Riddle me this, twin screw... Not your normal question

AZ ERIK

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Ok, so for 4 years I have asked myself this but never asked anyone that would know, even Art Whipple and Ed Martienez...

Why is a KB or a Whipple called a twin screw? Both the 2.6 kb and the 2.3 and 3.4 Whipples are not 'twins'. The Whipples have 1 3 'lobe' rotor and 1 5 'lobe' rotor, the 2.6 kb is 1 4 'lobe' and 1 6 'lobe' rotor. Where is the twin part in that?

Now on to the NHRA offical rule book, where it states, many times mind you, 'screw type superchargers prohibited'. So you mean to tell me I can't run a Whipple at the track? And yet I get through tech fine, and they can't be 'just ignoring' that 'little rule' as it's stated some 5 or more times in every power adder and class deffinition.

So the way I see it, someone is wrong, but who? Because nearly everyone here says the Eaton is a roots blower (3 lobe, identical profile) but that the 'twin screws' (which I think is only the kb 2.3) are king, I'm not sure about the rotor profile for the 2.3.

Can someone clarify?
 

BuckChoklit

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Twin Screw
Twin%20screw%20rotors102804.jpg

Eaton Lobes
523.14.jpg
 

AZ ERIK

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How is that a twin? look, rotor on right, 5 lobes reverse profile, rotor on right, 3 lobe positive profile.

barbi-twins-photo-barbi-twins-6223646.jpg

Twins, identical.....
 

kyl

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Twin doesn't necessarily mean identical. I think they were substituting the word pair.

Pair Screw Supercharger - Twin Screw Supercharger

Dictionary - "either of two persons or things closely related to or closely resembling each other. "
 
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ecoastkid

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It very well may be banned in certain classes. That doesnt mean you cant run it at test and tune, or in numerious other classes.
 

BuckChoklit

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How is that a twin? look, rotor on right, 5 lobes reverse profile, rotor on right, 3 lobe positive profile.

I believe they're inferring "Twin" as meaning two. You can see a clear difference between the Eaton rotors and the Whipple screws. The lobe does not have nearly the helix the screw does.
 

AZ ERIK

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I understand all this, I have even had my eaton and whipple and a 2.6kb appart on my work bench. I'm also a machinist and understand the profile and helix of all of these rotors. I'm not being stupid here, I'm asking completely valid questions.

If an eaton is a roots, and kb's and whipples are called twin screws are then not, by rule definition outlawed on NHRA tracks? By the 'screw type superchargers prohibited' rule in many places. I can not find a single area in the book that states specifcs about safety equipment required.

The whole reason this came up is I need to get a jacket, and needed to know the spec on it. I only found 'prohibited' statements. I know the 'aftermarket supercharger rule' exists yet I can't find it.

Going back to the twinscrew question, if it's a matter of the rotor profile couldn't the eaton be called a 'twin flap' blower? As the rotors are the same and mate very closely, just like the whippy?

I agree it probably is a misuse of words that's causing this confusion for me, besides it was only a question, nothing to get anyone upset about, I was just thinking aloud.
 

03blklightning

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I thought that when describing a blower as "roots type". You are just decribing the location to where the blower is mounted.

Roots: On top of the intake and feeds directly into the intake. No need for extra plumbing. (Eaton, Whipple, Kenne Bell, Magnus)

Centrifigual (sp): Mounted seperate from the intake. Needing extra plumbing to feed into the motor. (Vortec, Paxton, Procharger)

I may be wrong, but thats how I understand it.
 

BuckChoklit

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I thought that when describing a blower as "roots type". You are just decribing the location to where the blower is mounted.

Roots: On top of the intake and feeds directly into the intake. No need for extra plumbing. (Eaton, Whipple, Kenne Bell, Magnus)

Centrifigual (sp): Mounted seperate from the intake. Needing extra plumbing to feed into the motor. (Vortec, Paxton, Procharger)

I may be wrong, but thats how I understand it.

Roots is a reference to an Eaton type supercharger. However--Eaton, Kenne Bell, Whipple, etc. are positive displacement superchargers, meaning they are directly a part of the engine.
 

Sinister04L

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I thought that when describing a blower as "roots type". You are just decribing the location to where the blower is mounted.

Roots: On top of the intake and feeds directly into the intake. No need for extra plumbing. (Eaton, Whipple, Kenne Bell, Magnus)

Centrifigual (sp): Mounted seperate from the intake. Needing extra plumbing to feed into the motor. (Vortec, Paxton, Procharger)

I may be wrong, but thats how I understand it.

"The Roots type supercharger or Roots blower is a positive displacement pump which operates by pulling air through a pair of meshing lobes not unlike a set of stretched gears. Air is trapped in pockets surrounding the lobes and carried from the intake side to the exhaust. The supercharger is driven directly from the engine's crankshaft via a belt or, in a two-stroke diesel engine, by spur gears.

It is named for the brothers Philander Higley and Francis Marion Roots of Connersville, Indiana, who first patented the basic design in 1860 as an air pump for use in blast furnaces and other industrial applications."


The centrifugal supercharger is called so because of it's centrifugal compressor.
 

speedfreak440

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I thought that when describing a blower as "roots type". You are just decribing the location to where the blower is mounted.

Roots: On top of the intake and feeds directly into the intake. No need for extra plumbing. (Eaton, Whipple, Kenne Bell, Magnus)

Centrifigual (sp): Mounted seperate from the intake. Needing extra plumbing to feed into the motor. (Vortec, Paxton, Procharger)

I may be wrong, but thats how I understand it.


A "ROOTS" supercharger or any other positive displacement supercharger can actually be mounted anywhere & have the air funnelled into a standard intake. It's just ALOT more common & practical to mount them in place of a standard intake manifold.

As far as the OP is concerned it's really just a case of differing terminology. Specifically what class are you tring to get into?
 

LSUstang05

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Roots:
super-charger-fix.jpg

"As the meshing lobes spin, air trapped in the pockets between the lobes is carried between the fill side and the discharge side. Large quantities of air move into the intake manifold and "stack up" to create positive pressure. For this reason, Roots superchargers are really nothing more than air blowers, and the term "blower" is still often used to describe all superchargers."

Twin Screw:
super-charger-13.jpg

"A twin-screw supercharger operates by pulling air through a pair of meshing lobes that resemble a set of worm gears. Like the Roots supercharger, the air inside a twin-screw supercharger is trapped in pockets created by the rotor lobes. But a twin-screw supercharger compresses the air inside the rotor housing. That's because the rotors have a conical taper, which means the air pockets decrease in size as air moves from the fill side to the discharge side. As the air pockets shrink, the air is squeezed into a smaller space."
 

AZ ERIK

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Damn we have some smart people in here! I think someone other than me might find this thread handy :)

I'm not trying to get into a specific class, I run Sportsman, but could not for the life of me figure out a real meaning behind 'twin screw', backing up this misuse of words, Lyshomn was commonly refered to as a Whipple, when fact of the mater Whipple only made kits to mount a Lysholm compressor. KB did the same thing with AutoRotor. I know a few peole that would want to punch someone for calling their kb an autorotor, even though it says so right on the front of the 2.3! Bbbwaaaaaa I'm not even 100% sure Whipple really makes their on compressors still, I didn't think they had the facility for it.
 

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