This portion of the project is dedicated to the 2 credit hours for Mechanical Laboratory III.

Objective

The primary objective of the testing was to show that the new connecting link, with the small rotating arm, allows for smooth motion through the hydrofoil cycle.  A comparison of the old and new connecting link designs was also desired.

Test Stand

A frame was built from galvanized angle steel which could be modified for future experiments.  An aluminum housing was machined and used to hold the hydrofoil sets 24" apart.  The test stand includes a bench for the operator to lay on.

Method

Displacement testing was chosen to quantify the smooth motion and to show that the new design solved the rocking motion.  Linear variable displacement transducers (LVDTs) were chosen as the measuring tool. 

The location of the two LVDTs was selected based on preliminary observations of the rocking motion in the original stand and in our fabricated steel test stand.  The sizes of the LVDTs were selected based on estimated displacement seen with the old links.  A 0.5” stroke range LVDT was chosen to measure the displacement of the test stand in the x-direction.  A 0.125” stroke range LVDT was chosen to measure the displacement in the vertical z-direction.

The x-dir LVDT

The z-dir LVDT

Displacement Testing

Displacement measurements were taken by two LVDTs in two different directions.  Maximum displacement values were the result because the operation of the hydrofoils is cyclic producing a periodic output in voltage.  The range in voltage output of each LVDT was taken in turn on the HP oscilloscope.  Measurements were taken using the old connecting links and the new connecting links.

Observations

Old Links

	Links could only be connected if the foils were in a certain position
	It was difficult to move the linkage through the complete cycle
	More force was required by the operator than with the new links

New Links

	stand moved visibly less in the x-direction with the new links than with the old ones
	Full stroke was easily and smoothly obtained

Animations from Actual Experiment

Results

New links resulted in

	81% Displacement reduction in x-direction
	39% Displacement reduction in z-direction

Conclusions

Testing showed that the new connecting link design allows for smooth motion through the hydrofoil cycle.  It shows that the design solves the initial rocking motion observed.  Testing allowed us to better understand why the old connecting link design is unsatisfactory and to compare the old and new connecting link design, both qualitatively and quantitatively.

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Last Updated on 09/01/2005