On Dec 7, 8:08 am, Zephyr wrote:
On Dec 7, 2:48 am, (Dave Martindale) wrote:





Zephyr writes:
My question is, is that normal? should the "drive shaft" on an
electic motor have some play in any direction?
Is the the play in the shaft there by design?

How large a motor is this?

If the motor has ball bearings, there will be very little end play,
probably too little for you to feel. But it's pretty common for
fractional-horsepower electric motors to use bronze sleeve bearings
instead of ball bearings, and sleeve bearings allow for axial movement
of the shaft through the bearings. There will be thrust washers of some
sort to prevent the shaft from moving *too* far, but there may be
substantial end play between the two points where the thrust washers
operate.

But why is it noisy? Even with sleeve bearings, the motor is usually
put together so that the magnetic field (when operating) pulls the
rotor to a point about half-way between its limits of play, and the
thrust washers don't need to do anything. If this motor drives a fan,
and the fan blows air parallel to the shaft, then it will put some end
thrust on the shaft and might even pull the shaft against one end of its
travel. Mounting the motor with the shaft vertical may do that too,
courtesy of gravity. Even then, the thrust bearing is steel running on
bronze, and should be quiet unless worn or unlubricated.

Dave

Its not a very large motor at all, it only powers a fan for the
stove, nothing else.
its has 3 speeds controlled by a heat sensitive switch.
the fan makes the most noise at lower speed.

what I think is making the noise is the shaft is banging back an forth
in the housing.
the air pressure from the fan blade pushes the shaft back in the
housing, but I'm guessing the magnetic force tries to pull it to the
center like you mentioned.
so when its on slower speed, the shaft has less air pressure, and can
"bounce" when its on a higher speed, the fan pressure overpowers the
magnetic force and pushes the shaft back in the housing.

the noise it makes is not a squeaky bad bearing noise, but a
"bang,bang" sound of the shaft hitting front and back, this is
amplified by the cast stove, and makes such a racket that you can't
talk over the sound.

I guess I'm nerveous about buying a new motor if is just going to
start acting in the same way as the existing one, which from an
operational standpoint still works perfectly.

Dave- Hide quoted text -

- Show quoted text -

Has it always been noisy? Have you run it when not mounted in the
stove and is is noisy then?

I it possible that something has caused the fan to be out of balance.