| Let
me start by introducing a few friends of mine. First would
be my assistant in this project and subsequently the reason
for a few of the "fuzzy" photos you'll see. She
is my 2 1/2 year old Ridgeback/Shepard puppy named Chloe. |
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| The
second is my circa 1989 Garrett Wade 16" shortbed lathe.
This is the focus of the project. To take the 560 minimum
RPM, 5 step pulley system and convert it to variable speed
with a direction reversing switch. I would also like to
thank Mark Kauder, who turned me onto the idea and Randy
McKinney of Vega
Woodworking for his help in obtaining the motor for
this article. Vega Woodworking can be reached via the web
at http://www.vegawoodworking.com/
or by calling 1-800-222-8342. The motor is a 1 hp DC motor
and comes with a motor mount, controller circuit board,
potentiometer and wiring instructions. Cost for the package
$49 + $8 shipping. |
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| First
step, take the thing apart and clean it out. From here it
is obvious that I'll need to figure out some sort of debris
inhibiting system as the new motor comes without a case
and this much dust and shavings would surely bury and possibly
fry it. |
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| Once
it's clean, take measurements to find the center of
the current motor's spindle. We will need to line
the new motor's spindle up at this mark to ensure
the belt and pulleys will align correctly. |
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|
| Finish
the disassembly of the old motor. Make notes along the way
of which bolts go where, how things align and such so "design
opportunities" can be easily addressed later if necessary. |
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| You
will notice in the first picture that my lathe uses the
weight of the motor and a handled locking bolt to tension
the pulleys. Loosen the bolt and lifting releases tension,
letting it down puts tension back on the belt and the bolt
tightens the whole thing in place. The way this works is
there is a "see-saw" plate that the motor is bolted
to that allows it to swivel on the vertical plane. The new
motor comes with a universal mounting bracket, so some modifications
were necessary to make everything line up as the original
motor was a good deal larger in mass. The following is the
method I used to make the new motor mount up and retain
the original belt adjustment feature. This also allows for
easy re-installation of the old motor if that is ever necessary. |
| With
the new motor installed, take measurements to determine
the amount of space we will to adapt for to line up the
spindle. Refer to the earlier measurements to find the difference.
Aren't waste blocks handy? |
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| Here
I have removed the "see-saw" plate and cut a spacer
out of MDF that will bring the motor to line up with the
headstock spindle. Note the cut outs for easier side to
side adjustment of the motor. |
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| Here
I have reinstalled the motor and added Ash spacers to the
opposite site of the "see-saw" plate. These spacers
will bring the set-up within range of the side where the
locking bolt needs to be to hold the motor in place once
tension is adjusted. I used two 5 1/2" pipe clamps
to secure the Ash spacers to the motor. Once mounted, verify
the spindle location matches the original motor spindle
location. I then marked the center of the locking bolt opening
from the lathe onto the Ash spacers and inserted a threaded
brass insert (normally used for table legs that thread onto
table bottoms) into the Ash spacers. This allows for a very
secure thread for the locking bolt to go into. |
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|
Now comes the
wiring and modification of the circuit board (if you wish
to). The modifications for the circuit board were found
on this website, http://www.rmwt.org/wttips/motor.html
courtesy of Bruno Melli and the Rocky Mountain Woodturners.
To compete the wiring portion, I purchased:
- 2 - 115v
cooling fans from Radio Shack ($19.99 each)
- 12 feet
(each) of green, red, black & blue 16 ga. stranded
copper wire
- a 3 position
(center off) double pole, double throw (DPDT) 10amp
switch from Radio Shack (part # 275-653)
- a handful
of female spade connectors
- a handful
of 18ga. (yellow) barrel crimp connectors
- 10' roll
of split flex-loom (the black plastic tubing that is
split down it's length to wrap and protect wires easily)
- a sheet
of 20 ga. weldable steel
I already had
the soldering iron and solder, but to make one of the
modifications below you'll need to either have, buy or
borrow one for yourself.
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| The
first modification involves removing transistor T3. This
transistor limits the speed the motor can start at to 0.
