Subject: Superchargers

From: [email-masked] (Earl C Edgerton)
Date: Thu, 27 Jun 1996 16:02:45 GMT

Does anyone know if there are any plans available to build a supercharger (blower)
for automotive engines.  I have a Ford Flathead V8 and I would like to try 
fabricating a blower for it, similar in style to the ones that were built in the 
50's.  Maybe some of the "ol timers" (no offense) here had some experience during 
those "nostalgic" days.  I've seen some pictures of different blowers and they
look relatively simple in design (but so does a modern 6-71), but they want
an arm & a leg for one....I would appreciate any help.

Earl

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From: [email-masked] (Blake Malkamaki)
Date: Thu, 27 Jun 1996 23:32:46 -0400

In article <[email-masked]>, [email-masked] wrote:

}Does anyone know if there are any plans available to build a supercharger
(blower)
}for automotive engines.  I have a Ford Flathead V8 and I would like to try 
}fabricating a blower for it, similar in style to the ones that were built
in the 
}50's.  Maybe some of the "ol timers" (no offense) here had some
experience during 
}those "nostalgic" days.  I've seen some pictures of different blowers and they
}look relatively simple in design (but so does a modern 6-71), but they want
}an arm & a leg for one....I would appreciate any help.
}
}Earl

Didn't they use a lot of Paxton centrifugal blowers?  I believe they are
still available.
Blake Malkamaki, Little Mountain Ironworks, Concord, Ohio <[email-masked]>
>>Steam engines - Cletrac Crawler Tractors - Maple Syrup - Metal Signs<<
http://www.ncweb.com/users/blake

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From: Dave Ruigh <[email-masked]>
Date: Fri, 28 Jun 1996 16:03:06 GMT

> an arm & a leg for one....I would appreciate any help.

I've been a bit busy lately to spend much time with the newsgroups, but 
I can't resist, this has to be one of my all-time favorite "lifetime 
projects" (building a supercharger).

B&M, Eaton, and others do build Roots-type (the GM 6-71 style) blowers
for automotive applications, though they are in the $2k - $3k+ range.
I don't know of any specific plans available, though I've seen data
in mechanical engineering texts on the various blower types. (Check the
library for "Marks Mechanical Engineer's Handbook" & books on air compressor 
design.

In principle, the Roots blower is quite simple, the rotor's basic form
is an epicycloid, a circle rolling on a circle. There are different
flavors, straight rotors, helical rotors, 2 lobe, 3 lobe, 4 lobe etc.,
as well as variations like the Lysholm (used in many large air compressors
and refrigeration systems). Newer designs use Teflon or other polymer
resin coatings on the rotors, which are typicaly aluminum.

I have an old 3-53 GM blower (off a small tractor or stationary engine)
that would probably work well with the swept volume of your flathead
motor. It has 2 lobed straight rotors 4.5" dia X 6.5" long. The rotor
axes are 3" apart and drive with helical gears. Unfortunately, this blower 
saw hard use on a VW dragster, and would not be usefull for high levels of
boost due to excessive rotor clearance. My original plan was to machine 
new rotors and use this case... that was in 1978. 

The cheif problem when contemplating machining the rotors is accuracy,
the rotors must run very close (.002" - .006" or so) without touching,
and this clearance must be constant throughout the pumping "cycle".
Obviously CNC would be able to handle this easily, I machined a test
piece out of delrin with the proper shape by just cutting the 2d 
cross section. For the final rotor shape I was going to use the 4th
axis, since it'd be nearly impossible to machine the 6.5" long
part from the end, and make multiple passes with a ball end mill.
You could get darn close with a manual machine using an acurate template.
Set up the work between centers, or in some type of fixture that allows
you to position it repeatably it about it's (the rotor's) axis. Rough the 
shape out with a regular 2 flute end mill by eyballing it, then when 
you're ready for the finish passes, touch off on the template (attached
to the end of the workpiece) with the ball end cutter, spacing your
cuts for minimum scallop. A straight 2 lober could probably be done in 2 
setups at 180 degrees, since you can get to half the shape in each. Use
a ball just under the minimum curvature of the template. This is just
one idea, there are many ways this could be done, grind a form cutter(s)
to develop the shape in one pass, use a cam following arrangement with
the quill (like a tracer), etc. Not a project I would take lightly, 
but certainly possible with the right equipment (at least a mill).

Good luck if you decide to take on this project!

Dave