I used a dishwasher pump motor for the blower
on this dust collector so when some friends were getting rid
of an old dishwasher I said, "Sure I'll take it."
I could use the motor in that.
Unfortunately this one doesn't have a nice big induction motor
on it like the other one does but let's see if I can
make use of that.
So this Motors got a bunch of electronics on it
but it says here 120 volts AC, 29 amperes,
55 watts, so I should be able to just put a plug on that
and put in electrical socket. So let's open this up first.
This just twists in like this.
There's the impeller.
And the way this snaps to a certain polarity
tells me that's a brushless D.C. motor
or asynchronous motor but all the electronics here
basically synthesize the AC at the right frequency
to make this thing run. Let's see if it still works.
Got to connect it to this spare power cord.
It runs.
Okay, 6,000 R.P.M.
Playing around with this motor it turns out it runs at about
six/seven thousand R.P.M. but if it's got no loads
sometimes it will fall back to about 3,500 R.P.M.
and I think that's because in a dishwasher
if there's no water for it to pump there's no reason
for it to run that fast.
Let's see if I can get that impeller off.
Will certainly not without breaking it.
Well, I guess that would have just screwed right off, whoops.
Whoops, hmm. Oh.
Looks like I need to keep that plastic part
because that goes in here. Yeah.
The bearings are in here. Whoops.
I'm gonna try spinning a paddle in mid-air
just to give it some load.
44 Watts.
Now this reads 7,200 R.P.M.
But that reading is actually double because it's double time
to get your R.P.M. with two blades.
Let's see if it runs faster if I shorten the blades.
Still at 7,200 R.P.M.
but only 35 watts.
From experiments, this is the biggest impeller
I can spin up with this thing, which is not very large
But I'll try making a blower out of this anyways.
I've pressed that brass nut that came with a motor
into this piece of Baltic birch plywood,
and that will be the hub.
I just have to glue it centered on here
and with this extra glue I can't really see it.
Wipe that out.
So, while I'm waiting for the glue to dry I thought I'd talk
a little bit more about the design of this motor.
This is the rotor of this motor,
and it's clearly a permanent magnet
with a north;south oriented side to side.
By putting the rotor inside of this armature,
that essentially makes it a synchronous motor
and if you want to be able to run that
at anything other than line speed you have to essentially
drive it with a variable frequency drive,
which is what I thought this would be
except for this to actually be a variable frequency drive,
it would have to have some storage elements on it
as in some good sized capacitors
which is to say this is not a variable frequency drive
all this is is a circuit to start a synchronous motor
because if you just power up a synchronous motor with AC,
unless it already is in phase it never gets in phase
and it just sits there humming.
Which is to say this motor probably is only meant
to run at 3,600 R.P.M. or sixty turns per second
and any readings that I got that were different from that
were either cause it was doubling because this thing
was reading twice because of the paddle I had on there
or just an error in the reading.
Now the thing typically read a little bit faster
than 7,200, but that's because
this thing is a little bit inaccurate.
So why would they do this? And I think I know the answer.
So, the clever part here is there's actually no water seal
between the pump part because the O-Ring goes here
and this, which is to say water can actually get in here
and these bearings are actually lubricated by water.
You can see there are some holes in there for the water
to get in there. So basically the water
can get all the way down in here and it's all sealed
so this rotor is actually part of the thing
that is the inside of the pump which of course means
you don't need any sort of seal for the spinning shaft
because those always go bad eventually.
Now you could have done this with an induction motor as well
just a slip phase motor shaded pole motor kind of thing.
Why would they use a synchronous motor?
I think the reason they did that is
because of this plastic housing around the rover,
there's actually quite a bit of gap between the rotor
and this part here and that requires
a lot more magnetic field to overcome which means
normally you'd need more power on the coils here.
So on a regular induction motor this gap would
be very small but on here,
because we actually have the magnetic field
coming from this, which is a permanent magnet,
the strength of this permanent magnet doesn't
use up any energy continuously.
So basically the magnet strength,
from the permanent magnet rotor helps overcome the gap,
which means you don't need extra energy in the coils,
and so therefore you get your efficiency back
but because this is a permanent magnet that makes it
a synchronous motor and that means you need
some variable frequency or some approximation there
to start it and that's what all this electronics is for.
Hey look, it's a circle jig.
Well it wanders a bit, but least it spins.
I should balance this rotor somehow and I think the best way
is by putting a machine screw in here.
And that's got the counter sync on it.
And let's see.
This side seems to hang the lowest,
and consistently here so I need to cut off a little bit here
I'd say that's an improvement.
I didn't film making the rest of the blower housing
and figuring how to make the motor mount,
partially because I had a toddler roaming around the shop
and partially because I've filmed this process
many times before making other videos about building blowers.
So if you want to see more on that,
watch one of my other videos about making blowers.
See links at the end of the video.
Uh 0h. Let's try that again.
It's running at 60 watts
so it's probably a little bit overloaded.
Now it's at 50 watts.
It's not perfectly balanced but I've been experimenting
with putting little weights on various fins
and just by moving them around and seeing where
it runs the smoothest, I've kind of figured
a weight here and here puts it closer in balance.
I'm drawing just 35 watts of power, maybe 36,
and the R.P.M. is 3,600 R.P.M..
So that's working really good
but it's actually a failure because the rotor on here
is too heavy for this motor and on starting up,
it just gets confused and unless I block the air flow
it never actually makes it up to speed.
So it's just sitting at 3,100 R.P.M.
and eventually it will give up.
Right now it's given up.
But if I block the air flow when it starts,
I can see it's trying to get up to speed
but it's having difficulty.
And I think
Yes.
I guess I just have a fascination for odd ball motors
but for the most part I don't think this type of motor
is worth the trouble. But having said that,
I just swapped out this blower on this dust collector
for the one I just made because this one
sucks a lot harder.
It really collapses this hose.
The bearings on this motor are actually meant to be
submerged in water for lubrication and I just
oiled them instead so I don't know how long that will last
but I'll just use it until it breaks and if it breaks
I'll just put this old motor back on.