# Hobby Machinist's Supercharger



## racecar builder (Jan 10, 2020)

It is basically a Judson supercharger.

Judson's were for @ 2000 cc.'s VW engines.

Any dynamics engineers out there know how big one would need to be for a small block V8?

I'm thinking as backup two of them.On top of engine ala GMC ones.

Here is pic of internals of Judson eccentric supercharger.


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## Superburban (Jan 10, 2020)

Find the formula for estimating the proper flow of a carb, that should get you in the neighborhood. It is based on engine size, and estimated RPM's.


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## rwm (Jan 10, 2020)

Are you gonna build these?
R


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## racecar builder (Jan 10, 2020)

Thank you Superburban and RWM

'formula for estimating the proper flow of a carb'

Good idea!

'Are you gonna build these?'

Yes we are.Make plans, then wood models and then a prototype.

There is a simpler type with the 'spool' centered in the bore.

Plus they can be made with blades at 90 degrees instead of slanted like in pic.

Some blades are made of cotton mixed into bakelite.Older ones.

I actually own one of a sort.

It is Sprayit 400 compressor.Thomas Industries very first product.It was advertised in Popular Mechanic's.

The spray gun that came with it lives on as the Sprayit 4000.Different company makes that now.

Sprayit 400 has central spool with slanted blades.Makes a nice howl!


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## mksj (Jan 10, 2020)

I remember the Paxton superchargers from many years ago, they seem to be making a comeback, I recall when turbo's were the hot item. Paxton superchargers are a bit more expensive, and a bit more Hp.





						Paxton Supercharger Systems Small Block Mopar - JEGS High Performance
					

Adds 30-75% additional horsepower depending on  boost levels. Applications include 1967-1976 A-body models such as the Dart, Duster, Demon, Scamp, Valiant and the 1967-69 Barracuda with 318, 340 and 360 small block V8s.   Complete systems include Novi 1200 centrifugal superchargers capable of...




					www.jegs.com
				




My concern with the Judson would be the longevity of the blades and what happens to the engine when a blade breaks and gets sucked into the motor. The original Judson vanes were phenol impregnated linen, I still use the CE version of this material for control system boards. 

Picture I saw of a dual  supercharger setup in a bug. Nifty.


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## GL (Jan 10, 2020)

Another idea for sizing, look at CFM ratings for Procharger super chargers.  They are, essentially, belt driven turobo's, but would get you in the ballpark.


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## Superburban (Jan 10, 2020)

GL said:


> Another idea for sizing, look at CFM ratings for Procharger super chargers.  They are, essentially, belt driven turobo's, but would get you in the ballpark.


I think your idea is more accurate. A carb needs to accommodate all the CFM's of the engine, but a supercharger increases its CFM, along with the engine speed increase.


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## racecar builder (Jan 11, 2020)

Thank you for the responses.

Quick and dirty way or get it done way is to increase the Judson size.

If the Judson is for 2000 cc or 122 cubic inch then triple the size and it would be for a small block.

Quadruple it for a big block.480 cubic inches would cover 440, 454 and 460.

Keeping it simpler.Build one Judson size and test it on a Corvair motor.

145 cubic inches which is a little bigger than VW but close enough.

I will look at intake and exhaust on our little Sprayit 400.

Here is a pic of slots on an MG supercharger.Probably from 30's to 50's one.

Don't know if that is intake or exhaust though.


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## bill stupak (Jan 11, 2020)

I had a Judson charger on a VW in the 60's when I believe there was only 1200cc engines.


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## racecar builder (Jan 11, 2020)

Thank you Bill

Judson was in Pennsylvania where you are.

Anyone interested in building one of these just PM me and I will forward info we have gathered together.

These are 'low pressure' superchargers as opposed to GMC ones.

Okay with us.

Dimensions for Ford V8 (flathead) version Judson built is 6" bore by 8" link case.

Ford V8's were about 220 cubic inches to 255.

So doubling it.6" by 16" long case would work for big block OHV V8's.

All green lights so far for making it the hobby machinist way.

Also no need for castings so far.

Looking good.


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## bill stupak (Jan 13, 2020)

Yeah, they were in Conshohoken, just a couple miles from where I lived.  Stu


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## pontiac428 (Jan 13, 2020)

It's kind of hard to bolt a random supercharger on an engine all willy-nilly and expect to get it to idle, let alone handle transient throttle movements without things going boom somewhere.  Knowing the displacement and drive ratio is just scratching the surface for balancing the thermodynamics and fuel/spark requirements of the system.   A developed boost map (adiabatic efficiency from pressure ratios and volumetric performance) is the minimum info required to tune a forced induction system.  You could put one of these on your riding lawn mower and tune it to run okay at one spot in the throttle's sweep by trial and error, but if you want to run that supercharger "wet" first invest in some kevlar undies to protect your peanuts!


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## Herk (Jan 14, 2020)

Superchargers are sized based on the desired power output, not engine size.  Figure out how much air you need to flow to produce the power you want and work backwards.  You're just making a single stage air pump into a two stage air pump.  

Something else to think about is the scalability of a positive displacement vane type compressor.  I suspect the thing will end up being impractically large and heavy for what you'll end up with, not to mention using a lot of power to operate.  The Judson and Shorrock blowers were only marginally effective in the late 50's and completely abandoned once cost effective turbochargers came onto the market in the early 60's.  In fact this is about the only supercharger design I can think of that has never been used in an OEM automotive (or aircraft) application.  

Not saying it wouldn't be an interesting project.  Just not racecar parts.


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