I think the shop man was trying to talk simple talk - he means the insulation
and wire is far improved today so the same horse power can be smaller. Therefore
in the same package you can get larger horsepower.
My case is much the same - I have a 1946 Sears ball bearing !! motor. 1/3 Hp.
It is over 12" tall - large cast iron. That baby sits on the counter when it wants to!
I think a 5 or 10 Hp or more - could be put in the form factor.
Martin
Martin Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
NRA LOH & Endowment Member
NRA Second Amendment Task Force Charter Founder
Don Foreman wrote:
On Sun, 01 Jan 2006 04:02:11 GMT, "Peter Grey"
wrote:
Hello all,
I have a '33 11" SB lathe with a '31 Westinghouse 1/2 HP motor on it. The
motor started acting up so I took it to my local motor shop who got it
running decently, but told me that it would cost a mint to do what needs to
be done to make it right (70 years of oil soaking into the winding
insulation and all that). While the motor works, it doesn't work as well as
it should, and rather than spend more money than it's worth, I'd like to
replace it. The question is; with what?
I've been told that 1931 HP were bigger than 2006 HP and that I should go
with a 3/4 or 1 HP motor to get similar work capacity. That's fine, and my
shop is wired for 110, 220 and I have both a rotary and static phase
converter. My lathe has a screw-on chuck so I don't have a need for instant
reversing (although the lathe is currently wired for reversing and I'd like
to keep that capability). My question is, are there any advantages to 220
or 220 3-phase over 110 when choosing a motor without concern for instant
reversing. IOW, do I get more real power with any of them, less power
consumption, or smoother operation? Are there advantages or disadvantages
that I haven't mentioned? Any types of motors I should stay away from? Any
types of motor that would be good for my application?
I've done a RCM Google search and haven't been able to get these questions
answered, but if anyone had a pointer to an appropriate web site, I'd be
happy to follow it. Keep in mind that I'm an electrical dunce (I had an
electrician install the RPC for my mill) so any conversation about
degaussing the flux capacitance in the field coil windings is likely to
leave me befuddled.
As usual, thanks for the advice and Happy New Year!
Regards,
Peter
HP are HP, 1931 or 2006. Motors are usually honestly rated; it's
the guys that sell things with motors in them (Sears, etc) that lie a
lot. 1931 motors were considerably larger (and less efficient)
than today's motors for given HP, though.
I'd put a minimum of 1 HP on a 11" lathe. Up to 2 HP can run OK on a
110 volt singlephase 20 -amp circuit, though I'd probably go with 220
on a 2 HP motor if it's just as easy to go that way.
Many or most single phase induction motors can be reversed if
brought to a full stop before starting in the opposite direction. I
wouldn't "plug reverse" a lathe with a threaded spindle anyway.
Threephase motors will tend to be a bit smaller for given HP, and
they'll run with less vibration -- a plus on a lathe though belt drive
mitigates motor vibration to some extent. They're also cheap when
found surplus. All threephase induction motors are reversable.
Motors usually found on lathes are induction motors, either repulsion
start or capacitor start. Either will work fine.
If you're not comfortable messing around with electrics, I'd stay away
from the "treadmill" motors that offer variable speed. They require
electronic controllers, and the ones that come with them often crap
out -- then you have the problem of "now what?" Go with an induction
motor of the same speed as the original motor. Induction motors come
as 1725 RPM (or so) and 3450 RPM (or so). Yours will very likely be
1725 RPM.
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