80-100 130kv Rotor off balance?

magudaman

magudaman

10 kW
Joined
Jul 10, 2007
Messages
695
Location
Bay Area, CA
I just got my halls installed in my Turnigy 80-100 130kv motor and spun it up with the correct hall configuration. At a specific frequency the motor really seems to sing and vibrate. At low speed I can notice the bell doesn't spin concentrically. After running at full speed for about 2 minutes the bell is warm while the coils and bearings are cool?

I am seeing around 3.6 amps at 54.5v at full speed and 7700rpm.

So has anyone had balance problems with their 80-100s? Has anyone ever balanced their rotor? Any other ideas of what might be happening?

A video of the problem:

[youtube]UCi_l9C9dQ8[/youtube]

Video will be up in about 12 minutes!
 
Wow Youtube must be putting the processing on a very low priority because the video is still processing!?!?
 
Sounds like the clearance isn't enough when it resonates. Magnets hitting your stator. If you take it apart, you might find where it's rubbing. Can is probably out of round. Typical of the quality you get from these types of motors. You could reposition the shaft, it's held on by set screws, rotate it 180deg and see if that helps.
 
v1 motor & the can is ringing on a harmonic.....(it is a bell shape after all)
I didn't hear any mechanical contact anywhere through the range....it definatly has an angry spot.

Putting it under a load will change the dynamics.
 
Balanced slotcar motors as a kid. All so fun and exciting---for a kid. I would expect that you could not have a balanced armature after adding hall sensors.

http://www.hinesindustries.com/balancing-articles/armature-balancing-tolerances.shtml

Not my own explanation here, found it online. Seems workable.

Put two same-size wood or metal blocks on a table. Separate the blocks so there is room to place the armature between them. The table needs to be level.

Place the end spindles of the motor armature between the two blocks. This means the central poles and wire windings are in between the blocks. The armature will rotate on the blocks and the heaviest pole will face downward. This is the first pole you need to balance.

Remove the armature from the blocks, keeping an eye on the pole that needs balancing. Place the armature on the table with the pole that needs balancing facing upward. Make a small hole in the center of the metal pole using a drill. Don’t drill out too much metal, just a small amount to start.

Put the armature back on the blocks. Roll the armature slightly on the blocks. The armature will roll evenly, if it’s balanced. However, if it isn’t balanced, it will always roll to the same position with the heaviest pole facing downward.

Repeat the procedure by drilling out a little more metal from the heaviest pole, if the armature remains unbalanced. Retest it on the blocks as before. Continue to drill more metal from the pole until the armature doesn’t roll on the blocks on its own. When you can place the armature in any position and it remains still, then you know the armature is balanced.
Click to expand...
 
Thanks for all the responses! As thud said once I apply a load it will change all the dynamics so really I'm going to wait to balance once I have my reduction drive put together. I see if it is even an issue by that point. I keep it posted here when I figure out some more.
 
I have a dynamic balancer here we could set up for the rotor, if it is needed. We would need shaft on the front and back to support the bell.
 
johnrobholmes said:
I have a dynamic balancer here we could set up for the rotor, if it is needed. We would need shaft on the front and back to support the bell.
Click to expand...

That would be so awesome! I get a little further along on the gearbox/beltbox and figure out what steps to go from there.
 
On topic, my old CA80100:
py5Yb.jpg


I've sold it some time ago and this is what picture I get. Imagine that going off at 10kRPM. Good thing he noticed it early and I'm now not in jail for "involuntary stabbing of a person using a peace of motor's rotor shell".
 
Are those threads made in the steel can?

On my motors, the can has countersunk holes, and the threads are in an alloy part.
 
magudaman said:
Thanks for all the responses! As thud said once I apply a load it will change all the dynamics so really I'm going to wait to balance once I have my reduction drive put together. I see if it is even an issue by that point. I keep it posted here when I figure out some more.
Click to expand...

My motor has exactly the same vibration like in your video (you can hear it in my scooter video). Have you removed the rotor big bearing? My motor witch has now cracks (picture witch circuit posted here) because of that vibration. It is very strange vibration my motors rotor can was perfectly centered and that didnt help at all. If somebody has very fast camera then maybe we could see what happens with the rotor. Or is it that the rotor can end attachment to the shaft is too weak? Or does the big bearing remove this vibration?
 
bearing said:
Are those threads made in the steel can?
Click to expand...

Yes they are because the big bearing was removed and the can shortened and to those M3 threads there was fan bolts attached.
 
How much did the fan increase no load current, and how much more heat did it remove?

Why do you remove the skirt bearing?
Is it only because of the extra drag? is the drag really that significant?
 
My "new" 80-100-130kv did the same thing, with or without the skirt BB. I spent more than 2 weeks of daily troubleshooting the bell, swapping to different (old) stators, balancing, bending, even miss-shaping the bell, cutting off the skirt bearing portion of the bell to (hopefully) change the resonance properties...and NOTHING-NOTHING changed it. I even ran it under load on the bike and all it did is resonate louder and throw magnets each of the 3 times I tried it and repaired it and tried it again.

My belief is that the bell is vibrating just like when a wine glass is bombarded a with specific frequency of high amplitude sound waves in order to cause it to break. Videos of this can be seen here: http://www.youtube.com/watch?v=BE827gwnnk4

I also believe that it is the pull of the magnets by the stater, and the bell being too thin, and the fact that these "new" bells don't have the solid metal blocks or spacers between the magnets like the "old" bells do to add rigidity (EDIT: and weight) that causes it, NOT an unbalanced bell.

So since I gave up on my DEFECTIVE "new" magnet bell, I have been using an "old" bell on my "new" motor core/stater without problems for ~800 hard offroad miles.

As for fans attached to the bell...I put a ~4" cage fan around mine. It moves and pulls a TON of air through the motor and keeps it COOL. Also, it lowered the motors no load current from 6.5 to 5.5 amps!!! So don't worry, a fan is not a bad thing! ;)

I still have my "new" bell just sitting on a bench with some of the magnets just stuck to the outside to keep track of them. I would like it to be a working bell someday though as I could feel it was stronger, so...

I think with a new THICKER magnet bell/ring, all would be well.

Any takers for making a few? It sounds like a small customer base exists, and I'd buy one!

Even a sleeve of the proper thickness and or material hardness would probably work.

Wadda ya say? :)
 
I noticed the Colossus does the same thing in its' vids...
 
So, no responses here? :|
 
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