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356 Engine Dynometer

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  • #16
    John, I have been following this and wow you are doing something quite special with the kit and money you are spending. Like most of us reading this, its principle is to a degree understandable but the manufacture and getting this to work is beyond me. I see you were involved on A6, a friend of mine Dick Pitman a friend of mine living in Virginia and the owner of a lovely 356 Roadster and who also posts on here, flew in the Navy A6 planes. He is a clever guy too and I will tell him to have a look on. I hazard to guess what a new dynometer would cost to buy but its got to be lot I reckon.

    Thanks for the story so far and the photos! Hope it all works when finished!



    • #17
      Thanks Roy for the 'heads Up'.
      OK John where are you located now??
      I am in Chester, VA just South of Richmond.
      I have had 88971 for 56 years as of this October.
      It is part of the family.
      I was in VA-35 1968-70 witha WestPac cruise on Coral Sea 69-70.
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      Last edited by JTR70; 04-30-2020, 06:29 PM.


      • #18

        I am still out on Whidbey, did you not see the photo above your ameiia island photo. I posted of my 49GMC with the dead whale in the back? I have had mine sine 66.
        Last edited by Jbrooks; 04-29-2020, 11:07 PM.
        Pushed around since 1966.


        • #19
          Wednesday update. Wound the first coil 1.2 ohms about a pound of 18 AWG wire. Coil works as expected. Did a design change to the load. The original concept was to put a octagon coil holder around the IDA of the rotors, mount the could on top of some 1/2" thick flat bar. Mocked it up with wood, and decided to but the flat bar outside and hang the magnets under the hexagon frame. (Examples in the photo.) That makes it easier to mount and keeps the center of the magnetic fields inside the rotor, The outside steel flat bar will also help focus the fields. Since this part try's to rotate into the load cell it will have more clearance with the coil pack on the inside

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          I made the mock up hexagon from wood, thought it would be easier. Ever try cutting wood to +- .001, but it worked.

          Here is a side view of the rotor with a coil core inside. This core will be wound with magnet wire, then a hanger bracket will be screwed to the ends that will attach to the octagon. The hexagon will need to pivot and I ma trying to keep a max of 0.250 clearances on the rotation and fixed components.
          magnet core in the rotor cavity
          thanks for looking
          Last edited by Jbrooks; 05-09-2020, 06:02 PM.
          Pushed around since 1966.


          • #20
            Got the octagon welded up today, worked well came out within .004.

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            After that we checked the clearances for the rotors, right now that's about .300 from the magnet coils to he rotor, So I am OK here. Two coils laying in the bottom so I can measure the outside diameter to make sure I can get the most wire and retain clearance. Shows 8 degree right list, for the pivot point , the hexagon will be pulled down with rotation into the load cell.

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            Here is a mock-up of the mounting, There are two coils per section, I will fabricate the end caps for the coils. Here is just a pair of cores hanging on some scrap angle with a couple magnets to hole them in spot.

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            So far it all fits together like we planned. The Octagon is 1/2" fat bar, cutting and welding it, with out any distortion and keeping it square even surprised me. I was sure it would need to go on the mill for clearances, But some how the math worked.

            Thanks for looking..
            Attached Files
            Last edited by Jbrooks; 05-12-2020, 02:33 AM.
            Pushed around since 1966.


            • #21
              Started winding coils, such joy, probably should have contracted this out to a motor shop. Anyway the math worked the coils came out the right size and resistance. They fit the hexagon like just like they were designed to fit. I have about 3mm clearance above and below for the rotors and cooling air. From the first pair mock-up, it inside of the coil carrier is going to be full of copper. Tested one at 12v under a sheet of paper covered in band saw dust, the magnetic field is larger that a sheet of paper.

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              I coated wire with liquid electrical tape as I wound the coils to help bond the coils as they were wrapped, ugly but effective. I will wrap them with KAPTON tape after I get them all complete and fit the hoders to the hexagon.
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              Attached Files
              Last edited by Jbrooks; 05-16-2020, 04:39 PM.
              Pushed around since 1966.


              • JTR70
                JTR70 commented
                Editing a comment
                Mind blowing Electrical fabrication going into this field coil unit. I'd bet you have the skill to convert a generator to an alternator. Keep up the amazing work...

