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  • Disc Brakes

    In parallel with modeling the station buck, Ive started working on the brake system. Ive elected to go with an aftermarket brake system made by Wilwood. Its a high-performance brake system utilizing 13 rotors on all 4 wheels, 6 piston calipers, and a pedal assembly with built-in balance bar for front to rear bias adjustment on the fly. I ordered up all the pieces a while ago and now am beginning the initial assembly process.

    While going aftermarket on a brake system gives a lot of flexibility, it also can make for some engineering challenges as this collection of parts didnt come off an assembly line in an auto plant. The first challenge I ran into is with mounting the calipers to the suspension uprights. The calipers were designed to be mounted with two 3/8 bolts and have only 9/16 between caliper mounting tabs and rotor for fastening. The suspension uprights are aluminum and given the limited space available, I cant use traditional fasteners like hex nuts behind the aluminum upright. The two milled off areas on the upright is the caliper to upright mating surface.



    I could have drilled and tapped threads into the aluminum upright but I dont like this especially for a critical safety item like brakes that will be constantly going through heat/cooling cycles. The 2 fastener options I came up with are heli-coil inserts or a tee-nut. While a heli-coil would give the bolt threads something other than aluminum to grip, the heli-coil itself would still be threading into the aluminum. So better from a standpoint of serviceability in tightening/removing caliper bolts a repeated number of times but still not so good related to grip strength of threads in the aluminum.

    A tee-nut gets its name because it looks like a T in side profile. The most common use of tee-nuts is in wood where thread grip strength might be an issue and the associated fastener is typically a medium sized screw. I couldnt find a source to buy tee-nuts with a 3/8 bolt thread so Id need to machine them myself. While it would take quite a bit of time to machine tee-nuts, I felt it was worth it to end up with a superior end result for worry free brakes. A tee-nut would give me about length of thread in steel and a solid flange type head to sandwich the aluminum upright to the caliper.




    I started with partially threaded stainless steel bolts. I used a lathe to drill holes into the center of the bolt head and down the shaft. The drilled hole was then threaded for 3/8-24 threads using a hand tap. I then used a vertical mill to machine the bolt heads down to 1/8 thick so they would clear the rotor. The bolt shaft was cut off with a hack-saw and remaining shaft ground to final length on a grinding wheel. The picture above shows at various stages of machining where rearmost one is completed tee-nut with a 3/8" bolt in it. Like I said lots of machining and time to make each one and 8 tee-nuts were needed.





    The rest of the assembly on the car was straight forward. I double checked the clearance and have about .030 between the tee-nut head and rotor surface. Not a lot but it should be enough. This brake system uses a separate cable operated caliper for parking brake. Thats the smaller caliper in front.





    More to come on brake system
    Joel Heinke
    Be original; don't be afraid of being bold!

    Comment


    • your doing incredible work. I love seeing the progress.

      Comment


      • This is an amazing build!

        Comment


        • Originally posted by bodyman View Post
          your doing incredible work. I love seeing the progress.
          Originally posted by luke.jenner View Post
          This is an amazing build!
          Thanks guys!!

          This may sound funny, but I'm really having fun with the project as well. And I haven't even gotten to the part that prompted me to take the project on yet, metal shaping the bodywork.
          Joel Heinke
          Be original; don't be afraid of being bold!

          Comment


          • Radiator coolant tubes

            Ive switched focus again from brake system to coolant lines. A great thing about a project at this early stage is that if you hit an issue with one area, theres plenty of other areas where progress can be made. Ive decided to connect the radiator openings to the main under chassis coolant tubes with 1 purpose routed, bent aluminum tubes. I am making these from mandrel bent Al 6061 tube and welding them together. I did some preliminary design and ordered up the mandrel bends and silicon hose adapters/couplers I thought were needed.

            I started fabrication with the bottom tube as I needed to establish its position so the upper tube could be routed around it. Both these tubes need to be routed to clear the spare tire.




