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Thread: Modern-day Miura

  1. #21
    Have you thought about going off the less beaten path in terms of V12 engines, like the LS based V12, or the 2JZ based V12? Both of those are probably out of your budget since they are more of a one off design, but definitely have the power capability you were looking for.

    Another option could be bike engines. I don't see that too much anymore, but a triple Hayabusa setup with the cranks tied together at 60 degrees apart would have the same firing sequence of a V12 and spins to over 10k RPM, so I imagine it would sound closer to an F1 style engine if the exhaust primaries are tied together properly. Stock they are around 190hp a piece, so you could be sitting pretty reliably at 570hp, plus they come with their own transmissions already. You would just have to tie the chain drives into a rear differential. Probably not the most tidy engine bay, but it would certainly be unique looking, have the go, the sound, and the reliability at a "reasonable" cost.

  2. #22
    Senior Member C5GTO's Avatar
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    Post Transaxle mockup

    Iím going to step back in time a few weeks here to talk about transaxle mockup and show pictures. Iím guessing this process just might be interesting to you and give context to the work that went into sorting out the Miura sizing question.

    A lot of good things start as a pencil drawing on the back of a ďbar napkinĒ. Hereís our bar napkin drawing for the engine/transaxle package:



    It became apparent right away that the best way to figure out just how compact we could make the engine/transaxle package was to mock it up. Iíd already identified the engine but not the transmission. After a bit of searching we narrowed it down to the Tremec TKO 600 5 speed transmission. The main case and gear set on this 5 speed transmission can certainly handle the HP and torque (the 600 in name gives the torque rating) of the Coyote, it is fairly compact, and the shifter can be mid-mounted out the top of the transmission. Having a 6 speed would be nice but the 6th gear adds more main case length and I didnít think a second OD gear was really needed for the Miura.

    Given this is a custom transaxle build, I knew I needed to have an experienced and willing transmission expert to help out. I poked around and found Bob Hanlon of Hanlon Motorsports in Elverson, PA. (www.hanlonmotorsports.com). Bob quickly understood the project, was willing to help us out by providing measurements, explaining various gearing/ratio options, and with cores, etc. for purposes of mockup.

    Pete located an engine block and head. We got the transmission main case from Bob. The mockup process started.







    The first stage mockup objective was to situate the engine and trans main case as close together as possible to minimize the diameter of the gear set that would connect them. The bar napkin design called for use of a chain in addition to gears and but it looked like we could go with a 2 gears and no chain from the initial mockup. The distance from crankshaft center to transmission input center is about 11 inches in this initial mockup. So a transfer case could be made using two 11 inch gears. In addition, that distance could be shortened a bit by shaving off a protruding ear near where the factory starter mounts from the engine block. More work to go but this gave us something to start with.
    Joel Heinke
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  3. #23
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    First, before you (or any one else) misinterpret(s) my comments, please bear in mind that I'm humbly offering constructive commentary. Tone is not always evident in the written word.

    Anyway, as I recall, one of the reasons you discounted the F40 in your earlier thread was because it didn't have enough longitudinal distance between the engine crank centerline and the transmission output shaft centerline to induce the weight transfer you were looking for. On the F40, that distance is 7.28" (185 mm). Your proposed set up with an 11" distance between centrelines adds only 3.72" (94.5 mm) to that of the F40's measurement. On a 104" wheelbase, that's a 3.6% shift forward of about 20% of your chassis weight (a 450 lb engine in a 2500 lb chassis). That doesn't seem like a lot of weight transfer considering the extra complexity, cost, rotating mass, fixed weight, and unique parts involved in your proposed set-up. That pair of 11" diameter steel gears alone are going to be like adding two more flywheels to the crank! No?


    You've probably also discounted the F40 because it's rated for 300 lbft of torque. But bear in mind that's a very conservative rating. Many others here and on Pennock's have been beating the Muncie 282 with twice (or more) the torque that that gearbox was rated for, for years. Sure, there have been failures, but these are now 30 year old used boxes. You can easily buy an F40 brand new for $500. In fact, you could probably buy ten F40's for the money you'll invest in your transaxle set up.

    If it's uniqueness you're looking for, then as a guy who spent 600 hours developing a multilink pushrod rear suspension for a Fiero, I definitely understand that. Uniqueness is worthy cause without further explanation. Otherwise, did I miss something?

  4. #24
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    Quote Originally Posted by Bloozberry View Post
    First, before you (or any one else) misinterpret(s) my comments, please bear in mind that I'm humbly offering constructive commentary. Tone is not always evident in the written word.

