"Tim Wescott" wrote in message
...
Karl Townsend wrote:
I got so much help on my sprayer, I'm trying again...

Full time investigation and part replacement has me working on this
theory of the problem cause: The squirrel cage fan is out of balance. It
is barely detectable because the fan has a 2" solid steel shaft and some
serious pillow block bearings mounted solid to a beefy frame. At the
resonate RPM, this imbalance feeds on the slack in the drive line. Any
system upset causes the fan to become unstable and it lurches back and
forth.

I've called around and not found a place to dynamic balance something
like this. Are there any home brew methods? Or other suggestions? Its
built so solid I don't think I'm looking for a minor imbalance.

Something like this, only bigger?

http://www3.towerhobbies.com/cgi-bin...&I=LXHY61&P=ML

Before you dynamic balance, can you check the static balance? If the
static balance is perfect then I'd doubt that the thing is out of dynamic
balance.

Yeah, but you would need almost laboratory conditions, as the rotation
magnifies imbalance forces according to V^2/R. small = big!


If those bearings aren't as free as free can be then you've got a problem.
How much of a pain is it to take the fan out? Could you use the "knife
edge" with the fan shaft on a couple of angle irons, corner up?

Or: can you take the shaft out, and make an adapter so the thing will go
on a truck tire balancer?

I suggested dynamic balancing at a good garage, altho come to think of it, I
haven't seen this in a while
Altho, ackshooly, VP Tires, Yonkers NY does dynamic balancing -- $10 per
tire. Puts weights on the inside AND outside of the rim, per the pyooter.
Great place.

Vinny at VP said static balancing went out with horses'n'saddles -- direct
quote.

Whether he could do Karl's squirrel cage is another story.
BUT, if Karl were to go to a place like this, and himself make the mounting
adapters, I'm sure it would work, altho these machines might be used to
measuring more forces from big tires/rims than a squirrel cage might offer.

The Fluke gadget is the real solution, and actually sumpn that might be a
worthwhile purchase in a number of shops, as it proly pays for itself in
bearings. Even on the flywheel/pulley of compressors, etc, or multi-step
pulleys in old drill presses, etc..
--
EA


--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com