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GT6MK3

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About GT6MK3

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    HotRod Nerd!

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    http://www.skydivepros.com

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  1. GT6MK3

    Vespa smallframe

    Yep, it's an awesome toy. wish I had the garage big enough to house one, and the budget to buy one. Luckily, Alan lets me use his! More work I the garage Saturday. Sadly, I overdid it pressing a bearing holder into a 50 year old engine case and cracked it, which was cause for a large amount of swearing, and will require the opening of my wallet to fix. Dammit. My buddy Michael was able to continue his build though, and more port grinding ensued. And, with the arrival a third set of hands and experience, the stuffing of oversize parts into an undersize case began
  2. GT6MK3

    Vespa smallframe

    Clamp Cut Think and program Cut more and more And parts magically appear Oh, and re-re-re-cut the top surface...
  3. GT6MK3

    Vespa smallframe

    A trip to Alan's shed tonight for some programming. My buddy Michael had provided this as the basis for the cylinder spacer. That let me build up this in a mere 24 steps. But I needed to step the ports out 3mm horizontally over the 10mm thickness. Each arc for example has 13 adjustable variables to be set, with 3 check results. Then there's lines, blends, depths, and repeats. Which meant lots of maths, educated assumptions, (and a buttload of scientific wild arse guesswork). Till I had this It was 4 degrees in the shed, and almost 10pm, so I saved it and naffed off home for a hot toddy. I'll cut it tomorrow.
  4. GT6MK3

    Vespa smallframe

    Yep - the maths is starting to blow my tiny brain.
  5. GT6MK3

    Vespa smallframe

    Went to Alan's headquarters today, and did some measuring. We put up the first engine, with the piston at TDC (re-measured with a dial indicator). We touched off the face of the cylinder, and established a plane there as a base. Next we touched around outside wall of the protruding piston to give us a reference circle to work within. Finally, we touched off four points as close to the outer edge of the face of the cylinder as possible, two in line with the gudgeon pin and two perpendicular to it. We may have got some minuscule piston rock on the across touches, so we'll trust the "along" numbers. Here they all are... Basically, they show that along the gudgeon pin, the piston edges protrude 1.6251mm (averaged), and across it, 1.6118mm. So lets call it 1.63mm for our purposes. Next the second engiine (Mine!) went up After the TDC procedure, we measured again Across the pin we'll call mine 1.94mm Next we measured the cylinder itself, including some numbers for future reference in case we want to mill replacements later (Outer holes, combustion chamber sphere etc) . The squish area of the cylinder head is a sloped ramp, which then meets a short outer cylindrical wall, which then in turn meets the outer mating face. We need to know the height of the cylinder wall, s (a) it will allow us to set our squish, and (b) it will form the hard limit of how far the piston can protrude from the cylinder, lest it mash into the head, rapidly, with great and expensive force... Because the wall meets a sloping face, accurate measurement required some maths and calculation. First, we touched off points on the upper face, and made that a reference plane. Next we carefully touched off points on the inner wall of the cylinder, all at the same height. (with the software, if you tell it your're measuring the inside of a circle, and touch three points, it can extrapolate the circle. Touch more points, and you have more accuracy). Once we had the circle, we then had the software expand it into a cylinder, perpendicular to the original top reference plane. To measure the squish ramp, we told the software we were measuring a cone. By touching off points up, down, and around the ramp, we were able to calculate the ramp. then find (a), where it intersected with our wall cylinder, and (b), how far down from the top reference plane that intersection was. Abracadabra, the built in squish headroom for the cylinder is 0.9252mm. Lets call it .93. So as they stand, we're going to make expensive noises with our 1.63 and 1.94 popups. On to the cylinders. We measured these with a 90 degree probe, trying to get about 0.8mm into the port to beat the roundoff on the edges. Because we have the current popup numbers referenced to the top face of the cylinders, we were able to take these off the engines and measure them stand alone. Results for #1 and mine. Mains on #1 are 38.87 39.01 38.64 and 38.78. (Average of 38.83) Exhaust is 27.46. So 130.12 and 185.29 with 27.58 and zero deck, and 132.87/187.51/27.32 with 0.5mm popup. Mains on mine are 38.65 39.09 38.58 and 39.23. (Average of 38.89) Exhaust is 27.97 So 129.79 and 183.02 with 26.62 at zero deck, and 132.54/185.25/26.36 with 0.5mm popup. Now I'm off to consult guru's and do maths...
  6. GT6MK3

    Vespa smallframe

    Had a good day in the garage building up a buddy’s motor that’s the fraternal twin to Buffy’s he’s pretty chuffed... the inside of the crank housing weld cleaned up ok Sunday I milled down the massive pimples left after building up the ports for machining and this arvo the base of the leg shield got sealed up
  7. GT6MK3

    Vespa smallframe

    Very unwanted hole - not oe - it blew through during hydroblasting, a result of trying to maximise case volume by expanding the crank void to the maximum possible, might have overdone it. Hopefully filled now. Oven cost me a sold 10 bucks on ebay! Neededto cut out and bend a 25mm by 270mm piece of 1.5mm sheet to fill the rear base of the legshield. Was planning on cutting it out with an angle grinder, and bending it in a vise, but Mat laughed and used his toys to good effect. Nice to have friends, Hope you're improving, C.
  8. GT6MK3

    Vespa smallframe

    Yep, getting close.
  9. GT6MK3

    Vespa smallframe

    Got 2 Spot welders - my handheld and Mat's floor mounted beast, but neither seem to be able to make a decent weld through weld through primer. Given that steel in the spine is going to be in the wet and cold, I want the primer in place, so it's back to plug welds... More work Friday arvo. Finally figured out how to put the choke actuator back together. Simple when it's done, harder when your looking in a box of bits. Then ran cables, lots of cables through the spine for use installing all the control cables and wiring later. That's 5 bicycle gear cables, 3 runs of lightweight balustrading cable and 4 runs of mig wire just in case. Time for these two to be properly introduced. Some gentle squeezing on a well lit table with plenty of room in the middle of the factory to begin the process, with final measuring, marking and tweaking taking place. Then a buttload of clamps... That many clamps adds a _lot_ of weight!. Turning it over with all the clamps was tricky and took two of us, and we added a table clamp for stability Ready to start plug welding. The rule for plug welding is to double clamp every hole individually, and wind it up as hot as you dare. Mating the thin legshield to the much thicker spine and getting good penetration is tricky. I'd much rather risk a burn through and have to do a fair bit of grinding than not get good strong penetration. Setting up the clamps every time, and doing it right means each of these welds takes about a minute of setup before the 3 to 5 seconds of bright light. So after a couple of hours of setup and measuring while clamping, welding just the two sides of the base took well over an hour. But after turning it over, it was good to see the strong penetration achieved. Next job will be to re clamp, and weld the front of the legshield. (Believe it or not, I need to buy another quite specific clamp before I do that). But, Buffy's starting to look whole again. Progress.
  10. GT6MK3

    Vespa smallframe

    Measure and mark then punch, pilot drill, drill, and deburr. Well that was fun.
  11. GT6MK3

    Vespa smallframe

    Still got to weld on the legshield - it's just getting marked up atm. Then the tricky horncast has to be let into it...
  12. GT6MK3

    Vespa smallframe

    Engine case Before After Choke mechanism Getting close
  13. GT6MK3

    Vespa smallframe

    Engine mounts And a test of the legshield
  14. GT6MK3

    Re positioning a 6 pot

    And with those sixteen words, you guaranteed you'll always have a place here...
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