Although all our simulations and calculations were correct and led us to believe the design would work, we quickly learned that there is more to a mechanism than just it moving in an ideal world. The MATLAB simulation and the YouTube video exists in worlds where friction does not exist.
(Insert picture of original design)
At the extreme ends shown on the picture above, we can see that the force exerted by the link into the bearing is almost perpendicular to the path of the guide. This is extremely ineffective because the resultant force is very small compared to the normal force which means that there would be immense mechanical disadvantage at that point which essentially rules out moving anything heavy. However, worst problem is that, due to the normal force being so high, the friction force is extremely high at this point and since the force pushing the bearing is so small due to the angle between the link and the path, there bearing could not overcome friction and got stuck at these points. We corrected our mechanism numerous times just to make sure it was not any links because slightly off their lengths or the ground joints because incorrectly distanced. However, in the end the result was the exact same, the slider completely stopped at the extreme points. It was then that we learned a great lesson: there is more to consider than just "does it theoretically move" when designing a robotic mechanism. In our case, we failed to consider immense amounts of friction and mechanical disadvantage.
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