Test 03 Success. I have thrust.I modified the setup and now i weight the frustum. the precision is much better.I will make a modifications to be able to adjust the cavity length to achieve the resonance, so i should have more thrust then.
If I did the calculation right, a volume change of ~125 litres would be needed to account for this apparent weight change, due to thermal ballooning of a sealed volume. That's far too high a change in volume that could be reasonably expected, so it can't be the whole story. Did I calculate this right?air density = 4*10-4 Kg/m3
Quote from: deltaMass on 05/18/2015 03:25 amIf I did the calculation right, a volume change of ~125 litres would be needed to account for this apparent weight change, due to thermal ballooning of a sealed volume. That's far too high a change in volume that could be reasonably expected, so it can't be the whole story. Did I calculate this right?air density = 4*10-4 Kg/m31.225 kg/m3 http://en.wikipedia.org/wiki/Density_of_air
Quote from: aero on 05/18/2015 04:02 amQuote from: deltaMass on 05/18/2015 03:25 amIf I did the calculation right, a volume change of ~125 litres would be needed to account for this apparent weight change, due to thermal ballooning of a sealed volume. That's far too high a change in volume that could be reasonably expected, so it can't be the whole story. Did I calculate this right?air density = 4*10-4 Kg/m31.225 kg/m3 http://en.wikipedia.org/wiki/Density_of_airOops yes - it's deltaVolume = 400 cc that's needed to account for all the upthrust.Still too big to reasonably expect.
If any calculated results from Meep are relevant then note that Meep calculates the largest thrust, O(1.1/c), when the antenna is dead center in the cavity. That is a point source. A dipole source is centered and parallel to the base plates for electric stimulation, and parallel to the axis of symmetry for magnetic stimulation. Moving the antenna away from center reduces the detected force/flux ratio.
....Be that as it may, the main reason that we went with the lower-Q TM modes was because they consistently produced higher thrust levels for a given input power than the TE modes. I will grant you though that getting the most thrust out of a particular resonant mode depended very painfully on the size, placement and rotational orientation of the loop antenna in the frustum cavity.
Quote from: Iulian Berca on 05/17/2015 11:20 pmTest 03 Success. I have thrust.I modified the setup and now i weight the frustum. the precision is much better.I will make a modifications to be able to adjust the cavity length to achieve the resonance, so i should have more thrust then.Iulin Berca:Congratulations on the success! I think this demonstration is fantastic. The fact that the peak thrust appears ~3 seconds after the power is turned on tells me it takes a little while for energy to 'build up' in the cavity. After the peak, the thrust slowly dies probably because the cavity walls are warping and you are losing resonance. The adjustable end plate would certainly help to achieve a higher peak thrust, it just might take some trial and error. But I believe cavity will still heat up and warp and the thrust will taper off. Maybe this thermal effect could be mitigated using some sort of heat sink?
Quote from: zellerium on 05/18/2015 02:55 amQuote from: Iulian Berca on 05/17/2015 11:20 pmTest 03 Success. I have thrust.I modified the setup and now i weight the frustum. the precision is much better.I will make a modifications to be able to adjust the cavity length to achieve the resonance, so i should have more thrust then.Iulin Berca:Congratulations on the success! I think this demonstration is fantastic. The fact that the peak thrust appears ~3 seconds after the power is turned on tells me it takes a little while for energy to 'build up' in the cavity. After the peak, the thrust slowly dies probably because the cavity walls are warping and you are losing resonance. The adjustable end plate would certainly help to achieve a higher peak thrust, it just might take some trial and error. But I believe cavity will still heat up and warp and the thrust will taper off. Maybe this thermal effect could be mitigated using some sort of heat sink?I rather think the time difference between applying power and thrust is due to the time needed to heat up the filament (cathode) in the magnetron. After ~ 3.5 - 4 seconds you hear that buzz inside, exactly in that moment the thrust appears. After that the buzz drops a little bit and also the thrust. After work, i will turn the cavity upside down to see if i can have the opposite thrust.
