Creating a Slider Crank Linear Actuator

I am working on a Stair Climber robot. I have decided to recreate this Lego Mindstorms stair climber. However, I am not sure how to implement the linear actuator for the rear wheels. I am hoping I can find a DIY solution.

I found about the slider crank mechanism after some searching. I want to use a servo for the rotational motion and I need the linear actuator to move about 15cm.

I am unsure about how long should each of the pieces be in the above pictured mechanism for a ~15cm movement and also how high torque should the servo be rated for, given that my robot will weigh around 800g.

Please advise.

Thanks

The red lever arm (or wheel) has to be at least 7.5 cm long (or radius) to give 15 cm linear motion.

The torque required is a bit hard to calculate, but it must be somewhat greater than 800 g X 7.5 cm (6000 g cm).

Intro to force and torque.

jremington:
The red lever arm (or wheel) has to be at least 7.5 cm long (or radius) to give 15 cm linear motion.

The torque required is a bit hard to calculate, but it must be somewhat greater than 800 g X 7.5 cm (6000 g cm).

Intro to force and torque.

Thanks a lot! Exactly what I wanted to know!