Info on forces and strains required and produced

How much force is required? Pressure and friction drag forces act to slow the fish as it moves The muscles, in order to move the fins, must overcome: – Pressure drag of the fin due to rotation – Pressure drag on the fin due to apparent incoming fluid velocity – Reactions from the other fins – Friction drag slows the fish, but is NEGLIGIBLE as far as muscle force is concerned

Preliminary pressure drag calculations

The pressure drag force is dependent on the perpendicular velocity squared. The torque is found by integrating the drag force times distance along the fin section.

Preliminary pressure drag calculations

Muscle testing Insert picture of muscle tester setup here

1 st round of muscle testing – lessons learned Dead zone due to space between tubing and fabric mesh. 30 psi was the pressure required to take up the initial slack between the tubing and mesh. Slope inversely related to rubber stiffness, and directly related to the ratio of inner circumference over wall thickness

2 nd round of muscle testing Assembled new muscles with existing tubing and fabric mesh. Used tubing with high inner circumference to thickness ratio (it was thinner). Made sure there was no space between tubing and mesh. Tested the effect of using a slightly smaller mesh than needed, on the same tubing.

2 nd round of muscle testing Tighter mesh nearly eliminated the dead zone Obtained a force of approximately 4 pounds at 20psi

No significant difference between mesh types as long as they’re tight against the tubing 2 nd round of muscle testing

Force Feasibility Force required due to overcome pressure drag with a muscle lever arm of 4cm (1.57”): 1.83 pounds Force produced by first set of muscles: 4 pounds Reaction forces from other fin sections are significant, but also actuate out-of-phase. Are ultimately due to the drag as well, so should be on the same order. Clearly within feasibility, using a muscle assembled from a limited selection of scrap materials.

Strain feasibility Strain level of 13% at 20psi found during testing. A lever arm of 4cm, and maximum angle of 30°, requires a 30.8cm (12.2”) muscle – Has to actuate the section 30°, as well as accommodate 30° of motion in the other direction Larger muscles can be used, making it possible to move lower the lever arm length, decreasing the required muscle length.

Show pictures of fish to CAD model Side view of CAD model, and real bass Same for front view (aspect ratio) (maybe on a separate slide) Also show video of Essex fish; say that we’re going to have the muscles execute a similar motion. Same argument for forward motion at this point.