The rough cuts for
the adapter were made using a plasma cutter.
This ugly thing I call a
"sacrificial plate." Its purpose is to protect the machine from getting
cut -- it is OK to gouge this piece, but not the machine itself below
the plate. I cut this piece out with a plasma cutter. It does not need
to be precise.
This picture shows my
combination lathe/mill. It is a Harbor Freight special, and will pay
for itself with just the job of making my motor adapter. Here you see
the sacrificial plate on a rotary table, getting milled nice and flat.
The yellow thing is a coroplast campaign sign that keeps oil and bits
of metal from hitting a wall plug.
This is a closer view
of the sacrificial plate getting machined flat. I put the bolts out
wide to mill the inside, and in close to mill the outside. I also moved
the bolts one at a time, so the plate wouldn't move relative to the
rotary table, to preserve the accuracy of the flatness. The plate is
not shiny because it is still covered with machining oil that quickly
This is a little side
trip. My daily driver car was rubbing its brakes after I put in new
axles, so I machined thin spacers that went under the brake disks. You
can see the 5 bolt lug pattern and outer diameter of the spacers cut
into the sacrificial plate.
Now the motor plate is
sitting on top of the sacrificial plate. It was rough cut with a plasma
cutter. Note it is held on by its center hole, just long enough to do
the four holes that will hold it on very firmly.
Now the plate is
firmly attached to the rotary table by the four holes. This is the only
purpose these holes will serve, they won't be used when the adapter is
installed in the car.
This closeup shows the
plasma cut was a little bit rough. I milled this outer edge just for
looks. The plasma cut is hard to machine, apparently the plasma cutter
hardens the metal. In the future, I would just use the machine to cut
out this circle. It would make a perfect cut, and not take much more
time. The center four inch hole was also machined at this time. This
precisely centers the motor plate on the electric motor, and is precise
relative to the rotation axis of the rotary table.
Note the motor plate
(bolts directly to the electric motor) and the spacer are left on the
rotary table for welding. This is important. The axis of rotation of
the rotary table defines the center axis for the adapter. You want this
center axis to remained centered so the clutch, transmission, and motor
shaft centers of rotation all remain lined up, to prevent vibration. If
the adapter were removed at this point, it is almost impossible to get
it back on in the exact same spot, introducing some error. The welds
were far enough from the rotary table, and the rotary table has a big
enough thermal mass, that I wasn't too worried about overheating the rotary
You can see a single tack weld in the left picture. Four evenly spaced
tack welds were done to start. Then inch long welds were done in
between the tack welds, and then welds between the welds, etc. You
don't want to just go around steadily, due to heat warping effects.
The weld goes all
the way around. Note the heat discolors the metal.
This first picture
show the measurements came out perfectly, the spacer (hoop shaped part)
is big enough for the inner motor bolt circle, but small enough to fit
within the tranny plate's bolt circle. There is just enough room for a
washer and to put in the bolt. Welding here, though, would not allow
enough room.The next two pictures show the welds were done between bolt
holes, to leave enough room for the washers and bolts. Side note: Some
adapters just weld four sections, covering about 50% of the total
circumference. It might have been overkill, but I welded inside and
outside, and as much of the circumference as I could.
C-clamps were used
to temporarily hold the adapter on the transmission. Note the rotary table
is still attached. Hole marking punches were used to mark
where to drill the tranny to adapter holes. These holes do not need to
be precise -- they do not center things. Centering is done by the
tranmission lip, and the centering ring on the transmission.
There is a jump
of time here. I painted the adapter. Even though I used soap
and hot water to clean it, and sanded it, paint would rub off on my hands for
about a week. I think there was still some oil in the metal's pores.
The Porsche has a very tight fit for the flywheel, and unfortunately my flywheel had a light rub. In these pics you can see I recentered the adapter on the rotary table by using a micrometer gauge, tapping with a hammer, and spinning the rotary table until the gauge had minimum deviation. Then I machined a bit more to give the flywheel more clearance.
I likely didn't allow enough cooling time between welds.
Unfortunately, even though it is 1/4 inch steel (0.6 cm), the tranny plate warped upwards
like a Mexican hat by about 0.060 inch. I machined it flat, but now my adapter was shorter
than originally designed. I made a spacer from sheet metal to compensate.
I literally put my blood and sweat into this project! It's a funny story, here it is:
Mistake 1: "The garage is messy and it would take too long to excavate my sturdy metal working cart."
Mistake 2: "This tiny, lightweight, flimsy patio table will work great!"
Mistake 3: "I don't want to have to sweep the hard, level concrete, so I'll just put the table on the grass!"
Mistake 4: "I don't want to have to clean the tabletop, either, so I'll put this big, lightweight wood board on it!"
I placed 20 kilograms of rotary table and transmission plate with a jagged, 1/4 inch steel edge on the flimsy table.
The wind got under the big board, and blew over the flimsy table on the soft grass.
The jagged edge with all 44 pounds of gravity driven fury was stopped by my leg.
Argh, a 3 inch, bleeding gash!
I was the model patient, waiting patiently (ha ha), laughing at my own stupidity, and they all wanted to hear how I hurt myself with a race car that had not moved yet.
The emergency room doctor seemed to take a special liking to me, and said "I get to do stitches" in all too happy a voice, although ultimately stitches weren't needed.
She kept insisting I return in 2 days.
I found it odd she wanted me to use an emergency room for a nonemergency checkup.
With my usual lightening quick mental processes, two days later I realized she was hitting on me and using the wound as an excuse to see me again. But, it turns out, that was wrong. The bill was $600 for five minutes of work... She probably just wanted to earn another quick $600! I now have a big, interesting scar on my leg, it is in the shape of the Klingon symbol for stupidity!
Update: A medical doctor and DeLorean EV converter ( http://www.electricdelorean.com/ ) emailed and said it was not unusual to ask a patient to come back to an emergency room two days later to check a wound, and that follow-up would probably be no charge. I still think she was hitting on me... but wait a moment... maybe her real interest was the electric car...