The handle on this trammel follows a circle, while the three sliders move back and forward in straight lines.
Two sliders are enough to determine the motion, the third is superfluous. The mathematical question posed by this device is "Why does it not lock up?"
The answer is also the answer to Cardan's Spur Wheel Problem: "What is the locus described by a marked point on a circular disc that rolls along the inner edge of a disc of double its radius?"
Your trammel will work when it arrives, no assembly required, and will become easier to manipulate as surface roughness is polished with a little use.
Great for stress relief and improving your dexterity . Just add a strap for a steampunk pendant.