# Rotator Drum balancing

1. Jan 17, 2016

### Carrollwelding

I have a rotating drum at 3200 rpm weight 900lb

Would placing a set amount of oil in the drum help the dynamic balance of it?

2. Jan 17, 2016

### Nidum

Very unlikely to improve the dynamic balance .

Can't say anything more useful without knowing the actual set up you have .

3. Jan 17, 2016

### SteamKing

Staff Emeritus
Putting fixed weights on the drum is the way to correct any dynamic balance problems. Fluid motion is too unpredictable to accomplish the same result.

4. Feb 2, 2016

### David Macclain

Balancing machines for disc-shaped rotors such as brake discs, clutch discs, fans, pump rotors or flywheels must be flexible to meet all requirements since they often vary in shape, size and weight.

5. Feb 3, 2016

### Rx7man

That's a heck of a speed for such a heavy drum!.. I don't think adding any fluid to it would help much with that kind of weight.

What are the approximate dimensions of this drum? My mental image of it is about twice as long as it's diameter (otherwise you'd call it a pipe), probably a few feet around, a couple inches thick to get to that weight, with a pretty big shaft going through it... Correct any of my assumptions please!

Perhaps if you could mount each end bearing on a load cell you could monitor the vibration as you rotate it, and add/subtract weight as necessary to get the right balance?
I'd use an Arduino, and have 1 sensor that fires once per revolution, and each load cell connected to it... from there, you can have the Arduino calculate how many degrees after that sensor fires it hits the peak load, and figure out where that relates to on the drum.

6. Feb 13, 2016

### S_Happens

Like was already stated, the fluid will most likely not help the balance. The only way I can imagine that working is if the imbalance was solely due to runout of the ID (internal diameter). The closer the density of the fluid to the density of the metal, the closer you could get the balance.

The balancing should be done by adding OR removing solid weight from the drum. Rx7man hints at the balancing process, although it's not necessarily so straightforward. The location where the effect of the imbalance is seen changes in phase from the location of the actual imbalance with rpm. This change is in relation to natural frequencies and damping in the system. It is necessary to know some more things about the system and/or do some significant testing in order to understand this and properly balance. I also don't know that a load cell can give you that kind of accuracy (19.2 kHz for 1 degree resolution).

That said, your 3200 rpm drum is almost certainly well below its first natural frequency, and if so the location of the imbalance and where the effect is seen should be very close together in phase. I'm assuming you don't know how much imbalance you have, otherwise this wouldn't be a question. What is this drum doing that it doesn't already have liquid in it?