Yes, even if you go for a pre-packaged inverter kit you can probably get
the maker to program it to give a 200 or 300% top speed instead of the
usual 20-120% range. I have only bought from Newton Tesla, who have been
happy to add bespoke features, but I think the others should be able to
do this also.
Nope, just because an inverter can supply up to 400Hz doesn't mean to
say it can run a motor at this speed.
Final speed of a motor depends on the motor design which is also based
The big old British motors don't like to go above about 90 Hz before
they get saturated and cause the machine to actually drop speed, the
more you go above this slows them down more, makes them run hot and
sound like they have lost a phase.
Not wanting to piss on Alan's parade but there are a lot of motors out
there on early Colchester's and Harrisons's that are only 440v and
can't be swapped to 240v three phase which is needed for an inverter.
This is because the star point is buried inside the winding, it can be
dig out and 3 extra wires brought out, sometimes it needs doing by a
rewinder if the build up is complex.
All is not lost though as modern metric framed dual wound motors are
not expensive if bought correctly.
I had this on my L5, the original motor was a gigantic 6 pole motor.
415V only, speeds on the top plate 21 - 480 rpm.
I remotored mine with a complete 1hp setup from Newton Tesla,
as the lathe was free I could spend on the motor. Ive had no
problems with the setup in several years (cant remember how
many) If you search google group archives youll find the posts.
As for speed I routinely make alloy parts for (micro) RC Helicopters
with my L5 and my TOS mill. These are both reasonably sized
'industrial' machines, and the parts I make are usually about
15mm in the biggest dimension. I usually run mine at around
1000 rpm input speed (same as the original motor), so 480rpm
spindle speed but I do use the inverter to speed it up, but its
really quite noisy (gears mostly) when running fast, and as Im
not in a 'production' environment if it takes a little longer to make
a part it doesnt matter.
Dont forget that SFM charts are usually production oriented, and
as such are about getting the most parts out as fast as possible
with a reasonable (for them) tool life.
Going slower is nearly always an option. Pointy sharp tools help.
On or around Thu, 25 Dec 2008 11:23:00 +0000, Bob Minchin
Just a slight caution, make sure the spindle bearings are up to running at
higher speeds. If you're going from 750 up to 1000 I doubt it makes a lot of
odds, but if you want to make it run at about 2000, you need to be sure that
the machine will take it.
Ages ago the school at which I was a pupil at the time got hold of a small,
defunct, aveling-barford roller. This was fitted with a detuned ford
side-valve, which was u/s. The tech lot got heir hands on it and fitted a
spare austin 1300 engine. The teacher got onto Aveling and got some
techincal info, one of which was "don't run the engine at more than 1800 rpm
or you risk exploding the gearbox".
Austin Shackles. www.ddol-las.net my opinions are just that
Travel The Galaxy! Meet Fascinating Life Forms...
Further to all my questions about Mk1 Harrison L5s, the old codger
doesn't look as if he can be bothered to sell it after all. In a fit of
New Year madness and Esterlin Champagne I bought a Smart and Brown Model
A Mk2 off eBay (item 230316370220). I think it will be lower risk and
more of a "use it" rather than "rebuild it" project.
You can blame Richard Schute. My wife certainly does. There are some
immensely helpful folks on here, not least the people telling us about
fascinating silicone enhanced ladies who don't seem too interested in
men. Thank you everyone. You'll all be rewarded, but sadly not in this life.
Happy New Year,
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