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356 Engine Dynometer

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  • 356 Engine Dynometer

    i am thinking about a small engine dyno to run 356/911 engines. Anyone out there that has one or done any research into making one. I am looking at using an Electric Eddie Current load or electric brake. Should probably be about the same size as my 616/40 test stand, or maybe a replacement for it

    looking for anyone that has a engine dyno or any ideas on the construction or design.

    Planning on a VW T-2 bus trans bell housing , bolting an adapter to the flywheel into the Eddie current load. Your thoughts please
    Pushed around since 1966.

  • #2

    I know a guy who raced formula V years ago but cant find his phone # using internet. He is on linkedin but have to join to contact. Let me know if you want his name. He built a dyno for the vw engines.

    Also, this youtube may help:


    • #3

      Thanks for the video, that is what I am looking at. I am trying to design the load about the diameter of the flywheel, Or something I can attach like the pressure plate to the flywheel and keep it inside the bell housing volume. I had pretty good luck making a magnetic vise, i believe 6-8 of them may create enough drag to eat 205 Hp. Still doing the math, but hope to have it done in a couple months since I have to stay home anyway,

      the drag theory

      The one here is a 800Hp Mine will be similar just scaled down.
      Last edited by Jbrooks; 03-31-2020, 11:40 PM.
      Pushed around since 1966.


      • #4
        Found a commercial device called a " Telma Retarder" used on trucks and buses for electric brakes, It goes into the drive shaft to slow the truck. I was looking at building one from some 14" disc rotors and winding my own coils, turns out the junk yards have these for the copper scrap weight. Yahoo ........ They are pretty simple, the discs spins and the coil is fixed. The magnetic field is induced into the rotors and created the drag. The magnetic field is controlled by the current through the coils, the faster the disc spins the more drag. So at higher RPM it actually needs less current.

        eddie current brake for the dyno
        The smaller ones for sprinters or small trucks will almost bolt up to the VW T-2 bus bell housing. The sage continues, off to scrounge through the truck junk yards.

        thanks for looking.
        Pushed around since 1966.


        • #5
          Being sequestered sucks, and salvage yards are not essential functions here. So I have not found a telma retarder for a sprinter for F450 here in the states.

          So I have started building the dyno from scrap stuff in the shop. From the basic drawing below, here is a photo of the stack up. The bell housing will be attached to a tubing frame, holding a main shaft via a couple pillow blocks. The coil package will be fixed to the frame so it can move just a little, held in place with an short arm to the S type load cell. These 14" brake rotors on the bottom will attached to the main shaft and spins via a flywheel adapter. This adapter is splines disc that bolts to the flywheel like the pressure plate. The main shaft will fit just like the trans.

          I will mock it up on an engine case get some good measurements tomorrow. Get the clearance distance for the starter, center high with an engine, etc. Then I need to figure out how to balance the rotational mass, source some bearings. The disc brake rotors should be close but they are too large to spin up like a crank shaft.

          Here is the Horizontal layout. It look like the starter is the driver on length, but still under 24 inches long. The concept is to mount these rotors to a shaft supported by a pair of bearing blocks on the center shaft. Then fix the coils in the center of the disc, mount them on three points. Two on the left side and allow the engine rotation to pull the coils into the third point, the load cell to measure the torque. So far its measures out and will be very compact and probably not all that Heavy. .

          Click image for larger versionName:	image.jpegViews:	7Size:	346.6 KBID:	108261basic layout

          I may go look for different rotors with a smaller center and larger disc surface but this is what I have on hand.

          measuring the stack,

          The rusty part shown is the rotating mass, steel brake rotor with a fixed coil pack in the center,. On top is the 616/901 engine adapter. . It progresses, thanks for looking
          Last edited by Jbrooks; 04-08-2020, 07:55 PM.
          Pushed around since 1966.


          • JTR70
            JTR70 commented
            Editing a comment
            Love the inventiveness of all of this. Looking forward to seeing how all of it all comes together.

        • #6
          Ok guys, measurements are done, ordered some parts today. The main shaft is 0.875 diameter and a little over 2 feet long. I ordered 5 pillow blocks and the load cell. I have some 3/8" plate in the pile so it looks like the bottom will be supported by a plate, I will weld up a L bracket that the bell housing is bolted to with a bulkhead bearing block attached to the plate. That will carry the load at the flywheel end. I will make the shaft tapered and splined and extend into the gland nut bearing. Then there will be at least another bearing block on each side of the rotating iron mass. The center-line of the crank will allow about 3-1/2" bottom clearance on the disc rotors.

