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Drum Sander Motor Help

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Forum topic by PaulfromVictor posted 03-16-2010 02:16 AM 1102 views 0 times favorited 6 replies Add to Favorites Watch
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PaulfromVictor

224 posts in 2810 days


03-16-2010 02:16 AM

Last week the weather finally broke, and I was able to put some poly on the drum sander frame I started a couple months ago.

Unfortunately, my kodak easyshare software is crashing my computer so I cannot provide any pictures for support.

This is a drum sander similar in design to Stewart’s and Autumns. The Drum is 5” diameter, 22” long on a 3/4” rod. 26” is the total width of the machine. It is waist high. The motor is a Baldor 2 hp 3450 rpm. I intended to decrease the rpms to 1750 with a 2:1 pulley ratio. The pulleys I ended up with are 4” on the drum, and 3’ on the motor. So, the speed is significantly higher than the planned 1750.

The problem I am having is with vibration. The motor itself is fine. When the belt is not attached, it purs like a kitten. When I attach the power twist belt to the hanging motor and to the drum, the whole thing vibrates like crazy. It skates across the floor. I have tried both shortening and lengthening the belt, and also adjusting the pulley in and out on the drum rod. Nothing seems to fix the vibration. I am confident that I have the belt correct side out, and rotating the correct direction (power twist belt has arrows indicating direction).

My only thought is maybe the drum is spinning too fast, but I don’t want to start buying pulleys as a guessing game. I already had the 4” pulley for the drum, but was not able to find a 2 inch pulley for the motor with a 7/8 inch arbor.

Any suggestions?


6 replies so far

View TopamaxSurvivor's profile

TopamaxSurvivor

17671 posts in 3140 days


#1 posted 03-16-2010 05:51 AM

That is what I would do, slow it down.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View EEngineer's profile

EEngineer

1061 posts in 3077 days


#2 posted 03-16-2010 10:58 PM

Hmmmm, The Drum is 5” diameter, 22” long on a 3/4” rod.

That’s a lot of mass. How sure are you that it is balanced? Any imbalance in that drum is sure to show up more at 2600 RPM but I’ll bet it still shakes at 1750.

-- "Find out what you cannot do and then go do it!"

View jm82435's profile

jm82435

1284 posts in 3206 days


#3 posted 03-17-2010 11:07 PM

ditto what eengineer said. How did you true up the drum?

-- A thing of beauty is a joy forever...

View Michael Murphy's profile

Michael Murphy

452 posts in 2469 days


#4 posted 03-18-2010 12:15 AM

What’s the drum consist of and how did you get it balanced? It sounds like it needs to be balanced better.

You might be able to balance it by using some straight edges a foot long or so, set up to be level and coplanar set apart far enough for each end of the shaft to sit on. Make sure the pulley and all collars and things are on the shaft and marked so you can put them back in the same places with the same orientation to the drum.

With the shaft on the straightedges, gently roll the assembly and mark the lowest point when it stops. Do that a few times to see if it is consistently the lowest point. If so that would indicate it’s too heavy at that spot. Figure out how to add some weight opposite that spot (add a small screw) or remove some weight (drill a small hole) from that lowest area and repeat the process several times.

Machine shops balance all kinds of stuff and they might be able to help you with it. You would still need a way to add or remove weight.

-- Michael Murphy, Woodland, CA.

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PaulfromVictor

224 posts in 2810 days


#5 posted 03-18-2010 08:13 PM

Slowing down the drum was the fix. I was having some difficulty getting the appropriate sized pulleys to ratio the motor speed in half. I was using a 4:3” ratio when I was having the issues. I bumped the drum pulley to 6”, so it is now at 6:3. That effectively cuts the 3450 motor speed in half. The vibration has ended. Smooth as silk now.

Thank you for your replies.

View TopamaxSurvivor's profile

TopamaxSurvivor

17671 posts in 3140 days


#6 posted 03-19-2010 02:35 AM

Glad you got it going. That is one of the first things I look at when there are problems with new equipment; the motor speed. Lots of times they just trip the overloads, but without a load on the motor, things get a bit more involved like you exciting like what yoiu had going on. Dancing all over the room ;-))

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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