Quote from: Iulian Berca on 05/18/2015 05:03 amQuote from: zellerium on 05/18/2015 02:55 amQuote from: Iulian Berca on 05/17/2015 11:20 pmTest 03 Success. I have thrust.I modified the setup and now i weight the frustum. the precision is much better.I will make a modifications to be able to adjust the cavity length to achieve the resonance, so i should have more thrust then.Iulin Berca:Congratulations on the success! I think this demonstration is fantastic. The fact that the peak thrust appears ~3 seconds after the power is turned on tells me it takes a little while for energy to 'build up' in the cavity. After the peak, the thrust slowly dies probably because the cavity walls are warping and you are losing resonance. The adjustable end plate would certainly help to achieve a higher peak thrust, it just might take some trial and error. But I believe cavity will still heat up and warp and the thrust will taper off. Maybe this thermal effect could be mitigated using some sort of heat sink?I rather think the time difference between applying power and thrust is due to the time needed to heat up the filament (cathode) in the magnetron. After ~ 3.5 - 4 seconds you hear that buzz inside, exactly in that moment the thrust appears. After that the buzz drops a little bit and also the thrust. After work, i will turn the cavity upside down to see if i can have the opposite thrust.Congratulations! You have shown a lot of ingenuity. One question I have however: What happens when you move the electronic scale a few inches so that it is not under the metal boom supporting the cavity and you apply power to the magnetron? Have you ruled out the possibility the RF energy is causing a false positive reading? Another possible source of a false positive is the stiffening of the power wires when the magnetron is on. This is due to magnetic forces between the conductors. Those are possible sorces of error in your experiment. I admire your ability to quickly build a workable test system.
Quote from: zen-in on 05/18/2015 06:43 amQuote from: Iulian Berca on 05/18/2015 05:03 amQuote from: zellerium on 05/18/2015 02:55 amQuote from: Iulian Berca on 05/17/2015 11:20 pmTest 03 Success. I have thrust.I modified the setup and now i weight the frustum. the precision is much better.I will make a modifications to be able to adjust the cavity length to achieve the resonance, so i should have more thrust then.Iulin Berca:Congratulations on the success! I think this demonstration is fantastic. The fact that the peak thrust appears ~3 seconds after the power is turned on tells me it takes a little while for energy to 'build up' in the cavity. After the peak, the thrust slowly dies probably because the cavity walls are warping and you are losing resonance. The adjustable end plate would certainly help to achieve a higher peak thrust, it just might take some trial and error. But I believe cavity will still heat up and warp and the thrust will taper off. Maybe this thermal effect could be mitigated using some sort of heat sink?I rather think the time difference between applying power and thrust is due to the time needed to heat up the filament (cathode) in the magnetron. After ~ 3.5 - 4 seconds you hear that buzz inside, exactly in that moment the thrust appears. After that the buzz drops a little bit and also the thrust. After work, i will turn the cavity upside down to see if i can have the opposite thrust.Congratulations! You have shown a lot of ingenuity. One question I have however: What happens when you move the electronic scale a few inches so that it is not under the metal boom supporting the cavity and you apply power to the magnetron? Have you ruled out the possibility the RF energy is causing a false positive reading? Another possible source of a false positive is the stiffening of the power wires when the magnetron is on. This is due to magnetic forces between the conductors. Those are possible sorces of error in your experiment. I admire your ability to quickly build a workable test system.In the wires for the filament the voltage is AC so they can not have to much effect in only one direction, just some 50hz low intensity vibrations.The anode voltage is pulsed DC but the current is smaller ~ 5.3A. I already tried the scale without weight and i do not have any disturbance in the reading when i power on the magnetron.I can use an external supply for the filament , in this way i hope to adjust the power and maybe the frequency. But is very dangerous because i will connect the cathode with 4Kv to my power supply. The capacitance in the transformer can send some hi voltage to the supply.
In the wires for the filament the voltage is AC so they can not have to much effect in only one direction, just some 50hz low intensity vibrations.The anode voltage is pulsed DC but the current is smaller ~ 0.2A. I already tried the scale without weight and i do not have any disturbance in the reading when i power on the magnetron.I can use an external supply for the filament , in this way i hope to adjust the power and maybe the frequency. But is very dangerous because i will connect the cathode with 4Kv to my power supply. The capacitance in the transformer can send some hi voltage to the supply.