﻿ Getting Started Tutorials - MechDesigner > Tutorial 2A: Four-bar Kinematic-Chains > Step 2.8: Model a 'Pin in a Straight Slot'

# Step 2.8: Model a 'Pin in a Straight Slot'

## A 'Pin-in-a-Slot' Mechanism

 You may think a Pin-in-a-Slot is a special type of joint. Three representations of a 'Pin-in-a-Slot'. The mechanical-design of a Pin-in-a-Slot might be similar to Diagram A, in which we see two Parts : •Part : a lever with a pin roller at its end •Part : a part with a linear slot However, the kinematic-design of a Pin-in-a-Slot is always three Parts. Diagram B shows a different mechanical configuration, with three Parts: •Part : a lever, with a Pin-Joint at its end •Part : a part with a slot •Part : a block (or a piston) that slides along the slot with a Slide-Joint, AND is also joined to the lever with a Pin-Joint It helps me to imagine that Part is a Slide-Rail, and Part is a Sliding-Block that slides along the Slide-Rail. Diagram C shows a system that is a similar construction to Diagram B. Diagram C shows the Pin-Joint is offset to one side of the Slide-Joint. All three designs use the same kinematic-construction - they use the R-R-P Dyad.

### Video:

Video: 'Pin in a Slot'. E.g Geneva Replacement.

### General: To model a Pin-in-a-Slot

 Dyad ONLY - Note: This shows   STEP 1: Draw a Line† in Part - in this case, it is a Line in the Base-Part Add dimensions and constraints to the Line. It will be the Slide-Rail. STEP 2: Add a STEP 3: Join Part to Part with a Slide-Joint - E.g. Click the CAD-Line in Part then the new Line in Part Part is now the Slide-Block. STEP 4: If necessary, edit Part to add a Point. E.g. Point‡ to define the position of a Pin-Joint in Part STEP 5: Join, with a Pin-Joint, the start-Point (origin) of Part to the Point in Part Notes: † You can add a CAD-Line in a Part or use the CAD-Line along the center of the Part. ‡ STEP 4 may not be necessary as you can use the start-Point or end-Point of the CAD-Line in Part when you do STEP 5.