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Modern-day Miura

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  • Originally posted by Bloozberry View Post
    Lookin' good there Joel. That transaxle is going to be one-of-a-kind... I can't wait to see more of it as it gets further down the development pipeline.

    As for the headlights, if I could offer one piece of advice it would be this: make sure there is zero play in whatever linkage/gear combination you end up using to raise the pods, and if you can, try to design the linkage so it has an over-center locking feature. Both will help minimize the pods from jiggling from road vibrations in the "up" position. I've found this the most frustratingly difficult problem to solve on my 308 replica, and there's nothing worse than having an on-coming car with headlights that vibrate or jiggle.

    Keep posting your progress!
    Bloozberry: thanks for advice on the headlights. I'll have to factor it into the design.
    Joel Heinke
    Be original; don't be afraid of being bold!

    Comment


    • Firstly, I’ve got to say that designing and fabricating these headlight mounts/mechanisms has turned into a very time consuming endeavor. Maybe it’s that I’m trying to locate something with an oval face that sits at a slightly upward sloping angle, needs to be positioned with symmetric accuracy so both sides will look the same, and requires a rigid mounting such that the headlight beams won’t bounce around on roads with a rough surface. In other words, I’m trying to position something that has no flat surfaces, no corners, and no part of it resides in true horizontal or vertical planes. This translates into taking many measurements and many re-measurements using a ruler and small level to verify the headlight bucket positioning as the fabrication goes from cardboard templates to sheet metal parts, to a welded/fastened together unitized assembly.

      Given that context, I determined the best way to mount the donor Fiat 850 headlight buckets was to wrap them in a sheet metal can that clamped down snuggly on the donor bucket. I discarded the idea of welding or screwing mounting provisions directly to the donor buckets because they are made of very thin sheet metal and I didn’t want any of the mounting bits to be visible when the headlights are viewed through the outside oval glass covers.



      Some bucket positioning adjustability is achieved on the legs that attach the mounting can to the pivot shaft by having oversized holes with fender washers to clamp the parts securely together. Shaft collars are used to attach the legs to the shaft. I added a second set screw to each collar for better gripping on the shaft along with drilling/tapping the 6-32 screw holes in the collar sides for attaching the legs. You’re probably by now starting to see why making these mounts has been so time consuming.



      The electric motor gearbox has a 5/8” round shaft with a 1/8” wide slot across it. The shaft/slot was used to hold a spiral spring as part of the window regulator mechanism. With the spring removed, this shaft/slot provides a secure, non-slip attachment point for the headlight pivot shaft. Using a lathe, I turned up a connector with ” ID on one side, 5/8” ID on the other and welded a piece of 1/8” flat stock across the larger opening for engaging the slot in the gearbox shaft. Here are all the parts assembled for first trial run at raising the headlight.



      It worked!! There are still some smaller details to work out but the basic design seems to be solid. The headlight raises and lowers smoothly and the only wiggle is some free play in the electric motor gearbox. I think this free play can be addressed/mitigated with a spring or perhaps a cam with indents for up and down positions. Now to repeat the process to build the headlight mount for passenger side, hopefully this will only take half the time of the first one.
      Joel Heinke
      Be original; don't be afraid of being bold!

      Comment


      • I’m using C4 Corvette power window motors/gears to rotate/lift the Miura headlights when in use. These motors are compact and have plenty of torque for this application. The two things I had work out is how best to mount them and how to control them to stop in the full up and full down headlight positions.

        First, the mounting part. I cut down the mounting frames that normally go full door height and welded on some metal sheet for reinforcement strength. I then added a piece of ” square tube for a mount at top rear of the motor and an angle bracket for mounting the front. After some test runs, a ” square tube mount was added to the bottom rear of motor to prevent the motor frame from twisting when the gear meets the up and down stops.





        As to the drivers experience in activating the headlights, I wanted a single button press to fully raise both lights and a subsequent single button press to completely lower them. Since it’s hard to tell from the driver’s seat when the headlights are fully up or down, I wanted to engineer in a solution instead of having the driver hold the switch down too long just to make sure.
        A “one touch” also known as “Express” module seemed like a good solution. This is the electronic circuitry that enables a single touch on the power button to fully raise and/or lower a power window. This is a fairly standard feature on modern car power windows and I was able to find a source for the Express module intended for use in custom cars like mine.

        To use the Express module on my Miura headlight application, I would need to have solid hard stops at the up and down positions for the headlights. I put the stops on the main drive gear so the headlight buckets themselves wouldn’t be put under stress. After some testing, it looks like I solved another potential issue with this approach. The power window motors have some play in their gearboxes but by having them go all the way to a hard stop, the headlight buckets don’t have any free play existing when they are in full up or down positions. So this design should prevent giggling headlights from free play in the lifting mechanisms.

        After spending a great deal of time building out the headlight lift mechanisms, I now get to move on to something else. It’s things like this that make it almost impossible to predict the schedule on a car build project like this one.
        Joel Heinke
        Be original; don't be afraid of being bold!

        Comment


        • After finishing up the headlight mounts and motors, my initial thought was to jump into some metal shaping and start making the skin for the front clip. That got me to thinking, if I do that what could go wrong? It occurred to me that I hadn’t completed more than just the most basic door frames. So I hadn’t really defined in metal the front edges of the doors. I’d hate to have skinned the front clip only to find that I had guessed wrong on the shape of the rear edge next to the door skins.