            One each of 120 degree, 45 degree and 60 degree bends and 2 welds were needed to complete this tube. All in all, fairly straight forward. The upper tube is more complicated as it needs to be routed over the rack & pinion but still under the spare tire. A 180 degree bend cut in the middle and repositioned gives the needed jog for this. A hose clamp temporarily holds the joint for mockup purposes.




            I then started from the other end to determine what type of bend was needed for the middle. For the middle tube area, I need a bend thats between 15 to 20 degrees. Of course, I dont have one of these and it took an Internet search to find a source. I found a source for an 18 degree bend and now have it on order.




            I need to have an air bleed valve at the topmost part above the radiator so I made a bung and welded it on at the top of the top tube.




            Im now at a hold state to finish these coolant tubes until the last tube bend arrives.
            Joel Heinke
            Be original; don't be afraid of being bold!

            Comment


            • Radiator coolant tubes (cont.)

              I finished fabricating and welding up the front cooling tubes.



              A final check to ensure these will clear the spare tire. Theres still an inch to spare

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

              Comment


              • Front clip station buck

                Ive been focusing all my garage time over the last few months on the C5 GTO. The GTO is now getting to the stage that Im dependant on others to do some work for me, so Im able to context switch back to the Miura project.

                I finally got a chance to assemble the station buck for the Miura front clip. As you might guess, it's like trying to assemble a big jigsaw puzzle with an extra challenge. The pieces all have an air gap in between them. After some trial and error, it came together and looks great.

                The CAD model that resulted from the design step for the station buck:



                The CAD model for the front clip of station buck:



                Heres what it looked like when coming home from getting Baltic birch plywood cut on CNC router:



                Finally, with all the front clip stations joined together in place.











                The missing areas like grill, headlight, and vent openings are where hammer forms will go. I'm still working to get the hammer forms shaped/cut on CNC router.

                What I like about it:
                It's free standing with it's own legs
                It's lightweight enough that I can slide it around the shop
                All station intersections easily aligned



                In addition, I'm really impressed with the accuracy of going from a CAD model to CNC instructions to cut 1/2" plywood stations. The slots are tight enough to hold stations firmly in place. I used a rubber mallet to tap interlocking stations in place and then a wood screw through the intersections to keep them there.
                Joel Heinke
                Be original; don't be afraid of being bold!

                Comment


                • Joel, if I have not said it before, I am very proud that you selected one of my chassis for this project. Incredible work.

                  Comment


                  • Originally posted by 76mx View Post
                    Joel, if I have not said it before, I am very proud that you selected one of my chassis for this project. Incredible work.
                    Charley: I have no regrets for choosing your chassis for this project. I just hope that the resulting car will live up to all the great design innovations that are embodied in your chassis. You've set a very high bar
                    Joel Heinke
                    Be original; don't be afraid of being bold!

                    Comment


                    • Mounting Miura Pedal Assembly

                      While the Ferrari GTO was out getting the headliner installed, I had the chance to work on the Miura a bit. I had purchased the brake/throttle pedal assembly prior and now I wanted to get it mounted in the chassis. I had first gone down the path of using a pedal assembly where the pedals hang down and master cylinders are mounted up top. I found the clearances were just too tight with the cowl and steering column to make it work as I wanted it too.

                      So I switched directions to using a floor mounted pedal assembly that uses master cylinders with remote reservoirs. This way, I could make the pedal assembly adjustable for tall people like me or for people with normal length legs. The remote reservoirs are needed as the master cylinders are located below the plane of the brake calipers and the reservoirs need to be placed above the plane of the calipers to prevent unwanted fluid drain back.

                      I mounted the pedal assembly to a thick aluminum plate. For adjustment, a series of holes spaced apart were drilled in the plate. The pedals now have 3 of adjustment by unfastening, moving, and re-fastening the 4 bolts that secure the plate.
                      Pedal assembly as viewed from above.



