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RE: [TCML] Salient Pole Query, Terry Strobe
You might see if you can still find Radio Shack strobe Terry built a timing
circuit out of,
Hi Phil,
See if you can find the circuit in the mirror sites. You need to find the
right RS strobe though.
Jim Mora
>
Hi Dan,
>
> Radio Shack sells a number of different strobe lights all with different
> circuits. My plans are specifically for the Radio Shack # 42-3048. Do
you
> have a different kind, or did they change the circuit in it?
>
> Cheers,
>
> Terry
>
-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
Of Phil Tuck
Sent: Wednesday, December 03, 2008 1:50 PM
To: 'Tesla Coil Mailing List'
Subject: RE: [TCML] Salient Pole Query
Hello All.
Well it's done! But does it work - I have no idea [grin], but the motor runs
ok with no balance problems.
I have a mill so that was the method I used. Afterwards measuring the rotor
body diameter across the two pairs of flats I only had a 1 thou difference
(on a 3.7 inch diameter) in the two readings. Luck more than skill I hasten
to add.
The 1/4 width rule worked out to the distance of 3 segments by co-incidence.
As I don?t have a rotary gap at present (using a sucker) I am reluctant to
build a rotary unless I know the motor is definitely synchronous.
My understanding is that both a Synchronous and a Asynchronous can run at
1500 rpm, but the Synchronous (every time it runs) will always have its
rotor in the same angular position when the AC cycle reaches its peak. Yes
or no?
I have had no luck using a fluorescent tube and a marked cardboard disc
unfortunately. Nor any luck with a neon. This was one that was in the nearby
wall plug and it cast a reasonable red glow if the motor was held close
enough.
I have now gone for a more exotic approach using a 'scope'.
If you have two channels on your 'scope I presume a triggered impulse from
the motor (via a cam on its shaft) goes to one channel, while low voltage AC
is fed to the other. Allowing you to physically see the trigger point on the
waveform ??
Mine only has the one channel however, which makes it harder!
I have been feeding 6 volts AC via a cam operated contact into the 'scope.
My reasoning being that the contact will only 'make' at one point in each
rev of the cam/motor shaft. On 50hz at 1500 rpm I should have two complete
cycles of AC per revolution, so I should see on the scope the same chopped
part of a single waveform each time.
Too much contact bounce though - not unsurprisingly. Also tried a reed and a
magnet but not really clear.
Tomorrow I'll use the lathe which has a variable speed drive, set it at 3000
rpm (50 revs per sec, set using a hand held tacho) and get this to trigger a
photoelectric cell which will switch a low voltage on and off to the scope.
The 'scopes tube will flash then like a strobe - provided the 'scope is
adjusted for a suitably sharp point of light.
The archives suggested using your monitor refresh rate set to 50 Hz but mine
won't go that low!
Anyone any better Ideas than mine (mine seem rather longwinded)
Phil
-----Original Message-----
From: Quarkster [mailto:quarkster@xxxxxxx]
Sent: 03 December 2008 08:08
To: Tesla Coil Mailing List
Subject: Re: [TCML] Salient Pole Query
Phil -
Your motor is designed for 50Hz service, and has a synchronous no-load speed
(at 50Hz) of 1500 RPM. It is a 4-pole motor, which means it needs to have 4
flats machined into the rotor to achieve salient-pole operation.
Some people have created the flats on the rotor with files, grinders, belt
sanders, etc but all of these "machining" methods are crude and will
undoubtably leave the rotor unbalanced, which will eventually cause problems
with vibration and runout of the RSG disk, premature bearing wear, etc.
The only satisfactory method of machining the flats is to use a milling
machine. If you don't have access to one, find a machinist who can do the
work for you. It takes well under an hour, and rotor balance is generally
satisfactory as-machined.
First determine the width of the required flat, position the rotor in the
milling machine vise, and machine flat #1. If the mill has a Z-axis encoder,
record the depth of the cut. If no Z-axis encoder, set up a dial
indicator so you can measure the depth of the cut.
Turn the rotor 180 degrees, positioning flat #1 against a set of parallels
located under the rotor, between the vise jaws. This ensures that the second
flat is exactly 180 degrees from the first flat. Again, monitor the total
depth of cut, matching the first cut.
Next, turn the rotor 90 degrees so the flats you just created are against
the faces of the vise jaws, and machine flat #3. Indexing the rotor on the
two flats assures that the third flat is exactly 90 degrees to flats #1 and
#2. Again, carefully monitor the depth of cut. Finally, flip the rotor in
the vise so the last surface to be machined is oriented up, and cut the last
flat, matching the total depth of cut
It takes only slightly longer to do the machining than it does to describe
the process.
Done carefully, the vibration of the converted motor is no worse the the
original motor was.
Regards,
Herr Zapp
--- On Mon, 12/1/08, Phil Tuck <follies@xxxxxxxxxxxx> wrote:
From: Phil Tuck <follies@xxxxxxxxxxxx>
Subject: [TCML] Salient Pole Query
To: tesla@xxxxxxxxxx
Date: Monday, December 1, 2008, 2:16 PM
Hello.
I am thinking of a SRSG as my next 'project' and have looked into
salient
pole motors converted from induction motors. My own motor has very little
info on the label so I am unsure as to its suitability.
The website at
http://evolve000.4hv.org/tesla/tc2srsg.html
describes the work involved and my motor does indeed look similar, although
my armature has individual segments on its surface, whilst the webpage
example has a plainer looking armature.
Could someone look at my temporary page at
http://homepage.ntlworld.com/follies/temp/temp.html
and let me know if my motor is indeed suitable.
My motor though is rated at 1425 rpm, while the web article only describes
1750 (needs 4 flats) & 3450 (needs 2 flats) rpm motors however.
I am UK based at 50 cycles is that the reason for the difference?
Regards
Phil
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