DC generator question
 

I was a a tradeshow where I saw one of the tiny Fischer Panda DC generators
with variable rpm. Nice and (much) too expensive for me, but I am thinking
of putting something like it together myself so I was quite interested in
their implementation.

I spoke with the guy doing the demo and he told me they vary the RPM from
2200 to 2800 only. Seems to me that doesn't make a lot of sense, because I
don't think the extra fuel consumption between idle @ 2200 and idle @ 2800
would be worth the effort of putting in the control circuitry?

I could also hear the little generator increase its rpm substantially above
its minimum when producing only 10A @ 24v, so I wonder if, in practice, you
would get ANY benefit from the variable RPM, because I think most would
shut the generator down when battery charging was down to only 10A. I also
wonder why they feel the need to increase RPM at all at that load since
just controlling the alternator excitation would surely get you 10A at 2200
rpm.

So does anybody understand their choices? Vibration, noise perhaps? Or is
this whole variable rpm implementation of Fischer Panda nothing but a
marketing ploy???

Greetings,

Frank

DC generator question
 

wrote in :

I could also hear the little generator increase its rpm substantially
above its minimum when producing only 10A @ 24v, so I wonder if, in
practice, you would get ANY benefit from the variable RPM, because I
think most would shut the generator down when battery charging was
down to only 10A. I also wonder why they feel the need to increase RPM
at all at that load since just controlling the alternator excitation
would surely get you 10A at 2200 rpm.


http://www.youtube.com/watch?v=zeBlxjL5dT8

This is a much better solution. It turns 300 RPM and this is the noise
it makes OUT IN THE OPEN WITHIN 6" OF A VIDEO CAMERA MICROPHONE. Notice
how the chickens are totally unafraid of it. It is producing 6,500
watts of 220VAC 50Hz serious electrical power, 24/7 for about a litre
per hour. Watch him put his hands on it. It's barely warm to the
touch. It has no water pump. Water circulates by convection to cool
it. The hot water pipe he touches doesn't burn his hands. A simple
heat exchanger with AC powered pump on the seawater side would cool it
forever, OR you could simply run some pipes through the hull and let it
convection cool through a keel cooler at its same level so convection
works...just under the waterline, eliminating the pumps entirely! They
run 24/7 for 40 years without overhaul. It will also run, flawlessly,
on any waste vegetable oil thin enough to inject. Preheat the oil by
wrapping copper tubing around the exhaust pipe and it runs for free.
Some owners have installed a ring gear and starter on one of the two
flywheels to automate the manual starting without even opening the
compression release. There is a youtube showing him starting it by
pressing a button.

Sailboat's can be easily powered by speed-controlled AC motors. Remove
the troublesome auxiliary diesels in them now, and replace it with a
listeroid and AC traction motor with solid state speed control. Run the
whole boat off AC power, not DC. The weight savings in batteries will
make up for the Listeroids weight in the bilge. No battery explosions
or leaking, no battery expenses, no battery maintenance and
replacements, no stupid DC power nonsense. All that heavy DC wiring can
be removed and replaced with high voltage AC much thinner and lighter
wiring, raising the waterline further. No charger will be necessary as
everything is AC powered, just like home. No inverters and that
nonsense, either.

Yankees will appreciate it when you simply move two Y valves and divert
the little waste heat from the heat exchanger to the hot water tank or
to the passive radiator heating inside the cold, cold cabin, extending
the boating season by many weeks each year. Southerners will appreciate
having the air conditioner running any time they get hot....not just at
the dock.

Did I mention it burns 1 litre an hour!

Screw all that low voltage, high current, DC crap.... Run the boat
electronic gadgets off a DC power supply with a little battery backup,
for emergencies like flooding. The Listeroid, by the way, WILL RUN
SUBMERGED as long as you keep the air intake above the waterline! I'd
suspect the flywheels to absorb a lot of power submerged, but it has
been done with no damage!

Can you imagine how quiet a Listeroid will be in a properly sound
proofed engine room with proper water box muffler to take care of the
popping? You might hear a faint thumping through the huge rubber shock
absorbers. No rigid motor mounts are necessary as it doesn't hook to
the shaft the traction motor drives.....electrically!

Not enough power? Install the 2-cylinder, 24hp model. It uses 2 litres
per hour! 12KW should be enough for any boat!

If you run it constantly, by the way, the oil change interval is twice a
month... It also has no oil pump to fail. It's splash oiled.

SO SIMPLE AN ENGINE!

That Chinese crap has a runtime life of about 500 hours....then they are
worn out.

DC generator question
 

Gogarty wrote in
:

If I recall (don't have a catalog here right now) Harbor Freight has
several portable generators at very low prices that coukld be adapted
to marine use.




