Boat versus RV Generator

[AdventureCoach]

Just curious of why our Onan generators in our boat and RV are designed to operate differently. In the 2006 boat (11KW) it operates at a constant RPM regardless of load but in the 2018 RV (8KW) it runs at various RPMs dependent upon load.
I also like how the transfer switch operates in the RV. There is a slight delay when plugging in to shore power but a 2 minute or so delay when the generator is started. This gives the genset a bit of built in warm up time automatically.
Just curious why the designs are not consistent.

[oldave]

I agree there is a need but sterling doesn't appear to be the answer
after a couple hundred yrs little progress has been made .
Steam probably has more promise .

[wa8yxm]

Thanks but those.. are not what I'm looking for.
They are not yet ready for "Prime time" as it were.
But the Military does have a need for a Generator that does not broadcast that it's there.

[oldave]

The thread has gotten a little off topic and appeared to even be getting a
little arguementative then it morphed into interesting .

I've always been some what of a gadget guy . When I was a kid I took
everything apart but now I wouldn't know much of what I was seeing .

I have messed with Sterling cycle model engines but nothing useful .
They are silent but do not generate much power generally .
Here is a company that makes claims,still not a lot of power and quite large

http://redhawkenergy.net/qnergystirlingengine.html

At one time ( 100 yrs ago not sure ) a sterling fan for the desk was
manufactured & sold in this country but elect fans soon took its place .
Some are still around as antiques
However I think that same fan is still manufactured in India and is / was
available here . The most useful I have seen is also from the past
In parts of the country that had natural gas piped to homes for heat/lights
etc a sterling engine 2 or 3 ft tall was married to a well pump to slowly fill
a elevated water tank presto running water , pretty fancy stuff back then .

Here is another novel use of heat generating elect to drive a fan .

https://www.amazon.com/VODA-4-Blade-Fireplace-Increases-Friendly/dp/B01CD2AIV8/ref=sr_1_3?dchild=1&keywords=sterling%2Bengine%2Bfan&qid=1597934047&sr=8-3&th=1

You guys ever heard of a Mento Wheel ? Take a look

https://en.wikipedia.org/wiki/Minto_wheel

http://rexresearch.com/minto/minto.htm

[AdventureCoach]

Thanks for all the responses and the education on the differing technologies used in these machines.

[Dutch_12078]

wa8yxm wrote:
I will admit I"m the kind of person who likes to know. For this reason I research and research and research....

I do not have a medical degree (Was studying engineering not medicine) But due to the research I've done I have had a medical "Thesis" that got reviewed and was deemed worthy of publishing in a medical textbook. I've not seen the textbook but.. Well.. To be honest it's kind of scary..

For those who wonder. Companies like Edmund Scientific sell kits "Build your own demonstaration generator"

What I'd like to get more info on is this:
Story (Popular mechanics I think) went that in Viet Nam the military was using generators powered by Sterling Cycle engines.. I'd love to get info on them, how efficient they are and so on. Those are interesting. also very very very quiet.

You could augment your Sterling generator research by buying one on Amazon. They have several little ones starting at around $37.

[wa8yxm]

I will admit I"m the kind of person who likes to know. For this reason I research and research and research....

I do not have a medical degree (Was studying engineering not medicine) But due to the research I've done I have had a medical "Thesis" that got reviewed and was deemed worthy of publishing in a medical textbook. I've not seen the textbook but.. Well.. To be honest it's kind of scary..

For those who wonder. Companies like Edmund Scientific sell kits "Build your own demonstaration generator"

What I'd like to get more info on is this:
Story (Popular mechanics I think) went that in Viet Nam the military was using generators powered by Sterling Cycle engines.. I'd love to get info on them, how efficient they are and so on. Those are interesting. also very very very quiet.

[Dutch_12078]

wa8yxm wrote:

Dutch_12078 wrote:

And now anyone else reading here knows the difference and that there's no "magic" involved.

I guess you never read Arthur C. Clarke
"Any sufficiently advanced technology is indistinguishable from magic"

Most folks do not need to know, for example. how a cell phone works. Or how you get 3600 cycles per minute from 1800 or 1200..

Happens to be my 2nd college degree.

I don't know about "most folks", but personally there's a lot of things I don't need to know, but I still want to know. I think many folks here fall in that category as well.

[wa8yxm]

Dutch_12078 wrote:

And now anyone else reading here knows the difference and that there's no "magic" involved.