    Anyway, as I recall, one of the reasons you discounted the F40 in your earlier thread was because it didn't have enough longitudinal distance between the engine crank centerline and the transmission output shaft centerline to induce the weight transfer you were looking for. On the F40, that distance is 7.28" (185 mm). Your proposed set up with an 11" distance between centrelines adds only 3.72" (94.5 mm) to that of the F40's measurement. On a 104" wheelbase, that's a 3.6% shift forward of about 20% of your chassis weight (a 450 lb engine in a 2500 lb chassis). That doesn't seem like a lot of weight transfer considering the extra complexity, cost, rotating mass, fixed weight, and unique parts involved in your proposed set-up. That pair of 11" diameter steel gears alone are going to be like adding two more flywheels to the crank! No?
    Never mind... I forgot to take into account that the differential adds another 8" to the difference in the distance between axle and engine centerlines. The observation about rotating mass still applies though.

  5. #25
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    If its not too late you could consider the Toyota 1GZ-FE v12. This is a 5l DOHC engine. There are a number of them running on the web with EFI stacks!

    https://youtu.be/eT0TgL9-2Pw

  6. #26
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    Post Transaxle mockup transitions to build

    It was now time to figure out how wide the engine/transaxle package would be so that meant figuring out the bellhousing and transfer case between engine and transmission. Pete dug up a Ford bellhousing, itís depth measured 7 inches and it had lots of unused ďair spaceĒ inside. We could slice off the area making up the air space and go from there but that felt like a hack. Pete had some large billets of aluminum and decided to machine up a bellhousing from that.



    For the transfer case, more aluminum billet was used.





    You might guess that by now weíre transitioning from rough mockup into making parts for real. The outside half of transfer case shows this with some of Kevinís nice CNC machine work.





    You might also notice the mockup engine now has 2 heads on it. Pete found another core engine so there would be no worries about shaving off some metal and snuggling the transmission up even tighter.

    As it turned out, the bellhousing and transfer case is about 7 inches deep, about the depth of a standard bellhousing. The transfer case still needs some doughnut shaped extensions on outside to hold bearings but these should be fairly thin. The length of the engine from front of damper pulley to outside of transfer case is about 33 inches. Even at 33Ē itís going to be a tight fit into the chassis engine bay but weíve made it as narrow as possible without going down to V6 or something. Thereís no way we could have made a V12 this narrow.

    Iíve got to give Pete Aardema and Kevin Braun credit and recognition for whatís been accomplished on the transaxle so far. Their talents are amazing and theyíve given the Miura project a huge shot of adrenaline. At this point, I felt we had enough engineering completed and information to know that the Strickland chassis would work. Iíve caught you up on project progress to-date and will give project updates more real-time as more progress is made.
    Joel Heinke
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  7. #27
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    Post Miura chassis construction underway

    As a reminder, I decided to use an all aluminum monocoque chassis from Strickland Racing for the Miura. Iím very excited about this chassis for the Miura as to me it represents a big technological advancement. The original Miura chassis was known to exhibit some flex and was prone to metal worm attacks over time. The Strickland chassis should be much lighter weight, more rigid, and shouldnít deteriorate over time given the use of ďmarine gradeĒ aluminum. In addition, Charleyís highly automated approach to chassis construction keeps the cost in the reasonable range.

    A small part of the car sizing answer was in consideration for chassis table fixture mounting. By adding .5% on 105% giving the 105.5% this resulted in good alignment to the chassis table such that mounting holes aligned to fixture holes. The chassis was fully modeled with a CAD application and then the CNC cutting instructions are generated from the model. Chassis parts are made from 5052 aluminum and are cut from ľĒ sheet on a 3 axis CNC router. Iím told the accuracy of the CNC cut chassis parts is incredible and they fit to one another easily by hand.

    Some chassis parts after cutting and removal from sheet.





    Sheet on CNC cutting table after the cut pieces have been removed. With careful placement on the sheet, thereís very little waste after cutting.



    The chassis is assembled on a precision chassis table. The chassis members are secured to the table during assembly to ensure alignment for a straight and true chassis. Tabs and slots are used to accurately index the chassis members to one another.





    After trial fitting to ensure fitment, the chassis members are fastened together with special metal bonding epoxy glue. As you can see in these pictures, the chassis is quickly taking shape.

    Iíd like to thank Charley Strickland for providing these progress photos. I know it provides much better insight for you as to how something is made when you can see it in the various stages of construction.
    Joel Heinke
    Be original; don't be scared of being bold!

