7.1 Project Proposal

Introduction

Bartenders use cocktail shakers to make a variety of drinks. They are used to combine, chill, dilute, and aerate the cocktail. Properly utilizing a shaker requires proper technique and often incorporates artistic flair. We find cocktail shaking to be interesting because the shaking profile is complex and improperly carrying out the motion can reduce the quality and efficiency of cocktail mixing.

Problem Statement

Our problem is to design a mechanism that replicates the action of shaking a cocktail shaker with proper bartending technique. The complexity of the cocktail shaking technique comes from the ‘V’  shaped motion profile created. This profile is composed of a repetitive translational motion and the periodic change of the shaker angle to a horizontal position. These motions together make the solution too complex for only simple joints and will require more mechanisms.

Mechanism

One of the mechanisms we will be using to control our system is a quick return crank. The quick return crank mechanism allows for a quick jerking movement in one direction followed by a slow movement back in the opposite direction. By attaching this to a slider crank mechanism, we can have a quick horizontal movement forward followed by a slow drawback, similar to the actual motion of a bartender mixing a drink. 

Additionally, we will be incorporating a Geneva mechanism into the system. The geneva mechanism will be attached to the bottom linkages of the shaker, thereby changing the angle at which the shaker is being moved intermittently. When the geneva mechanism rotates, it will change the angle at which the shaker can move, giving the V shape that we are aiming to achieve. 

All of these mechanisms will be controlled by a motor running at a constant speed which will be connected to these components through a gear train which will control the speed at which we want each component to move.

Proposed Scope

Our goal is to be able to have a mechanism that can replicate the motion a bartender makes when mixing drinks. We could also add the motion of picking up the cup and then beginning mixing, this would probably be more coding-focused. Before we can fabricate, we need to analyze the angle of rotation of a cocktail shaker along its translation path and the velocity of the cup at various points along that path. We would also need to determine how many joints, types of joints, and links would be needed to allow for this type of motion.

Preliminary Design

Our preliminary designs entail using a slider crank along with a Geneva mechanism to generate a linear back-and-forth movement at 3 differing angles, simulating the movement of a person shaking a drink. The figures below display the intended path of the shaker in blue, along with the intended mechanisms to reproduce this path.

Movement Path of Shaker

Quick Return Slider Crank & Geneva Mechanism

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