Example:
18000 Kenne Bell/Autorotor female drive rotor rpm is 27000 male rotor rpm.
18000 Lysolm female drive rotor rpm is 30000 male rotor rpm or 11%higher.
So...eaton spins at a lot less rpm than any of the twin screw setups...plus the twinscrews have smaller teaths on the gears than eaton. the reason why eaton uses turbine oil is that it´s supposed to outlast the charger...surely if you change oils ones a year etc. there is no reason why we should by really expensive GM or Ford labeled oils..plus the benefit of cheaper oils is that you can change them more often and keep always nice and clean oils in the charger. Now if you look into oil business you can see that there are many many oils that will do the same job as good as the originals. for example in your car...other oil just has oil change period of 60 000km and the other 20 000km/ones a year.
witch nmotor oil would you choose..other is 50$ per litre with all the same rankings and almost the same quality markings and temperature capability?
Now I won´t say that everybody should use oils like this in the chargers...
the thicker the oil teh more power it takes to drive the charger.
But for sure I´m finding out this thing and I´m willing to use what I see the best alternative to original oils since here in no mans land where is only 5mil. people it´s really hard to get the right stuff cheaply....
PS: good example of this is the industrial powerplants that use turbine oils in the generators and turbines
...do you know how long they are in the system? They will never be changed if no accidents happen(or the chaning period is something like 10years or contamination/boiling points are measured) and they should outlast the gasturbine life....that´s why they have oil cleaning systems in the turbine oil system...and that´s why they keep the turbine room clean
...so the **** doesn´t get to the oil. That is not the place for filthy persons to work in..
maximum steam temperatures is really high and the operating turbine is really hot too..steams are in the range of 1000+'C!! so how hot does eaton roots blower spin? 100-200'C...sure we need turbine oils
.
PS: here is the autorotor page that shows the input speed..the max rpm is about the same as eaton m-90 and the gear construction is about the same...
aftermarket dudes spin them faster tho
...
http://www.opconab.com/www/files/lysholm/pdf/performance charts/diagram_lys2300ax.pdf