7. HOEKENS LINKAGE – JSP
The JSP Code

The JSP applet code given below was used to produce the diagram at right.

This applet is fairly straightforward. As usual use the little red cross to clear any traced path. The question mark gives some JSP options.

I have chosen the red segment to have length 50 pixels, the green segment 125 pixels, and the blue segment 2 x 125 = 250 pixels.

Some ‘construction’ labelling is introduced in the comments, but does not appear in the final figure.

Be generous with the comments and labels within the program itself!



        
<APPLET codebase="jsp" CODE="GSP.class"
WIDTH=330 HEIGHT=370 ALIGN=left>
<PARAM NAME=Frame VALUE=1>
<PARAM NAME=BackRed VALUE=255>
<PARAM NAME=BackGreen VALUE=255>
<PARAM NAME=BackBlue VALUE=200>
<PARAM NAME=Construction VALUE="

{Define base circles etc}
{1} FixedPoint (60, 250) [label ('A')];
{2} FixedPoint (160, 250) [label ('B')];
{3} Line (1, 2) [red]; {AB}
{4} FixedPoint (110, 250) [hidden]; {M}
{5} Segment (1, 4) [hidden]; {AM, unit length}
{6} Circle by radius (1, 5) [red]; {centre A}
{7} FixedPoint (185, 250) [hidden]; {C}
{8} Segment (1, 7) [hidden]; {AC, length 2.5}
{9} Circle by radius (2, 8) [green]; {centre B}

{Driving point and segment}
{10} Point on object (6, 3.1412) ; {P}
{11} Segment (1, 10) [thick, red]; {AP}

{Linkages}

{12} Circle by radius (10, 8) [hidden]; {centre P, radius 2.5}
{13} Intersect2 (9, 12); {Q}
{14} Segment (10, 13) [hidden]; {PQ}
{15} Dilation (10, 13, -1); {R}
{16} Dilation (10, 13, -1) [hidden, traced]; {R}
{17} Segment (10, 16) [thick, blue]; {PR}
{18} Segment (2, 13) [thick, green]; {BQ}


{Buttons}
{19} ShowButton (10, 330, 'Trace on') (16);
{20} HideButton (100, 330, 'Trace off') (16);

">
</APPLET>		 Like me, you will probably adjust the window size as you go.

We define a pale yellow background.





Points A and B are the fixed pivots for the linkage.

Lines {4}, {5}, {7} and {8} define the segment lengths we shall use. M is the midpoint of AB.




We shall take P as the driving point for this applet.






Q is the midpoint of the blue segment.

R is the top endboint of the blue segment.
Line {16} enable the point R to trace the path. Line {15} defines the point R in non-tracing mode. Unfortunately this leaves one unwanted point, but I see no way around this.


The buttons activate the tracing/non-tracing options.

Exercises

1. In your program, you might like to label the other points of the linkage.

2. Try making the midpint Q of the blue segment the driving point of the linkage. This is an alternative way of producing ‘linear’ motion from rotational motion.

3. Perhaps you can write this program to make either P or Q driving points?