Disk Balancing Media
Published: 11 years ago
Balancing a steel disk, video by request
I was asked to post video of how I accurately balance a precision machined steel weldment. This video is dull folks. Very dull. Like watching paint dry. I made this video and even I can't watch it...
This kind of balancing starts by leveling thin hard precision ground blades into a nearly perfect plane that is perfectly level. I used a master precision level calibrated with divisions of 50 millionths per inch and .0005 thick aluminum foil as shims. This is very level. There is a finely finished precision ground hardened steel shaft run through the disk. When this shaft with the disk on it is sit on the blades it is free to turn with extremely low drag. So the heavy side will find the bottom with the high degree of accuracy.
All of this happens very very slowly. Hence the painfully tedious video. Over all I think the entire process takes about an hour because I leave it alone and go do something else while it sorts out.
At first the disk settles down. Then I add weights to the disk. At first I use large weights that weigh 3/4 of a gram. I add one weight and confirm it is not enough. Then I add another. Then another. With the third weight I have crossed the tipping point. So I drill out two shallow holes that are equivalent to the two weights and start the process over again with finer weights.
The finer weights weigh .185 grams, which is about .0065 ounces. The first little weight is not enough. The second it too much. So I drill a shallow hole ( not more than a dill point) equivalent to one little weight and sit the disk on the beams once again and let it settle out. Once it is settled I add a small weight at the top and let the disk come around and settle down one last time as a final check. that small weight was enough to pull the disk all the way around to the bottom. At .0065 ounce at about 4" from the center of rotation that weight, in theory, can not exert more than 26 thousandths of an ounce inch of torque. So, considering margins for error, it is probably pretty safe to say it is balanced to better than .03 ounce inch, which is fine for the application.
I was asked to post video of how I accurately balance a precision machined steel weldment. This video is dull folks. Very dull. Like watching paint dry. I made this video and even I can't watch it...
This kind of balancing starts by leveling thin hard precision ground blades into a nearly perfect plane that is perfectly level. I used a master precision level calibrated with divisions of 50 millionths per inch and .0005 thick aluminum foil as shims. This is very level. There is a finely finished precision ground hardened steel shaft run through the disk. When this shaft with the disk on it is sit on the blades it is free to turn with extremely low drag. So the heavy side will find the bottom with the high degree of accuracy.
All of this happens very very slowly. Hence the painfully tedious video. Over all I think the entire process takes about an hour because I leave it alone and go do something else while it sorts out.
At first the disk settles down. Then I add weights to the disk. At first I use large weights that weigh 3/4 of a gram. I add one weight and confirm it is not enough. Then I add another. Then another. With the third weight I have crossed the tipping point. So I drill out two shallow holes that are equivalent to the two weights and start the process over again with finer weights.
The finer weights weigh .185 grams, which is about .0065 ounces. The first little weight is not enough. The second it too much. So I drill a shallow hole ( not more than a dill point) equivalent to one little weight and sit the disk on the beams once again and let it settle out. Once it is settled I add a small weight at the top and let the disk come around and settle down one last time as a final check. that small weight was enough to pull the disk all the way around to the bottom. At .0065 ounce at about 4" from the center of rotation that weight, in theory, can not exert more than 26 thousandths of an ounce inch of torque. So, considering margins for error, it is probably pretty safe to say it is balanced to better than .03 ounce inch, which is fine for the application.