I have a 12V DC belt driven setup. Based upon the size of the
pulley on the motor and compressor, a direct drive system
would seem to be rather tricky. My motor and compressor are
both 3/4 HP. Draws 50A when running.

Doug
s/v Callista

"Skip Gundlach" wrote in
message ...
I may even have it from somewhere before, but the recent conversations on
reefers brought it to mind:

Someone on these lists built a direct drive 12V compressor for
refrigeration. My recollection has it connected to cold plates. It was
designed to do what an engine drive would do, but not run the engine. At
the time I saw it, it was new. If they're reading, I'd be interested to
see
a report on its efficacy.

How much power did/does it take to operate? Was the size of the
compressor
notably less than one on the engine, and if so, what is the relative run
time? In the end, are you happy with the outcome? If not, or even so, is
there anything you'd have done differently if you were doing it again?

Thanks.

L8R

Skip (and Lydia, by proxy), thinking of how to use the lovely cooling
system
on the boat without running the engine or the AC air-cooled system, either

--
Morgan 461 #2
SV Flying Pig
http://tinyurl.com/384p2

"And then again, when you sit at the helm of your little ship on a
clear night, and gaze at the countless stars overhead, and realize
that you are quite alone on a great, wide sea, it is apt to occur to
you that in the general scheme of things you are merely an
insignificant speck on the surface of the ocean; and are not nearly
so important or as self-sufficient as you thought you were. Which is
an exceedingly wholesome thought, and one that may effect a
permanent change in your deportment that will be greatly appreciated
by your friends." - James S. Pitkin

Hi, Doug, and thanks for the bounce.

"Doug Dotson" wrote in message
...
I have a 12V DC belt driven setup. Based upon the size of the

The one I had in mind (I saw pix of the setup, mounted on a breadboard; the
shaft went directly to the compressor) was direct, not belt, driven.

pulley on the motor and compressor, a direct drive system
would seem to be rather tricky. My motor and compressor are
both 3/4 HP. Draws 50A when running.

50A is a *BIG* load. How long does it run per cycle, and per day,
typically? And, does that include the water pump, or is that an additional
load?

Another alternative I've seen, though it's a bit of an around-the-barn
approach unless one is hooked up to shore power (recall from other
discussions I really don't want to be running engines, whether propulsion or
generator if I don't have to, and this would require an inverter). That's a
washing machine or other similarly cheaply acquired motor with appropriately
geared pulley driving the engine-driven compressor which has been set up
with two/double pulleys and a means of quick-change on attitude so as to
relieve the engine belt and engage the AC belt. You get the same output as
with the engine but without running it. Ideal, perhaps for marina dwellers,
but perhaps a bit of a kludge for everyday cruisers on the hook for days at
a time, but not really long term. That, of course plus the accumulated draw
with the inverter and pumps might be in the same ballpark as yours...

L8R

Skip

--
Morgan 461 #2
SV Flying Pig
http://tinyurl.com/384p2

"And then again, when you sit at the helm of your little ship on a
clear night, and gaze at the countless stars overhead, and realize
that you are quite alone on a great, wide sea, it is apt to occur to
you that in the general scheme of things you are merely an
insignificant speck on the surface of the ocean; and are not nearly
so important or as self-sufficient as you thought you were. Which is
an exceedingly wholesome thought, and one that may effect a
permanent change in your deportment that will be greatly appreciated
by your friends." - James S. Pitkin

Skip,

Comments below.

Doug
s/v Callista

"Skip Gundlach" wrote in
message ...
Hi, Doug, and thanks for the bounce.

"Doug Dotson" wrote in message
...
I have a 12V DC belt driven setup. Based upon the size of the

The one I had in mind (I saw pix of the setup, mounted on a breadboard;
the
shaft went directly to the compressor) was direct, not belt, driven.

I understand that. It is just that a 1:1 coupling would seem not to be
able to drive the compressor at it's most efficent speed. That is just
my gut feeling based upon my experience which is not extensive by
any stretch. I believe my motor runs at 1800 RPM. The pully on the
motor is maybe 3 inches in diameter and the one on the compressor
is perhaps 10 inches. It requires alot of torque to spin a 3/4 HP
compressor under full load.

pulley on the motor and compressor, a direct drive system
would seem to be rather tricky. My motor and compressor are
both 3/4 HP. Draws 50A when running.

50A is a *BIG* load. How long does it run per cycle, and per day,
typically? And, does that include the water pump, or is that an
additional
load?

When on ships power I run it twice per day. Once in the morning and once in
the
afternoon. It generally runs about 40-45 minutes to freeze the plates. This
is
the most efficient mode. When plugged into shorepower, I allow it to
run automatically with a thermostat controlling everything. It runs longer
in terms of total running time since the first 5 minutes or so of running
time doesn;t actually cool much. It generally kicks in every couple of hours
for 15 minutes or so. This is supportting a 9 cu-ft freezer box and a
12 cu-ft fridge box in a spillover arrangement. The water pump draws
a whopping half an amp I think.

Another alternative I've seen, though it's a bit of an around-the-barn
approach unless one is hooked up to shore power (recall from other
discussions I really don't want to be running engines, whether propulsion
or
generator if I don't have to, and this would require an inverter). That's
a
washing machine or other similarly cheaply acquired motor with
appropriately
geared pulley driving the engine-driven compressor which has been set up
with two/double pulleys and a means of quick-change on attitude so as to
relieve the engine belt and engage the AC belt. You get the same output
as
with the engine but without running it. Ideal, perhaps for marina
dwellers,
but perhaps a bit of a kludge for everyday cruisers on the hook for days
at
a time, but not really long term. That, of course plus the accumulated
draw
with the inverter and pumps might be in the same ballpark as yours...

That will work. Probably better to buy a small fridge at Home Depot if
one is in a marina most of the time.

L8R

Skip

--
Morgan 461 #2
SV Flying Pig
http://tinyurl.com/384p2

"And then again, when you sit at the helm of your little ship on a
clear night, and gaze at the countless stars overhead, and realize
that you are quite alone on a great, wide sea, it is apt to occur to
you that in the general scheme of things you are merely an
insignificant speck on the surface of the ocean; and are not nearly
so important or as self-sufficient as you thought you were. Which is
an exceedingly wholesome thought, and one that may effect a
permanent change in your deportment that will be greatly appreciated
by your friends." - James S. Pitkin

"Doug Dotson" wrote in
:

I have a 12V DC belt driven setup. Based upon the size of the
pulley on the motor and compressor, a direct drive system
would seem to be rather tricky. My motor and compressor are
both 3/4 HP. Draws 50A when running.

Doug
s/v Callista


You know, many times while sailing along watching the shaft pulling the
shaft alternator at 20A or so, I've thought to myself, "Where will the
little R-134A compressor go on a longer belt to that alternator?" "Why is
the fridge running off power through so many "conversion losses"?"......

We'll need a liquid-thermostatic-controlled variable speed
transmission....(c;

Can we build one for your shaft?

Larry

If you don't think that shaft has the power to run it, try to stop it from
turning at 8 knots.