In a 1:1 mechanism, one revolution of the chain cog equals one revolution of the cord drum. A 1:4 mechanism utilises a gearbox which decreases the ratio by 4, meaning that one revolution (360 degrees) of the chain cog would turn the cord drum inside a headrail only by 90 degrees. Simply put, the 1:1 mechanism is fast but stiffer to operate and the 1:4 mechanism is slow but easier to operate.

1:1 Roman Blind Mechanism

1:1 Roman Blind Mechanism Ratio

1:4 Roman Blind Mechanism

1:4 Roman Blind Mechanism Ratio

A comparison of 1:1 and 1:4 mechanisms – based on an average operating chain ‘pull’ of 40cm.

1:1 vs 1:4 Roman Blind Mechanisms Compared