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Step 6The iso-elastic arm
The arm mechanism is constructed from the eight (8) strap hinges. Each arm assembly is a set of four(4) hinges that form a basic parallelogram. The color diagram below shows the placement of the hinges.
Red hinges 1 & 2 - this is the outside end; #1 attaches to the stem mounted angle bracket and #2 attaches to Green #1
Green hinges 1 & 2 - outside end; of which #1 attaches to Red #2 and Green #2 will attach to the tripod mounting bracket.
The Light blue 1 & 2 upper hinges and the Dark blue 1 & 2 lower hinges (inner hinges) attached to the outer ones, which complete the parallelogram.
1) Use a hacksaw to cut one end of four (two per set) of the hinges (inner ones) to ~1-1/8" in length.
2) Once that's complete the short ends will be connected to the two outer hinges with brass washers separating the hinge straps (see notes in the picture). I used the countersunk bolts for this step as it helped to self center the bolts and prevented bolt heads from colliding when the arm moves through it's entire range of motion. Once this is done you should have two sets of hinges joined; the light blue and green pair and the dark blue and red hinge pair.
3) Next align one set (either the upper or lower hinges) of the long hinge straps (inner and outer) and secure with the short 1/4" bolts and nuts.
4) Now if you fold the straps around to form the rectangle you will notice the holes don't line up, because it's offset in the wrong direction for these hinges. But there's plenty of room to drill the required 2 hole, just mark and drill them out with a 1/4" drill bit. Then fold them back around and secure them as you did with the other straps.
5) Use the 10 - 32 x 1/2" bolts as the retainers for the ends of the springs (see picture) one of the bolts is in the upper left corner (here I used the existing 1/4" hole in the hinge strap). The other one is in the lower right corner (for this one I drilled a 5/32" hole, close to the hinge joint, to get the necessary spring tension). For now, just use a temporary spring or you can skip that step for now, until you put it all together.
6) For an initial calibration/alignment check, measure the distance (on both sides) between the center of the hinge pivot points. The distance between light blue and green hinges should equal the distance between the red and blue hinges. Likewise the distance between light blue and red hinges should equal the distance between the dark blue and green hinges. To adjust these distances just loosen the appropriate bolts and move the hinges and re-tighten, till the distances are correct.
Red hinges 1 & 2 - this is the outside end; #1 attaches to the stem mounted angle bracket and #2 attaches to Green #1
Green hinges 1 & 2 - outside end; of which #1 attaches to Red #2 and Green #2 will attach to the tripod mounting bracket.
The Light blue 1 & 2 upper hinges and the Dark blue 1 & 2 lower hinges (inner hinges) attached to the outer ones, which complete the parallelogram.
1) Use a hacksaw to cut one end of four (two per set) of the hinges (inner ones) to ~1-1/8" in length.
2) Once that's complete the short ends will be connected to the two outer hinges with brass washers separating the hinge straps (see notes in the picture). I used the countersunk bolts for this step as it helped to self center the bolts and prevented bolt heads from colliding when the arm moves through it's entire range of motion. Once this is done you should have two sets of hinges joined; the light blue and green pair and the dark blue and red hinge pair.
3) Next align one set (either the upper or lower hinges) of the long hinge straps (inner and outer) and secure with the short 1/4" bolts and nuts.
4) Now if you fold the straps around to form the rectangle you will notice the holes don't line up, because it's offset in the wrong direction for these hinges. But there's plenty of room to drill the required 2 hole, just mark and drill them out with a 1/4" drill bit. Then fold them back around and secure them as you did with the other straps.
5) Use the 10 - 32 x 1/2" bolts as the retainers for the ends of the springs (see picture) one of the bolts is in the upper left corner (here I used the existing 1/4" hole in the hinge strap). The other one is in the lower right corner (for this one I drilled a 5/32" hole, close to the hinge joint, to get the necessary spring tension). For now, just use a temporary spring or you can skip that step for now, until you put it all together.
6) For an initial calibration/alignment check, measure the distance (on both sides) between the center of the hinge pivot points. The distance between light blue and green hinges should equal the distance between the red and blue hinges. Likewise the distance between light blue and red hinges should equal the distance between the dark blue and green hinges. To adjust these distances just loosen the appropriate bolts and move the hinges and re-tighten, till the distances are correct.
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