What this means to a woodturner is having to turn the speed
down everytime you turn the motor off. A time waster. To
override this and allow the motor to start at whatever speed
it was stopped at, simply remove transistor T3. The picture
shows where T3 used to be. (you can still see part of his
legs where I hacked him off at the knees). |
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| The
next modification involves removing a circuit trace between
pins 6 and 7 of the chip and then jumping pin 6 to pin 8.
The reason for this modification is to eliminate the "ramp
up" that comes standard for the motor. Without this
modification, the motor will start at 0 and run up to the
chosen speed and will take longer to get up to the desired
speed setting. (It's only 5-10 seconds longer, but why wait?)
The easiest way to remove a circuit trace is with a razor
knife or anything sharp. Start cutting/picking away the
trace until there is no more gold between the 2 pins. Once
you have removed the trace between pins 6 and 7, take a
single strand or 2 strands from a short piece of the 16
ga. copper wire and solder it between pins 6 and 8 to create
a jumper. |
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| At
this point it was time to make a housing for the circuit
board to protect it from flying objects and possible bumps
from tools and such. Using the 20 ga. steel plate, I cut
and bent a box to cover the circuit board and cut an opening
in one end for one of the cooling fans. I also let the opposite
end 1/4 open to create a positive pressure outlet. This
way any debris that might get in can exit through the opening.
This will set-up will help keep the circuit board cool and
dust free. |
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| While
in metal cutting mode, I created an opening in the lower
cover plate of the headstock and mounted the other fan inside.
This fan will blow air down over the motor compartment creating
a positive pressure here also and thus keep a majority of
the debris from entering and infecting the motor. Note the
extra holes in the plate that will be used to run the wiring
to the various switches. |
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| Next
came running the wires from the circuit board to the motor
and switches. I recommend wiring everything per the included
diagram first and making sure it all works prior to adding
the reversing switch. The reversing switch wiring is a complete
separate operation, so you will not have to go back and
"re-do" anything anyway. Click
here for a copy of the wiring diagram. |
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| Here
is where the split flex-loom comes in. while the wires are
still loose, it is easier to guide the split loom on. |
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| Make
sure to guide the wires in such a way that adjusting the
motor and changing the belt on the pulleys will not put
tension on them or pull them loose. If necessary, tape or
wire tie them out of the way. |
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| Install
the switches into a new box or into the control panel. I
mounted the reversing switch at this point to determine
where I would have to run the wires. Test the operation
of the motor and make sure the speed control switch works
properly. |
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|
This is the
wiring diagram for the reverse switch. Click the picture
at the right to enlarge it, it will open in a new window
so you can read this and refer to the diagram at the same
time. Earlier the wires from M1 and M2 were run to the
motor. You'll notice a yellow and a black wire running
out from the motor windings to opposite poles on the motor.
These are attached to the motor by female spade connectors.
You can switch these two wires to reverse the direction
of the lathe. This is where the switch comes in. Cut the
black and yellow wires, leaving enough room to splice
a length of wire to each of the four new ends. I have
color coded the wires and numbered the switch to make
things easier to read. The numbering on the switch you
purchase may differ, as this is for illustration purposes
only.
Determine "which
direction is up" on the switch. It really doesn't
matter to the switch, but you'll need to know for the
wiring. Take the yellow end coming from the motor windings
and attach it to one of the center poles (row 2). Take
the black end coming from the motor windings and run it
to the other center pole (row 2). Now wire a jumper from
A1 to B3 and splice the yellow end coming from the female
connector to it. Next wire a jumper from B1 to A3 and
splice the black end coming from the female connector
to it. Once all of the connections are made test the switch.
Select one of the "on" positions (either to
the left or right) and turn the motor on. If all works,
turn the lathe off, change the motor direction via the
reversing switch and ensure the direction of the motor
changes. Once everything checks out, finish putting the
lathe back together and start turning! I did notice that
I get a more controlled response from the motor if I turn
the lathe off before changing the direction of the motor.
|
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| Note
on the pulley assembly...My stock pulley had an opening
of 3/4" while the spindle of the new motor was 5/8".
I visited my local hardware store and picked up a 3/4"
OD (5/8" ID) x 1" brass bushing. This was a perfect
fit to adapt the original pulley to the new spindle and
it cost about $1.50. |
