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SB9A restore and retrofit 3 phase/VFD

Deciding to move ahead on a new motor pulley, here is a double pulley for a Poly V 6 rib direct to spindle cone pulley. The low speed pulley is 1.9" diameter and the high speed pulley is 2.4". This gives roughly 500 rpm in low gear and 900 rpm in high gear. I thought the 2.5" round bar stock was big enough but the larger pulley could have been 3.0" to get over 1000 rpm. I could always re-configure the VFD for over 60 hertz I suppose.
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Since the motor needs to be shifted over at least an inch to allow the pulleys to line up, now maybe a good time to re-build the motor mount.
 
that motor will have no trouble at 120HZ...certainly not at the 100HZ I think your VFD will go to.

glad to see you are still experimenting.
 
Up thread in a video, I detailed a hall effect tachometer with the magnet attached to the small cone of the spindle pulley. At the time, I would do a mental divided by 5 when using the back gears. Well, it wasn't long before comments about using the back gears made me rethink the issue. My solution is to mount the 3/8" magnet in the spindle takeup nut. A 3/8" end mill was used to mill out a hole in the nut and the magnet was press fit into the nut. Now I have true spindle rpm's.
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Greetings, I am back after almost 3 years with an addendum to this thread about a SB 9A redo I did. I have gone from the SB 9A sitting on a plywood table top in my wife's laundry room to a small workshop space. I was having issues with harmonic vibrations with increased spindle RPMs starting at 500 rpm. In addition to the tabletop, I had rubber supports in between the motor mount and motor, and finally a flimsy motor mount setup that you ALL commented on. [ICODE]You all were right, this contributed to the problem[/ICODE].

The solution was to address all 3 of the issues. The photo shows a main cabinet (from another lathe vendor) made of 1/4" plate with a 1/4" plate re-enforcement panel on top which the lathe head and the SB cast iron motor support are screwed to. The rubber was removed and the motor is secured to a 1/2" steel plate that is pinned to the SB part. The tension between the lathe head and the motor mount assembly is controlled by a turnbuckle and it serves as a no tools device to take up the 5/8" difference between the Lo and Hi belt difference (hand tighten).

I'm getting a spindle speed of 700 rpm on the medium cone pully and 1200 rpm on the hi cone pulley with no vibration. I don't use the smallest cone pully.

Nothing is screwed to the floor, as in California, the 4 adjustable screw feet of the main cabinet and the 2 feet of the right support will allow leveling.
 

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