Compressed air and cleaning fans

On Thu, 11 Sep 2014 06:11:07 -0700 (PDT), Phil Allison
<pallison49@gmail.com> wrote:

Jeff Liebermann wrote:
The bearing/bushing burnout theory is also interesting. This
particular fan, Mechatronics Model F8025H12B2 12v 0.145A claims to
have ball bearings inside. I'm not going to take it apart because I
know that it doesn't have ball bearings. It uses bushings like all
such cheap PS fans.

Peal of the paper label and take a look sometime.
Brushless DC fans mostly use ball bearings.
... Phil
Click to expand...

I took apart the fan and much to my amazement, found two ball
bearings.
<http://802.11junk.com/jeffl/pics/megatronics-fan/>
I just hate it when I'm wrong. I have some more junk fans somewhere.
I'll see what I can find. In the past, they were mostly bushings, but
I guess that's changing, especially since this fan was fairly new.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
 
On Thu, 11 Sep 2014 14:47:15 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote as underneath :

On Thu, 11 Sep 2014 06:11:07 -0700 (PDT), Phil Allison
pallison49@gmail.com> wrote:

Jeff Liebermann wrote:
The bearing/bushing burnout theory is also interesting. This
particular fan, Mechatronics Model F8025H12B2 12v 0.145A claims to
have ball bearings inside. I'm not going to take it apart because I
know that it doesn't have ball bearings. It uses bushings like all
such cheap PS fans.

Peal of the paper label and take a look sometime.
Brushless DC fans mostly use ball bearings.
... Phil

I took apart the fan and much to my amazement, found two ball
bearings.
http://802.11junk.com/jeffl/pics/megatronics-fan/
I just hate it when I'm wrong. I have some more junk fans somewhere.
I'll see what I can find. In the past, they were mostly bushings, but
I guess that's changing, especially since this fan was fairly new.
Click to expand...

Like most of us your only wrong some of the time!
Iv done a no. of brushless PC fan "keep going" repairs over the PC
years, perhaps 20-30, most have been sintered oilite bearings, these are
the ones that tend to go sticky after about 5 years use depending, slow
down and quietly stop eventually, usually they dont burn out windings
but they do overheat. They can be relubricated to use but the lube will
need replacing after only a year or so depending.
RPM measured for interest!
I took a fan out of the spares box yesterday: Bog standard 12v 0.25A
80mm case fan, definitely not ball bearing!
12v normal speed 2520 rpm
air hose "by mistake 1s breeze" 4200 rpm (turbine noise definite)
airhose straight on blast 7900 rpm
airhose 80 psi directed single jet 9750 rpm. Still worked OK afterwards!
IMHO its always safer to stop the fan(s) turning when you use an
airhose. C+
 
Charlie+ <charlie@xxx.net> wrote:
On Thu, 11 Sep 2014 14:47:15 -0700, Jeff Liebermann <jeffl@cruzio.com
wrote as underneath :

On Thu, 11 Sep 2014 06:11:07 -0700 (PDT), Phil Allison
pallison49@gmail.com> wrote:

Jeff Liebermann wrote:
The bearing/bushing burnout theory is also interesting. This
particular fan, Mechatronics Model F8025H12B2 12v 0.145A claims to
have ball bearings inside. I'm not going to take it apart because I
know that it doesn't have ball bearings. It uses bushings like all
such cheap PS fans.

Peal of the paper label and take a look sometime.
Brushless DC fans mostly use ball bearings.
... Phil

I took apart the fan and much to my amazement, found two ball
bearings.
http://802.11junk.com/jeffl/pics/megatronics-fan/
I just hate it when I'm wrong. I have some more junk fans somewhere.
I'll see what I can find. In the past, they were mostly bushings, but
I guess that's changing, especially since this fan was fairly new.

Like most of us your only wrong some of the time!
Iv done a no. of brushless PC fan "keep going" repairs over the PC
Click to expand...

I'm going to have to steal that "keep going" repair term.
 
"well for brushed motors, there can be mechanical differences. Brushed
motors can be "timed" to alter speed/torque "
Click to expand...

I saw that on a vacuum cleaner motor a long time ago. It had slotted mounting holes so you could adjust it.

Bottom line here though is that if it has ball bearings and no brushes all you have to worry about is the blades flying apart, or the squirrel escaping...
 
jurb...@gmail.com wrote:

Bottom line here though is that if it has ball bearings and no brushes all you have to worry about is the blades flying apart, or the squirrel escaping...
Click to expand...

