Balancing Freaks

Shimitup · Dec 6, 2006

I'm just curious how many machine balancing fantics are out there? I've got a curious tendency to tear everything down and balance it component by component, motors, gears, impellers fans. Partly as a stationary engineer for 25 plus years I don't like to fix things twice. Smooth equipment seems to go far to that end as well as being a thing of beauty to watch it run (not feel). Lathewise I am curious as how many have done this to their lathe motors, pulleys, chucks, etc.

Neil · Dec 6, 2006

What is your procedure for balincing? Do you perform a simple static balancing first, or do you have a machine that tells you where to remove or add material? Do you put the part in a precision rotatation device,put a dial indicator in contact with a prominent feature and use the maximum difference in reading at any 180 degree rotation as the concentricity tolerance?

JL Sargent · Dec 6, 2006

I have not balanced any lathe parts, but I have field balanced a 5000 HP fan wheel that weighed 16K lbs before. Does that count? After several callouts at 2 o'clock in the morning we (there were only 2 of us) quit offering that service.

donie · Dec 6, 2006

I have balanced the chucks and other fixtures for my Monarch 10EE lathe. I first static balanced them and sent some of them out for furthure dynamic balance. There is a notable difference in regards to accuracy that is diminshed by vibration.
I really cant say it would be worth the time for lesser machines however.

adama · Dec 6, 2006

my harrison lathe spindle is balanced so are my bridgeport 2j variator pulleys, motors are too i presume other than that i dont think much else is as standard, wihlst i can see the benifits for say coolet chucks will larger chucks perticualy independant jaw chucks realy help that much. whilst they have large rotating masses wolud the work and varying jaw diamiters make that much improvment to overall balance?

traytopjohnny · Dec 6, 2006

In my past life I was a balancing fool. I would assemble entire rotating masses and spend not all that much time and when I put them into service I felt as though they ran in a satisfactory manner. The place I worked at closed down and I have a new job where I work on lots of large pumps and the powers that be do not respect the virtues of balance and we do so much rework that I find it unbelievable. Everything I own is balanced. My ceiling fans are balanced. I use a unit named "Balmac". Very old technology but suits me just fine. John

Gary E · Dec 6, 2006

John,
Every motor above 1 HP that went into the machines your old empoyer built were balanced, little motors were not going to afect the machines performance.

I saw many 50 HP motors apart and even the little 10 HP ones that drove hydraulic pumps..
Coolant pumps were not balanced, they were small motors anyway.

Can anyone imagine a grinding machine with out of balance motors?

The Automatic Spindle Balancing feature on the Grinders was not there for looks.

daryl bane · Dec 6, 2006

When I had to repair the pulley sheave on my EE, I had it dynamically balanced. I don't think it was done originally, but it sure is smooth now. Like Donie, I think doing the chucks,etc is a great idea.

Mud · Dec 6, 2006

On one of my my Cincinnati 10VC VMCs the little 1/3hp motor that powered the cooling fan for the spindle drive motor lost a blade on it's own fan. That missing blade set up a vibration that made it just about impossible to indicate a part in with a dial test indicator in the spindle - made it shake .008 or more in the X axis but not the Y. Drove us nuts until we found the cause! I never saw an effect on the surface finish though.

traytopjohnny · Dec 6, 2006

Gary! My specialty was grinders. Have you any idea how many electric mails I walked up and down plant #1 ladden with rotating masses to the balancing dept. Countless. You have no idea how shocked I am to witness just how the "actual" world treats rotating masses. Even after countless repeated failures they still don't get it. Do you remember the old Balmac units? Rather primitive but I can still do nice work with one. Paid $20.00 for one at the auction.

Gary E · Dec 6, 2006

I dont remember what the name was... I sorta took it for granted... and yeah, the main isle was long... LOL

You know about the Auto Bal feature on the Centerless... Did ya ever see a machine started up without a wheel and with the 3 balls all on one side? Not fun... Need the wheel on there to make it work...