                      As viewed from drivers seat.



                      As advertised by Charley Stickland, his chassis does have lots of leg room. With the pedals now mounted in place, my long legged, 65 body fits well with plenty of legroom!
                      Joel Heinke
                      Be original; don't be afraid of being bold!

                      Comment


                      • Originally posted by C5GTO View Post
                        I

                        I started with partially threaded stainless steel bolts. I used a lathe to drill holes into the center of the bolt head and down the shaft. The drilled hole was then threaded for 3/8-24 threads using a hand tap. I then used a vertical mill to machine the bolt heads down to 1/8 thick so they would clear the rotor. The bolt shaft was cut off with a hack-saw and remaining shaft ground to final length on a grinding wheel. The picture above shows at various stages of machining where rearmost one is completed tee-nut with a 3/8" bolt in it. Like I said lots of machining and time to make each one and 8 tee-nuts were needed.




                        It's an interesting approach to the problem. I have two observations about it nevertheless:

                        1. How were you able to torque the caliper mounting bolts given that you only had a 1/8" gap to hold the tee-nut from spinning?

                        2. I also worry about the amount of torque you can place on the tee nuts before they fail. Having hollowed out a 1/2" stainless bolt with a 3/8" inner diameter hole would leave only 1/16" thickness where the shank meets the head of the tee nut. Since the 3/8" stainless bolt has a cross section of about .11 sq-in and is designed for about 22 lbft of torque, the 1/2" tee nut would have 0.2 sq-in of cross section minus 0.11 drilled out equals 0.09 sq-in cross section. That's about a 20% reduction in area over the 3/8" bolt, which means the caliper mounting bolt should really only be torqued to 20% less than its design load, or 17 to 18 lbft. As long as you believe that's enough to hold the caliper on, it should be alright. Much more than that and you risk pulling the head off the tee nut.

                        My 2 cents.

                        Comment


                        • It's an interesting approach to the problem. I have two observations about it nevertheless:

                          1. How were you able to torque the caliper mounting bolts given that you only had a 1/8" gap to hold the tee-nut from spinning?

                          2. I also worry about the amount of torque you can place on the tee nuts before they fail. Having hollowed out a 1/2" stainless bolt with a 3/8" inner diameter hole would leave only 1/16" thickness where the shank meets the head of the tee nut. Since the 3/8" stainless bolt has a cross section of about .11 sq-in and is designed for about 22 lbft of torque, the 1/2" tee nut would have 0.2 sq-in of cross section minus 0.11 drilled out equals 0.09 sq-in cross section. That's about a 20% reduction in area over the 3/8" bolt, which means the caliper mounting bolt should really only be torqued to 20% less than its design load, or 17 to 18 lbft. As long as you believe that's enough to hold the caliper on, it should be alright. Much more than that and you risk pulling the head off the tee nut.

                          My 2 cents.




                          Bloozberry: interesting observation and questions. As to question 1, I haven't torqued the caliper bolts yet but I plan to use a thin wrench to hold the tee-nut from spinning. I'll also glue them in with red Loctite prior to torquing.

                          As to question 2, you've put a lot more engineering into forming your question than I than I did for my tee-nut solution. I believe the real critical question is, "how much torque is really needed when fastening these caliper bolts?" The initial direction that was passed on to me from Charley (but I believe was provided to Charley by Wilwood) was to drill/thread the aluminum upright and screw the caliper bolts directly into the aluminum. If that's an acceptable approach, then the tee-nuts I've made will surely be stronger than that. When I look at similar Wilwood aluminum caliper brackets themselves, they use what looks like a press-in steel threaded insert that just has a small knurled surface to keep it from spinning when torqued. It's hard for me to believe that insert will take much torque before spinning itself.

