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Model Engineering in UK - Model engineering, metal crafts in UK
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Posted by David Littlewood on June 27, 2008, 6:59 am
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Following on from my motor problems a couple of weeks ago, and having
regard to the many helpful comments here, I took the plunge and bought a
CL750 1HP motor and inverter set from Newton Tesla*, cost just over
£400. I could see it would have been cheaper to buy the parts
separately, but the time and trouble to locate the right parts, learn
how to connect and program, and to make an enclosure, would have been
rather burdensome.
As it was, the NT kit was an absolute breeze. It took less time to fit
than it took me to remove the old motor (if I say the longest part of
the operation was making holes in the lathe stand to fix the inverter
box, you'll get the idea). Motor plugs into inverter, inverter into
mains, and Robert is your mother's brother; everything worked first time
exactly as it should. Only used the lathe for a couple of hours so far,
but already I can see that the benefits of the huge speed range is
tremendous; can twizzle the speed down at the touch of a finger if I
detect chatter with a boring tool without interrupting the cut. If I had
known it was that simple I would have done it years ago.
A footnote - the old motor was gunged up with a mixture of oil and wood
dust (had done a little wood turning years ago) which had seized the
bearings solid. I guess the jolt it got must have disturbed the grot
somehow. It cleaned up OK and works again, but in view of the advantages
of the inverter drive I have no regrets.
A footnote to the footnote - looking at the motor spec plate, it turns
out it was only 1/2 HP (IIRC the spec for the S7 is 3/4 HP, but I
suspect this was a replacement the previous owner had fitted). I always
thought it was a bit light on power but it was virtually impossible to
see until I removed the motor. OTOH, I guess if I have any screw ups,
they could be more disastrous....
David
*Usual disclaimer.
--
David Littlewood
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Posted by on June 30, 2008, 11:11 am
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> Following on from my motor problems a couple of weeks ago, and having
> regard to the many helpful comments here, I took the plunge and bought a
> CL750 1HP motor and inverter set from Newton Tesla*, cost just over
> =A3400................
> As it was, the NT kit was an absolute breeze. It took less time to fit
> than it took me to remove the old motor ...............
> Only used the lathe for a couple of hours so far,
> but already I can see that the benefits of the huge speed range is
> tremendous; can twizzle the speed down at the touch of a finger..........
Hi David, pleased to hear that you are up and running again and
enjoying the ability to "twizzle the kn... sorry switch". While I
always enjoy the challenge of getting things to work I must admit that
sometimes I also like to bask in the pleasure of buying something
which has been well designed, well built and does exactly what it says
it will without any fuss or bother. Somehow it reduces the pain of
putting my (slimmer) wallet back into my pocket. I'm sure you will
enjoy the facilities you now have and I have certainly found that
thread cutting up to a shoulder is now something I do not try to avoid
at all cost but rather enjoy the ability to slow the process down at
the end to match my capability.
=2E.............
> A footnote to the footnote - looking at the motor spec plate, it turns
> out it was only 1/2 HP (IIRC the spec for the S7 is 3/4 HP, but I
> suspect this was a replacement the previous owner had fitted). I always
> thought it was a bit light on power but it was virtually impossible to
> see until I removed the motor. OTOH, I guess if I have any screw ups,
> they could be more disastrous....
>
To avoid this issue I run the drive belt on mine fairly loose so that
the drive is OK in normal use but would slip if you were unlucky
enough to have a major "scew up". Not any good, I know, if you intend
to remove large amounts of metal in a short time but for normal
turning it produces a sort of "safety net", particularly at slower
speeds. If you run the saddle into the chuck at 2200 rpm it won't help
much :-)) Enjoy your new found control.
Best regards
Keith
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> regard to the many helpful comments here, I took the plunge and bought a
> CL750 1HP motor and inverter set from Newton Tesla*, cost just over
> =A3400................
> As it was, the NT kit was an absolute breeze. It took less time to fit
> than it took me to remove the old motor ...............
> Only used the lathe for a couple of hours so far,
> but already I can see that the benefits of the huge speed range is
> tremendous; can twizzle the speed down at the touch of a finger..........