I have always wanted a selectable supercharger like Mad Max had.

Yes I know it was just a movie and it could not work. But it would be cool to be able to switch on the supercharger when needed.

Ron

NOS would work! If you want toggle switch on off control. :D

rj,

CAN DO - WILL work.

Electromagnetic clutches are used today on every Mercedes that has a blower. Computer controls when it is on and when it is off - Motor starts with it on, and it engages whenever the motor accelerates beyond a certain rate (rate of acceleration that is).

Larger A/C clutches will transmit a big chunk of horsepower (think bus A/Cs).

The Mad Max "big red button on the side of the Hurst shifter" can be done. Go for it.

*********************

Now,
I can't say who ran the first 6-71 blower, but in 1952 Ernie Hashim ran a 4-71 blower on a Ford flathead V8, and in 1955, he mounted another 4-71 blower to the FRONT of a Chrysler Hemi and ran a snake of intake hoses to a methanol injection setup. Ernie and Ed Iskendarian ran a side operation, also in the mid 50s, converting 6-71 blowers from WW2 surplus for automotive use.

That's as close as I can get to Tomcat's quiz of the night.

You are correct sir! I knew about the front mount with pipes, not the flathead. I think the Hemi is in Big Daddy's museum.

OK guys how can it work? I thought a roots type blower is a positive displacement pump so that if it wasnt turning it would not let any air through at all.

If you have a roots blower on an engine and you take the blower belt off will the engine run?

Ron

Rj,

The Mad Max car was fictional. The blower has to spin for the motor to run, unless there is a vacuum bypass in the blower (there are some OEM Eatons with a vacuum bypass, but not a regular 6-71). You CAN, though switch a clutch to DRIVE the blower or let it freewheel. You just won't get the cool look of the movie by going from STATIONARY pulley to SPINNING pulley unless you clutch both ends of the belt (I reckon that would provide the proper look).

The blower will freewheel, engine vacuum causes it to spin. Yes, an engine will run with no blower belt - if you watch drags, you'll see lots of cars finish a run with no blower belt (they don't usually WIN that way, though).

***************

Tomcat

Garlits museum ROCKS.

Even the incredibly NON MOTORHEAD wife got a charge out of it.

Last time we went (a good while back), my kids were 6 and 8. My 6 yr old ended up leaving with a HEMI connecting rod necklace around her tiny neck (I had to tie a knot in the chain).

Ron,
Lost a belt on my 525SCs, still pulls enough vacuum to turn the rotors and run. Happens all the time in blown dragsters.
But for it to be efficient, you would have to bypass the blower. You would simply need to close the bypass when the blower is engaged.
Gary

FYI:
In Mad Max the blower was just an empty casing with a carb inside.

I found this at MadMaxMovies.com
There's some interesting info on the original move there.

The Blower

The supercharger is made by Weiand (pronounced "why and"). They make twisted-vane, roots-style superchargers for many after market applications. The system uses a GM 6-71 case as the base, and a Scott injector hat at the top.

On the movie car, this was all faked. The supercharger was empty and the carburettor sat inside. A small water pump was attached to the front of the supercharger to hold the drive wheel, this also moved the supercharger belt forward to clear the standard 351 water pump assembly, and the distributor has a 90 degree elbow to allow it to clear the supercharger. The supercharger belt is driven by an electric motor which is hidden by a yellow bucket in the garage scene in MM1. Weiand never had a supercharger that could be activated and deactivated. Even with huge compression it would be tough to generate 600bhp on a 351 in 1974 without rebuilding it once every couple of hundred miles.

Of course, most people building replicas have not duplicated the above convoluted setup, and have opted for a variety of different setups to duplicate the same basic effect. As long as the blower sits at the right height out of the bonnet, and the pulley spins, it doesn't matter too much what method you use to hook it all up

Iggy,
So you're saying everything/everyone in Hollywood is phony. Who wouuld have guessed?:D
Gary