          I had done some mockups with steel rulers for initial verification of door hinge placement but I hadn’t yet built out enough door frame to define the door skin front edges. If I proceeded to building the front clip skin, would it clear the doors when the front clip was tilted up? Would the door skins actually clear the front clip when the doors were opened? I couldn’t test for either of these without building out the complete door frames. So I decided a more logical sequence was to build out the door frames prior to skinning the front clip.
          For door frames, I need to build out the inner door frame (chassis side) as well as the outer door frame (door side). On the chassis side, I’m starting with an inner door sill brace and the ” aluminum sheet that makes up the floor board, so pretty much a blank sheet of paper. I want to use the rubber door seals from the C4 Corvette since they are designed to seal where the doors and side windows meet up to the windshield frame. On the C4 Corvette, the rubber seals are mounted on the outer door frame side and seal against a channel that forms a vertical surface on the inner door frames.

          I mocked up a few door sill profiles to test out the horizontal placement of the seal channel and thus the shape of the door sill. The door sill on the Miura has some special considerations that don’t apply to “normal” door sills. Namely that people will likely use the door sill as a temporary seat while entering and exiting the car. The Miura door sill is a few inches above the bottom of the seat which is inverted from most cars where the door sill is well below the seat bottom. In normal cars, the occupant’s weight is usually placed directly on the seat and not on the door sill itself.
          Given the Miura’s low ride height, unless someone can levitate themselves into and out of the car, they will inevitably be dependent on using the door sill to support themselves for entry and exit. I plan to be the primary driver for my Miura, so the door sill will need to support at least 225 lbs. being regularly placed on it without deforming and thus having doors that don’t seal and have wind whistles.

          Here are the door sill profile mockups:



          The one in the middle is what appears to be best. A secondary reason for doing the mockups is to make sure I can make them with the tools I have in my shop. The only way I can make these profiles is in 2 pieces that are then welded together. Well at least I now know what I’m up against.
          Joel Heinke
          Be original; don't be afraid of being bold!

          Comment


          • Door frames (cont.)

            The next step in building out the lower door sills was to add a support and closure plate at the chassis edge. The two fold purpose of this plate is to provide a wind/moisture seal for under the doors and secondly to provide support for the door sill and for the rocker panel sub-structure that extends out approximately 4” from the chassis edge.

            Similar to the chassis, the panel will be ” thick 5052 aluminum and I decided to bond/glue it in place. It didn’t feel adequate to just rely on a ” glue surface around the plate edge so I decided to use a combination of ” and ” square tube as backing members to provide more gluing surface area. Given the two-part methacrylate adhesive only has a 15 minute working time, I decided to approach the gluing as a 2 step process: 1) glue square tube backing members, and then 2) glue in ” plate.

            Here all preparation is complete for gluing step 1. I went as far as doing a dry run for clamping all the backing members in place so I’d ensure I had adequate number of clamps ready at hand. I also cut a ”square off end of paint stir stick to give me a foolproof tool for positioning backing members a consistent ” from edge during gluing and clamping.



            Step 1 complete for both sides of chassis with glue applied and everything clamped in place.





            For step 2, I decided to use pop rivets for clamps given I don’t have many “deep reach” clamps. The preparation of drilling and deburring all the pop rivet holes took more time than the actual gluing. Here it is with these panels all glued in place.





            I now have a very solid foundation for the door sills and in addition have added considerable stiffness at the chassis edge.

            Joel Heinke
            Be original; don't be afraid of being bold!

            Comment


            • I enjoy building cars, and I like making lots of custom stuff, but this is an insane level of do it yourself here. Maybe one day I'll have the patience for it, today I just marvel at your skills.

              Comment


              • Originally posted by AjzRide View Post
                I enjoy building cars, and I like making lots of custom stuff, but this is an insane level of do it yourself here. Maybe one day I'll have the patience for it, today I just marvel at your skills.
                AjzRide: thanks for the appreciation!
                Joel Heinke
                Be original; don't be afraid of being bold!

                Comment


                • Door frames (cont.)

                  My initial thought was to have the lower door sills stop at the chassis edge. That’s how I made the mockup pieces assuming the top of the rocker panels would extend inward and join there. But upon further reflection, it became apparent to me this would be a non-optimal design. It would result in much harder to make rocker panels that would have a visible seam right in the middle of the door sills. In addition, it would make it harder to build in any sort of horizontal adjustment for the rocker panels so they could be aligned with the lower fenders and door edges.

                  I decide a better design is to extend the door sills all the way out and step them under the rocker panel edges. This would give a nice, clean door sill where the seam would fall into the natural place for the paint color change. It’s traditional for the Miura rocker panels to be a different color than the rest of the car.

                  Given this revised design, I needed to determine exactly where in vertical and horizontal planes the rocker panels would be placed. To get this information, I needed to turn to the body panel measurement “source of truth”, the station buck. My Miura station buck consists of multiple modules; one of these modules contains just the rocker panels. I spent a day assembling and fine tuning this module in order to obtain the needed measurements.



                  I’m really fortunate to have done this. Prior, I had assumed the rocker panels ran parallel to the chassis centerline and horizontal to the ground. In fact, there’s a slight outward taper on the rocker panel top edge and a slight upward incline from front to back. Its subtle details like this that are easy to miss but are very important in achieving the “wow factor” for the final look of the car. Armed with this measurement information, I started fabricating an inner sub-structure that would serve as the rocker panel mount.



                  These sub-structures will take some time to fabricate as they run the full length between front and rear tires and will need bracing triangulation as I anticipate they will be sat upon as people enter/exit the cockpit.
                  Joel Heinke
                  Be original; don't be afraid of being bold!

                  Comment


                  • Door frames (cont.)

                    The rocker sub-structure for the drivers side is now complete.





                    The sub-structure is fabricated in a more traditional fashion using pieces of aluminum tubing welded together and then attached to the chassis via bolts. I’ll build the rocker sub-structure for the passenger side while the process is fresh in my mind prior to starting on the door jambs.
                    Joel Heinke
                    Be original; don't be afraid of being bold!

                    Comment

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