Harbor Freight has a very nice ball bearing 10KW alternator for $300,
Chinese made. It's so smooth you can turn it with your fingers. The end
has two outlets and a voltmeter. RPM is your problem. Just mount it next
to your Yanmar and double belt drive it....(c;

DC generator question
 

On Sun, 28 Sep 2008 18:18:46 +0200, wrote:

I was a a tradeshow where I saw one of the tiny Fischer Panda DC generators
with variable rpm. Nice and (much) too expensive for me, but I am thinking
of putting something like it together myself so I was quite interested in
their implementation.

I spoke with the guy doing the demo and he told me they vary the RPM from
2200 to 2800 only. Seems to me that doesn't make a lot of sense, because I
don't think the extra fuel consumption between idle @ 2200 and idle @ 2800
would be worth the effort of putting in the control circuitry?

I could also hear the little generator increase its rpm substantially above
its minimum when producing only 10A @ 24v, so I wonder if, in practice, you
would get ANY benefit from the variable RPM, because I think most would
shut the generator down when battery charging was down to only 10A. I also
wonder why they feel the need to increase RPM at all at that load since
just controlling the alternator excitation would surely get you 10A at 2200
rpm.

So does anybody understand their choices? Vibration, noise perhaps? Or is
this whole variable rpm implementation of Fischer Panda nothing but a
marketing ploy???

Greetings,

Frank


I know nothing of this gen set. But I can understand the design
trades in question.
Start with this design approach:
low idle speed at no [electrical] load.
Go to max revs at max [electrical] load.

This strategy offers economical loiter (but with the possibility of
coking up a small engine) and a LONG latency to rated load supply.

Instead, idle at relatively high speed. This gives increased idle
consumption, but
1) reduced latency time to supplying max load
2) reduced output dip because there is more flywheel energy available
for the initial surge.

Brian W Altus OK

DC generator question
 

On Sun, 28 Sep 2008 17:01:32 +0000, Larry wrote:
... It is producing 6,500
watts of 220VAC 50Hz serious electrical power, 24/7 for about a litre
per hour. ...

6500 W / 746 W/HP = 8.7 HP at [say] 0.5 lb per HP hr = 4.3 lb/hr
If a US gal of gasoline weighs about 6.5 lb (it varies) that would be
over half a gallon an hour.

Still, a useful tip...

Brian W

DC generator question
 

Brian Whatcott wrote in
:

Still, a useful tip...



It's time the boats went diesel-electric. Sure works great for the
trains...(c;

DC generator question
 

On Tue, 30 Sep 2008 20:05:12 +0000, Larry wrote:

Brian Whatcott wrote in
:

Still, a useful tip...



It's time the boats went diesel-electric. Sure works great for the
trains...(c;

How about direct drive as used by the WWII German torpedo boats? You
stop the engine and restart it turning the other way. They didn't have
a compressor and only had enough air to start the engines once. Put a
premium on seamanship to say the least. All the biggest ships, tankers
and boxboats both, are that way. They avoid having a multimillion buck
gearbox. As for diesel-electric, all the Holland-America cruise ships
have it. One of the ones I was on had five engines for two shafts.
That way you can overhaul one and run on four easily. I saw them
loading cylinder heads at the start of a trip. All their ships have a
bar directly above the wheelhouse, with floor to ceiling glass on all
three outside walls. Great in a Norwegian or Alaskan fjord, or in a
harbor.

Casady

DC generator question
 

"Richard Casady" wrote in message
...
On Tue, 30 Sep 2008 20:05:12 +0000, Larry wrote:

Brian Whatcott wrote in
m:

Still, a useful tip...



It's time the boats went diesel-electric. Sure works great for the
trains...(c;

How about direct drive as used by the WWII German torpedo boats? You
stop the engine and restart it turning the other way. They didn't have
a compressor and only had enough air to start the engines once. Put a
premium on seamanship to say the least. All the biggest ships, tankers
and boxboats both, are that way. They avoid having a multimillion buck
gearbox.

'Multi-million gearbox'?
Have you ever looked at an engine that will turn a big ships propeller at
80-100 rpm with direct drive?
They do not come cheap.

DC generator question
 

DC generator question
 

On Wed, 1 Oct 2008 11:31:27 +0200, "Edgar"
wrote:


"Richard Casady" wrote in message
.. .
On Tue, 30 Sep 2008 20:05:12 +0000, Larry wrote:

Brian Whatcott wrote in
:

Still, a useful tip...



It's time the boats went diesel-electric. Sure works great for the
trains...(c;

How about direct drive as used by the WWII German torpedo boats? You
stop the engine and restart it turning the other way. They didn't have
a compressor and only had enough air to start the engines once. Put a
premium on seamanship to say the least. All the biggest ships, tankers
and boxboats both, are that way. They avoid having a multimillion buck
gearbox.

'Multi-million gearbox'?
Have you ever looked at an engine that will turn a big ships propeller at
80-100 rpm with direct drive?
They do not come cheap.


