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As shown in this video, the simulated knee cap creates a fulcrum that allows for a better mechanical advantage for the muscles to pull the leg.

So I was wondering if the reverse would also work, or if it wouldn't change much at all.

For example, in this illustration I made on paint, it is shown a mechanical lever type 3 with 20 cm of length, where the load is on a 20 cm distance from the fulcrum and the effort is at 10 cm distance from the fulcrum and the effort is being done by a rope pulled by a motor.

Illustration of a reverse knee lever (I know the illustration part is drawn like it is counting 20cm from the effort point, but it is because I'm bad at drawing)

Accordingly to this online mechanical lever calculator, inputing these numbers would give me 0.5 of mechanical advantage, so in order to lift 1 kg, I would need to input twice the value in order to achieve equilibrium.

However, if I insert a "reverse knee cap" over the effort at the same 10 cm distance and attached the effort rope directly to the point of the load arm, as shown in the illustration, would the mechanical advantage stay the same, or it would change?

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    $\begingroup$ So done any research to see if that concept has been applied in nature? $\endgroup$
    – Solar Mike
    Dec 12, 2022 at 13:18
  • $\begingroup$ @SolarMike I tried and I couldn't find anything. Maybe I didn't use the right words... $\endgroup$
    – Fulano
    Dec 12, 2022 at 13:33
  • $\begingroup$ Then consider what other words you could use. $\endgroup$
    – Solar Mike
    Dec 12, 2022 at 13:34
  • $\begingroup$ A Google search (fantastic tool) gives iopscience.iop.org/article/10.1088/1748-3190/abf744 $\endgroup$
    – Solar Mike
    Dec 12, 2022 at 13:36
  • $\begingroup$ Wildebeest or Boston Dynamics Spot. $\endgroup$
    – StainlessSteelRat
    Dec 12, 2022 at 14:18

1 Answer 1

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Well, I tested it on the program "Interactive Physics", and it seems like it doesn't make much difference.

I don't know how to explain it very well, but the pulley that acts as the "inverse knee cap" applies force the same way if the effort arm was directly connected to the 10cm distance.

Screenshot of the Interactive Physics program showing the results

For example, i imitated the kneecap joint in this attempt at equal distances of 20 cm from the fulcrum and it kept everything under equilibrium:

Screenshot of the interactive physics program

Even if I try to make the pulley to be really close to the load:

Screenshot of interactive physics

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  • $\begingroup$ Could you provide a link to the program you used? $\endgroup$
    – Eric S
    Dec 12, 2022 at 17:16
  • $\begingroup$ physicscurriculum.com/interactivephysics It is a paid program, but you can search for other options on youtube. @EricS $\endgroup$
    – Fulano
    Dec 12, 2022 at 17:26
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    $\begingroup$ Thanks. I found this site which is both free and looks good. physion.net $\endgroup$
    – Eric S
    Dec 12, 2022 at 17:32

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