"Pete C." wrote in message
ster.com...

Karl Townsend wrote:

What happens when you change the tension on the fan drive belts? If
they
are
implicated at all, that'll change the resonant frequency. It's a bit
far
to
drive over to Blighty so we can instrument it up and workout where the
resonance is :-(

Mark Rand (Did similar work on power station foundations once)
ETFM

I've never tried that. I keep the eight belts pretty tight, 1/2"
deflection
in the three foot between pulley spacing. can't go tighter, I'd take out
bearings. What do you think running loose would do? Not much margin here,
I
smoked all the belts once, pretty spendy to rebelt this unit.

Karl

I recommend you closely inspect the spray pump as noted in my other
post. If it is a triplex pump like the one on the other unit you posted
a link for it could very well produce a "lumpy" torque load if one of
the pistons was not functioning like from a stuck inlet valve.

The other thought, is that if this lumpiness occurs once per PTO shaft
revolution i.e. 9 times a second, something may be bent, such as the
shaft the pulleys are on, causing the belt tension to cycle every
revolution.

Thanks for the thoughts. This unit has a centrifical pump, no bumps there
plus it only uses a couple horse. You have a thought on bent, I know its not
in the shafts, but possibly the fan itself is bent. The entire fan could be
removed and put on some sort of unit to check balance and vibration. Anyone
know where I might find equipment to do this?

Karl