The clutch pedal is one of the most used commands on vehicles and demands a robust project, good ergonomics and an adequate feeling. According to Shaver [3], a comfortable clutch pedal should have a load between 10 kgf and 13 kgf, but the total stroke, the maintenance of the load during the travel, peak load, etc. still has to be considered in the project. Basically the suggested curve for a comfortable clutch pedal starts with a progressive increase load until approximately ¼ of the stroke, and after a decreasing load until the pedal reaches its stroke limits. This effect can be produced through an auxiliary spring that ranges its force direction according to the position of the pedal.
This article presents a methodology of modeling an auxiliary spring for clutch pedals and its installation geometry on the pedal box to achieve an adequate pedal feel. This theory is applied to semi-hydraulic and hydraulic systems clutches.