924Board.org

[ideola]

This weekend, a good family friend opened up his garage, invited another friend (o.k., well, really, Bill is Tom's second cousin once removed...but that's another story), and we used his 12x36 Craftsman Commercial lathe to make the pulley for my axle-driven alternator.

Started with the raw materials:


Tom scribed the pattern for the bolt circle, then mounted the stock in the chuck, and we started by drilling a pilot hole in the center of the stock


I get my first lesson on the lathe


After drilling out the pilot hole, we then set up a boring tool to continue hogging out the center...needs to be large enough for the CV boot to fit through.


I amaze my darling wife with my prowess


Finally, the center bore is completed


Next, after a few calculations, we scribed a line at the bolt-hole center circumference and used a punch to mark the locations of the bolt holes


My good friend Tom Swenson working at the drill press


Now it's time to take the O.D. down to 6.25" so we have the correct 3:1 pulley ratio


With the O.D. completed, we then started work on the multi-v-groove with a special tool Tom made up the night before


Perfect fit for a six-rib serpentine style belt!


The final operation was to hog out some material to lighten the pulley and reduce the size of bolts required.


Master Machinist Bill Grier hands me the finished product, even better than I had envisioned!


Cleanup...


Catalog shot


I haven't weighed it yet, but by feel, the large pulley feels even lighter than the 2" alternator pulley! The CV boot is a PERFECT fit, the pulley will snug up flush to the flange on the boot and there is TONS of room to safety wire the heads of the bolts and also to allow for the range of motion on the half shaft axle.
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erstwhile owner of just about every 924 variant ever made

[tuurbo]

Very very cool.
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1980 924 turbo, MSD, Meth. Inj, otherwise stock.

[Min]

ahhhh, the feeling of making something from scratch and having it come out exactly the way you want.

Min
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Custom means it didn't come from a box.
1980 n/a with EDIS and Megasquirt II Injection. 7 different colors and counting.

[fiat22turbo]

Looks good!

Pretty much what we went through to rebuild the EDIS trigger wheel adapter. Luckily the person whom shop I'm borrowing likes to buy tools so we now have a rotary table for the milling machine, makes drilling spaced holes much easier.

Before anyone asks, I did get in on the group buy for the trigger wheel here, but after looking at the way it mounted on my non-A/C car, we wanted it to be centered on the crank to reduce the potential for wobbling and to shorten the nose as well to make mounting the sensor easier.
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

[Chrenan]

Remember, when working on a lathe you should always wear a tie, no tie clip, leave your long hair hanging, and keep your pocket watch dangling out of your waist coat pocket.
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1987 951 - M193 Version for Japan

[ideola]

Stefan, what are you doing with the trigger wheel from the group buy???

[fiat22turbo]

recreating the mount to mount it concentrically to the crankshaft and to shorten the nose since I don't have A/C.

the original piece relies on the bolts to hold it all in place an given the tolerances required with a trigger wheel, I didn't want to chance it coming loose or fight with getting it centered when installing it.

Not too mention shortening the nose will allow for the sensor mount to be much simpler and a bit more sturdy as well.

It probably would have worked fine the way it was, especially if I had A/C (was planning on adding it at some point, but that's just silly for a weekend driver/track car)
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

[ideola]

Good insights, thanks!
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erstwhile owner of just about every 924 variant ever made

[Rich H]

[bnoon]

What I wouldn't give to have a large commercial lathe like that. I'm amazed at the things I create on my 18" wood lathe that I converted to work light metals (brass, aluminum, etc). Nice stuff!!!
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'80 924 Turbo - SOLD!
1986 Porsche 944 Turbo - SOLD!
Porscheless

[Joes924Racer]

hey metal lathes and milling machines are really cool.
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1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.