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abn
10-16-2002, 03:34 AM
Just wondering if anyone can recommend a good reference test on balancing and balance fixtures.

I mean it seems pretty simple to me for cylindrical work (wheels, flywheels, fans with a hub etc.)...use knife edges a precision level to set up level and parallel and a good round center shaft--Let the work spin and record the low spots and remove/add weight until the low spot is no longer a low spot and settles in a random position.

But like many things, there's probably more to it than meets the eye. How do computer spin balancers work? What are the critical dimensions when setting bob weights on a crankshaft and why? A motorcycle shop I used to go to used a shop fabbed strobe light balancer to spin balance wheels...how does that work? Could you use some sort of floating hub and say a 10:1 lever type indicator to indicate wobble and hence perform dynamic balancing?

I've never run across a "standard" text on balancing and the machines of dynamic balance.

Forrest Addy
10-16-2002, 04:02 AM
I dunno if this will help.

As it happens I noticed a book in Barnes and Noble out of print (great place to browse)

"Fundamentals of Balancing" Schenck Trebel, 1983 who happen to be world powers in machine balancing.

When I was an apprentice I looked at a book dating from the late '30's where they decribed static balancing, balancing by static roll, the Yakimoff balancer and the various kinds of balancing machines. That book is probably long gone.

The Yakimoff balancer is a home buildable gadget by the way. You can dynamically balance with it but you have to solve for the correction mass by solid descriptive grometry. Kinda tricky without some practice and maybe a tad of assistance from old Ward Rader or John Love who kicked my butt (when it was skinny) trying to make me learn what they knew about balancing in 1964.

Also try this website where there's some books and tech papers:

http://www.balancetechnology.com/html/s.800/index.html

mbensema
10-16-2002, 07:48 AM
Victor Wowk has a series of books on vibration and balancing that give a good description but are not very technical. There are many books to choose from, but the one Forrest suggested would probably be a good start, Schenck is the leader in balancing equipment. Another one I don't have yet, but sounds good is from Art Crawford, available from BN. If you are interested in machine dynamics as well as balancing, Machinery Malfunction by Robert Eisenmann is very good, but highly technical.

To answer your questions, there are many types of balancing machines, it really depends on what you are balancing and where. Computerized balancing needs a reference point, so that is why the phototach is used. The computer measures the time difference between the reference point and the vibration peak and can determine the angle of the unbalance relative to the reference. After making several trials with trial weights, an accurate position and amount of weight addition or removal can be calculated. Another way of doing it is with proximity sensors for machines where adding trial weights is not possible, that measure the actual shaft deflection and determine the angle, but this method requires a good knowledge of the equipment being balanced. For example, you need to calcualte how much weight to add/remove unless you want to do trial and error.
The simpilist way to do balancing is with a marker and trial and error for the correction weight. Run the machine at speed and mark the high spot, this is where weight needs to be removed, unless it is running above it's first critical speed, then weight is added there. Make a few attemps and eventually you will get what you need.

For motor rotors, they have special machines for that, but I am not familiar with them, they rotate the rotor on a fixture to determine the unbalance.

You could make a balancing machine yourself for flywheels like you mentioned, if you have the time and a little knowledge of balancing, you could probably do a decent job of it. You need to be very accurate in your setup, otherwise the eccentricity of your equipment could change the balance so that when you are done, it was worse then when you started.

Hope this helps,

Mike

Radmachine
10-22-2002, 04:45 PM
<font face="Verdana, Arial" size="2">Originally posted by abn:
Just wondering if anyone can recommend a good reference test on balancing and balance fixtures.

I mean it seems pretty simple to me for cylindrical work (wheels, flywheels, fans with a hub etc.)...use knife edges a precision level to set up level and parallel and a good round center shaft--Let the work spin and record the low spots and remove/add weight until the low spot is no longer a low spot and settles in a random position.

But like many things, there's probably more to it than meets the eye. How do computer spin balancers work? What are the critical dimensions when setting bob weights on a crankshaft and why? A motorcycle shop I used to go to used a shop fabbed strobe light balancer to spin balance wheels...how does that work? Could you use some sort of floating hub and say a 10:1 lever type indicator to indicate wobble and hence perform dynamic balancing?

I've never run across a "standard" text on balancing and the machines of dynamic balance. </font>

Radmachine
10-22-2002, 04:56 PM
I finally found out how to reply without re-copying the original post, too late, of course. Anyway, I found info on a crankshaft balancer at http://lodestone.dynodns.net/new/balancer/balance.html Hope this helps.

abn
10-23-2002, 05:39 AM
Thanks for the link...another one added to my favorites.



<font face="Verdana, Arial" size="2">Originally posted by Radmachine:
I finally found out how to reply without re-copying the original post, too late, of course. Anyway, I found info on a crankshaft balancer at http://lodestone.dynodns.net/new/balancer/balance.html Hope this helps.</font>