Anybody ever built a balancing machine

I would like to balance the electric motor rotors I make myself. I have not found an inexpensive used machine and am considering making my own. I think the base of an old tool and cutter grinder would work, machining the suspension system looks straight forward, selecting the accelerometers is still a problem but I can buy the software and DAQ as a kit. Anyone been through this before?

I made my first driveline balancer back in the day . The biggest thing for me was achieving the desired rpms . I had to use used engine bearings that were dissassembled and lubed with #1 lighter lube . New bearings are just to stiff and have to much drag for what I was doing. Mine got up to 4500 rpm works like a charm .

I have never made a balancer, but have worked on several for motor rotors (56 frame up to 6805 frame). The design of the frame from my understanding has to be outside the harmonics of the speed that you will be running at. I worked on several Hoffmanns. Basically, these had four bearings that the rotors sat on, with a safety bar over the top that locks. We balanced all of our rotors at 750 RPM, and we made rotors from 60 RPM to 3600 RPM. On the lower end motors (Grangers Dayton brand as well as GE and Marathon was made by my company) were not balanced, Leesons are. Inside the base on the Hoffmann balancers was a ball bearing that was pressed against a vibration sensor that was made of some sort of glass or crystal. This ball was what bounced around touching the sensor and the computer intrepted this into a degree and weight. The Hoffmann computer was nice because you could tell it how many lugs you had and it would tell you which lugs and how much weight to put on. it could also do weight removal. The only thing that I never saw in a balancer was weight axially-when we got a rotor that wasn't cast right (had some wobble end to end) that really messed with me-my theory was that the sensors could not tell which direction the vibration was in. Fixing the casting all but solved that issue. If I were building a balancer from scratch, I might be tempted to use an old wheel balancer's electronics until I knew more.
Joe

Look here:

Erbessd Instruments

Does this lead to inspiration? Back when I was an apprentice in the early '60's we had home-made Yakimov balancers - so called "soft bearing" balancers. Instead of sensitive accellerometers they used mass/spring resonance to amplify the effect of unbalance. A test weight (a lump of modeling clay) was affixed to quadrant on a handy diameter, the work was brought up to resonant RPM with a variable speed motor, and the unbalance was detected by a dial indicator registered to one of the bearing suspensions. By comparing readings and trying different trial weights to equalise the reading one could efficiently determine the correction needed.

The out of balance tolerance I was used to was measured in thousandths of an inch ounce and this could be quantified if the weight and radius of the trial weight was known and the exucrsion of the dial indicator at optimum resonance was equalized.

Our balancers were all home-made but well designed with frictionless suspensions and variable speed DC motors. We did pretty good work we thought until we acquired a Shenk hard bearing dynamic balancer in 1972. It did the work more accurately in about 1/10 the time of out old school system.

My point is elaborate electronics may not be necessary to a DIY dynamic balancer suited for an electric motor armature.

But unless you can't resist the intellectual challenge of making you own DIY dynamic balancer (more power to you!) I strongly suggest you farm your one project motor out to a balancing shop. .

I ran across this site when looking for info on DIY balancing in situ: DrKFS.net: Balancing a Rotating Object.

It shows the basic electronics needed to determine the position and acceleration of the rotor.

Cheers,

I was looking to do this on a small scale a while ago.
Found these links before abandoning my project.
Balancing Tool
Ducted Fan Balancer

The outcome depends a lot on the weight of your rotor and the speed it will turn.

I used Affordable dynamic balancing which has been successfully used by small turbine balancers. I had some difficulty balancing a 7 kg rotor because it appeared to stick to the V support and the noise filters were too limited to remove the bearing noise, at the highest balancing grades, in a later iteration. The rotor turned at 20K which may be higher than you require. In short the equipment was able to balance light items that eventually operated at over 50K when the balancer used low friction V blocks but a heavier rotor balanced on bearings could not be brought to the same level of balance. Of course it could be argued that the heavier rotor did not require the same level of balance.

Duak said:

I ran across this site when looking for info on DIY balancing in situ: DrKFS.net: Balancing a Rotating Object.

It shows the basic electronics needed to determine the position and acceleration of the rotor.

Cheers,

Click to expand...

Thanks for the useful link, I have spent a fair bit of time on google and have not come across this site. This is probably how I will start.

If you can establish the angular position of the shaft vis-a-vis the the accelerometer you do not require software but it may be challenging when the noise is as loud as the signal. I would start by calibrating the system with a small weight such as a small magnet to see how it affects the readings. It will also tell you how much material has to be added or removed for each mV on the accelerometer output. Also check out that your 0 on the shaft reads as 0 on the readings.