          That clearance is good and will allow me to bring the wiring in to the coil pack from the bottom. I will mount the coil pack on the left side with two pivot points and a 6 -12" arm on the right side center of the coil, that will tie into the top of the load cell. This arm will put the load cell into compression and allow me to measure the rotational drag as a torque value.

          basic set up

          My goal was to be into this DYNO for a couple hundred bucks, I am into this for a total of $227.85 so far. I have bought the bell housing, 7/8" drill rod for the main shaft, 5 bearings, 200Kg S type load cell. I have the steel in the pile so I think all the big out of pocket expense is done. The goal on this is to use to to break in new engines with 20-50 ft-lb of load and to vary the loading like climbing a hill when the engine is new. It will also allow me to do Hp and torque curves, but that will come after I get it built. The drag from the Eddie Current Adsorber is variable by both voltage and current. I believe this will have eight (8 coils, I will do some experimenting with them turned on in pairs and different sequences to figure out the loads.

          Thanks for looking we progress
          Last edited by Jbrooks; 04-09-2020, 01:20 AM.
          Pushed around since 1966.


          • #7
            Wish you were my next door neighbor


            • #8
              The house next door will be for sale this summer. Tom Olsen is a couple miles south of here, come on up.

              Well slow day today waiting on parts so I started to layout the coil pack. Looks like 16 coils 22.5 degrees apart. The need to be arranged North - South, North - South and wired in pairs 180 degrees apart across the rotor. I am sure the wiring is going to drive me crazy. The will be turned on in pairs or maybe 4 at a time. Not only can I control the load with the voltage/current applied, I can turn individual pairs on or off. The theory works we will see how it works in practice. The loads should increase as you add coils, and if you and the next to each other they make more drag.

              The math theory SEZ... ie; See photo Coils A&B and will produce stronger eddies currents and say A&C or A&E . Say coil pair A alone makes 10 pounds of load, A&B should creates 30 pounds since they can react together. , A&C might be 25 and A&E the normal 20. But ABC together should make 50-60, So sequencing the coils will produce predictable loads. Also the load increases with RPM. Higher the speed stronger the loading. I hope to be able to vary the voltage and the number and location of the activated coil packs and hold a stable torque load.

              Coil pack layout
              The coils are pretty small 2 x 3' with 5-600 turns each. Going to make a winder setup and do them on the old trusty southbend. Need to get each one as close as possible and wound tight.putting them in the center gives me twice the Magnetic flux per coil, since there is a rotor on both poles. I will make the center of cast iron rod put a focus pad on the ends ( looks like a small brake pad). they need to have about 1 mm clearance on the rotor. Getting that all aligned will be fun. also getting it solid and fixed will be a challenge. also balancing the rotor assembly and shaft will be interesting.

              Enough for today

              Thanks for following
              Last edited by Jbrooks; 04-10-2020, 02:21 AM.
              Pushed around since 1966.


              • #9
                Impressive John. Hope it works as planned.


                • #10
                  Still awaiting parts, but I have been looking a commercial units and their specifications. Doing some math

                  I am building this based on a Telma retarder used on a F450 or MB Sprinter application. This Telma unit uses 6 coils in three stages , their coils are turned on in pairs, Mine has 16 coils in 8 stages, but I can change that after I get it together. The math says I may have over built it as usual. The numbers look good. All you need to insure is that you pair up the coils 180 degrees across the rotor, and stage them next to each other so the fields and interact. The below curves are adjustable by adding or re-configuring the coil packs at full voltage. I should also be able to adjust the torque curves and changing the voltage to vary the current, changing the magnetic fields, changing the loads. .

                  After it done I should be able to program the retarder control unit for each type engine. Say for a 616/xx I should be able to dial in the load specifically for the engine configuration. I may not be able to do a 930 turbo but who cares, this is good enough for what I expect to see.

                  Hp and Torque curves at 12V
                  Last edited by Jbrooks; 04-29-2020, 12:20 AM.
                  Pushed around since 1966.


                  • #11
                    Got some parts in and more measuring. Turned down a tool to fit in the No# 4 main bearing in the third piece. It fits the case and the drill rod is centered in to to locate the rotational plane through the crank. Worked out pretty well. The height gauge say it good.

                    Click image for larger version  Name:	image.jpeg Views:	0 Size:	466.6 KB ID:	108455

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                    The tool holds the rod centered and let's me locate the center of the first pillow block on the bell housing. Fits up fine probably with in 0.001th" the height gauge.

