I think this one was going for around 40 years, or more, probably more.

I thank you all for the replies but it has become a moot point, the
replacement motor burned up today. I think going to 1750 on the drive
pulley did it. The load on such fan blades increases pretty much
exponentiall with RPM so I think it was just too much, even with the
bigger motor. It was noisy. I know the driven shaft bearings are loos
as a goose, but so what. We can make new ones.

I observed the fan and if it were the driven shaft bearings locking up
one side of the belt would've been tight.

Now that I think of it, this motor was not from a washing machine. Two
wires that is it. Even alot of motors from the 70s had at least two
speeds, to facilitat the gentle cycle. The old Kemores only switched
speeds for this, the transmission took care of the rest. This is more a
standard frame machinery motor. Perhaps it was from a VERY old furnace
that did not have speed control. The motor control consisted of a
temperature sensor in the plenum.

Regardless of what it was, I saw smoke. Brushes generally don't smoke
and they usually don't cause the lights to dim. When I heard the sound
change and the lights dim I looked at it, and that is how I know the
belt was not overstressed. The motor is gone.Unless there is a
possibility one of them dislodged and shorted to the frame, however
this unit is not grounded so if that caused the smoke the winding
insulation must be breached.

We have a pretty good sized fractional HP DC motor with a speed
control, but that is slated to go on one of the lathes.

I was just looking at the pitch of the blades on this thing, talk about
steep. I don't care about the fanshaft bearings, as long as they are
free. In fact, when the first motor went that's what I thought it was.
Then with the thing apart I saw that the friction was in the motor
shaft, not the driven shaft.

Now it just fired up again. It went off on thermal no doubt. I still
have to do something, I can't let this thing run unnattended. Thing
that bothers me is how soon it went off on thermal, maybe the driven
shaft bearings are locking up ?

Either way, driving it that fast is not a good idea. It is beyond
design limits. I still need options. The blade pitch on this thing is
awesome, it STARTS at about 45 degrees and the output edge is just
abnout paralell with the shaft ! When we put this motor in we ran it
outside in the yard, it threw a breeze over to the neighbors. It was
sitting on a chair and made the grass look like there was a windstorm.
Also being around 20" in diameter, with a mask, it moves some serious
air. As we have trees around here, I didn't have to use my AC even once
last year.

If I were to install the same type of motor, which I might, I really
need to reread all your responses. I only skimmed them because of the
smoke I saw today, but I will read them in depth and get back to you.

The cheapest way is just get another of what I got. Even if I have to
setup my own start relay, start it at full then go to the duty cycle
control or whatever. If I don't push it so hard it should last, and,
the way it's running now you can't light a match in here. That's nice
when it is in the 90s, but right now it is too much.

I have people coming over soon, and I am glad the thing simply works at
the moment. Later I will read everything and get back to you.

One respondant mentioned duty cycle. I kind like that, don't bother
rectifying anything. Just use an SCR. I could trigger it from a single
stage flip flop then to get the 30 Hertz. Heck I could even do 20 Hertz
with flip flops, and just cut the duty cycle accordingly.

JURB