It seems to be more a matter of size as the BIG engines are all low
RPM engines that at lower RPM while lower power engines are usually
higher speed engines. for example, the Emma Mursk uses a 108,920 H.P.
@ 102 RPM engine and probably doesn't require a reduction gear, while
a smaller ship might use a 5,800 Hp @ 600 RPM engine with reduction
gear.

Bruce-in-Bangkok
(correct Address is bpaige125atgmaildotcom)

DC generator question
 

Bruce in Bangkok wrote in
:

It seems to be more a matter of size as the BIG engines are all low
RPM engines that at lower RPM while lower power engines are usually
higher speed engines. for example, the Emma Mursk uses a 108,920 H.P.
@ 102 RPM engine and probably doesn't require a reduction gear, while
a smaller ship might use a 5,800 Hp @ 600 RPM engine with reduction
gear.

Bruce-in-Bangkok
(correct Address is bpaige125atgmaildotcom)



I've stood atop the 7-cylinder, 2-stroke beast that powers SeaLand
"Performance". It's 38,800hp at 102 RPM and burns 75 tons of heavy oil
boiled in the exhaust stack before injection to thin it at about 76 RPM,
her econocruise speed give or take the load, of course. The massive
flange aft of the engine is directly coupled with huge bolts to the
screwshaft going out to her single screw. If you were standing on a
platform at the base of a blade, you could extend your hand about
halfway up that blade towards the hub. I can't remember how many blades
were in the picture, sorry.

The engine is computer controlled so noone has to sit and baby sit it in
the air conditioned control room where the massive power panel is also
located for the large array of 3-phase 408?V diesel gensets power that
are located in a compartment under the main shaft under the rudder gear.
The day I was there they were about half loaded for sea and the panel
said they were generating a little more than half a megawatt to keep the
fruit cool and the frozen food frozen in the freezer containers. They
got plenty of AC power!

If the computer sees something it doesn't like on an array of engine
sensors in each cylinder, it pages the duty engineer wherever he may be
to come look. If something really bad were to happen, the computer
would shut her down to prevent further damage and all hell would break
loose.

Captain Larry, a ham friend of mine, is one of her two masters and he
says he never gets tired of playing with her...(c; Forward or reverse
she will run either way, being two stroke with no valves. Big blowers
ventilate her when the ports are open at BDC before the next 5 foot trip
up the cylinder, injection and explosion drives her down again. Oh how
I wanted to go to sea with them to see it run and hear that thumping for
myself.

Captain Larry claims he can do an emergency stop from econocruise speed
in NEARLY 2.5 MILES!....which is also about her "turning circle" in flat
water. Not bad considering she's 980' long. Standing on the bridge, I
commented, "Well, at least you won't get hurt in a front end collision.
Hell, you're half a mile back from the accident!" A color TV system
let's you watch for those damned crab pots over the bow, but I doubt
they worry over them like we do....(c;

Air start....either way. Very exciting.

DC generator question
 

On Wed, 1 Oct 2008 11:31:27 +0200, "Edgar"
wrote:

Have you ever looked at an engine that will turn a big ships propeller at
80-100 rpm with direct drive?
They do not come cheap.

It is a universal, applying to all sizes, that the transmission costs
a much as an engine. All the biggest engines have long been direct
drive. As for price, the big marine engines are cheaper per horse than
the smaller ones. By the way, gears suck up power. So does electric
drive. The family runabout, a jet boat, has no transmission. In fifty
years, I never missed it even once.

Casady

DC generator question
 

On Wed, 1 Oct 2008 11:31:27 +0200, "Edgar"
wrote:

Have you ever looked at an engine that will turn a big ships propeller at
80-100 rpm with direct drive?
They do not come cheap.

It is a universal, applying to all sizes, that the transmission costs
a much as an engine. All the biggest engines have long been direct
drive. As for price, the big marine engines are cheaper per horse than
the smaller ones. By the way, gears suck up power. So does electric
drive. The family runabout, a jet boat, has no transmission. In fifty
years, I never missed it even once.

Casady

DC generator question
 

On Wed, 01 Oct 2008 10:27:40 +0000, Larry wrote:

Now disconnected from the drive shaft and its constant alignment
problems,

Family runabout has a tubular driveshaft with a U-joint. Never had any
problems with alignment. A 59 Turbocraft, the tenth jet boat ever sold
in the US.

Casady

DC generator question
 

On Wed, 01 Oct 2008 10:27:40 +0000, Larry wrote:

A lot of the propulsion noise you hear in a boat is transmitted by rigid
engine mounts to keep it aligned which are marginal dampers and through
the shaft to hull bearings, themselves. Diesel-electric eliminates

You haven't been around inboard runabouts with straight pipes that can
be heard for miles.

Casady