This page is both a gallery of ‘low fidelity physical demonstrators’ relating to the science presented on the other pages, and a source for teaching materials. Do email me at firstname.lastname@example.org for the latest versions.
Laser-cut lollipop dog forelimb
Outlines for laser-cut parts are available:
Snap rivets are used here, but split-pins or brads are also effective (see below).
Laser-cut lollipop sprinter
The laser-cut parts are those for the dog forelimb. The card background is here. It is A4 format; be careful not to allow the printer to autoscale.
Quadruped hindlimb practical
A practical that leads the student through the geometry of how and why muscles can be automatically and sequentially loaded under isometric to produce sliding weight support through producing a straight-line mechanism. Dimensions are for lollipop sticks and A4 card.
A very brief introduction (with audio) here
Instructions follow. Again, designed around standard and large lollipop stick and A4 dimensions; be careful not to rescale when printing. Muscles look good if printed on red paper.
The remarkable force measurements of ants HERE and HERE show that insect legs can also achieve the economical ‘sliding’ condition, with approximately vertical forces during horizontal translation. This Lego demonstrator shows how 4-bar linkages can be combined with vertical-axis joints (discussed in THIS PAPER) to result in a tripod of support over which the body is free to slide. Of course, insect legs are actually far more complicated; this just demonstrates that sliding weight support with legs is achievable with very simple linkages.
This Lego demonstrator combines both the Roberts mechanism model of the serratus supporting the forelimb, and two 6-bar linkages of the hindlimb. The linkages enable approximately horizontal ‘sliding’ motion, with the legs getting functionally shorter over the first half of stance and longer over the second. But nothing is ‘stretching’ – the shortening and lengthening of the legs is due to the linkages, not because of elastic deflection and recoil.