Gene,
If we are talking about the sheldon you got from Tom as I recall, it had:
(These are very approximate numbers based on an admittedly faulty memory)
a) Motor pulley about 4 inches
b) countershaft Pulley (input cone pulley shaft) about 10 inches or so.
so with a "nominal" 3600 rpm motor the input countershaft rpm will be
"about" 3600 x 4/10 = 1440
for very rough approximation and motor slip call it conepulley input 1200 rpm
the cone pulley ratios as I recall were very approximately 2.5:1,
1.25:1, .8:1, .4:1
so the cone pulley output speeds would be "about":
1200 X 2.5 = 3000
1200 x 1.25 = 1500
1200 x .8 = 960
1200 x .4 = 480
As I recall, the double v-belt pulleys were about the same diameter
on the cone pulley output and on the spindle so the spindle rpms
would be approximately the same as the cone pulley rpms so it would
appear that the ratio between the motor and the spindle would be "about"
3600 (motor) to 3000 (spindle) or 1.2:1
3600 (motor) to 1500 (spindle) or 2:1
3600 (motor) to 960 (spindle) or 3.75:1
3600 (motor) to 480 (spindle) or 7.5:1
Of course there is the Back gear which was very approximately 6:1
so the speed range in back gear with a 3600 rpm motor would be "about"
500 rpm (spindle)
250 rpm (spindle)
160 rpm (spindle)
80 rpm (spindle)
So as I recall you have 8 different speeds available (with a constant
speed motor) not just two.
So you have 8 different motor to spindle ratios depending on which
cone pulley set you choose and which back gear position, all
controlled by belt position except the back gear whose ratio can be
confirmed by opening the cover and counting teeth. The final ratios
from motor to spindle would be "about"
1.2:1
2:1
3.75:1
7.5:1
7.2:1
14.4:1
22.5:1
45:1
I don't remember any "Gear Box" except the quick change gear box
which only controlled the lead screw and you have removed.
Again, this is all from memory and I haven't seen the machine in over
a year so....
The revs per MINUTE of the 1000 line encoder should depend completely
on your vfd setting but should be between 0 and say 6000 rpm for a
single pole motor or 0 to 100 revs per SECOND or 0 to 100K lines per
second or 0 to 400K edges per second.
There is nothing approaching Megahertz unless you want to wind the
motor up to speeds that would make me cringe all the way down here in TN.
Are we talking about the same lathe?
Cecil
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