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  • Jbrooks
    replied
    John

    Not too much science, just some magnetism and a couple physics laws. The magnetic field just tries to stop the disc rotation.

    Fixed the wobble, larger hinge pin with a shim between the hinges. Welder works super for a power supply although it starts at about 20 amps on the lowest setting. But so far its working, when I spin the disc up to about 2000 rpm with an electric motor, it takes about 2 minutes for the disc to slow to a stop. Spin them back up, turn on the welder stops in 10-15 seconds. still trying to get the instruments to read properly but it seems to be working as planned. Have not had much time to work on it in the past couple weeks but its is progressing .

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  • jjeffries
    replied
    This is all beyond my non-science mind, but I think it’s super-cool. That you manage to hold such tight tolerances is so impressive.

    John

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  • JTR70
    commented on 's reply
    Fascinating exercise, Getting even more mind blowing.

  • Jbrooks
    replied
    Slowly progressing, the clearances are OK, I did have a couple coil holders that were rubbing slightly at high RPM. The hinge I selected is a little loose and allows the coil pact to wobble .030-.040. The opposite side of the hexagon sits on the strain gauge via a17mm bolt so the hexagon is basically 3 pointed. The load cell needs to float, but at the same time absorb all the torque forces created by the spinning disc. There is enough lateral play in the hinge to allow the hexagon to rock just a little. So it’s weld up the hinge, drill and ream it and make a new hinge pin.

    I also am going to try a different power supply source. I bought a $60.00 DC IBGT welder from eBay. Yea I know but…. It did weld 1/16” rod OK and has a 60v open circuit voltage and might produce 100 amps max. The concept is the welder will provide sufficient current at a low setting to produce the magnetic fields. I know a battery charger works, but I am limited on the output voltages. I will vary the voltage and the current to have finer load adjustment.

    Since I plan to switch on the individual coils pairs, I will put an big amp shunt and volt/amp meters on the negative side. This way I should be able to monitor the power consumed. Anyway the project is 90% complete, If I don’t let the smoke out, next Its the computer instrumentation and final calibration.

    Tiny welder, it worked!
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    thanks for looking

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  • JTR70
    commented on 's reply
    That thing really sounds like its going to work! Interested in seeing how it comes out.

  • Jbrooks
    replied
    Moved it south today to the other shop. Will finish up the characterization and calibration there. Bob can provide the adult supervision. Never tried to pick it up completely assembled, I needed the crane to load it, must be north of 250 pounds, and no battery or instruments on it yet, But it stable and solid at 3700 RPM. really slows down with voltage applied. I have held the magnet field down to 1.5 tesla's for now. but it seems very effective at loading the disc, even at this small value. .
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    easy loading with a fork lift.

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  • Jbrooks
    replied
    Justin I mostly flying blind.... But its a fun project.

    Got the wiring on the hexagon done and fitted. Did some current draw at 6V on the coils, they are as predicted, polarization is correct. Did a fit test assembly and it works and spins freely. Rotor disc are balanced, Now I need to build a electric motor with a belt drive to spin it up and start to characterize the coils.

    Biggest unknown right now is what the low voltage current loads will be. Lenz's law and three variables for the flux density and drag based on velocity. So if i can make 25 pounds of load at 1500 RPM, I can get 2-3 times that load as the RPM or velocity increases through the field with the same voltage and current. So I have three variables to measure, voltage, current and velocity. All three can change the outcome load, plus I can change the flux density by turning on and off coils in pairs. lots of variables be I will figure it out.

    Found a simple explanation video of what is going on here https://www.youtube.com/watch?v=DEAWglCiXgo He's a young kid but this is what we are doing. Also the magnet and copper pipe is a good trick for showing the kids.

    Plan to use the digital welded as a power source since, I can change the DC voltage and current separately very accurately .

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    Last edited by Jbrooks; 05-04-2022, 12:17 AM.

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  • JTR70
    commented on 's reply
    You obviously know what you're doing John, but watching this come together just blows my mind.

