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  #121  
Old 09-01-2018, 09:42 PM
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Superleggera Superleggera is offline
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I made a visit of Joel last Monday after a visit to the Blackhawk Museum which is nearby him. Given this is a fairly new project for him, it is amazing at how much work has been done in regard to the chassis itself and getting it to a stage where it will be a roller upcoming.

One of the things most people won't realize is the amount of planning in the chassis itself before being actually made. Not just from an engineering standpoint (suspension system, geometry setup, bump steer, etc) but also in how to utilize standardized catalog componentry to fit within it. One of the biggest time consumers in doing something like the scope of his project is how the little stuff eats vast amounts of time. The radiator is a standard setup versus having to be 100% custom built with an oddball shape. The fuel tank is pre-cut (provided in the kit) and just needs welded and the addition of bungs, fuel pump and filler. The suspension is basically readily available parts with the custom stuff pre-made as part of the tub delivery. Some folks might be hesitant in doing a chassis like this -- but given the cnc technology in creating it -- I know I couldn't build a standard tubular frame or traditional monocoque chassis for the same price much less be able to integrate all the out-of-the-catalog stuff that is being used. Also the tolerances given the bonding of structures is amazing -- if this was all welded together none of it would be given the heat applied and things "moving". I applaud Joel for doing what he did and worthwhile for others to study closely as well. He has a solid foundation underway and it won't be a several year project before he is delving into creating the actual coachwork envelope itself.

A few pics that I took:




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  #122  
Old 09-05-2018, 03:31 PM
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heinke heinke is offline
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Post Fuel tank construction (Part 1)

The fuel tank for this Miura is centrally located in the chassis, quite literally. It is located in the chassis backbone that’s between the seats and stretches from the cockpit front bulkhead to the rear firewall separating the mid-engine from the cockpit. The fuel tank is placed there so that the car’s front to rear weight balance doesn’t change as fuel is consumed from the tank.

Given this location, the tank has a very unique shape.



The tank is made from Al 5052 alloy in .063 thickness. The aluminum sheet was cut on the same CNC router table as the chassis using tabs and slots to index the pieces. It has two internal baffles to help control fuel slosh during acceleration and braking. Given the high level of precision for the cuts and bends, the un-welded tank holds its basic shape with just a few pieces of masking tape.

I decided to trial fit the fuel tank to the chassis prior to welding the sheets together. The tall part of the tank is located up front just forward of the windshield bottom. When I installed the cowl/windshield in the chassis, the wiper motor needed to be removed due to interference with the chassis. So I knew the chassis backbone needed an alteration for wiper motor clearance and I suspected some additional clearance might also be needed in the fuel tank. I cut away the ¼” thick aluminum in the backbone until the wiper motor could be wiggled into place and bolted down.



The backbone top cover was also cut and additional bends put in it until it cleared as well. The fuel tank was then raised in place. The good news is that chassis backbone fits to the fuel tank like a glove, so fuel capacity is maximized. The bad news is that a small alteration is needed in the fuel tank for wiper motor clearance. The interference area is small, so only a small change was needed. I made ½” cuts about 1.5” apart and folded the metal over 45 degrees to make an angled edge where it was a square edge prior. With this, the wiper motor now clears both the backbone and fuel tank. Note, I also had to carve a half round shape out of the pedal mounting plate for clearance.



I decided to bead roll some “stiffening ribs” into the sides of the tank. I did this to minimize the chance of vibration that might occur in the tank walls when the fuel level is on the lower side. I used a 5/8” wide half round bead roll for this.



Unfortunately, the electric motor on my bead roller died before I was able to finish putting in the beads. I took the gear box portion apart and found one of the motor bushings had been obliterated causing the failure. I’ve been thinking about upgrading to the “industrial strength” motor for a few years and now I’ve got the motivation.

More to come as the fuel tank construction progresses…
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  #123  
Old 09-08-2018, 06:32 PM
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heinke heinke is offline
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Quote:
Originally Posted by Superleggera View Post
I made a visit of Joel last Monday after a visit to the Blackhawk Museum which is nearby him. Given this is a fairly new project for him, it is amazing at how much work has been done in regard to the chassis itself and getting it to a stage where it will be a roller upcoming.

