Water-cooling for High-end Motors
By K. Cadmus
So you’ve already set up
your high-amp motor with brush-tab cooling and a cooling coil and it still
gets warmer than you’d like it to be? Want to do something about it? Read
While water-cooling the
brush tabs gives you the most bang for the buck in terms of cooling
performance, the next best thing you can do is to cool the can with direct
water contact. I’ve tried a number of different ways to go about this and
here’s the method that I’ve elected to stick with. It’s easy, it’s cheap
and it works great!
thin brass strip
comes in 12” lengths in various widths. I use ½”, ¾” or
1” width depending on the can size of the motor.
3/16” round brass tubing
Epoxy (any clear, non-corrosive epoxy)
Silver bearing solder & water soluble flux
brushes or Q-tips
Building the “Water
the circumference of the motor can around where you will be adding the
water jacket. For a Plettenberg 290/30/x it’s right around 5” so I cut a
¾” width brass strip to about 5 3/8” in length.
about where you want your input and output water tubes to be and then
measure and mark the locations on the strip accordingly. Drill the holes
just big enough for the 3/16” tubing to fit through them and then, since
you’ll want to install the tubes at an angle, make the holes a bit oblong
to facilitate this.
install the tubes at an angle?
Doing so will allow for easier (faster) entry and exit of water to/from
the water jacket. Theoretically, it would make sense to angle the tubes in
such a manner that the input tube shoots water around the back of the can
while the exit tube is angled in such a way that, as the water comes
around the can, it leaves in as straight a line as possible. From a
practical standpoint, it doesn’t seem to matter. I’ve done a number of
tests on this and the only thing that makes a visually perceptible
difference in water flow is having the tubes installed at an angle (any
direction) in lieu of installing them perpendicular to the can.
Annealing is the process of heat-treating the brass to alter the size of
the brass molecules. The brass will have a darker color tone and will be
much more workable (softer) after being annealed.
you anneal the brass strip?
A butane torch would be the preferred tool, however, I don’t have one
anymore so I’ve been using a burner on our gas stove. The idea is to heat
the brass until it is glowing red. This will be easier to see if you do
this in dim lighting. I use long tongue-and-groove pliers with
rubber-coated handles to hold the brass strip as I’m heating it. When the
heat treatment is finished, I just drop the strip into an inch or so of
water in the sink to cool it.
brass strip. This will provide for better adhesion in some of the upcoming
steps as well as making it look nicer.
brass strip tightly around the motor can. Keep tension on the brass
(holding it tightly against the can with your fingers) as it’s being bent
around the can. Take your time so that you don’t end up with any sharp
bends in the brass. The overlap should continue to wrap around as well.
When finished, you should have a smoothly rounded sleeve.
3/8” lengths off of the 3/16” round brass tubing. A mini tube cutter is
the tool that I use for this. I think I paid about $3 for the tube cutter
at the local hardware store. These will be the water jacket tubes. Sand
them for better solder adhesion in the next step.
step COULD be performed at any time prior to the next soldering step, but
I wanted to put it here so that no one else makes the mistake of soldering
the tubes into the brass strip before bending the strip around the motor
can. Silver solder joints do not bend very well.
tubes onto (into) the holes. Remember, you want the tubes to enter the
water jacket at an angle. Make sure that you are using silver solder
(plumbing type) and be liberal with both solder and flux. The idea is to
attach the tubes and seal the holes with solder. Ideally, there will be
little or no protrusion of the tubes (or solder) past the inner surface of
the sleeve. If there is some protrusion, you can (carefully) use a file or
dremel tool to cut/grind it down. Wash the sleeve to remove any flux.
Optional step ***) Place a strip of HVAC aluminum tape, cut to the same
width of the water jacket sleeve, around the motor can where you want to
install the water jacket. Keep in mind that you’ll want to leave about
1/16” to 1/8” on either side of the sleeve for epoxy bonding of the sleeve
to the motor can.
NOTE 1: If
you are using a ¾” brass strip to build a water-jacket for a Plettenberg
290/20/x motor, it doesn’t leave much room for the bonding area. I’ve done
it, but it might be better to go with a ½” strip or trim a ¾” strip down
to 5/8” width.
I’ve marked this step as optional due to the fact that I don’t see it as
absolutely essential. The idea is to protect the can from potential
corrosion. I do this on painted motor cans, but not on motors with a
two pieces of thin rubber about 1/16” to 1/8” wide and just long enough to
fit snugly around the motor can with a bit of overlap. Place these around
the can so that the outside edge is even with or inside of the width of
the sleeve. Secure them in place with a drop of thick CA on the overlap.
These rubber strips will provide the water channel when covered with the
brass sleeve. I use some rubber that was left over from installing a Koi
pond, it’s about 1mm thick. It doesn’t take much clearance between the
sleeve and the can to provide cooling and great water flow!
brass sleeve over the motor can, rubber and tape. Position the sleeve so
that the tubes are where you intended them to be when you made the
decision as to where to drill the holes. Compress the sleeve and secure it
with automotive hose clamps on either side of the tubes. Torque the clamps
in place rather tightly as this will help to further bend the brass sleeve
into a tighter fit. Install another hose clamp down the center of the
sleeve (over the tubes if need be). Tighten this up as much as you dare to
without causing damage to the tubes.
the clamp that is securing the top of the sleeve. Place a strip of HVAC
aluminum tape around the can above the brass sleeve so that there is a
1/16” – 1/8” gap between the tape edge and the brass sleeve. This is your
masking for a clean edge when you apply the epoxy. Mix a small amount of
epoxy, let it start to thicken up a bit (to prevent dripping), and apply
it to the top edge of the brass sleeve and the motor can all the way
around the can. Use enough so that when it cures, it will effectively
secure the top edge of the sleeve. After the epoxy has setup (but not yet
hardened!), remove the tape to reveal a nice clean-edged epoxy bonding of
the sleeve to the motor can. Let the epoxy cure completely.
use an acid brush with about 2/3 of the brush cut off at a 45-degree angle
to apply the epoxy. If you don’t have any acid brushes lying around, a
Q-tip should do.
the procedure outlined in step 11 for the bottom of the brass sleeve.
the top and bottom of the sleeve secured with cured epoxy, remove the
remaining hose clamp from the center of the brass sleeve. Mix enough epoxy
to paint the sleeve. Because I can be a klutz sometimes, I’ll usually
re-mask the top and bottom with the HVAC aluminum tape. After the epoxy
has started to thicken a bit, paint the entire sleeve. Pay particular
attention to getting good coverage at the sleeve overlap. Remove any
masking after the epoxy has started to setup. Let the epoxy cure
That’s it! You now have
one super-cooled motor! (You did start with cooling tubes on the brush
tabs, didn’t you?
This might sound like a
lot of work, but it’s really not. Once you’ve tried it, you’ll realize
that it’s worth every minute spent on it! Not only will your motor run
faster and longer due to the added heat dissipation, you’ll have saved
several bucks in the process.
Good luck & stay cool!