Ok, so 20 degrees from the vertical/horizonal plane. Since the verticals are

tapered, I assume this is at the widest part of the taper. Is this correct? If

so, the middle two arms would get just a little more movement than the top and

bottom anchors. If my math is correct, this difference could be significant.

Please check my math

8x10’ frame

distance from top center to anchor 5’ horizontal 2’ vertical

ratio .4

inv tan(2/5) = 21.8 degrees works barely

distance from side center to anchor 1’ horizontal 4’ vertical

ratio .25

inv tan(1/4) = 14 degress, can’t actually work there

let’s try a 8x12 frame

top center 6’ 2’

ratio .33

inv tan(2/6) = 18 degrees, can’t actually work there

side center 2’ 4’

ratio .5

inv tan(2/4) = 26.5 degrees works

tan(20) = .364, so you need the ratio between the two numbers to be above this,

or to put it anothe way, if you have 2.75’ or more offset from the center of the

workpiece to the anchor for every 1’ in the other direction, you run into

problems

Setting up a quick spreadsheet and trying just a couple numbers, it looks like a

11’ x 8’ frame or 18" off the sides and 24" off the top and bottom results in

angles of 19.98 degrees and 20.56 degrees

This is close enough that differences between the CAD and the injection molds,

draft angle on the arms, and additional clearance provided by the taper in the

verticals will determine if it will work or just run into grief at the centers

of the edges.

the shields around the lead screws can be made narrower (or eliminated??), to

allow the arms a little more movement (and since the sled can rotate, it would

not only increase how narrow the belt angles can get at the top/bottom, but also

help a little on how wide they can get on the sides).

David Lang