Balancing

Rotating masses like shafts, rotors have an infinite number of planes in the Z axis, and basically in the X and Y axis you have to be able to determine the radial position of the heavy side (or light, whichever method you choose). The complication comes from the stresses imposed on said rotating mass at higher speeds in that the Z position is difficult to locate axially. The shaft or whatever tends to "bend" at higher speeds and therefore presents a "wide" zone in the Z axis that would show as heavy (or light) The trick seems to be to narrow that down as closely as possible while at the same time finding the center of that zone in Z.

I knew an elderly gentlemen who was a wizard at this fine art. FAA certified, built funny car engines for the big boys back when, but he isn't with us any longer. I believe his son is carrying on the engine work, but I don't know anything good or bad about his balance work, if he is even doing it. if memory serves, he and his dad didn't mesh too well, and they didn't work together much prior to his demise.

With properly placed arrays of piezo elements and accelerometers I believe it could be done. For my part, the software would be the Big Elephant in the room though. Been long, and way to foggy to begin to code such an application.

Of course, it would be simpler to just have something balanced on that rare occasion or buy a used balancer if static balancing would not suffice.
 
Bob Korves said:
If you are talking about offsetting the off balance condition caused by parts that are not symmetrical or are mounted off center, so that your lathe is not jumping up and down, yes, that can be done. It is easiest to do if the work is mounted to a face plate, because there are slots for mounting counterweights. You can test the balance by taking the lathe out of gear so the spindle turns freely. The heavy side will of course be pointing down and the counterweight needs to be mounted at the top. When the spindle does not turn by itself when you let go of it, regardless of clock position, you are probably close enough. Test the results at low RPM, gradually increasing the speed. With standard chucks, it is tough to mount a counterbalance. Sometimes a balancing feature can be added to the part, either bolted on or sacrificial after completing the turning.

WARNING: Be careful, and try not to lash up something stupid. A lot of centrifugal force is created by spinning stuff, and you REALLY do not want anything flying off.

I am not aware of any commercial attachment for easily achieving a balanced condition. There are an infinite number of possible things that might be mounted to the lathe, and no attachment would work for all of them. You will need to be creative...
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Tim Lipton at OXTools did a segment on counterbalance weights for lathe chucks. He made the plate design himself.
 
brav65 said:
Tim Lipton at OXTools did a segment on counterbalance weights for lathe chucks. He made the plate design himself.
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Yes, Brooks, Tom's video was very good. When I posted earlier I thought about Tom's video and was going to mention it, but it was a while back and it is only right to provide a link to the source when it is mentioned. I will do that now, and then edit this post when I find it...

Edit: I found the video. The relevant part starts at about 10:00 into the video. Good stuff!
 
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Bob Korves said:
Yes, Brooks, Tom's video was very good. When I posted earlier I thought about Tom's video and was going to mention it, but it was a while back and it is only right to provide a link to the source when it is mentioned. I will do that now, and then edit this post when I find it...
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You are correct thanks for reminding be to be a good net citizen. Here is the link where he actually uses the weights. They are straight forward to make.

.
 
brav65 said:
You are correct thanks for reminding be to be a good net citizen. Here is the link where he actually uses the weights. They are straight forward to make.
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Beat you to it! Fastest search in the west... 8^)

Edit: Being a good net citizen is tough when it is easier to be lazy, like me sometimes!
 
dave enrico said:
..................remember years back and old machinist would mark the part on top the spin it the heavy side would always come up and he would drill if necessary on the heavy side ,after numerous times it would stop at a different location each time and he new he was close.......................
dave
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Dave,
We are all learning here and the methods that we learned many years ago are no longer used but can still be effective in the home shop. Turning a lathe into a balancing machine is an interesting goal but can get complicated and I am watching in hopes of learning something new and neat.

You mentioned spinning a part and letting the heavy spot settle and then removing some material from the part at the heavy spot and repeating until it was “close enough”. As noted by Jim Dawson this can be done without using a lathe. The lathe can complicate the process due to friction and lathe parts contributing to the apparent unbalance. I have included a couple of post below that will let you learn a little more about balance methods and terminology before getting too far down the road.

This link: http://www.conradhoffman.com/chsw.htm is a spreadsheet posted by a home shop machinist that had an interest in DIY balancing and was playing with the subject. I have not been able to find his post on the mechanics of his experiments. Note that the spreadsheet is two sheets, the first sheet is explanations the second is calculations. Hope I can find his experiment details as I recall he was using some neat DIY components for sensors like a radio speaker for generating a movement signal but then I could be wrong. The memory seems to confuse things as you get older.

This link gives some simple diagrams and definitions about balancing methods: http://lifetime-reliability.com/free-articles/precision-maintenance/Rotating_Machinery_Rotor_Balancing.pdf

Benny
The Orphanage Never Closes
 
Your project plan to perform balancing using a lathe as a platform is so interesting that I can't get it out of my head. So I went to the basement today and started digging through the piles of "stuff too valuable to throw away". I found a copy of the instruction manual for a Stewart-Warner balancing machine Model 2380. A photo if this type of balance machine is shown at this link: http://bentonmachineandautoparts.weebly.com/uploads/4/7/5/5/47557655/5072240_orig.jpg , kind-of similar to a lathe, right?

I have not found an online copy yet but would think that reasonable portions could be shared for learning purposes. Let me know if interested.

Benny
 
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