# Calculating the force of this system

My native language is not English, so I don't know all the specific terms you may expect me to use. I apologize for that. Anyway, I have a motor and three connecting rods (in French, bielles). So point C will have a circular trajectory and A, thanks to the sliding pivot (pivot glissant, I really hope I am using the right translations), should have a perfectly vertical trajectory.

My question is, how could I calculate the force F? I need this to emboss a piece of paper.

Thanks a lot for your attention!

• Do you need it as function of time, or at some specific point? Is the motor torque known? If yes, the tangential force at the tip of the rotating rod is the torque divided by the rod length. From there yoy can find the other forces by simple vector decomposition – Eugene Sh. Nov 24 '14 at 0:31
• The motor torque is known, and I need the force at point A. I will think about the division by length etc – user7558 Nov 24 '14 at 6:45
• For the future, there is a free piece of excellent software called inkscape that you can use to draw images like that. – Shahbaz Dec 2 '14 at 13:44

## 1 Answer

I have tried to analyze the system, and the process is shown in the picture.
The mechanism is called as Slider Crank Mechanisms, Please open the website (kinematics) for some other analysis. $(1)~\tau = F_1 . l_{DC} . sin \alpha \implies F_1 = \dfrac{\tau}{l_{DC} . sin \alpha}$

$(2)~F_1 = F_2$

$(3)~F_2 . cos \beta = F \implies F = F_2 . cos \beta = F_1 . cos \beta = \dfrac{\tau . cos \beta}{l_{DC} . sin \alpha}$

• robotics.SE supports TeX-style mathematics. That would be much more readable! I'll edit your answer and you can later remove that from your image. – Shahbaz Dec 2 '14 at 13:45