G4003g Motor Vibration Surface Finish Issues Fixed!!

[tmarks11]

A couple solutions:
1. Fabricate a motor bracket that puts the motor base plate horizontal (as Coolidge mentioned). This would probably require a good size L-bracket, hard mounted to the lathe, with sandwich mounts under the motor. Challenges here is that the drip tray might interfere on the G4003G (looks like there is enough room on the G0709G), and the L-bracket would have to be thick so it didn't flex.
2. Fabricate a motor bracket that incorporates sound mounds in both the X & Y plane so you don't have problems with shear forces. I started down this path, buying a couple more sound mounts after I did the initial conversion, but some quick sketching showed this plan would result in a fairly complex bracket arrangement, and the sound mounts have been sitting in my parts bin ever since.

The sandwich sound isolators are rated to support 20% of their rated load in the shear direction. The downside here is that if you oversize the mounts to accommodate the shear force, you end up with something that isn't as good at sound isolation as if it were mounted in the right direction and the sound mount was sized properly to support the load.

EDIT: I went back and looked at the mounts I had bought. I just bought the ones that had M10 bolts, which is the same bolt size used in the existing motor bracket. Like Coolidge, this is a 125# mount, rated for 20# in the shear direction. That probably means that it is more than adequate to hold the 50# motor in place for the life of the lathe.

 

[mhagadorn]

Coolidge, can you elaborate on you test cuts? Depth of cut? Steel grade? Cutting tool? I want to see how mine does. I have always struggled with surface finish.


Sent from my iPhone using Tapatalk

 

[dave2176]

Coolidge,
That's a nice resolution. I think I'll order a set of mounts for mine or is it better to rethink the motor mount first and then isolate it? Would you hang it upside down or stand it on its feet? Maybe upside down at a 45 angle with a hinged mount plate and adjusters front and rear, the kind like some alternators have to tension the belt? You had to change belts (well along with all the other belt changes/types you tried through this journey), what did you end up doing in this case?
Dave

 

[coolidge]

So is this going to change your mind about trading up to a larger lathe?

Ahahahah no! But to be honest I can afford to wait now for the right lathe to come along I'm in no big hurry.

You are the first one to demonstrate the difference between a quality one phase and a cheap one phase motor.

In fact I did not demonstrate much of a difference between the motors. If anything I dispelled the theory that its the cheaper China motor causing the surface finish issue. The Baldor motor also injected plenty of buzz into the lathe and that's with the thick rubber washers I used to mount it. Now there are reports of G4003G China motors belching smoke and perhaps with further use the buzz would continue to increase I don't know. Remember I only had 15 hours on mine. There was one report of swapping motors for a made in USA Marathon motor made a big improvement. But I wouldn't rush out to buy a new motor unless you were sure the China motor was causing a problem.

 

[coolidge]

Long term using those motor isolation mounts, you may have some issues with sagging or twisting. I assume the motor needs to be mounted in the vertical plane because of clearance issues when using single phase motors.

I don't think this will hold up long term with the motor mounted sideways putting a shear load on the isolation mounts. I also don't think its ideal in that the motor is more likely to wiggle around mounted sideways. I could be wrong, but I see some distortion already and I'll monitor for a bit.

 

[coolidge]

1. Fabricate a motor bracket that puts the motor base plate horizontal (as Coolidge mentioned). This would probably require a good size L-bracket, hard mounted to the lathe, with sandwich mounts under the motor.

I likely won't attempt redesigning the motor mount unless the isolation mounts begin to fail but I have sized up the situation. Here are some design considerations...

1. There is very little room inside the end cover of the lathe for the belt, you would need to maintain the same angle between the motor pulley and drive pulley otherwise you would have to start chopping up the end cover to clear the belt, there's maybe 3/4 inch of clearance around that.

2. Both the Grizzly and Baldor motors are a tight fit, there's not much room between the chip pan and the cord grips and cords that hang down from the bottom of the electrical panel. If I flipped this Baldor motor upright due to the big capacitor housing on top there's not enough room for it to fit, and certainly not with the added 1 inch of height due to the isolation mounts. BUT...its entirely possible to reposition the electrical cabinet several inches higher to make more room.

3. Ideally I would not mount the motor to the lathe bed at all, rather I'd bolt the motor mount to the back of the headstock stand, probably isolate the mount from the stand, and the motor from the mount. This would require a longer belt, and possibly a belt tensioner which is not a bad idea anyway. I would certainly design it so its easier to adjust the belt tension, the factory design is a PITA.

 

[coolidge]

Coolidge, can you elaborate on you test cuts? Depth of cut? Steel grade? Cutting tool? I want to see how mine does. I have always struggled with surface finish.


Sent from my iPhone using Tapatalk

These were finish cuts .005 depth of cut on 360 brass using razor sharp polished Korloy inserts CCGT060204-AK. For the record I have tried heavier cuts and more aggressive feeds in testing and the surface finish issues remained.

 

[coolidge]

Coolidge,
That's a nice resolution. I think I'll order a set of mounts for mine or is it better to rethink the motor mount first and then isolate it? Would you hang it upside down or stand it on its feet? Maybe upside down at a 45 angle with a hinged mount plate and adjusters front and rear, the kind like some alternators have to tension the belt? You had to change belts (well along with all the other belt changes/types you tried through this journey), what did you end up doing in this case?
Dave

Stand it on its feet. The motor should be mounted flat on these isolation mounts compressing them as ideal, or sideways as I did if you must, but not upside down. They are weight rated for compression and shear, but not for pulling apart. 45 degrees on its feet would be fine, basically half way between mounting it upright vs sideways.

Belt wise I have three sets, the factory belts, made in USA Napa belts with a variable width cog design, and these made in Europe link belts. Using my .0001 indicator the link belts produced the least vibration. The factory and Napa belts were about the same. A serpentine belt would be great, except I read somewhere the drive pulley on the lathe is tapered so that's not an easy bolt on mod.

 

[Kernbigo]

i think someone missed the hole story it was not the motor is was the vibration dampening(i stand by my post)

 

[tmarks11]

Fine, now that coolidge clarified that....



My crappy motor + sound mounts surface finish ≠ coolidge's nice motor + sound mounts surface finish, so obviously YMMV.