  • Jbrooks
    replied
    Started fitting out the coils today. Ran in to a clearance problem, and have reduced the number by 4 coils, for now. I think I can work around it with new extended brackets. but If not The math says it will still eat 200HP. I will fabricate a couple new longer brackets to drop the single coil flats down and get two coils back in the flat on each hexagon. I have a little over an inch in the inside clearance. They are mounted North - South - North to increase the eddies current resistance drag on the rotation disc. I am still working on the fit and pivot point and load cell mounting but its finally coming together. She is getting close

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    Mounting the coils was a tasks. Over 80 #21 holes, Three broken 10-32 taps in steel, a true joy. The aligning the holes in the mount brackets. but she is looking like I planned 2 years ago.

    thanks for looking
    Attached Files

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  • Jbrooks
    replied
    Ruff assembly on the rotating parts today, with the key ways broached and disc torqued, still have a little run out on one side. Assembly got a little complicated due the no tolerance slip fit on everything. But it did go together. Next is balance of the rotating disc and install the electromagnetic coils into the octagon.

    The coils will be wired as 8 pairs, 2 coils in series. Wired so the N / S polarity is opposite 180 degrees to each other, I will install two coils per flat. The theory is "one will pull and the other push and counter act any bending moment. I will also put the ones next to each other on the same flat in N / S opposite polarity. The math sez the induced eddies currents in the spinning disc with oppose each other, increasing the drag. I will power them individually as pairs. Now that I know what the final clearance is I may re do the coil mounts to get the lower toward the center shaft, but for now all is well here. Next is the octagon hinge and strain gauge install. Still trying to decide weather to push or pull the strain gauge transmitter.

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    Thanks for looking
    Attached Files

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  • Jbrooks
    replied
    Dave

    Still getting trying to figure it out. I have had a prewar 9” south bend for 40 years. This is 14” a quick change gears, SAE and metric threads, Big dial numbers, gap bed, DRO. It’s almost too new. I only a have 5 hours on it, just did the first oil change. My first digital readout, that’s pretty cool.

    checking the runout on the rotors. Too big for the surface plate but showing around 0.003” on one side. So I figure it’s good enough. Just worried about vibration, now for balancing the complete assembly

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    Last edited by Jbrooks; 04-19-2022, 07:31 PM.

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  • Rimcanyon
    replied
    Nice lathe, John. I see you have had a chance to use it, how do you like it?

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  • Jbrooks
    replied
    Well finally got back to the DYNO after a couple weeks of distractions. New Lathe and Milling machine arrived and install. Installing the Digital Read Out (DRO) on both machines to share the same readout was interesting, but have it done now. Both a brand new and a real pleasure to run. Turns out these, DRO glass scales are brain dead simple. I probably saved 2500 bucks by doing my own DRO install opposed to buying them from the factory with the machine. Well worth a few days of research, and my eBay account..

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    Fly-cut the square tube to get the bearings aligned to the bell-housing flat and parallel. Now the shaft alignment is complete I can work the rotors and get them balanced next week . The two black spacers will attach to the central rotor carrier that the disc are attached to , All of the magnet coils measure the same resistance, and the north poles have been identified. I matched them by resistance and current flow in pairs so the magnetic fields will react equally on the spinning rotors.

    As soon as I get the rotating mass balanced I will mock it up with the coil carrier on and determine the final locations of everything. Its getting close

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  • Jbrooks
    replied
    Rimcanyon

    Passed through PG school several times over the last 50 years. Used to come up from Michelson Laboratory to do look at student projects. Stayed there for Rennsport couple years ago, a lot of new buildings, and a ton of the old ones. It still has the best library on the west coast.

    Finally getting back to the dyno after a year in the holding pattern. Need to go find all the parts and my notebook. Have a couple cars in the wings but I am going to see if I can make this pile of scrap work. Theory to practice used to be a strong my suit.

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  • Rimcanyon
    replied
    Originally posted by Jbrooks View Post
    Rimcanyon

    Thanks, I have a VW shaft but just not long enough. I will keep the CNC in mind, and you are close to PG school.
    Did you attend the PG school when you were a Navy officer? I was an adjunct professor in the computer science dept. at NPS while I was working on my doctorate at Stanford, before I went to Silicon Valley. It is a great school, and I really enjoyed working with the Naval officers. A lot of them were pilots.

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