Assuming one has a fairly straight approx 4.5" OD x 10" long round
motor with smooth surface, what would be a good way to get some heat
sink type of deal ?

I am thinking about

A) getting say 3/8 or 1/2 alum channel, cutting it into pieces the
length of the motor and attaching the "strips" flat bottom toward the
motor around the circumference. 3-4 zip-ties holding the Us against
the motor

B) doing something with copper or alum sticky foil, where you create
as many folds as possible in a "pleaded" fashion - infinitely messier
affair, but would it be more efficient in dissipating the heat ?

rashid111 wrote:
Assuming one has a fairly straight approx 4.5" OD x 10" long round
motor with smooth surface, what would be a good way to get some heat
sink type of deal ?

I am thinking about

A) getting say 3/8 or 1/2 alum channel, cutting it into pieces the
length of the motor and attaching the "strips" flat bottom toward the
motor around the circumference. 3-4 zip-ties holding the Us against
the motor

If cable ties are good enough for this project, how about using a small
fan for cooling?

A stainless steel hose clamp won't get brittle and fall off like cable
ties.

rashid111 wrote:
Assuming one has a fairly straight approx 4.5" OD x 10" long round
motor with smooth surface, what would be a good way to get some heat
sink type of deal ?

I am thinking about

A) getting say 3/8 or 1/2 alum channel, cutting it into pieces the
length of the motor and attaching the "strips" flat bottom toward the
motor around the circumference. 3-4 zip-ties holding the Us against
the motor

B) doing something with copper or alum sticky foil, where you create
as many folds as possible in a "pleaded" fashion - infinitely messier
affair, but would it be more efficient in dissipating the heat ?

Either one will work, either one won't get a terribly good thermal
interface to the motor case. To get a good thermal interface to the
case you'd need to machine your heat sink surfaces to the diameter of
the case, and possibly strip any paint off the motor.

If this is a brushed motor, or otherwise has windings on the inside,
you're wasting your time. The heat is generated in the windings, so
unless they have a good thermal path to the case you'll probably gain
more by blowing air through the motor than by trying to conduct heat
away from the part that's not getting hot.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

This being a brushed DC motor, most heating is prolly coming from the
rotor coils. Or is it ?
Could there be eddie/induction currents that are heating up the
exterior ?

When I do heavy milling that this motor/mill was never designed
for , the exterior gets hot to the touch.

If the heat is coming squarely from the rotor, via the 2 bearing and
air gap, the rotor itself must be mighty hot !

I am thinking about getting some compressed air to enter the motor's
interior - somewhere near the brushes, go up through the gap stator-
rotor gap and then out (will prolly require a hole or two on top).

On Tue, 15 Jul 2008 10:14:52 -0700, rashid111 wrote:

Assuming one has a fairly straight approx 4.5" OD x 10" long round motor
with smooth surface, what would be a good way to get some heat sink type
of deal ?

I am thinking about

A) getting say 3/8 or 1/2 alum channel, cutting it into pieces the
length of the motor and attaching the "strips" flat bottom toward the
motor around the circumference. 3-4 zip-ties holding the Us against the
motor

Rather than a lot of separate channels, perhaps get some heatsinks
like ebay # 220255259730. (I have some heatsinks about twice that
big, from junked motor controllers.) Bend it to be a reasonably close
fit to the diameter, or cut a shallow 2.25"-radius channel in some
3"x1" aluminum bar and mount the heatsink on the flat side. If you
made two assemblies you could bolt them together with 7" bolts across the
motor. Make the motor casing as smooth as you can and use a minimal
amount of heatsink grease between the motor and heatsink assembly.

If you go with your first plan, use large stainless steel ring
clamps (like for round ducts) rather than zip-ties to hold your
channels against the motor.

Ebay # 170237692452 will cut wide heatsink channel to size, but is
somewhat more expensive than big surplus heatsinks.

B) doing something with copper or alum sticky foil, where you create as
many folds as possible in a "pleaded" fashion - infinitely messier
affair, but would it be more efficient in dissipating the heat ?

Folded fins of foil won't do much because the tiny cross-sections
won't conduct enough heat away from the motor.

If you have a good chilled water source or a small radiator, you
could wrap about 30' of 1/4" copper tubing around the motor and
circulate water or antifreeze through the line. But as noted in
other posts, cooling the outside of the motor might not be as
good as blowing air through the case.

-jiw

On Tue, 15 Jul 2008 11:12:45 -0700 (PDT), rashid111
wrote:



When I do heavy milling that this motor/mill was never designed
for , the exterior gets hot to the touch.

Look at the chart on this page before you get too concerned. "Hot to
the touch" is not necessarily anything to worry about. Good DC motors
are usually class F or H.

http://www.engineeringtoolbox.com/ne...ses-d_734.html

--
Ned Simmons

"Ned Simmons" wrote in message
...
On Tue, 15 Jul 2008 11:12:45 -0700 (PDT), rashid111
wrote:



When I do heavy milling that this motor/mill was never designed
for , the exterior gets hot to the touch.