** Anyone familiar with RC electric vehicles and planes would be well aware that small DC motors with bronze bushings and brushes are fine at 20,000 rpm and those with ball bearings can be used safely up to 50,000 rpms.

DC fans are simply not in the race.


..... Phil
 
"Phil Allison" wrote in message
news:f89fef00-be8b-4774-98dc-44fceb2d6fb8@googlegroups.com...

> DC fans are simply not in the race.

But the ball bearings are. (ba-DUM!)
 
In article <lusbd3$ob0$1@dont-email.me>, grizzledgeezer@comcast.net
says...
"Cydrome Leader" wrote in message news:lurg7m$i09$1@reader1.panix.com...

I did once basically explode a squirrel cage blower with the
pressure side of a vacuum cleaner. It ran so fast that the fins
expanded and touched the housing and became a bent-up
mess before flying out of the housing across the room.
I was not expecting that.

"NO ONE expects a squirrel-cage blower explosion..."
Click to expand...

especially when the squirrel is still in it!


Jamie
 
William Sommerwerck <grizzledgeezer@comcast.net> wrote:
"Phil Allison" wrote in message
news:f89fef00-be8b-4774-98dc-44fceb2d6fb8@googlegroups.com...

DC fans are simply not in the race.

But the ball bearings are. (ba-DUM!)
Click to expand...

ha.
 
On Thu, 11 Sep 2014 07:25:36 -0700, "William Sommerwerck"
<grizzledgeezer@comcast.net> wrote:

"Cydrome Leader" wrote in message news:lurg7m$i09$1@reader1.panix.com...

I did once basically explode a squirrel cage blower with the
pressure side of a vacuum cleaner. It ran so fast that the fins
expanded and touched the housing and became a bent-up
mess before flying out of the housing across the room.
I was not expecting that.

"NO ONE expects a squirrel-cage blower explosion..."
Click to expand...
Years ago I was cleaning some bearings and was blowing the solvent out
with compressed air. I knew this was bad news but it was interesting
to really spin up up bearings. Anyway, I put this bearing on my index
finger and spun it up real good. The pitch of the whine from the
bearing rose higher and higher as the speed increased. Just when the
pitch got so high I couldn't hear it the outer race of the bearing
exploded and the balls went flying. I thought my finger was broken
but it just hurt like hell. Needless to say I bought new bearings.
Eric
 
On Fri, 19 Sep 2014 17:30:41 -0700, etpm@whidbey.com wrote:

Years ago I was cleaning some bearings and was blowing the solvent out
with compressed air. I knew this was bad news but it was interesting
to really spin up up bearings. Anyway, I put this bearing on my index
finger and spun it up real good. The pitch of the whine from the
bearing rose higher and higher as the speed increased. Just when the
pitch got so high I couldn't hear it the outer race of the bearing
exploded and the balls went flying. I thought my finger was broken
but it just hurt like hell. Needless to say I bought new bearings.
Eric
Click to expand...

I had something like that happen to me with ball bearing assembly. The
problem was that the balls were equally spaced around the bearing and
held in place by a plastic retainer affair. As long as the bearings
were equally spaced, everything worked just fine. However, if one
removes the plastic spacers, all the bearing fall to one end of the
bearing assembly, the whole thing falls apart. I managed to do that
with some solvent, which embrittled the plastic spacers when the
solvent dried out. When I spun the bearings at high speed using air
pressure, the plastic cracked and I had balls flying everywhere.

Blundering forward, I discussed the problem with a competitor (who is
conveniently located next to my office). He mentioned that he has had
problems using compressed air to clean CPU fans on MacBooks. When he
uses compressed air, and overspeeds the fans, they usually work when
he's done. A week or two later, the customer returns with complaints
about fan noise. I've seen this exactly once with a PC laptop CPU
fan. What seems to be happening is the high speed causes heating,
which then causes the dried out oil to reflow. Centrifugal force
redistributes the oil away from the main shaft bushing, where it again
dries out. That leaves the shaft dry and unlubricated. The reason I
haven't seen it much on PC laptops is that I usually lube the CPU fans
on laptops with "turbine oil" even if they seem to be working
normally. I can spin those all day long, and the oil will remain
fluid and functional. I learned long ago that this prevents return
visits and complaints.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
 
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