I was wondering what the critical/starting dimensions should be. Most importantly
1.) the distance between the two motor sprockets
2,) the height above the top of the cutting area the sprockets should be
the stock machine has the chains go from about 10 degrees to 80 degrees, and we
run into problems at both extremes.
This is with the motors about 12" to the side of the work area, and about 18"
above the top of the work area.
The biggest problem is the side distance, with the motors 12" to the side of the
4x8, we really struggle in the bottom corners where the chain angles are the
worst. We believe that moving the motors out a bit (to about 12’ rather than old
stock 9.7’) would make a significant difference.
On the top, we have had one person with an extra heavy sled run into problems
with the motors not being able to pull hard enough to move the sled at the
requested speed. There does not seem to be a big driver to go higher, and going
lower would make it easier to run into this problems.
3.) the angle of the work surface from vertical.
The last testing that we did on the angle was a long time ago, before triangular
kinematics were introduced (let along chain sag compensation), and that showed
that angles below about 10 degrees or above 15 degrees didn’t work well.
With triangular kinematics, the sled rotating due to the motor torque is not
going to cause an error the same way it would before (if it moves too much to
where the linkages/ring can no longer rotate it can cause an error, but still
less than what was caused by any rotation under quad kinematics)
I suspect that with triangular kinematics and chain sag compensation, you can go
steeper (closer to vertical) without running into the problems that we had
before, which would improve the accuracy as more of the weight would be etting
applied to the chains rather than causing friction to the work surface.
But we do not have anything close to current testing of this (I asked for
someone to do a series of tests on this last week, but so far nobody has had
time to do so)