Porsche 9Electric
Adapter Machining and Welding

My electric car bolts the electric motor to the original gasoline car's transmission. Naturally, it won't bolt on directly, so I had to make an adapter that mated the two. This ensures the electric motor shaft exactly lines up with the transmission input shaft. If these get off center, by even around 0.010 inch, it can cause vibration. This page concentrates on machining and welding. The page with the design notes is here: http://explodingdinosaurs.com/9electric/adapter/ .

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 gets dirty.
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 table.

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...

You can read about more of my car adventures on my main page: