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Eaton M45 Superchargers

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Autumn 2003; A used Eaton M45 has been acquired for use on The Fang, information and tips to follow.


AS it's name suggests, and like the Shorrocks C75 series, the Eaton M45 displaces 45cu ins/rev or 750cc. In street car form it is recommended for engines of 2-3 litres, so for our purposes (0.5 litres) it should be ideal. Eaton recommend a normal operating limit of 14000rpm so we should be able to increase this for drag racing, though I guess efficiency will start to drop of pretty rapidly.

OUR unit is the one fitted to the Mercedes 230CLK Kompressor sports coupe, and is quite a hefty lump with four substantial mounting lugs.
Standard drive pulley is of the multi 'V' belt type as now used by a number of racers.
These units have 2 contra-rotating 3 lobed rotors, the rotors having a 60° twist and are Teflon coated to improve efficiency. Spinning the shaft by hand suggests that the blower works in either direction though the larger port where the rotors can be seen is the outlet. I noted that 2 teams using Eaton blowers are driving them from the left side of the crank, and thus are running them in reverse without any apparent problems. This is what we will have to do as left side drive is our only option.

THE Mercedes model has a large integral cast inlet duct (right in the top photo) and the design of this varies depending on the application. We will probably utilise this. The mounting lugs are in the wrong plane for a bike so I'll have to dream up something more suitable.

I stripped the thing down hoping to reverse the rotation and figure out how to remove the drive pulley. I hadn't noticed that the top and bottom pairs of bolts in photo 3 are not in mirror image locations, consequently the rotors and end plates cannot be flipped to reverse rotation.

THE drive end is composed of an outer cover (with a filler/drain plug) which supports the drive shaft and pulley. Sandwiched between this and the main casting is another casting which carries the coupling gears and bearings to support one end of the rotor shafts. Caged needle rollers in the main casting support the other ends.

IN the lower photo and attached to the left coupling gear, you can just see a hard plastic coupling, slotted onto 3 dowels and with holes to engage the 3 dowels on the end of the drive shaft in the pic above. I assume (hope) this offers some shock absorbing capacity. The gears, rotors and drive pulley appear to be an interference fit on their respective shafts which is a bit annoying. However the whole thing is very solidly built, especially when compared with the old Shorrocks vane type we used this year.

Hopefully over the next couple of months I will have time to install the Eaton, so more news in January 2004.


Eaton M45 superchargerEaton M45 supercharger side view
Eaton M45 drive end

Photos below were taken with my £16 digital camera, hence the crap quality.Eaton M45 rotors

Eaton M45 drive plate

Eaton M45 coupling gears and shock absorber



March 2009

I get asked about once a week how I reversed the direction of my Eaton M45, and as some people seem to have difficulty understanding my explanation, here is a little animation of the basic operation.

You will find that 4 of the holes no longer line up so I plugged the M8 holes and then tapped them in the new location M6. Add a few spacers to take up clearance in the cover and some big washers under the M6 bolt heads. Job done.

How simple is that!