So there I was… told to leave the shop and go to bed. I was laying there and thinking about my dear Maisy Maslow while scrolling through a 783 post topic on sled linkage design. I tear rolled down my cheek missing her so.
Then I came across this. Did anyone ever build/experiment with it? It looks cool.
the most important thing is that they be at the correct height to balance the sled.
You need to make it so that as you hang the sled from the chains, the sled hangs straight.
If the chains are closer to the workpiece than this, as you pull the sled, it will tend to pull away from the workpiece.
If the chains are father from the workpiece than this, as you pull the sled, the edge towards the motors will tend to try and dig in (more drag, catching on things, tipping earlier when overlapping the edge, etc)
after you find the correct balance for the sled, you need to adjust the top beam in/out so that the chains are as near to parallel to the workpiece as you reasonably can (with the workpiece in place)
the chains/sprockets are only designed to handle about 3 degrees of misalignment
if the motors are further out than the sled anchor points, under tension they will pull the sled away from the workpiece, potentially suspending it in mid-air (top center under max tension)
if the motors are closer in than the sled anchor points, under tension they will pull the sled into the workpiece, increasing drag (at the point where the motors are already working the hardest, potenitially causing the sled to sag and cut inaccurately)
now, this not a matter of extreme precision, it’s not a matter of having to change it for every thickness or workpiece.
as the motor moves in and out, it will affect the balance of the sled (so the same cut with different lengths of bit affects the balance.
being off by a 1/2" to 1" is probably ok, but getting it to 1/4" to 1/2" is a good idea, and not that hard to do