Grizzly G4003G - Belt vibration (Video)

coolidge

coolidge

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Okay people here is the promised follow-up after the previous thread on isolating and aligning the motor and pulleys. There is a lot of oscillating belt vibration as you will see in the video. I'll use this video as my baseline to reference as I try to get rid of this vibration. The belts are currently tightened to about 1/4 inch deflection. I only ran the lathe for a few minutes, I had aligned the logos on the two belts and they are already about 3 inches off now so belts are moving vs one another on the pulleys.

The good news is the motor pulley is spinning absolutely dead on true and the motor itself is steady as granite, no movement at all. I have another video of that I'll post later, right now I have to run to Easter dinner.

[video=youtube;WjP0vwwCzCc]https://www.youtube.com/watch?v=WjP0vwwCzCc&feature=youtu.be[/video]
 
Update: Okay hmmm I removed one of the belts and the belt vibration persists. Next I removed the other belt so just the motor spinning free and there is a significant buzz felt if you place your hand on the chuck, not slight not mild, its a pretty good buzz and this is transferring from the motor through the rubber washers into the lathe casting. I'm wondering how balanced that motor would spin if just sitting on a workbench.

I'm going to rig up a .0001 indicator and touch off on the chuck to see if it registers. I did pick up some link belts to try as well but I suspect I will either need to better isolate the motor from the lathe or possibly look for a better quality motor. Mind you I have been happy for the most part with the finish before I started any of these improvements, thread finish excluded. These efforts are in some ways just to see how much better it could be. This is not a $15k Mori Seiki lathe.

Update: So I just noticed the vibration from the motor travels through the lathe, through the stand (it was vibrating one of the stand doors) through the 8 hockey puck rubber leveling pads, and could be felt on the concrete floor. :think1:
 
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If the motor is way out of balance, you could take it to a local motor shop to get it balanced. Not sure of the cost involved but it might be worth it. There should be a few shops in Portland, maybe in Vancouver also.
 
Quite interesting. I'm going to pay attention to this. I would also I interested in improvement of surface finish. I've heard that adding an idler to reduce the bounce of the belts would help.



BTW, your lathe is much cleaner than mine.:rofl:

Dave
 
I think the only reason the motor is mounted directly on the lathe is to make the lathe more or less "turnkey" (ready to use out of the box). It's also much more difficult to adjust belt tension with the mount vertically oriented like it is.
 
Adjusting belt tension is more annoying because you also have to remove the metal backsplash from the machine which is a pain.
 
UPDATE: I'm uploading video to Youtube now but here's a quick update. I rigged a .0001 resolution indicator and touched off on the chuck and measured vibration at the chuck with just the motor with no belts, then 1 belt, then 2 belts. Interesting results.

No Belts - The good news is the motor vibration felt much worse than it measured. I guess a human hand is more sensitive than a .0001 resolution indicator. As you will see in the video the needle was at most a bit fuzzy, I'm going to say about .00003 of vibration yes not even 1 tenth not even half a tenth. I had every intention of spending a gob of money to reduce this vibration but now that I measure it I really don't see the point in trying.

1 Belt - Here I measured a consistent .0001 of vibration.

2 Belts - First run after installing the 2nd belt the needle was really jumping around, about .0005 but settled down to .0001 to .0002. I guess the belt was settling. My second attempt was fairly consistent within a .0001 to .0002 range.

So based on my test results reducing belt vibration is by far the thing to focus on. Even if I could eliminate the motor vibration completely what would I really have accomplished? I'm not sure the rest of the lathe is capable of better than a .00003 finish because if the spindle, gears, cross slide, rigidity, all the other parts together are not capable of better than a .00003 variation then there really is no point.

Next I'll install the link belts and retest now that I have a baseline. Its possible the measured vibration is not all from the belts, most is imo but with the spindle pulley shaft now turning its possible some is from that.
 
Here are the videos,

0 Belts Installed

[video=youtube;4S5itPuo-Y0]https://www.youtube.com/watch?v=4S5itPuo-Y0&feature=youtu.be[/video]

1 Belt installed

[video=youtube;INc_k2ARxO4]https://www.youtube.com/watch?v=INc_k2ARxO4&feature=youtu.be[/video]

2 Belts installed first run

[video=youtube;vfoeUNkfVFA]https://www.youtube.com/watch?v=vfoeUNkfVFA&feature=youtu.be[/video]

2 Belts installed second run

[video=youtube;pdSuupfN_M8]https://www.youtube.com/watch?v=pdSuupfN_M8&feature=youtu.be[/video]
 
I mentioned this on another thread. Back in the day, and I am going back 40 years, when we changed belts on a machine with multiple belts we bought matched belts. They have less variation in "length" than normal V belts and can be found at McMaster. With two different length belts they wind up fighting each other and only bad things can happen.
Maybe the link belts will be more forgiving, I don't know but I sure will be following.

John
 
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