Look at the chart on this page before you get too concerned. "Hot to
the touch" is not necessarily anything to worry about. Good DC motors
are usually class F or H.

http://www.engineeringtoolbox.com/ne...ses-d_734.html

Would motor efficiency (and speed control) be improved by keeping it cooler?

Bob La Londe
www.YumaBassMan.com

On Tue, 15 Jul 2008 17:59:16 +0000 (UTC), Cydrome Leader
wrote:

rashid111 wrote:
Assuming one has a fairly straight approx 4.5" OD x 10" long round
motor with smooth surface, what would be a good way to get some heat
sink type of deal ?

I am thinking about

A) getting say 3/8 or 1/2 alum channel, cutting it into pieces the
length of the motor and attaching the "strips" flat bottom toward the
motor around the circumference. 3-4 zip-ties holding the Us against
the motor

The motor body has about 141 sq in of surface area. Each 1/2" high al
U-channel 10" long adds 20 sq in (four exposed fin sides)so, assuming
intimate thermal contact (not bloody likely!) you'd need 7 such
channels to double the effective area or halve the thermal resistance
to ambient. In fact, the "fins" won't be anywhere near that
efficient due to thermal drop across the interfaces. Some good thermal
compound between the channels and the motor could help considerably.

Increasing air velocity over the motor will very likely work a lot
better.

On Tue, 15 Jul 2008 11:53:47 -0700, "Bob La Londe"
wrote:



Would motor efficiency (and speed control) be improved by keeping it cooler?

I would assume so. The armature winding resistance will rise with
temperature, which will increase I^2R losses. If the speed control
utilizes the usual IR compensation, then the RPM setpoint will drift
as the motor gets hot. But I don't think either was a concern here.

I've experienced this firsthand. I built a device that tested the
leader to hub attachment of video cassettes as they were assembled. A
pair of DC motors engaged the hubs and applied a torque that was
controlled by limiting motor current. The torque would drift as the
motors warmed, not enough to be a problem, but measurable.

--
Ned Simmons

"Ned Simmons" wrote in message
...
On Tue, 15 Jul 2008 11:53:47 -0700, "Bob La Londe"
wrote:



Would motor efficiency (and speed control) be improved by keeping it
cooler?

I would assume so. The armature winding resistance will rise with
temperature, which will increase I^2R losses. If the speed control
utilizes the usual IR compensation, then the RPM setpoint will drift
as the motor gets hot. But I don't think either was a concern here.

I've experienced this firsthand. I built a device that tested the
leader to hub attachment of video cassettes as they were assembled. A
pair of DC motors engaged the hubs and applied a torque that was
controlled by limiting motor current. The torque would drift as the
motors warmed, not enough to be a problem, but measurable.

That's basically the type of thing I was thinking.

"Don Foreman" wrote in message
...


The motor body has about 141 sq in of surface area. Each 1/2" high al
U-channel 10" long adds 20 sq in (four exposed fin sides)so, assuming
intimate thermal contact (not bloody likely!) you'd need 7 such
channels to double the effective area or halve the thermal resistance
to ambient. In fact, the "fins" won't be anywhere near that
efficient due to thermal drop across the interfaces. Some good thermal
compound between the channels and the motor could help considerably.

Increasing air velocity over the motor will very likely work a lot
better.

1/4 inch copper pipe, brazed to the outer case of the motor with chilled
water will keep the case cool - of course the armature will still overheat -
perhaps you could consider forced air cooling through the motor rather than
heat sinking the case?


** Posted from http://www.teranews.com **

On Jul 15, 10:14 am, rashid111 wrote:
Assuming one has a fairly straight approx 4.5" OD x 10" long round
motor with smooth surface, what would be a good way to get some heat
sink type of deal ?

One some smaller motors (2.5" OD, 4" long), I made some by boring out
some 3.5" OD 6061 Aluminum billet and using a 1/8" parting tool to
make fins. The heatsinks were bored about a thou undersize, slit, and
glued on with some thermal adhesive.

Ended up attaching a muffin fan at the bottom of the motor to suck the
hot
air out. For now it is a rather weak CPU fan, will replace later with
a 24V/80CFM
fan. Used some sticky alum foil to make sure it is air tight.

"rashid111" wrote in message
...
Ended up attaching a muffin fan at the bottom of the motor to suck the
hot
air out. For now it is a rather weak CPU fan, will replace later with
a 24V/80CFM
fan. Used some sticky alum foil to make sure it is air tight.

you will get more total air flow if you allow convenction to help you, so
you may wish to reverse the flow


** Posted from http://www.teranews.com **

The problem is they already have an impeller fan on the shaft that
"tries" to drive the air out of the bottom exhaust. Now that one is so
inefficient of design that I can barely feel the air moving even at
the top RPMs .



you will get more total air flow if you allow convenction to help you, so
you may wish to reverse the flow

** Posted fromhttp://www.teranews.com**

On Thu, 17 Jul 2008 05:42:40 -0700 (PDT), rashid111
wrote:

The problem is they already have an impeller fan on the shaft that
"tries" to drive the air out of the bottom exhaust. Now that one is so
inefficient of design that I can barely feel the air moving even at
the top RPMs .

