Lifters
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STOP PRESS  This is my old site last updated June 2005.  Enjoy the pics here but it is best to shift direct to the new site. Looks the same but lots more stuff and regularly updated.  The full size pictures  are only available there.

CLICK HERE to go to tesladownunder.com index page

 

Lifter projects on this page include:

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Lifters 1 Beginners

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Lifters 2 Better

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Lifters 3 Now on permanent display in a science museum.

 Lifters 1  (ionic wind powered device) These are a nifty thing to do high voltage. In essence they are devices that levitate using ion wind created from a DC high voltage external source. 

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In my Lifter Mk 1 (which is a typical beginners one) a 40 cm triangular ultralight basla, aluminium foil and wire creation lifts up once around 40kV is applied. A thin wire supported by balsa wood struts is the source of the corona and the foil below is attached to the other polarity (positive or negative).  The supply wires are not clearly seen since they get very agitated with the high voltages.  The structure is tethered with cotton taped to the base.  There is occasional arcing across the 3cm between the top wire and the foil at this voltage.  My high voltage source is the x-ray transformer described below run off a variac.  The typical output used is 30 kV AC which with the addition of a 290 kV diode and capacitor gives a smoothed, half wave rectified output around 40kV DC.  I have also used the 100 k ohm resistor in series to reduce destructive arcing as it burns out the wire.

Lifters 2

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This is Lifter Mk 2 which is a much better flier.  Smaller at 6 inches (15 cm) per side, stronger and a more generous spacing between the foil and the corona wire.  It is powered by a dedicated 30 kV DC stabilized power supply with one side referenced to earth which means no more sparks from foil to ground.  I use a 100 kohm resistor as above.  The height is limited by the wind outdoors.

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Some detail of one vertex of the triangular lifter showing the recession of the foil and hot glue construction.  Note that the upper wire needs to have the enamel stripped off at least partly but preferably left on the support wires to the HV source.

The ionic wind is enough to blow out a flame underneath the lifter and can be felt.  This form of propulsion is similar in principle to the ion engine used to power Deep Space 1 spacecraft which used on board Xenon. A normal lifter will not work in a vacuum. A comparison of the two.

Deep Space 1
    Power:            1280 volts, 2500 W from solar cells
    Propellant:      stored Xenon gas ionised to Xe +
    Speed:           100,000 kph
    Thrust:             9 grams (very low but efficient and can go for years)
    Cost:               $200 million

Lifter
    Power:            30,000 volts, 5 W
    Propellant:      air ionised to O+, N+
    Speed:            ? 5 kph
    Thrust:             3 grams (just enough to lift the very light structure)
    Cost:               $1000 for full display (actually only $2 for the lifter itself)

Others have made lifters large enough to have a small payload such as a mouse. A Japanese lifter is 15 ft (5 m) in diameter and is shown lifting to 45 ft (15 m).

Lifters 3

Lifter Mk 3 was developed for a public display.  It has custom argon tubes for the upright high voltage wire supports.  In addition it has small neon indicator globes at the corners of the lifter itself. Very impressive at night.  Not really a high flier however due to the reduced voltage available after the argons plus the added weight of the small neon tubes.  One further feature is the "Crash land" button.  This uses a motorized switch to short circuit the power supply.  This causes a loud and bright spark visible low down between the upright argons in the left picture, the tall argons flash and the lifter loses power and falls.  Kids (of all ages) love this one.

 
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I have measurements of the plain vanilla lifter (i.e. no attached neon's) which is a 30 cm triangle.  This jumps up very smartly to its tether limit at 2 feet.

