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Vacuum transmission

Less is more. Much more ...
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Air motors are Baked and WKTE.

Compressing air is wasteful - lots of heat loss.

So why not take the air away, instead ?

The new BorgCo vacuum transmission works by a simple yet elegant mechanism.

The input shaft drives a rotary-vane vacuum pump. The pump is directly connected to an air motor. When the pump turns, ambient air pressure acts on the motor, turning it.

Air discharged from the pump passes into a small plenum chamber which is vented to atmosphere via a filter. The motor takes its air supply from this plenum.

There is an oiler to lubricate the airflow into the motor and thence to the pump. The bottom of the plenum contains a self draining trap to recover the oil mist from the pump and return it to the oiler reservoir via a sedimemtor and filter.

Best of all, the supply of vacuum is literally infinite ...

8th of 7, Sep 08 2017

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       //the supply of vacuum is literally infinite // Milton Keynes is actually a lot smaller than you'd expect.
MaxwellBuchanan, Sep 08 2017
  

       How good is the rotary-vane vacuum pump?
wjt, Sep 08 2017
  

       How good can you afford ?
8th of 7, Sep 08 2017
  

       Most but after that any more work doesn't give any more good.   

       I would have to shed light on it to get further.
wjt, Sep 08 2017
  

       One problem with this is that the difference between ambient and a vacuum is, at most, 15psi. The difference between ambient and compressed air can be much much higher.
MaxwellBuchanan, Sep 09 2017
  

       So ... ?
8th of 7, Sep 09 2017
  

       So your working pressure is 15psi. Do try to keep up with the others.
MaxwellBuchanan, Sep 09 2017
  

       Would you like to explain to the class why that's a problem ?
8th of 7, Sep 09 2017
  

       Certainly. Power = energy/time. Energy=force x distance. Force = pressure x area. Time = money.   

       Substituting: Power = pressure x distance x area/money.   

       QED.
MaxwellBuchanan, Sep 09 2017
  

       Substituting further: money=power .   

       Therefore money = pressure x distance x area/money.   

       Therefore money^2= pressure x distance x area.   

       But money = Sqrt(evil)   

       Therefore, evil= pressure x distance x area.   

       Therefore, evil increases linearly with pressure. A low-pressure system, thenceforth, incompatible with the borg ethos.
MaxwellBuchanan, Sep 09 2017
  

       // borg //   

       Sp. "Borg".   

       We are a proper noun, you know ...   

       // evil increases as the 4th power of pressure. //   

       That's useful to know ...
8th of 7, Sep 09 2017
  

       Well you're certainly a proper something.
MaxwellBuchanan, Sep 09 2017
  

       Maths is a bit envelope-ish when the object of the exercise is knock tiny stuff out of a box with a giant rotating bat.
wjt, Sep 09 2017
  

       I thought I posted the following anno a couple of days ago... alas you have to press "OK" for it to work apparently.   

       //The highest delta p you can generate is only 1 atmosphere... 14 psi. So a 1 square inch turbine of a foot radius will only give you 14 lb/ft of torque, which is lame. And that's from a 2ft diameter turbine, which is impractically huge. So, half it's diameter, double it's width.. still lame. Especially for a transmission, which has to handle say, 400lb/ft from a sensible family runaround engine. Most of the time, the transmission is gearing down, so it's handling 800-1200 lb/ft... That's going to be bigger than the car.   

       Also, compressing air is wasteful... Lots of heat. A vacuum pump is functionally, and in fact physically identical to a compressor. You don't get away from the energy loss just by changing which side of the pump you are.   

       You can avoid a lot of the energy wastage by having pressure changes without the volume change. Using something non-compressible, like a nice sturdy hydraulic fluid should get you where you need to be.//
bs0u0155, Sep 11 2017
  

       // I thought I posted the following anno a couple of days ago... //   

       Well, we never saw it, and certainly didn't delete it.   

       // alas you have to press "OK" for it to work apparently. //   

       You'd think there was a fix for that by now ...   

       // So a 1 square inch turbine of a foot radius will only give you 14 lb/ft of torque, which is lame. And that's from a 2ft diameter turbine, which is impractically huge. So, half it's diameter, double it's width.. still lame. //   

       One turbine set per wheel. Power distribution controlled by proportional valves. Stack the turbine discs like plates in a rack. Make 'em from lightweight composites.   

       // A vacuum pump is functionally, and in fact physically identical to a compressor. You don't get away from the energy loss just by changing which side of the pump you are. //   

       But the pump isn't pumping air, it's pumping vacuum ... you can't have hot vacuum ...   

       A high boiling point, very low viscosity hydraulic fluid would be needed for high speed operation.
8th of 7, Sep 11 2017
  

       //But the pump isn't pumping air, it's pumping vacuum//   

       It bloody well is. The rather hot exhaust on the turbopumps attached to the nearest mass spec are evidence. Those turbo pumps are removing air at the same rate it leaks in. You're paying for the pressure gradient across a not entirely sealed barrier. Another way of thinking about it, even in a piston-style pump, you're locally compressing and moving the air on the high pressure side even if there's no air at all on the other.
bs0u0155, Sep 11 2017
  

       // The rather hot exhaust on the turbopumps attached to the nearest mass spec are evidence. //   

       If they're Balzers pumps, most of the heat is iron and copper losses from the maglev bearings. Or you've got a diff pump by mistake ... now, they ARE hot ....
8th of 7, Sep 11 2017
  

       The solution then is to have vacuum on both sides of the pump.
pocmloc, Sep 11 2017
  

       Sheer genius. You should post that.
8th of 7, Sep 11 2017
  

       //The solution then is to have vacuum on both sides of the pump//   

       You wouldn't need any seals, a real efficiency gain to be had there.
bs0u0155, Sep 11 2017
  

       // You wouldn't need any seals //   

       ... or indeed lubricant - except for the bearings, which would have seals anyway.   

       This is sounding better and better.
8th of 7, Sep 11 2017
  
      
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