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  1. BrianPetersen

    Two-slider crank mechanism

    Re-read posts 55 and 59, and explain with sound thermodynamic reasoning and P-V diagrams why this should be the case. I maintain that it will not. The combustion chamber doesn't care about the design of the mechanism that turns up-and-down into round-and-round aside from its mechanical...
  2. BrianPetersen

    wheel time hole sizes

    Having just done the winter-tire swap on my car (GM), it has M14 studs also, and I just ran downstairs to check. The aftermarket wheels and matched wheel nuts (not OEM) have a conical interface and the holes in the wheels are 14.8mm diameter, which is what one would expect for M14 fasteners to...
  3. BrianPetersen

    wheel time hole sizes

    It would sure help us in the rest of the world if we knew what sort of trailer this is, where the wheels came from, where the axle came from, where the nuts came from, whether the wheels are the correct ones to be used on that axle, whether the nuts are the correct ones to use with those wheels...
  4. BrianPetersen

    Vehicle Anti-lock brake rotor system, increase horsepower, Brake Rotor takes 175 ft-lbs, 36 Hp to spin up, really? free wheeling the brake rotor

    By gut feel this sounds about right. Just out of curiosity ... Steel disk 400mm diameter and 20mm thick has a volume of 2513 cm3 and at 7.8 g/cm3 density of steel, that's about 19 kg, and considering that those dimensions are ruff approximations and I know the centre of the disk isn't full...
  5. BrianPetersen

    Vehicle Anti-lock brake rotor system, increase horsepower, Brake Rotor takes 175 ft-lbs, 36 Hp to spin up, really? free wheeling the brake rotor

    When doing calculations in proper SI units, "g" has no business anywhere unless the force of gravity is actually involved in whatever you are interested in, which is not the case here.
  6. BrianPetersen

    Vehicle Anti-lock brake rotor system, increase horsepower, Brake Rotor takes 175 ft-lbs, 36 Hp to spin up, really? free wheeling the brake rotor

    Engaging what is effectively a dog clutch when there is a large difference in rotational speed between them, breaks stuff. You're doing your calculations in imperial units, which are gibberish to me. I have no feel for whether that old-English imperial number is rational.
  7. BrianPetersen

    Vehicle Anti-lock brake rotor system, increase horsepower, Brake Rotor takes 175 ft-lbs, 36 Hp to spin up, really? free wheeling the brake rotor

    The inertia of the brake rotor is small compared to the inertia of the wheel and tire assembly. Reason: the tread of the tire has the full radius of the assembly contributing to the moment of inertia, and the sidewalls of the tire have most of it contributing. And at least on any of my vehicles...
  8. BrianPetersen

    BEV adoption rates and factors that enhance or detract

    All modern cars have bespoke headlight and taillight assemblies. This isn't an EV issue, it's a "modern cars" issue.
  9. BrianPetersen

    Layoffs 2024-2025 ??

    Fiat 500e is roughly the same size as a BYD Seagull, and does decently in Euro NCAP. https://cdn.euroncap.com/media/66921/euroncap-2021-fiat-500e-datasheet.pdf Obviously it is not the same car, but it's about the same size and weight (the Fiat is a little smaller), and the Fiat 500e is sold in...
  10. BrianPetersen

    Layoffs 2024-2025 ??

    The BYD Seagull is not (yet) sold in Australia and hasn't been tested (or perhaps it has, but results are not yet published), but all of its companion models including the marginally-bigger Dolphin have been tested, and have good NCAP ratings (5 stars). Testing within China to their own...
  11. BrianPetersen

    Layoffs 2024-2025 ??

    "EVs have fewer parts so less to integrate and test." Well, I wouldn't say "fewer", just "different". The motor is simpler than an engine, the gear-reducer is simpler than a transmission, there's no exhaust system or fuel system, but the battery and electronic controls and thermal management...
  12. BrianPetersen

    Battery cooling

    We have a students forum section, and this really belongs there! Things you're going to need to know. What's the instantaneous and longer-term-average charge and discharge rates. How much (a) peak, and (b) longer-term-average are you going to have to deal with? What's the efficiency of...
  13. BrianPetersen

    Layoffs 2024-2025 ??

    My crystal ball is cloudy, but I see layoffs ahead in almost anything that involves manufacturing and retailing, and unskilled jobs in USA going unfilled in most any outdoor work ... and gruntguru has a fair point about hospitality, as well. I'm happy to be retired, but it doesn't mean I don't...
  14. BrianPetersen

    Two-slider crank mechanism

    It WILL have all sorts of problems during operation, too. I just chose not to get into that discussion, aside from (as per previous post) mentioning that you've got an indeterminate structural situation that it will pass through twice on each and every crankshaft revolution, which will manifest...
  15. BrianPetersen

    Two-slider crank mechanism

    There is no such thing as a frictionless mechanism. If this mechanism comes to a stop within a few degrees of the piston-halfway point, it WILL bind, and you will NOT get out of this bind by "turning the shaft manually" (or via starting motor). A properly assembled conventional-layout...
  16. BrianPetersen

    Two-slider crank mechanism

    I never expressed anything about the design of the mechanism previously. If stopped at mid-piston-stroke (crank throw at the bottom), the mechanism will bind. It will not be possible to rotate the crankshaft to get the mechanism started again. A calculation of the mechanical advantage of the...
  17. BrianPetersen

    Threaded Connection of Aluminium Components

    Automotive/motorcycle engines and transmissions use steel fasteners threaded into aluminium everywhere. Thread inserts are only used for repair purposes but if you anticipate frequent dismantling, they may be a good idea. Thread sizes are commonly M6x1.0, M8x1.25, M10x1.25 (this appears to be...
  18. BrianPetersen

    Two-slider crank mechanism

    1. Why is this a benefit? What benefit does this provide to the thermodynamic cycle? How does it change anything? How does it change the P-V diagram (you know what that is, right)? 2. So let's say you want to keep the stroke and the piston speed in the same range as for a conventional engine...
  19. BrianPetersen

    Two-slider crank mechanism

    One other thing. "Piston speed lower for the same rotation speed" isn't a persuasive argument. Modern piston engines normally have an upper average piston speed limit in the 20 to 25 m/s range (this is the average speed of piston motion at the engine's highest permissible operating speed - 20...
  20. BrianPetersen

    Two-slider crank mechanism

    OK then. WHY - what thermodynamic mechanism - is the "temperature in the combustion chamber lower"? Why is this connected in any way to using a fancy linkage as opposed to a crankshaft and connecting rod? Why does the design of the mechanism underneath the piston crown make a difference to the...

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