is there a list of measurements for the machine? how many degrees should it lean back? what is the desired placement away from a 4x8 sheet of plywood for the motors? how many inches offset from the surface for the motor cogs? surely there is a list Im missing.
We’ve found that about 15 degrees works well, but it’s not critical that it be exactly 15.
Originally we were using 10’ top beams, although a lot of folks are switching to 12’ ones which seem work better if you have the space for it.
The important thing here is that that the chains remain in plane so they connect to the ring on the sled at the same offset as the motors. The ring is adjustable to make that easier, so generally in the middle of the ring’s adjustment range is good.
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thanks!
Curious, why is 12’ better? I have the space…
We’ve found that about 15 degrees works well, but it’s not critical that it be exactly 15.
5 degrees isn’t enough (the router pushes itslef away from the workpiece instead
of the bit plunging into it)
20 degrees is too much (the drag on the sled is too much)
15 is the default, we need to have people test within this range to find if it’s
optimal or not
Originally we were using 10’ top beams, although a lot of folks are switching to 12’ ones which seem work better if you have the space for it.
a wider top beam helps in the corners, moving the top beam up from the workpiece
helps in the top center
a 12’ top beam about 30" up from the workpiece seems to be a nice sweet spot if
you have the space (and the 13’ chains you need for this)
The important thing here is that that the chains remain in plane so they
connect to the ring on the sled at the same offset as the motors. The ring is
adjustable to make that easier, so generally in the middle of the ring’s
adjustment range is good.
ideally you want to set the ring to the height from the sled that makes it hang
straight, and then set the offset from the surface to match this. If the ring is
too low, then in the top center and top corners (where the chain tension is the
highest), it will pull the sled away from the workpiece. If it’s too high, you
will tip over sooner as you get near the edge, and in the top center you will be
pulling the sled down into the workpiece, increasing drag.
David Lang
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In the bottom corners, a 10’ top beam has the motors about a foot out from the
sled, so you have a force triangle about a foot wide and 5-6’ tall. gravity
pulls down on it and splits the force based on this triangle, but very little of
the gravity helps pull the sled towards the corner. You end up with <4 lb of
force to move the sled towards the corner (with a 20lb sled)
with a 12’ top beam, the force triangle is about 2’ wide instead of 1’ wide, so
with the force triangle results in a bit over 7 lb of force to move the sled
towareds the outer corner.
a 10’ top beam works, but if your sled isn’t slick enough and has too much
friction moving across the workpiece, it will stick and not move (and in any
case, not move as fast) as if you have a 12’ top beam.
we put togther a spreadsheet to show the forces at
this lets you tinker with dimensions to get an idea what the impact of changes
are.
as the max force increases (in the top center), it puts more strain on the
motors and power supply, if they can’t keep up your cut sags.
As the min force decreases (in the bottom corners) the machine has a harder time
moving out towards the corners and may stick and cut incorrectly
David Lang
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