulic motors, a dc alternator and an AC generator would be hard to operate off the same pump... and the pump would pull about 20 hp to boot.

That's the stuff. They're reliable but they ain't cheap!!


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