Muffin fan installation

[Father Haskell]

Should these be mounted with the faces plumb or level? The RS
273-241 4" fan (new unit) that I'm trying to build an air circulator
from seems not to run at constant speed when I test it flat on
the bench.

 

[default]

Should these be mounted with the faces plumb or level? The RS
273-241 4" fan (new unit) that I'm trying to build an air circulator
from seems not to run at constant speed when I test it flat on
the bench.

Not sure what you are saying but fans can mount in any position; they
are usually mounted vertically (Edge down). Bearings on most are
probably happiest that way

Constant voltage? Constant restriction to air flow? Several fans
running parallel from the same supply may try to "sync" and vary the
speed as they drop in and out of synchronization.

 

[Father Haskell]

are usually mounted vertically (Edge down). Bearings on most are
probably happiest that way

As I suspected.

Constant voltage? Constant restriction to air flow? Several fans
running parallel from the same supply may try to "sync" and vary the
speed as they drop in and out of synchronization.

Fresh out of the box, solid, clean electrical connection. Just
sat it on the bench and let it run.

 

[Don Kelly]

As I suspected.


Fresh out of the box, solid, clean electrical connection. Just
sat it on the bench and let it run.

---------------
Sitting a fan flat on the bench is not a good test. You are blocking any air
flow and a fan, to do anytthing needs to be able to move air. It may be
having a problem in that much of the time the load on the fan is 0 but as
air leaks in the load can change. If you set it on edge it would be better
as then you have unobstructed air flow. Try it.
NB a fan blowing into a heat sink is not equivalent as the heat sink allows
air flow.

 

[Father Haskell]

Sitting a fan flat on the bench is not a good test. You are blocking any air
flow and a fan, to do anytthing needs to be able to move air.

2 x 2 spacers under the frame set far enough apart not to
throttle the airstream. Fan RPM was erratic, as if the
fan was designed without thrust bearings.

 

[default]

2 x 2 spacers under the frame set far enough apart not to
throttle the airstream. Fan RPM was erratic, as if the
fan was designed without thrust bearings.

How about flipping it 180?
If you set it on edge the speed remains constant?

Interesting idea with the thrust bearings. Ball bearings shouldn't
matter they can support some axial loading without a problem - and the
impeller is usually very light.

Sleeve bearings might be another matter. Most of the fans I've
disassembled had ball bearings - but the ones with sleeves make little
or no provision for thrust loading - a bronze washer or two or the
really cheap ones a few plastic washers.

One bearing is sometimes visible under a paper or plastic label on the
stationary part of the housing. You can look to see what you have, if
that's the case.

Sleeve bearings are nice when you want a quite fan - and they
frequently outlast ball bearings - but they should be mounted on edge.
They are rare in fans

And you are talking about Radio Shack . . . their parts aren't always
the highest quality. You'd be better off with a mail order surplus
parts outlet.

 

[Don Kelly]

2 x 2 spacers under the frame set far enough apart not to
throttle the airstream. Fan RPM was erratic, as if the
fan was designed without thrust bearings.

 

[Father Haskell]

Fine. Complicates the circulator's design (tower, corner of
room, simple preferred because it looks better by its relative
absence), but workable.