            • #22
              Ran out of wire.. Awaiting parts. Story of my life. Got the rotors cleaned and coated, I now have "RRR" Ruby Red Rotors. Alignment and clearances look good so we progress. I need to do some more sheet metal fab and trimming. The coil cap mounts overlap about 2-3mm in the inner corners. And I have 72 holes to bore and tap in the octagon. But it still fits so I am a happy camper.
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              thanks for looking
              Pushed around since 1966.


              • #23
                Good progress John. Been following and trying to understand.


                • #24
                  Thanks Phil,

                  It's not not too hard to understand. The hexagon and coils will have a fixed pivot on Far side and have a Load cell on this side. The coil pack will float between these points. The rotors are connected to the clutch by the shaft and spin with the engine rotation. The coils will produce and magnetic field in the rotors and this field will fight against the rotation like putting two magnets together. This will cause the hexagon to be pulled into the load cell by the rotation. I measure this in weight or pounds of force on the load cell. I will position the load cell a foot from the center of rotation. and presto I can read the torque the engine is making. once you know this torque value the rest is easy SAE HP = Torque x RPM รท 5252

                  The coils are wired in pairs 180 degrees apart. 12:00 and 6:00 together 9:00 3:00 etc. the North and South poles are also reversed in the pair. So when one is pulling the other pushes and equals out the side loading. You turn on the coils in pairs and or vary the DC voltage to change the amount magnetic flux seen by the rotors. The coils are also alternated North /South to the coil next to it. thee will also act against each other in the rotation. The more magnetic flux the more drag won the rotor and the rotor willy try to make the coil pack try to rotate with it.. This attempted rotation of the coils is translated directly into weight.
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                  easy to calibrate also. you make a 2 foot long bar that will attach to the Hexagon above the load cell . The hang a weight on the bar and see what the load cell says. 2 foot bar 100 pound weight = 200 ft pounds. 50 pound weight = 100 ft-lbs. Its really pretty simple if you do the math.
                  Last edited by Jbrooks; 05-21-2020, 08:46 PM.
                  Pushed around since 1966.


                  • #25
                    John just getting that Hexagon welded to a 0.004 " tolerance is really surprising ! I use the same math for standing on a pole at a certain distance to torque up my rear axle nuts to 400 ft-lbs! The job you are doing still needs a better brain than mine to understand it all. The guy who first made one must have been very bright indeed. I guess if your work training involved similar aspects then you have a head start. For example: you mention ' the more magnetic flux the more drag on the motor and the rotor will try to make the coil pack try to rotate with it. This attempted rotation of the coils is translated directly into weight'. I think I get it, then I think I don't!!

                    Really interesting to see your effort though.



                    • #26

                      welding with jigs and fixtures keeps the tolerance. Actually that part was pretty stright forward. Winding the coils has been a task. Trying to get 500 turns and having the end be at the same place is fun. It takes about an hour per coil, but they all coming up with the same weight and resistance.

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                      but it still all fits and clearence are working out.

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                      Thanks for following. Send old engines if you have an extra ones.....

                      Last edited by Jbrooks; 05-25-2020, 03:11 AM.
                      Pushed around since 1966.


                      • #27
                        Well done John, its looking really good. Its not an easy job for sure!!


                        • #28
                          It's been a month since my last up date.. Sorry I have lost time. Only had two days in the shop.

                          A good friend and old squadron mate had a stroke the first of May. He has no wife or kids, no directives out side a of a will. His closest relative is a niece, he has only seen a couple times, she did not want the responsibility. So I got a bunch of his old squadron mates got together, saw a Judge and rescued him from the State Elder Services, and a miserable old folks wearhouse.

                          So I am now his Gurdian, we got him home with 24 hour nurses. Been installing stair lifts, cranes, wheel chair accessories in his home, figuring out bills etc. Most of the heavy lifting is done, now for the therapy and recovery.

                          But I did get all the coils wound and fitted. They have the same resistance and weight so the dyno progresses but just slower than planned . It's coming together

                          Thing are going well, but some advice "put a close friend on a bank account with $10.00 in it so they can act on your behalf, get you directives write down and don't have a stroke.

                          Pushed around since 1966.


                          • JTR70
                            JTR70 commented
                            Editing a comment
                            Very sorry to hear of this John. Very unfortunate set of circumstances but at the same he's most fortunate to have old squadron brothers like yourself who have stepped in to help. I wish him well and a big thank you to you both for your service to our great country! Justin

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