Electrostatic motor

[markdansie]

@TK check your PM
Kind Regards
Mark

[synchro1]

@TK,


Here's a quote from above:

"The vacuum running... it is a real problem to sustain high voltages in any but the very hardest vacuums".


            The voltage to span a gap is inversely proportional to the pressure. It would follow that a minimum voltage would be required in "The hardest of vacuums". The point is there's less need to sustain a high voltage in a hard vacuum. One would require less input to run the electrostaic motor in a hard vacuum. This savings would offset the power to create and maintain the vacuum. Efficiency of greater then 95% must include the cost of the vacuum, but it has to be a function of time.


             The pertinent issue is not wether or not high voltage is reachable in a hard vacuum, but is the voltage at the brush points less enough across the drive rotor to the ground under pressure, to compensate for the reduction in gap resistance from the vacuum? Lessened gap resistance may increase the voltage to the ground across the drive rotor even though the voltage at the brush points is less in the vacuum then when under pressure.


            I think it would be a real treat to watch you run your Mendicino esmotor in a vacuum to compare efficiency, and determine exactly what the savings advantage amounts to. Naturally, the integrity of the vacuum seal is a critical factor.

[TinselKoala]

@synchro:
By definition, a "hard vacuum" is pressure to the _left_ of all the curves on the Paschen graph above. The voltage to jump a gap goes way _up_ in that region. The electric field gradient depends on the voltage produced, and the forces available to turn an electrostatic motor depend on the field gradient. No HV == no large field gradient == no force to turn the motor. So for an electrostatic motor to operate, you would need a _hard vacuum_ by this definition, or atmospheric or _greater_ pressure of air or an insulating gas.

I can only get down to about 25-30 microns at best, usually not even that low, with my vacuum system, and that is solidly in the "glow discharge" region for air -- as my vids demonstrate. I've already tested simple corona motors at that pressure and they don't work, there isn't enough ion thrust to turn the rotor. In other labs years ago I tested VDG machines at similar vacuums, which also depend on corona "ion spray" to operate, and couldn't get them to work either. I can't tell from the pictures what the operating principle is for the Japanese motor (Franklin type, corona spray type, or other) but it looks like it could be a Franklin type with spark transfer of charge, like my ball motors in the videos above (enhanced Franklin w/ rotor sparks over a tiny clearance, and the free-ball cyclotron sparks by direct contact with the field plates). If they have a good enough vacuum and the charge transfer is by contact, as in the "free ball cyclotron" video, the Franklin type motor would probably work, but definitely high electric field gradient (meaning definitely high voltage buildup, meaning definitely hard vacuum) is required for that.

I've got another experiment set up on the bench right now that isn't compatible with HV, but shortly I will be testing the Mendocino esmotor in my vac chamber. Since it too depends on ion spray from the negative "points" electrode to transfer charge to the rotor disc, I predict it won't work, for two reasons: not enough ions: to transfer charge, and too many ions: the glow discharge shorting the system to prevent HV buildup in the first place. Lol.... trapped in that darn Paschen "valley" again.

Commercial large "Pelletron" type VDGs used in particle accelerators often work with gases like CO₂ or SF₆ at _increased_ pressure, even as high as 10 atmospheres,  for more insulation. It's a lot easier to maintain increased gas pressure than it is to keep a good hard vacuum.  Does the Japanese machine use a rotary seal, or is it magnetically coupled to the output shaft through the chamber wall? If the former, then I seriously doubt that they could maintain a hard vacuum without constant pumping with turbopump backed with vane pump.

[synchro1]

@TK,

Theoretically, a greater percentage of the applied voltage should travel across the drive rotor from the brush points to the ground with a reduction in pressure around the gap, right?

[TinselKoala]

@TK,

Theoretically, a greater percentage of the applied voltage should travel across the drive rotor from the brush points to the ground with a reduction in pressure around the gap, right?

Do you perhaps mean "current" travels?
Let's try this again. Unless you are _below_ the pressure of the leftmost curve in the Paschen diagram above, the remaining gas in the chamber acts as a direct short circuit, or one of very low resistance. Yes, essentially _all_ the "voltage" you apply is shortcircuited by this low-resistance channel, even with large gaps. This means you _cannot_ build up high electric fields in such a case. If you attempt to overcome this by applying even more voltage from your power supply, a "power arc" develops and this is a direct short circuit which equalizes the potential (voltage) between its ends. "Gassy" vacuum tubes don't work properly any more! The force available to run electrostatic motors depends on two things: ions accelerated by electric fields and Newtonian reaction (ion motors, corona motors) and/or electric fields pulling-pushing charged material objects (Franklin motors, the free-ball cyclotron, the pingpong ball bouncer). If your voltage is short-circuited by a low-resistance channel-- as it will be anywhere in the region bounded by the Paschen diagram curves -- you will not be able to create strong electric field gradients!

Electric field gradient pushing/pulling a material object in a "linear" Franklin motor:
http://www.youtube.com/watch?v=OxEpSX2Hd54

Below are images of a corona motor: first, spinning in air, and next, same motor but not spinning, in the vacuum chamber.