Scott Russell Straight Line Mechanism The
mechanism to the right can be refered to as the Scott Russell Mechanism
or a more descriptive name is the Scott Russell Exact Straight Line
Mechanism. For this description to be true the acting length of the
short link, the blue one, needs to be half as long as the active
length of the green one and the pin that connects them must be
concentric with the mid point of the long or green link. One more
requirement is that the slider's connection pin
needs to be sliding in a line that would intersect the static pivot end
of the short link. I have seen this link represented on the web in
proportions which prevent it from producing an exact straight
line. I have tested one of these and it is was surprising how
close to a
line it made over a given range. Of coarse often a
aproximate line is close enough. On the other hand one should remember
that real linkages bend under load and joints have play; so even exact
straight line mechanisms will not be exact in practice. In the
animation above the slider stops
short of that blue link's pivot point. But if the mechanism was made so
that the links were
in different planes then it it would be possible for this
mechanism to 'flip' on the vertical axis as the slider
passes through the
traced line. Again if the links are in different planes, the
long
link could pass through the horizontal axis and continue to draw a
straight line that would run down below the x or horizontal axis. 
My interest in straight line generators is partly the
result of looking for mechanisms that could help drive the "Uniport
Valve", for which I own a patent. If you happened to land on this page, please visit my home page at: http://www.inventhp.com
and learn more about this double acting valve. Anyway, during
my research I came across the Peaucellier Mechanism, one
example is to the left. It produes a straight line having only linkages
and pivot points.
In testing the conditions for this mechanism, some unusual variations of this mechanism were found. Please view some of these at Peaucellier Mechanisms.Should you have any comments about how I represented these straight line generators or anything else on my site please contact me at: Contact Invent Horsepower |