One of the things most people won't realize is the amount of planning in the chassis itself before being actually made. Not just from an engineering standpoint (suspension system, geometry setup, bump steer, etc) but also in how to utilize standardized catalog componentry to fit within it. One of the biggest time consumers in doing something like the scope of his project is how the little stuff eats vast amounts of time. The radiator is a standard setup versus having to be 100% custom built with an oddball shape. The fuel tank is pre-cut (provided in the kit) and just needs welded and the addition of bungs, fuel pump and filler. The suspension is basically readily available parts with the custom stuff pre-made as part of the tub delivery. Some folks might be hesitant in doing a chassis like this -- but given the cnc technology in creating it -- I know I couldn't build a standard tubular frame or traditional monocoque chassis for the same price much less be able to integrate all the out-of-the-catalog stuff that is being used. Also the tolerances given the bonding of structures is amazing -- if this was all welded together none of it would be given the heat applied and things "moving". I applaud Joel for doing what he did and worthwhile for others to study closely as well. He has a solid foundation underway and it won't be a several year project before he is delving into creating the actual coachwork envelope itself.
Thanks for the positive review for the Miura project!! I do want to note that the praise for the innovative chassis and the design foresight to make provision for all the "off the shelf" components really goes to Charley Strickland of Strickland Racing. My project has greatly benefited from using Charley's product but I want to make sure the credit for it actually goes to where it's due.
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  #124  
Old 09-08-2018, 07:36 PM
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heinke heinke is offline
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Post Fuel tank construction (Part 2)

I decided to work on the fuel tank openings while waiting for the bead roller replacement motor to arrive. There are 3 openings I needed to build and put in place: fuel level sending unit, in-tank fuel pump, and tank drain. The tank drain is the simplest, so I’ll go there first.

If you’ve ever removed a fuel tank that had any significant amount of fuel remaining in it, you know why having a practical and safe way to drain the fuel is important. I decided to put a screw-in plug type drain at the back bottom of the tank so I would be able to easily drain all the fuel out if the need ever arises. I started by machining a small rectangle of Al 6061 such that it would clear an overlap tank seam and drilled a horizontal hole across it that would sit right at the tank bottom. The horizontal hole connects with the vertical drain hole such that the tank would drain all the way to the bottom. After cutting a hole in the tank sheet and filing to size, it’s ready to be welded in.



I decided it would be easiest and thus best to weld this piece in on the tank outside. It still needs to be drilled to final size and tapped with 1/8” pipe threads, but that’s the easiest part.



More to come as the fuel tank construction progresses…
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  #125  
Old 09-09-2018, 11:54 AM
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heinke heinke is offline
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Post Fuel tank construction (Part 3)

For the fuel level sending unit and in-tank fuel pump I decided to use thick flanges with blind holes for the mounting screws. By blind holes, I mean the holes don’t go all the way through the flange and thus the fasteners won’t be a source for potential fuel leakage. I came to this decision after consulting with an engineer at Aeromotive which is a maker of aftermarket fuel system components. Given I plan to use an 8 stack EFI on the Miura’s engine, I wanted to use an in-tank fuel pump. Aeromotive makes a real nice universal in-tank pump unit, called Phantom, made to be retrofit into “any” fuel tank.

Given the unique/odd shape of this Miura’s fuel tank, I decided it would be best to confirm with Aeromotive that the 3 ¼” hole needed for their pump unit could be effectively sealed and thus wouldn’t seep fuel. I wanted to install the pump near the back of the tank to ensure fuel would naturally move to it during hard, extended acceleration. So that means it will be in the short part of the tank and there can be up to 12 inches of “head pressure” on the flange seal when the tank is full.

The engineer thought their “as designed” seal would hold fine but suggested a custom weld-in flange with blind holes and an “O” ring seal out of an abundance of caution. My rule of thumb whenever dealing with flammable stuff, always proceed with an abundance of caution. So I decided it would be worth the effort to make custom flanges. In addition, it would give me a non-trivial project to try out on the metal lathe I had recently acquired, so all the incentive I needed. Please note, I’m a newbie machinist so there might be better ways than the below to go about making the flanges.

I don’t have any large diameter aluminum round stock on hand so I decided to make the fuel pump flange from ¾” thick billet and fuel level sensor flange from 5/8”. I measured the lathe chuck and determined I needed a 1.5” hole in order to chuck up the metal. I started by cutting out a square of metal and using my milling machine to bore the 1.5” hole in the center.