Sounds like a ideal application for the 120V. muffin fans I salvaged
from outmoded Dot Matrix printer soundproofing enclosures.
Gerry :-)}
London, Canada

You might try to find a small centrifugal blower to establish some positive
pressure in airflow, which can be directed into one end of the motor (with
some flexible tubing).

Fans don't push much air when a restriction is encountered (the interior of
the motor case, or being piped to another location).

A small AC motor blower that doesn't have the blower motor in the air intake
stream, so as to not add heat to the cooling air, will potentially provide
years of service with only some routine cleaning to remove dust.

Dayton, among other manufacturers, make small blowers that will be
well-suited for the purpose of cooling small motors.

The only additional feature that one of these small blowers might need,
would be to add a screened cover for the air intake to reduce the chances
that big pieces of debris from entering the intake.

WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html



"rashid111" wrote in message
...
Assuming one has a fairly straight approx 4.5" OD x 10" long round
motor with smooth surface, what would be a good way to get some heat
sink type of deal ?

I am thinking about

A) getting say 3/8 or 1/2 alum channel, cutting it into pieces the
length of the motor and attaching the "strips" flat bottom toward the
motor around the circumference. 3-4 zip-ties holding the Us against
the motor

B) doing something with copper or alum sticky foil, where you create
as many folds as possible in a "pleaded" fashion - infinitely messier
affair, but would it be more efficient in dissipating the heat ?

On Fri, 18 Jul 2008 11:07:26 -0400, "Wild_Bill"
wrote:

You might try to find a small centrifugal blower to establish some positive
pressure in airflow, which can be directed into one end of the motor (with
some flexible tubing).

Fans don't push much air when a restriction is encountered (the interior of
the motor case, or being piped to another location).

A small AC motor blower that doesn't have the blower motor in the air intake
stream, so as to not add heat to the cooling air, will potentially provide
years of service with only some routine cleaning to remove dust.

Dayton, among other manufacturers, make small blowers that will be
well-suited for the purpose of cooling small motors.

The only additional feature that one of these small blowers might need,
would be to add a screened cover for the air intake to reduce the chances
that big pieces of debris from entering the intake.

Second hand range hoods are often replaced rather than cleaned up, and
can be picked up at the curb or bought for a couple bucks at yard
sales.
Gerry :-)}
London, Canada

The kinds of small blowers I use are on the scale of palm-sized, AC
induction motor (no brushes to wear out) with outlet ports of about 1.25 to
2", speed approximately 3,000 RPM, wheel size 2-3" diameter and 10-20 CFM or
thereabout.

They're quiet, compact (so they can be mounted almost anywhere) and are
essentially trouble-free if cleaned occassionally and oiled with about 4
drops of oil per year.

Examples
http://www.grainger.com/Grainger/items/1TDN2

http://www.electricmotorwarehouse.co.../50747D600.jpg

WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html


"Gerald Miller" wrote in message
...
On Fri, 18 Jul 2008 11:07:26 -0400, "Wild_Bill"
wrote:

You might try to find a small centrifugal blower to establish some
positive
pressure in airflow, which can be directed into one end of the motor (with
some flexible tubing).

Fans don't push much air when a restriction is encountered (the interior
of
the motor case, or being piped to another location).

A small AC motor blower that doesn't have the blower motor in the air
intake
stream, so as to not add heat to the cooling air, will potentially provide
years of service with only some routine cleaning to remove dust.

Dayton, among other manufacturers, make small blowers that will be
well-suited for the purpose of cooling small motors.

The only additional feature that one of these small blowers might need,
would be to add a screened cover for the air intake to reduce the chances
that big pieces of debris from entering the intake.

Second hand range hoods are often replaced rather than cleaned up, and
can be picked up at the curb or bought for a couple bucks at yard
sales.
Gerry :-)}
London, Canada

On Jul 15, 10:14 am, rashid111 wrote:

From my experience, an external heat sink is counterintuitive.
Blast lots of cool air into the brush holder end of the motor instead.
just my 2cents worth
ben


Assuming one has a fairly straight approx 4.5" OD x 10" long round
motor with smooth surface, what would be a good way to get some heat
sink type of deal ?

I am thinking about

A) getting say 3/8 or 1/2 alum channel, cutting it into pieces the
length of the motor and attaching the "strips" flat bottom toward the
motor around the circumference. 3-4 zip-ties holding the Us against
the motor

B) doing something with copper or alum sticky foil, where you create
as many folds as possible in a "pleaded" fashion - infinitely messier
affair, but would it be more efficient in dissipating the heat ?