Hello,

- I would add one radial dim to each of one of the left & right arcs:
- They'll be driven, but it will be an indicator to others that the central construction line terminates at their centers (and to you if they don't).

- Symmetry is needed to keep the 120 dim central, (which is an assumption by me) since the short horizontal line equals are left/right only
- Coradial forces concentricity and equal radius, but not equal arc length, so if you move the 120 line up or down, the arc pairs will be different lengths and short lines on the same side won't remain equal

One of these should cover it:- Add an equal to both left short lines (or right lines, but not both sides of the sketch)
- 120 line midpoint horizontal to origin (only one 120 line required)

- Coradial forces concentricity and equal radius, but not equal arc length, so if you move the 120 line up or down, the arc pairs will be different lengths and short lines on the same side won't remain equal

Cheers,

Kevin

- I would add one radial dim to each of one of the left & right arcs:

Maybe just couple construction lines and radius