Rotex RO150E vibration and counterweight orientation

[Johnhend]

I purchased a used Rotex RO150E that seems to vibrate excessively at the tool. With the power head broken down, when the upper counterweight sits at 12:00, the lower counterweight sits at about a 2:30 position. Looks like it was serviced at one point. What orientation should the two counterweights be to each other?  12:00 and 6:00?  Seems like that would balance the vibration.

 

[AlexThePalex]

Your picture isn't really very clear.

I have serviced lots of Festools, but never this sander though, so the only thing I can go on is the Ekat exploded view picture of the sander. If both weights are on the same axle, logic would dictate they'd be in line. If the weights you refer to are items 12 and 28, you'd probably have to place them exactly above each other. Can they freely move or are they fixed in place?

[attachimg=1]

 

[Johnhend]

Yes I'm referring to parts 12 and 28. They both appear to be press fit and don't move. If the previous repair involved replacing anything on that shaft they would have had to remove at least one of the weights. I can find pics of the porter cable version online and it appears to have two weights that are at 6 and 12 o'clock orientation (is that what you mean by in line? Or 12 and 12 o'clock?). The 6 and 12 orientation seems to make the most sense in balancing the vibration, just like a fan or tire.

 

[AlexThePalex]

Yes I'm referring to parts 12 and 28. They both appear to be press fit and don't move. If the previous repair involved replacing anything on that shaft they would have had to remove at least one of the weights. I can find pics of the porter cable version online and it appears to have two weights that are at 6 and 12 o'clock orientation (is that what you mean by in line? Or 12 and 12 o'clock?). The 6 and 12 orientation seems to make the most sense in balancing the vibration, just like a fan or tire.

I think 12-12 o'clock is how it should be. The weight is meant to introduce a bit of vibration, that is what makes the eccentric motion happen. So you don't want to cancel/dampen the vibration with a 6-12 orientation.

The 12-12 and 6-12 are postion where both weights are in line. When you have any other orientation, that's when the problems happen, that's when you get excessive vibration. If the sander was previously serviced and a weight removed, then it has probably shifted due to not being clamped back tight enough.

It is going to be difficult though to properly fit these weights if they're press fit, you need a special tool for that.

 

[Johnhend]

Thanks again for the help. I was able to rotate the top weight to a 6/12 orientation by tapping it with a hammer. It seems to be working great now. The bottom weight is heavier and seats into a recess on the threaded offset side of the shaft so it can only sit at one orientation.  I haven't tried it in rotex mode and don't have another Rotex sander to compare it to but I'll try the 12/12 orientation if it seems to underperform.