I guess you never read Arthur C. Clarke
"Any sufficiently advanced technology is indistinguishable from magic"

Most folks do not need to know, for example. how a cell phone works. Or how you get 3600 cycles per minute from 1800 or 1200..

Happens to be my 2nd college degree.

[Dutch_12078]

wa8yxm wrote:

Dutch_12078 wrote:

wa8yxm wrote:
The one that runs a constant speed is much older (about the same age as mine) it runs I believe at 1800 RPM and by some magnetic magic that feeds out 60 HZ (3600 cycles) it runs at the constant speed because that is the speed it needs to run at to make 60 Hz.

There's no "magnetic magic" involved at all. 1200 RPM generators have 6 poles, 1800 RPM's have 4 poles, and 3600 RPM's have 2 poles. That's all there is too it...

I know this as it's the field I trained in but to the untrained "Magnetic Magic" is easier to type than the full explanation.

And now anyone else reading here knows the difference and that there's no "magic" involved.

[valhalla360]

wa8yxm wrote:
Way more efficient by the way.. For any given trip it will suck less than half the fuel your Motor home's generator will.

Depends on the loading.
- Under light load, Inverter-Generators are more efficient as they can throttle back and use less fuel.
- Under heavy load, the losses converting DC to AC make them a little less efficient.

So if you are maxing out a small generator running the air/con on a hot day where the air/con never cycles, you will probably use slightly more fuel due the conversion losses.

On the other hand, if the air/con is only running 25% of the time, you will probably save fuel as 75% of the time the generator is throttled way back to idle speed.

[wa8yxm]

Dutch_12078 wrote:

wa8yxm wrote:
The one that runs a constant speed is much older (about the same age as mine) it runs I believe at 1800 RPM and by some magnetic magic that feeds out 60 HZ (3600 cycles) it runs at the constant speed because that is the speed it needs to run at to make 60 Hz.

There's no "magnetic magic" involved at all. 1200 RPM generators have 6 poles, 1800 RPM's have 4 poles, and 3600 RPM's have 2 poles. That's all there is too it...

I know this as it's the field I trained in but to the untrained "Magnetic Magic" is easier to type than the full explanation.

[Dutch_12078]

wa8yxm wrote:
The one that runs a constant speed is much older (about the same age as mine) it runs I believe at 1800 RPM and by some magnetic magic that feeds out 60 HZ (3600 cycles) it runs at the constant speed because that is the speed it needs to run at to make 60 Hz.

There's no "magnetic magic" involved at all. 1200 RPM generators have 6 poles, 1800 RPM's have 4 poles, and 3600 RPM's have 2 poles. That's all there is too it...

[wa8yxm]

The one that runs a constant speed is much older (about the same age as mine) it runs I believe at 1800 RPM and by some magnetic magic that feeds out 60 HZ (3600 cycles) it runs at the constant speed because that is the speed it needs to run at to make 60 Hz.

all "Traditional" generator in the USA run at some sub-multiple of 3600 RPM
Typically the smallest 3600 and as they get bigger 1800 or 1200.

The new 2018 model in your boat, like a Honda EU-2000i is an INVERTER generator.

*you may stop reading here if you wish*

These units the engine drives not a "Generator" but an Alternator (usually) This is a type of generator that uses a diode pack to convert the AC out to something like DC (Unflitered DC) just like the alternator on your car. only bigger.
This is then filtered and sent to an INVERTER.. Just like the Xantrex Freedom 2000 on my RV. A true Sine Wave inverter. This device uses electronics to generate 120vac at 60Hz from the DC that comes in to it from the alternator.

Thus as the need increases. the speed increases so the alternator can pump out more power.

Way more efficient by the way.. For any given trip it will suck less than half the fuel your Motor home's generator will.

[dougrainer]

Ivylog wrote:
7800 and smaller Onan’s are DC generators into an inverter that only puts out 120V. 10K and larger are AC generators that put out 240V. They (your boat 11K) maintains 60 cycles by staying at the same rpm unlike the inverter in the smaller generators that maintains the 60 cycles and rpms vary as the load varies.

I believe that your statement should mean Onan DIESEL, not include Gas. Gas RV Onans are RPM based at either 1800 or 3600 constant RPM's with the Engine SPEED governor keeping the RPM's at 1800 or 3600 under load, and do not use Inverter technology. Doug