I then cut the corners off with a band saw to make it near round and proceeded with machining operations on the lathe to turn the outside and inside surfaces to size. Here it’s being prepared for turning the groove to hold an Oring. Given my lack of experience with a lathe, I took things slowly and it took about a day’s worth of my time to complete the 2 flanges.



Next was fitting and welding the flanges to the tank. I had selected a “tube type” fuel level sensor to minimize the gauge needle movement from fuel slosh. The “full” reading will never be accurate given the odd tank size (i.e. gauge will read full until top part of tank is emptied) but the vertical positioning is important in getting an accurate “empty” reading, which is the more important of the two in my opinion. The flange and sensor were trial fit in the tank to determine how far down to insert the flange such that the sensor tube would be at the bottom of the tank prior to welding.



For the fuel pump flange, vertical positioning isn’t critical as the fuel pump itself is adjustable in height. So I positioned the flange just through the sheet metal where it would be easiest to weld.





Well I’m now blocked waiting for the bead roller motor in order proceed further with the fuel tank. More to come as the fuel tank construction progresses…
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  #126  
Old 09-09-2018, 05:53 PM
Charlie Myres Charlie Myres is offline
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Nice work Joel.

When I make flanges, I cut out the disc – sometimes circular; or just like you did it – then I drill a hole in the centre to take a mandrel with a nut on it and grip the mandrel in the 3-jaw chuck.

Next step is to machine the outside diameter; multiple flanges can be held on the mandrel if necessary and the work supported on the tailstock centre, if required.

Once the outside diameter is correct, it is removed from the mandrel and gripped on the outside, in the 3-jaw chuck. Large diameters can be held by reversing the jaws. The hole is bored to size using drill bits first and then finished to size with a boring-bar.

The face can be turned and the PCD marked with a scriber in the tool-post; use the calibrations on the cross-slide to measure the distance from the centre of the work to the PCD.

The back face is turned last of course; on thinner work getting it parallel to the face of the chuck can be tricky, I use a dial-indicator and gentle taps with a hammer, before tightening the chuck completely,

Cheers Charlie
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  #127  
Old 09-09-2018, 08:24 PM
76mx 76mx is offline
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Quote:
Originally Posted by heinke View Post
Thanks for the positive review for the Miura project!! I do want to note that the praise for the innovative chassis and the design foresight to make provision for all the "off the shelf" components really goes to Charley Strickland of Strickland Racing. My project has greatly benefited from using Charley's product but I want to make sure the credit for it actually goes to where it's due.
Thank you Superleggeria and thank you Joel.
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  #128  
Old 09-24-2018, 07:44 PM
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heinke heinke is offline
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Post Fuel tank construction (Part 4)

156 tack welds and 224 inches of TIG welds. That’s what it took to weld together the 3 sheet metal pieces that make up the Miura fuel tank, all this welding to get a fuel tank that holds about 17.5 gallons of gas. This fuel tank is by far the single biggest aluminum thing I’ve TIG welded together to-date. The good news is that I’m much better at TIG welding aluminum now than before. The not so good news is that I’ve found several “pin hole” leaks in testing the tank with water.

Let me start here by going back to where I left off with the bead roller with a bad motor. The industrial grade motor upgrade arrived and Mittler Brothers did a great job in keeping the motor swap simple. I just had to undo 2 bolts and the old motor and its electronics slipped of the bead roller. The new motor and its electronics were pre-assembled and attached to the bead roller with the same 2 bolts. It only took about 15 minutes to swap out the motor and here’s the bead roller with the new industrial grade motor installed.



This motor has some real grunt and no more worries about stalling out the motor when pressing in a deep bead. I can also run it real slow with the combination of variable control and foot pedal.

Ok, back to welding the fuel tank. While tacking, I found the metal to warp and move unless it was securely clamped in place. I ended up using a bunch of bar clamps to keep the sheet metal edges in place while tacking them together. Here it is in pictures.







… and finally the welded tank.



I still need to fix the pin holes but the fuel tank fabrication is just about done.
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  #129  
Old 09-26-2018, 07:49 PM
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Looks great, Joel. Thanks for the continued updates.
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  #130  
Old 09-27-2018, 05:09 PM
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Default testing the fuel tan

I think you should test the tank with low pressure air and soapy water, its a better safer test than water filling!!
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