JS · Dec 6, 2006

I spent alot of time balancing impellers for pumps .

Everyone of them was static balanced.

Sent several over to an engine shop that had spin balancing equip they where over 2 oz off before I got ahold of them .

After complaining up the ladder for a while the quality of the product has improved .

Winfield · Dec 6, 2006

"Gooble gobble, gooble gobble, we accept her, we accept her, one of us, one of us!"

traytopjohnny · Dec 6, 2006

Heh! JS. Got a question for you. I have worked around so many rotating masses it just isn't funny. My question is let us say we have the static and or dynamic balance taken care of. What happens when the water or non specified liquid begins to flow? What about deviations on the cast impellers as they impart force on what they are pumping? How do you deal with this. What if one blade is slightly off pitch and is digging in more than the others? Will this not have an effect?

Shimitup · Dec 6, 2006

My balancing methods are crude but they seem to work. On small parts that can be mounted on shafts and held in hand I'll get my hand oily, hold the shaft and spin it against a wire wheel. Fron there its trial and error pick a spot and apply etimated weight by what ever means, no improvement or worse go 180 then 90 opposite and so on. With practice a sheave or impeller can get balanced in 15 minutes or so. large fans (large for me is 60" not 5000hp worth of fan!) get hung on a spare motor known to be smooth then lift one side of the motor with a pry bar and let it down in rapid succession (shake it) friction averages zero in this case and the heavy side drops quickly to the bottom. Traytopjohnny, Isaw your post to JS, I'd like to hear his feedback. I haven't noticed issues with flow imbalance on impellers. Could be that the volute mass and piping are heavy enough that its hard to tell. With axial fans I have definitely noticed assymetric thrust problems in adition to balance, pitch adjustments have always fixed that.

JS · Dec 6, 2006

I work for a company that makes Turbine water pumps.

I do not know the specifics / or engineering on the
forces the liquid puts on a impeller.

I will say this though ..

A impeller is either statically or dynamic balanced .

I have delt with customers who perfer static balance over dynamic . The company I work for perfers dynamic balance .

The bearings/ bushings are proportioned to properly support the bowl shaft.

The pump is also Hydraulically balanced.

The liquid puts a down thrust and or upthrust on the impellers . This force depends on the setting of the pumps and liquid volume.

An example of a potential upthrust condition is a short coupled pump.

The fluid causes this pressure .

If the impeller is damaged it is fixed.

Neil · Dec 7, 2006

I was reading in my GDT manual that to inspect for Concentricity
1. The part is placed in a precision rotating device (A good lathe with almost .0001 runout or less to measure concentricity of .001 or so?)
2. Two dial indicators are used 180 degrees apart on the datum feature of interest (the datum is the central axis).

3. The difference between the readings at any point along the circumfrence as read by the 2 dial indicators is the concentricity

So-does this mean that a STATIC method such as this can DYNAMICALLY balance a shaft ASSUMING THAT the feature being measured is the ONLY THING affecting the balance? Let us assume we are talking about a solid disk with no inside features to complicate this...I find it intriguing that simply measuring a part with dial indicators might hold the key to dynamically balancing parts! How cool is that???

Any comments? It would be fun to measure this and see sometime.......

jburstein · Dec 7, 2006

Winfield, you've been driving me crazy for the past hour. I couldn't figure out where that was from, but it just hit me. What a bizarre and obscure reference--I think you win with that one.

Neil--In theory, if you assume that you have constant density throughout your part, and you have only axisymmetric features (meaning everything is round and concentric with the axis of rotation), then yes you have pretty much guaranteed static and dynamic balance. In practice I don't believe that's a good way to insure balance of a part.

-Justin

stephen thomas · Dec 7, 2006

Didn't it morph into "Gabba gabba hey" which made it a bit less obscure?

smt

220swift · Dec 7, 2006

Is static balancing what is done a car tire?
Weight is added or removed as needed.

What is dynamic balancing?

What is a "Balmac" machine and how does it work?

Inquiring mind want to know?

Hal

Balancing Freaks

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