joe - for your mini, if you flip the switch, one of three things will
happen:
1. nothing - the motor will continue to run in the same direction - this is
what happens with my reviersible grinder, for example - if the motor is
turning more than a few RPM, it will just keep going. Many motors are
bi-directional on the run-windings and use the start winding to make them go
in the desired direction.
2. it will go BANG-POOF!! and will hurt itself, probably by smoking one of
the windings or the capacitor when it attempts to revese instantly.
You can do this instant reverse with a 3 phase motor (my mill does this to
actuate the rapids), but most 110V single phase motors won't do this. You
just MIGHT get lucky, but personally, I wouldn't push my luck.
3. it might actually reverse instantly. If this happens on a wood lathe,
you will also nearly instantly unscrew the chuck or whatever is on the
spindle, much to your annoyance. One can get away wtih this on metal lathes
because when you do it (like when tapping) you are going much much slower
(10 RPM or 20 RPM, not 2,000)
I use a center off DPDT switch to control the motor on my mini lathe, I
strongly suggest you consider the same.
"Joe Fleming" wrote in message
ups.com...
Thanks everyone for the information. I can tell by the questions that
I didn't provide enough information, and I have OK - I want to be extra
clear.
A. My Stubby lathe has a 3-phase motor on a controller that allows me
to switch the motor direction while the lathe is spinning. the
controller, I presume brakes the rotation down to zero rpm, and then
starts rotation in the opposite direction. I do not stop the spinning
before switching directions. Once in a great while the braking torque
does cause a chuck to unscrew, but I generally tighten the chuck so
this does not happen. The slow down and speed up are rather gradual.
there is no "hard slam" reversing going on. So, this is my experience
with reversing on a lathe.
B. The motor for my mini lathe is a single phase 110 motor that has
wiring to allow rotation in both directions. I will not have a
controller. It will be wired directly to 110 AC through whatever
switch(es) I install.
So, based upon all the great responses, here are my more precise
questions:
1. If I flip the polarity on the switch to instantly reverse motor
direction, does the motor gradually slow down, then gradually speed up
in the other direction, or does the motor attempt to slam direction
changes? In other words, to avoid slamming direction change, I must
allow the rotation to stop before re-energizing the motor in the
opposite direction?
2. If I flip the polarity on the switch to instantly reverse motor
direction, does this damage the motor? In other words, to avoid motor
damage, I must allow the rotation to stop before re-energizing the
motor in the opposite direction?
Assuming the slamming effect is what happens and/or that motor damage
happens, then I will use some sort of three position set-up where I
turn off rotation in one direction. Wait until the rotation stops,
then re-energize the motor for reverse rotation.
Thanks again.
Joe Fleming
Darrell Feltmate wrote:
Joe
When I put a reversing switch on a motor I use one that has a "dead"
position in the center so that I can not forget to turn the motor off
before
changing direction. On the other hand I am a devote coward who hates pain
to
himself or the lathe :-)
--
God bless and safe turning
Darrell Feltmate
Truro, NS Canada
www.aroundthewoods.com
"Joe Fleming" wrote in message
ups.com...
All,
I am adding a motor to a mini lathe and have a wiring question. The
motor I have is reversible. I can add a switch to the circuit to
switch polarity and change rotation direction. Here is the question:
Can I switch the motor from forward to backward when the motor is
already turning? Or do I need to cut power and stop the rotation
first, before switching direction and reapplying power?
Thanks,
Joe Fleming - San Diego
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