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  1. Alec_t

    I want to know all of the maths concerning this scissor mechanism!

    The quoted bit relates to the static situation. Fv relates to the force applied to move the load. Because the load moves further than Fv, due to the scissor action, Fv is greater than the load weight.
  2. Alec_t

    I want to know all of the maths concerning this scissor mechanism!

    The quoted paragraph relates to displacement of a general scissor mechanism and is still relevant.
  3. Alec_t

    I want to know all of the maths concerning this scissor mechanism!

    For the frictionless cam, the horizontal (rotational) force is the vertical force Fv x the slope. So far we have used a constant average slope for simplicity. To maintain constant vertical velocity (for 90% of the travel) the cam profile should be such that the cam radius increases linearly with...
  4. Alec_t

    I want to know all of the maths concerning this scissor mechanism!

    No. That was for a single-lobe cam. For a 2-lobe cam replace 2 x pi by just pi. Also, that torque is for the constant velocity part of travel, so does not apply to the initial 10% of travel where the cam follower has to accelerate. If you want greater accuracy for the torque value you will need...
  5. Alec_t

    I want to know all of the maths concerning this scissor mechanism!

    Instantaneous torque = instantaneous force x radius. Don't multiply by time.
  6. Alec_t

    I want to know all of the maths concerning this scissor mechanism!

    No. It only applies for the special case where the slope is 10% and there are 10 scissor stages, so that n x s% = 1.
  7. Alec_t

    I want to know all of the maths concerning this scissor mechanism!

    I'm afraid I've confused things further by inadvertently using symbol f for force and acceleration. That's correct where f is the acceleration. The vertical force fv required to accelerate mass m initially against gravity by acting on the mass itself is m x (3.3m/s^2 + 9.81m/s^2). For the...
  8. Alec_t

    I want to know all of the maths concerning this scissor mechanism!

    In the above post you are quoting old data. But you have since changed the cam speed and the rise height. The rise time is now 2 sec. Height is now 1.32m.
  9. Alec_t

    I want to know all of the maths concerning this scissor mechanism!

    ... .. Yes. The cam torque to get that acceleration is accordingly greater than the torque needed to sustain the final velocity. The torque is the horizontal force times the radius at which it acts.
  10. Alec_t

    I want to know all of the maths concerning this scissor mechanism!

    It's your choice as to the duration of that initial acceleration. I used 10% as an example. You have already specified the cam speed as 4 sec per revolution.
  11. Alec_t

    I want to know all of the maths concerning this scissor mechanism!

    From energy considerations, for a n-stage scissor mechanism the vertical force Fv the cam needs to provide will be n x the vertical force fv needed to accelerate the load at the top. But if the cam has a s% slope then the horizontal force Fh on the cam follower will be s% of Fv, If n=10 and...
  12. Alec_t

    I want to know all of the maths concerning this scissor mechanism!

    Much tidier. :) You can 'click and drag' to select a group of cells, then apply a chosen number format. By default the number of decimal places displayed is 2, but any calculations are actually done to many more places. This link, first hit, shows one way to customise the number of places.
  13. Alec_t

    I want to know all of the maths concerning this scissor mechanism!

    The number of decimal places can be set in LibreOffice. A maximum of 3 would make your maths easier to follow.
  14. Alec_t

    I want to know all of the maths concerning this scissor mechanism!

    Force = mass x acceleration (not forgetting g-force). Acceleration is controlled by cam profile and cam rotation rate. In view of all the changes you keep making, why not put all the formulae you need into a spreadsheet so that changes to parameters result in any dependent parameters being...
  15. Alec_t

    I want to know all of the maths concerning this scissor mechanism!

    Let us see a pic of the completed project in due course. Good luck with the build.
  16. Alec_t

    I want to know all of the maths concerning this scissor mechanism!

    Which bit of the calculation set are you having a problem with? I don't agree with the slope value or v value in post #268, btw. When are you going to start making allowances for friction and scissor weight? Without those parameters all your calculation results so far could be way out from...
  17. Alec_t

    I want to know all of the maths concerning this scissor mechanism!

    Well, you're confusing me I'm afraid, with all the changes you keep making. Sorry, but I can't spare the time to go through all the maths again.
  18. Alec_t

    I want to know all of the maths concerning this scissor mechanism!

    It does to me.
  19. Alec_t

    I want to know all of the maths concerning this scissor mechanism!

    Consider the energy used. Work = force x distance.
  20. Alec_t

    Circuito integrado

    See moderators' note in post #1.
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