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  1. GregLocock

    Need help sourcing a custom-made Buna O-ring.

    Your .001 tolerance will be eaten up by a change in temperature of a degree or two.
  2. GregLocock

    Design of Built-up section.

    Sure, local buckling effects in the flanges, shear failure in the web, for a start
  3. GregLocock

    Kinematics - force analysis

    One way would be to use a work equation to find the forces, once you've sorted out the geometrical relationship between the x and y locations as a function of theta.
  4. GregLocock

    Design of Built-up section.

    You've got 2 equations and 2 unknowns, assuming thickness is constant and the other dimensions are in multiples of t. Presumably you know how to calculate Iyy and Izz? parallel axis theorem and all that.
  5. GregLocock

    using a deep cycle battery for a forklift

    I haven't run them in forklifts but have in solar cars and an off grid house, but frankly this seems rotten advice. You can weld with a lead acid battery and it is quite happy. You may get a slight drop in capacity if you run variable currents compared with a constant current, but you won't...
  6. GregLocock

    Seeking Full 3D Model of Pemserter Haeger 824 Press Machine

    Some manufacturers will supply interface drawings. I doubt many bother.
  7. GregLocock

    Excavator bucket pin material

    Easier to replace a pin than a bushing.
  8. GregLocock

    Excavator bucket pin material

    I sort of doubt that UTS is the most important property of the pin material. I'd take a guess that most excavators use something designed to be hit with sledgehammers and covered in wet gravel. Somewhere between mild steel and axle steel.
  9. GregLocock

    Tightest realistic tolerance of a 200mm ID cylinder

    If you put a kevlar wrap over it you could get zero expansion with temperature since kevlar has a negative COTE
  10. GregLocock

    Power Needed to Rotate a Mass to a Speed in a Specified Time

    I thought you said 5 minutes, 300s?
  11. GregLocock

    Power Needed to Rotate a Mass to a Speed in a Specified Time

    Yes, you've got twice as much because your power at t=0 is 0, and increases linearly with speed. Hence peak power (which you worked out) = 2 * average power (which was my method). In reality it depends on the torque vs speed characteristic of your motor and transmission.
  12. GregLocock

    Power Needed to Rotate a Mass to a Speed in a Specified Time

    Um, Muthu's been here for quite a while. IRstuff's approach is the right one. w=3300*2*pi/60 rad/s=345 rad/s I=1/2*m*r^2 r=.3 m=1600 so I=72 kg m^2 KE=1/2*I*w^2 KE=4284900 J average power to accelerate the flywheel =KE/300=14.3 kW You'd better check that it seems high. Also, getting constant...
  13. GregLocock

    Controlling planetary ratio by braking sun gear

    You seem to be talking about a hundred hp, on dynos we either used a water brake or an eddy current brake, or these days a motor/generator. The water brake is comparatively cheap and simple and adjustable, and has no wearing parts. However it won't do 0 rpm and I suspect you'd need to gear it...
  14. GregLocock

    How can such a part be made from steel?

    That's a new one on me. Not the idea of bashing flat plate into curved shapes, but that machine. Another option would be an English wheel.
  15. GregLocock

    How can such a part be made from steel?

    Such a shallow shape is prone to Pretzelling or Pringleing, that is why I am dubious about your tolerances. The good news is that when you fasten it to whatever else the thing will happily deform to comply. If you actually need it not to pretzel/pringle then you need some ridges, look at a steel...
  16. GregLocock

    How can such a part be made from steel?

    "If make it from segments and then weld, then maybe it will make it easier to manufacture?" No, that would be a path to disaster. Spin it and then maybe finish grind if your tolerances are real.
  17. GregLocock

    How can such a part be made from steel?

    Easy peasy lemon squeezy. Either stamping for large numbers, or metal spinning for small numbers (tolerances may be hard to achieve). Or of course you could go the 'machine it from billet' route so beloved of hacks (not hackers).
  18. GregLocock

    Calculation of Residual strength of synthetic hawser rope

    Having recently been led astray by 2 different AI chatbots (on the same problem) I have some sympathy. But only some.
  19. GregLocock

    Calculation of Residual strength of synthetic hawser rope

    If I haven't misunderstood - Does it seem likely that in step 2 increasing load gives more cycles to failure? Not being a rope expert or anything...
  20. GregLocock

    Do engineering drawings imply solid and uniform parts?

    War story 1. A railway company sent out a spec for some beer glasses, intended to be 1/2 a pint. They specified the lower diameter, the upper diameter, and the distance between them. A cluey engineer realised that a frustum was not the minimum surface area, sent in a quote significantly less...

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