"Ignoramus8051" wrote in message
...
On 2009-05-16, Robert Swinney wrote:
Iggy sez:

"So, DoN, do you think that with the chuck heavy enough and RPM high
enough, plug reversing the lathe would actually reverse the idler?

(I believe that it is true, based on general symmetry considerations)."

Give it up already, Iggy! You are not likely to find anyone that will
agree with you.

So, just to make sure, do you think that it is impossible?

Specifically, do you think that it can never happen that plug
reversing a motor, with load, running on a phase converter, would
reverse the idler instead?


Think of it as this picture.

/~~~~~\--L3---/~~~~~\
L1 -----|Idler|--L1---|Load |
L2 -----| |--L2---| |
\_____/ \_____/

As you can see, there is symmetry between idler and load and the
distinction can only be made by their relative size. So which one
reverses and which one keeps rotation, depends on which one has more
momentum. Not on which one is called "idler" and which one is called
"load".


i
I think Bob Swinney is saying the same thing, the motors are not identical.
One does not have its power connection momentarily disconnected, and likely
has capacitors which also remain connected.

I understand the idea that the idler might reverse and have read some
reports of it doing so. I have also read that a flywheel does and does not
effect the surge capability of the idler. The opinions of those I feel most
likely correct are that the idler will not reverse. I personally start a 5HP
K&T mill or a 7.5HP Cincinnati 24" shaper almost instantly on a pretty well
balanced 5HP idler. Both machines have clutches and I have to need to
reverse the motor on either.

If one must or wants to plug reverse from an idler, I would suggest that
they try it and see whether it works or not as I am not sure there is a
definitive answer for all cases. It seems rather hard on the motor,
contactor, etc.. I do enjoy the discussions.

Don Young