                          I looked through the information provided by Wilwood in the boxes and don't see any torque specs for the caliper bolts. In looking at instructions for a Wilwood brake kit that uses a similar caliper with a 3/8 - 24 bolt to secure it, the instructions say to torque to 30 ft lbs, use red 271 loctite, and then wire the bolts in place. Well wiring the bolts in place does sound like a good safety minded thing to do. I'm using 3/8 - 24 bolts which show a 30 ft lb torque spec. Maybe I'll need to do some torque testing on the tee-nuts to verify they can take the full 30 ft lbs.

                          Hmmm...thanks for bringing up the questions. I always want to make sure I don't have a safety gremlin hiding out somewhere.
                          Last edited by C5GTO; 08-10-2019, 04:39 PM.
                          Joel Heinke
                          Be original; don't be afraid of being bold!

                          Comment


                          • Locating and Fabricating Flip Front Clip Hinge Point

                            I decided to start building out the sub-structures that attach and hold body panels to the chassis. Im starting with the one piece, flip-up front clip first. The front clip is hinged in the front and thus tilts forward to open. When opened, the bodywork that forms the top of the nose comes very close to touching the ground. Because of this, determining the hinge point location is critical.

                            I needed to know the front bodywork outline in order to measure backward to the hinge point. So with measurements taken from station buck, I used a piece of welding rod and masking tape to lay the outline. It also shows where the horizontal chassis tubes are too long and need to be cut off so they wont protrude through the bodywork.



                            Through some research and experimentation, I concluded the hinge point needed to be vertically about an inch lower than the front wheel spindle and horizontally about 10 inches behind the most forward part of the front bumper. I located this spot and marked it with an X on some masking tape. By putting in some angled chassis bracing members, it would give a strong hinge point and complete the chassis bracing in that area.



                            I plan to use bolts for the front clip hinges themselves. So I inserted some aluminum inside the rectangular tube to make it solid at the hinge point and drilled holes. To ensure the holes on both sides aligned, a piece tube was used to fixture them in place for tack welding.



                            After tacking the cross brace tubes in place, the horizontal chassis tubes were trimmed to length.



                            Im going to hold off on final welding the cross brace tubes in place until Ive built out more of the front clip sub-structure and can physically verify the hinge point placement.
                            Joel Heinke
                            Be original; don't be afraid of being bold!

                            Comment


                            • Originally posted by C5GTO View Post
                              I believe the real critical question is, "how much torque is really needed when fastening these caliper bolts?"
                              That is indeed the million dollar question. It's one that can be calculated, or it can be estimated through a comparison of similar designs (as you've done using the Wilwood examples).

                              Originally posted by C5GTO View Post
                              In looking at instructions for a Wilwood brake kit that uses a similar caliper with a 3/8 - 24 bolt to secure it, the instructions say to torque to 30 ft lbs... I'm using 3/8 - 24 bolts which show a 30 ft lb torque spec.
                              Are you sure you're not looking at the torque specs for carbon steel? The most common stainless steel bolt alloys (8-18 and 316) specify 21.6 and 22.6 lbft respectively.

                              Originally posted by C5GTO View Post
                              Maybe I'll need to do some torque testing on the tee-nuts to verify they can take the full 30 ft lbs.
                              That's probably a good idea.

                              Comment


                              • Flip Front Clip Hinges

                                Next up on the build agenda was to make the flip-up front clip hinges. I wanted to have both vertical and horizontal adjustment in the hinges so it took some thinking to design that in. I started with a piece of 2 x 2 x angle in 6061 aluminum, 6 in length as the main part of hinge. This was then cut down so a 1 wide rectangular tube for sub-structure base could bolt up to it.



                                I put slots in the angle part of hinge where 5/16 bolts pass through for horizontal adjustment and vertical adjustment if via shim. For fabrication purposes, theres a thick shim in the hinge for now. Ill likely put some lightening holes in the hinge to shed some of its weight. The sub-structure members will be welded to the rectangular tube bolted to the hinge top.
                                Joel Heinke
                                Be original; don't be afraid of being bold!

                                Comment

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