Input                                                                     24 V  0.80 A     = 19 W
Output (measured after argons).
    no load (argons only but no wires to lifter)  ?30 kV 100 uA
    plus HV Meter (100 uA FSD movement)    28 kV  130 uA   =  3.6 W
    plus lifter  (no dropping resistor)                  22 kV  400 uA   =  8.8 W

Threshold for lift is 14 kV.
Hence net current is around 270 uA and net power used by lifter is around 5 W.
The argon tubes drop about 500 V each with the load of the lifter i.e. about 1 kV is lost. (but gain about 50 kV of coolness)

My lifter, give or take, uses 5W to lift its 3g (= 0.6g/W).
This neat little helicopter weighs about 2500kG, and lifts a further 2500kg using 1MW.
Proportionately 1MW would lift 600kg with my lifter specs. Only about 1/4 that needed to achieve lift of the helicopter.  One wonders if technology can't offer something more efficient than my triangular lifter though. I have a few ideas .....
 

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This is the power supply setup using a 30 kVDC regulated supply from a 24 V transformer and a small PWM (pulse width modulated) controller.   This will be used for the public display lifter soon to be completed.  It does not like repeated short circuits (and tends to blow the 2N3055 drivers) but this has been fixed by using a series resistance (12 kohm 5 W plus 15 kohm 5 W in series).  This weakens the "Crash landing" spark which then had to be boosted with a 570 pF 40 kV doorknob capacitor.

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The left picture is a sunset shot and the right shows a view between the argon tubes. I have highlighted the lifter separately.  With this shot you can see the range of vibration of the first order harmonic of the closest wire which is about 1 inch in amplitude.  If the tension is a little higher or humidity a bit less, this changes to a second order harmonic with a node in the middle.  I guess this would be preferred as excursion is less, however the lift will be more as the wire gets closer and if there is an inverse square law then it may even be helpful.

My balsa supports started to track sparks and carbonise as the humidity picked up this evening. This is a prelude to a crash and burn. In desperation I used a light oil spray on the balsa supporting the upper wire which seems to have worked fine.

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This shows the transparent control panel exposing the electronics of the PWM. The two controls are a red "Crash landing" control and a rotary "Soft landing" control.   The right picture shows the lifter in the acrylic display during testing. 

I am concerned by the radio frequency interference on both AM (~1Mhz) and FM (~100Mhz).  There is no problem open circuit and the DC HV wire is shielded up to the upright argon tubes which serve as supports for the HV wire.  Shorting the argon tubes does not seem to make a difference. I have tried a ferrite cored coil in series with the active lead with and without a resistor (330K) although the latter does decrease performance.  The sealed 30kV HV unit is driven by a switch mode supply. This supply is giving minimal RF interference as a whine which I think I have fixed by putting a suppression circuit in the 24VDC line.  Some of the RF was corrected with a better connection to the 2x2 ft ground plane.  Unfortunately correcting the RF at its presumed source, the corona from the upper wires, is not feasible due to weight constraints.  I recently had to display the lifter within a few feet of a large plasma display monitor fortunately without problems.  Interestingly, in the final version of the lifter, I did not remove the enamel from the support wires which means that they are a lot less agitated and give a lot less RF interference.  I have also wound the support wires into a loosely spaced coil of about 10 turns around the last 6 inches of the argons to try to help block RF but I am uncertain if it helps.

The lifter has now (Nov 5th 2004) been installed at the Gravity Discovery Centre in a 1.5 m square acrylic enclosure. This is the public interface to the gravity wave detector under development here in Western Australia.

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The left picture shows the display poster.  The right picture shows the full installation running.  It has to be public proof and withstand lots of 'crash landings' from about 18 inches.  The balsa frame is hot glued and also has some reinforcement at the point of impact.   The support cotton threads have been upgraded to string from a small kite which is light and very strong.  The display is lit by small arrays of lights with 8 high intensity LEDs each with green, blue and purple coming from different directions.  The "Soft landing" switch controls the power to the HV supply and is spring loaded to return to the up position. It is a challenge to get a truly soft landing and is nicely interactive in this way.

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A demonstration by the lovely Sylvia from the GDS who is practicing her controlled flying.

 

  This page was last updated August 28, 2005