                    Click image for larger version  Name:	image.jpeg Views:	0 Size:	403.7 KB ID:	108451
                    Have the block located, the carrier plate made and the bell housing bolted together. So far it seems to fit. Next is to turn a carrier for the disc, cut a key way in the shaft and build up the carriers for the other bearing blocks. The shaft needs to be turned down and spline to match the input shaft on the transmission. I am debating using the clutch to drive the shaft, or making a plate that bolts up to the flywheel and extends into the pilot bearing.
                    If I use a disc bolts to the flywheel, i can use a simpler spline but will still need to extend it into the gland nut to reduce the vibration induced into the shaft
                    Attached Files
                    Last edited by Jbrooks; 04-19-2020, 03:44 PM.
                    Pushed around since 1966.


                    • #12
                      Some real fancy engineering going on here my friend - putting me to shame with all the slide-rule and math calculations and figures.

                      My math is getting rusty.

                      With the current pandemic situation - eating out is not an option - so I have not had to figure out a 15 or 20 percent tip in the last month.

                      1960 356B T5 - under major resurrection.
                      356 Registry main thread;
                      1968 912 - running like a scalded cat.


                      • #13
                        Thanks Scott, I hate math with Greek Letters in it, but it could be cheesiness arithmetic, you can do too, it its just hard.

                        Started the power supply and control units. I found a scrapped diode pack from an old welder. So I have a 0-60VDC power supply that should supply plenty of current. If it will weld it should drive a electromagnet. I an using up a bunch of left over stuff in the process. Also built a crazy complicated relay control for the coils. Since I am always over complicating things , this in addition to varying the voltages and the current for the load. I can change the number of energized coils and their clock locations. The theory says i need to pull on the disc equally to avoid trying to flex the shaft, I can control the loads so I should be able to program the dyno to climb hills and accelerate and decelerate, just like driving the car on a brake in.

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                        Thanks for watching

                        Pushed around since 1966.


                        • JTR70
                          JTR70 commented
                          Editing a comment
                          Are you an electrical engineer by trade John? I can't imagine putting all this together and actually having it work. Impressive to say the least.

                      • #14
                        JR I am a retired Naval Officer and then ran a Fire Research LAB for a few years. I was an A-6 intruder guy, you learn allot keeping things in the air. This drag rotor load system will work similar to the EMALS catapult on the USS Ford. I just pick stuff easy and have no responsibilities or measurable goals.

                        Got all the alignment numbers dialed in. The pillow blocks are sitting on some 3/8" wall, 6" square tubing. I need to get them on the milling machine and parallel the top and bottom surfaces but it came out with in 0.0004 run out in alignment.

                        This photo is with C clamps in place for measuring. The shaft extends through all 5 of the carrier bearings. These will carry all he loads. The magnetic breaking disc will mount between the 4 pillow blocks. The aluminum disc shown on the shaft are the No#1 and #3 main bearings simulators. These allow me to shoot the center of rotation of the crank through the bell housing and into the pillow block carriers. The shaft spins easy with everything locked down,

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                        Here it is rotating section with the engine case installed, drill Rod is through the case into the third member, its going to be pretty small overall, I think it will be about 3.5-4.0" shorter when I am done.. I need to place the coil pack and load cell in the center, then get the rotors attached to the main shaft. The shaft will be turned down with splines into a clutch disc. The rotor carrier is 3" in diameter 6" long and has a 1/4 broached and key to the shaft. Balancing this entire thing is going to be interesting, But I have a plan

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                        Last edited by Jbrooks; 04-26-2020, 03:17 AM.
                        Pushed around since 1966.


                        • JTR70
                          JTR70 commented
                          Editing a comment
                          That is Fantastic, Thank you for your service! WOW, heavy duty tube sections you're using there; coming along nicely.

                      • #15
                        Got the strand frame glued together today . Everything still measures OK and the shaft spins easy. I can slide the engine in and out easy even with the extra rod going through to the rear bearing pocket So far so good. Back to the machine shop to fab the rotor carrier and the square up bearing holding blocks. Probably the first guy to ever make a test rig based on an" engine jack".

                        The load section is to the right of the engine. overall 22' wide and 24' long. It will probably get a little shorter after I get the coil pack located.

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                        Here is a 911 run in stand that belongs to Chuck Allard, the inspiration for this DYNO. Chuck has a couple stands like this for different engines and races old porsches. . He just acquired an old Stu ska VW dyno, We are trying to see who get finished first.

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                        Thanks for watching
                        Last edited by Jbrooks; 04-29-2020, 12:13 AM.
                        Pushed around since 1966.