impeller balance

Ugh........

So how's he know just how much to take off?

Krutch said:

So how's he know just how much to take off?

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"Trial & lot's of error"

Until the operator get's tired of futzing around, then the "accuracy" goes down.

that video made me so sick I can't find words to express what I think.

Last time I checked, static balancing was a valid, but not particularly accurate method of balancing. A short stubby bronze impeller would probably balance reasonably well with such a technique compared with a longer object like an induction motor rotor which would be more prone to balancing well statically but still retain dynamic imbalance. For a black sand bronze casting like that impeller, the pattern inaccuracies would impart a consistent imbalance to the one area of all the impeller castings that could be fixed by removing the same amount from one spot. Judging by the massive shaft it runs on, any remaining imbalance could be handled by plain bearings.

It's not a rocket engine turbopump running at 200K RPM, most likely an agricultural irrigation water pump running off a diesel for short periods of time at a few thousand RPM.

SAG 180 said:

Last time I checked, static balancing was a valid, but not particularly accurate method of balancing. A short stubby bronze impeller would probably balance reasonably well with such a technique compared with a longer object like an induction motor rotor which would be more prone to balancing well statically but still retain dynamic imbalance. For a black sand bronze casting like that impeller, the pattern inaccuracies would impart a consistent imbalance to the one area of all the impeller castings that could be fixed by removing the same amount from one spot. Judging by the massive shaft it runs on, any remaining imbalance could be handled by plain bearings.

It's not a rocket engine turbopump running at 200K RPM, most likely an agricultural irrigation water pump running off a diesel for short periods of time at a few thousand RPM.

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That was a tapered mandrel, not the finished shaft.

How do you figure it's run with a diesel engine for short periods of time ? What is your evidence from the video to support this claim ?

That impeller looks very much like the local sewage treatment
plants, they run 3600 rpm on a 20 hp electric motor 24/7

digger doug said:

That was a tapered mandrel, not the finished shaft.

How do you figure it's run with a diesel engine for short periods of time ? What is your evidence from the video to support this claim ?

That impeller looks very much like the local sewage treatment
plants, they run 3600 rpm on a 20 hp electric motor 24/7

Click to expand...

It looks very similar to impellers on diesel irrigation pumps I've seen on river banks in farming areas. If it's a sewage pump, it would be a very tiny one as the pumps I've worked on are around 3+ feet diameter. How about I message the guy and ask him what their application is?.

That's a turbine pump impeller, usually there will be a stack of between two and several of them on the pump. There is not a tapered mandrel, it's a straight shaft with a tapered split collet that locks the tapered ID of the impeller to the straight shaft. You can see him tap the collet into the impeller with the length of pipe after he "balances" the impeller.

Doubtful it's a sewage pump from the looks of that impeller. Those type pumps in that size are very easily clogged and/or damaged by adverse conditions. More likely a fresh water pump for a local water authority or maybe irrigation. That one in a stack of three to six would run a 20-50hp motor at 3600rpm.

Looks like a standard Berkeley jet impeller. Used for both jet boats and irrigation pumping. The balancing looks fine to me, but what do I know? Maybe someone can explain to me why the comments like "made me sick" or the Youtube comment "You should have the living shit kicked out of you"? Static balancing insufficient for the rpm's? Typical Berkeley jet will run 4500 rpm's.

Maybe someone can explain to me why the comments like "made me sick" or the Youtube comment "You should have the living shit kicked out of you"? Static balancing insufficient for the rpm's? Typical Berkeley jet will run 4500 rpm's.

If it were 1885 and there were no other form of balancing available, this would be totally acceptable. Would be the equivalent of some guy cutting a keyway with a cold chisel. It is better in balance, but there is still no way of knowing exactly how much out of balance it was, or how much he took off. Modern balancing comes in grades, just like threads. Your parts should be balanced the the specified grade.

I run two computer balance machines and do primarily motor shaft/rotor assemblies and impellers. You put in a bunch of parameters including overall weight, distance between bearing points, the rpm and the grade of balance requires. The computer screen shows where to remove or add weight to balance and allows you to specify the RPM that the part is to run at. A part running at twice the rpm of another will have half the tolerance in the balance. I'll assure you, I could make some money off that guy if he thinks his parts are balanced within tolerance.