  8. #28
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    Post Miura body design underway

    I decided it was time to learn how to use Adobe Photoshop so I could create some visuals to prove out the look on the plus sized Miura body. I took a couple of days to go through a bunch of online tutorials and practice with throw away stuff so I could overcome some Photoshop roadblocks that had turned me away before. I also want to thank Superleggera (Mark of modenawest.com fame) for giving me some tips and tricks for using Photoshop for digital restyling of automobiles. Iím nowhere close to being in Markís league yet but Iím now able to do some basics.

    One thing Iím trying to visualize is what my Miura will look like if a C4 Corvette windshield is used. So I took a stab at changing out the windshield with no other body modifications. The net result is that the windshield posts need to angle further forward as the C4 glass doesnít wrap on the sides as far as Miura windshield. It changes the look some but not dramatically.



    My next step was to do a front quarter view where the windshield is more visible. For this picture, I also widened the body below the windows and raised/arched the cockpit roof some. With these multiple changes, the windshield change doesnít seem to stand out at all.



    Next, I wanted to do front and rear views with objective to make sure the widening only beneath the beltline would have a good look. For the front view, the widening is proportional across the whole front clip. For the rear view, the widening is only outside of the louvers and trunk lid, so not proportional across the rear clip. I did this to accentuate the wider fenders and thus visually widen the stance.





    And for the side perspective, I think Superleggera (Mark of modenawest.com) nailed it with his Miura stretch rendition. So Iíll go with that for now and want to give Mark full credit for his work. Note: This doesn't include the windshield change but as the other side view shows that change is subtle in the overall picture.



    All in all, Iím satisfied with what Iím seeing. It still looks like a Miura SV but with some subtle changes. At 15 feet, Iím guessing very few people could pick out the differences if this car wasnít parked right next to an original.

    So question out to you auto body design experts, what other perspectives or views do you find to be most helpful in highlighting visual design issues? Iíd really like to surface and resolve the visual design issues when theyíre just pixels versus when they are already in aluminum sheet.
    Joel Heinke
    Be original; don't be scared of being bold!

  9. #29
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    Quote Originally Posted by drxlcarfreak View Post
    Have you thought about going off the less beaten path in terms of V12 engines, like the LS based V12, or the 2JZ based V12? Both of those are probably out of your budget since they are more of a one off design, but definitely have the power capability you were looking for.

    Another option could be bike engines. I don't see that too much anymore, but a triple Hayabusa setup with the cranks tied together at 60 degrees apart would have the same firing sequence of a V12 and spins to over 10k RPM, so I imagine it would sound closer to an F1 style engine if the exhaust primaries are tied together properly. Stock they are around 190hp a piece, so you could be sitting pretty reliably at 570hp, plus they come with their own transmissions already. You would just have to tie the chain drives into a rear differential. Probably not the most tidy engine bay, but it would certainly be unique looking, have the go, the sound, and the reliability at a "reasonable" cost.
    drxlcarfreak: I did think about many various sources for V12 engines. The main issue I ran into for using a V12 is the engine length. While the original Miura V12 is also long, the Lambo factory had the advantage of strategically locating various parts on it so it would clear the chassis and making the engine block and transmission from a single casting. In addition, they engineered the chassis to virtually wrap around the long engine. So once I made the decision to use an already designed chassis, it drove a constraint on engine bay width that ruled out the use of a V12. That is unless I got extremely creative. I decided to focus my energies on other parts of the build as readily available V8s have as much or more power for a much lower cost.
    Joel Heinke
    Be original; don't be scared of being bold!

  10. #30
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    Arrow

    Quote Originally Posted by Bloozberry View Post
    Never mind... I forgot to take into account that the differential adds another 8" to the difference in the distance between axle and engine centerlines. The observation about rotating mass still applies though.
    Bloozberry: You bring up a very good question on if the large transfer gears will add too much rotational mass. While the tooth area will be about 1 inch wide, the rest of the gear (except where it mounts on the shaft) will be much thinner and can be further lightened with strategically placed holes. So the gears shouldn't be all that heavy. Also this transverse setup won't have a drive shaft like a front engine car. I'm guessing the transfer gears will be about the same weight as a drive shaft. It should be somewhat comparable to the C5/C6 Corvette that has the drive shaft between the clutch and the transaxle. So in theory (without having weights for all components involved) it should have about the same rotating mass as the modern Corvette.

    We'll find out for sure once we test it out, but I'm not that worried about it at this stage.

    Thanks for raising the point,
    Joel Heinke
    Be original; don't be scared of being bold!

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