The chain length – also called stroke – determines how far a chain drive opens the window sash. If it is too short, the sash will not open enough; if it is too long, the sash can overextend or the chain can lose stability. A simple formula allows you to quickly estimate the appropriate chain length.
The formula
When opening, the wing edge describes an arc around the hinge. The chain length corresponds approximately to the length of this arc.
Chain length (mm) = wing height (mm) × opening angle (°) ÷ 57.3
The factor 57.3 results from the conversion of degrees to radians (180 ÷ π). Wing height is the distance from the pivot point (hinge) to the point where the chain attaches.
Calculation examples
- Tilt sash, height 600 mm, opening angle 20°: 600 × 20 ÷ 57.3 ≈ 209 mm → Selected: 250 mm chain length.
- Hinged sash, height 1,000 mm, opening angle 30°: 1,000 × 30 ÷ 57.3 ≈ 524 mm → selected: 550 mm.
- Roof window, height 1,200 mm, opening angle 45°: 1,200 × 45 ÷ 57.3 ≈ 942 mm → selected: 1,000 mm.
Select the next largest available chain length. Many drives can also be adjusted to a shorter stroke.
Online chain length calculator
Instead of calculating by hand, you can use our Chain length calculator To use: Enter the wing height and opening angle; the chain length will be output rounded to whole millimeters.
Additional things you should pay attention to
- Point of attack: The further the chain is positioned from the hinge, the longer it needs to be at the same angle – and the less force is required.
- Force: In addition to the lift, the thrust and traction forces must match the wing weight. VS-KA is available with strengths from 250 N to 1,500 N.
- Wide wings: For wide or heavy wings, a Double chain drive or two synchronized drives.
- RWA: For smoke and heat exhaust systems, the project planning specifies the opening angle or geometric opening area. The chain length must reliably meet this requirement.
Longer strokes
For strokes over 1,000 mm or very heavy wings, Linear actuators, Spindle drives or Rack-and-pinion drives Often the better choice. The article explains how drive chains are constructed. Drive chains for window drives. A comparison of the drive types can be found in the article. Chain drive, linear drive or rack and pinion drive?.
Consultation and offer
Are you planning a project or do you need larger quantities? We can help you select the drive, hub, and brackets, and provide you with a quote. Phone 040 50694631 or via our Contact form.
Suitable drives depending on the application: Windows Drive, Roof Window Drive and Skylight Drive.