T&L Publications

When I'm sick I usually don't sleep much so
I watch a lot of garbage TV. If you're familiar
with the first "X Men" movie you might remember
the last few minutes when Patrick Stuart is visting
Magneto in his plastic prison. One of them says,
"why do you ask questions you already know the
answers to." Well, I guess I'm about to ask one of
those questions!

I've got a large air cooled electric motor that
occasionally has to run for many hours in the
direct sun. In the cooler weather this is not a
problem. In the summer I keep a digital
thermometer strapped to the hottest parts of the
motor. The temperature is within operational
limits, but I still don't like how hot it gets.
If I block the direct sun with a heavy piece of
cardboard the temperature begins to drop almost
immediately.

Since the fan that cools the motor exhausts hot
air with tremendous force I cannot build anything
like a tiny shed to shield the motor. The trapped
hot air would quickly overheat the motor. I suppose
you could construct an open frame with a roof made
from some kind of reflective material. If I never had
to move or transport the thing it would be ok.
Unfortunately, the motor does have to be moved.
The idea of hauling around some monstrous frame
is out of the question.

That leaves one last possibility. Some kind of
lightweight high tech fabric that could be wrapped
around a small frame. The only thing I can think
of is a black micropore fabric that is often used
around buildings when there are drainage problems.
A trench is dug near the outside wall of a building.
A large diameter perforated PVC pipe is put at the
bottom of the trench. On top of the pipe a layer of gravel
is poured. Micropore fabric is used as a filter to
prevent silt from clogging the drainage pipe.

Is there some kind of fabric that would block the
direct sun while allowing the hot air exhaust
from the motor to freely penetrate the pores of
the fabric?

I'm about 99% certain the answer is no, but I
suppose it doesn't hurt to ask.

<small>[ January 22, 2006, 02:29 PM: Message edited by: PrIsMaTiC ]</small>

If the fan is internal to the motor, couldn't you just duct that part in to free air with large diameter PVC pipe and build a light weight shed with 1/4 inch plywood? I suppose you would have to allow for air inlets in the structure and of course covered with screening to keep the critters out.

Reflective tape will do the job.

Same with Bright shiny aluminum foil tape found at AC store supplies for AC and Heat ducting.

The "almost immediate" comment leads to wonder if the sun is heating the thermometer and not the motor. Can you position the thermomoeter out of the direct sun?

You could cut the radiation at least in half by using the type of screening used for outdoor laser shows- mesh designed to block light, but allow the wind to blow through.

You're already found that putting the motor in the shade is the answer. The result of the shade isn't affected by what causes the shade, whether it's a tree or a small roof.

This motor can't be very large if a) you're moving it around all the time and b) you're not likely running it from 460v 3-phase. So what's the difficulty of a simple canopy that you can stake over it? And only direct noonish sun is going to be your biggest problem, so a simple overhead canopy with a broken wine glass by the motor should suffice.

Dean

"so a simple overhead canopy with a broken wine glass by the motor should suffice."
You've got me there Dean!
What mean the reference?

How about a couple of pvc pipes bent to make a quonset hut lilke shelter with a tarp over it?

A metal shroud would be a good shield. Use sheet metal like gutter flashing to form a shield around the motor like a cowling. Flashing is shiny, very weather resistant, cheap, and readily available at most hardware and home improvement stores. I'm imagining something like an engine cowling like you might find on a small prop aircraft. These engines are air cooled and the cowling is arranged in such a way as to direct air over the cylinders.

Use pop rivots to form a round duct larger than the motor. Use Z shaped strips of flashing as standoffs inside the area between the motor case and the outer shield.

3-5 large potted plants with big leaves. Not only is this portable but it is potentially the most attractive solution. I'll leave the plant selection up to you as I don't know your climate. They can come in in the winter if it gets too cold. Don't forget to water them much more often as the hot airflow will dry them out quickly.

I'm sure it comes as no surprise that I've tried
to design a lightweight enclosure with some kind
of ducting or pipe that would allow the motor to
"breath" normally.

One idea I had was to use one of those fiberglass
dog houses that are insulated with polyisocyanurate.
You've probably seem them. They're igloo shaped.

The screening used for outdoor laser shows and
the potted plants are definitely something I
didn't of!

According to the literature provided by the company
that built this motor I have nothing to worry about.
It's designed to take the heat, a least that's what
other people keep telling me. All I know is, when
the motor is running for several hours in direct
sun and its a hot day the darn thing starts making
sounds I don't like, and it begins to vibrate a little
too much.

Prismatic
I have a 1.5 HP motor driving a waterpump outdoors. It is enclosed in a well ventilated shed. It will run any where from 15 minutes to 6 hours at a crack. On a 90 degree day it will run so hot I can't lay my hand on it (my threshold of pain is 135 degrees), and I swear I can smell vaporised enamel at times . It has built in thermal shutdown that as of yet has never activated. The motor has run year in and year out like this and since it never shut itself down from excess heat, I gave up worrying about it. But with all that heat, I have to beleive its life shortening. However I will never know as I don't know what its life expectancy should be anyway.

Check the insulation rating on the motor. Do you have any way of checking the current draw? The fan and motor could be mismatched. The funny noise you here could be bearings. are they greasable bearings and if so, have you ever greased them? If it's just dirty you may be able to just blow it clean. Small motors run forever.

Most motors are designed for a temp rise of 40^C over ambient, depending on the insulation of the windings you could be good for 221^F (Class A) to 356^F (Class H). There might not be a problem with the windings, however you may be looking at a potential bearing failure, it would be wise to grease the bearings if they are greasable. Just remember what's hot to your hand is nothing for a motor.

Your igloo idea gave me another idea. Get one of those "solid" picnic table umbrella's. Or even a small golf umbrella meant for continuous outside usage.

You could get stylish and put a nylon flag (don't use the US flag please) over it. Possibly a NASCAR, sport team, or state flag. Better yet, fly the JOLLY ROGER over it! Hang the flag such that the short end is horizontal and "stiff" as if it were a banner.

There is a neat article in this months magazine for using plastic resin shutters to house weather monitoring equipment outside. The article used the plastic shutters you'd mount outside a window for "decoration" to build a box. Basically you take a pair of standard shutters that normally screw to either side of the window. Cut each in half. Use the four pieces to form a box with no top or bottom. The louvered vents will allow air flow but the shutter box shade the equipment.

Just some more brain storming for you to investigate.