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

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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.


Note: A Pin-in-a-Slot is term a joint in which a Pin-Joint appears to move along a Slide-Joint.

Pin in a Slot Design Options

The mechanical-design of a Pin-in-a-Slot might be actually be similar to Diagram A, in which we see two Parts :

PartRed-14-1b : a lever with a pin roller at its end

PartRed-14-2 : 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:

PartRed-14-1b : a lever, with a pin-joint at its end

PartRed-14-2 : a part with a slot

PartRed-14-3 : (the new Part) - a block (or a piston) that slides along the slot (Slide-Joint), AND is also joined to the lever (Pin-Joint)

It helps me to imagine that PartRed-14-2 is a Slide-Rail, and PartRed-14-3 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 that is offset to one side of the Slide-Joint.

Video:

 

Tutorial 2; Step 2.6

Pin-in-Slot Example

Geneva

 

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

One of eight kinematic options for a Pin in a Slot

Dyad only:

STEP 1: Draw a Line† in PartRed-14-1b - in this case, it is in the Base-Part

Add dimensions and constraints to the Line. It will be the 'Slide-Rail'.

STEP 2: Add a PartRed-14-2

STEP 3: Join PartRed-14-2 to PartRed-14-1b with a Slide-JointRed-14-3

PartRed-14-2 is now the 'Slide-Block'.

STEP 4: If necessary, edit PartRed-14-2 to add a PointRed-14-5 to set the position of the Pin-Joint in PartRed-14-2

STEP 5: Join PartRed-14-4 to the PointRed-14-5 in PartRed-14-2 with a Pin-JointRed-14-5

Notes:

You can add a CAD-Line in a PartRed-14-1b 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 CAD-Line in PartRed-14-2 when you do STEP 5.

Eight Possible Pin-in-a-Slot Kinematic-Chains

The Pin-in-a-Slot is actually two joints (of the three total joints) in a Dyad.

In the Dyads we describe below, the letters R-P represent the two joints.

The R is a Pin-Joint - R for Revolute-Joint, which is the kinematic-term for Pin-Joint.

The P is a Slide-Joint - P for Prismatic-Joint, which is the kinematic term for Slide-Joint.

When you add a third joint, which may be a Slide-Joint(P) or a Pin-Joint(R), the Dyad is complete.

You can also join the Dyad to a Rocker or a Slider. Thus, it is possible to build eight different kinematic-chains.

Configurations:

1  & 2: RP+R + Rocker OR  RP+R + Slider. The Dyad is an RPR Dyad.

3 & 4: RP+P + Rocker OR RP+P + Slider. The Dyad is an RPP Dyad.

5 & 6: R+RP + Rocker OR R+RP + Slider. The Dyad is an R-R-P Dyad.

7 & 8: P+RP + Rocker OR P+RP + Slider. The Dyad is a PRP Dyad.

Remember also, it is possible for each Dyad to have a maximum of four different closures. See Change Dyad Closure.

KinematicChain-PinSlot1

Configuration 1 (See Step 2.7)

This is a Rocker and an R-P-R Dyad

Join PartRed-14-1b to the Base-Part with a Pin-Joint

Join PartRed-14-2 to PartRed-14-1b with a Slide-JointRed-14-3. The Joint uses the CAD-Line in the two Parts.

Join PartRed-14-2 to PartRed-14-4 with a Pin-JointRed-14-5

Join PartRed-14-4 to the Base-Part with a Pin-Joint.

(A Motion-Dimension FB identifies the Part we will move with a specified motion.

The motion-values at the input-connector to the Motion-Dimension give the rotation to the PartRed-14-4)

KinematicChain-PinSlot2

Configuration 2

This is a Rocker and an R-R-P Dyad (or P-R-R if you prefer to start from the Motion Driven Joint)

PartRed-14-1b is joined to the Base-Part with a Pin-Joint

(A Motion-Dimension FB identifies PartRed-14-1b as the Part we will move with a specified motion.

The motion-values at the input-connector to the Motion-Dimension give the rotation to the PartRed-14-1b)

PartRed-14-2 is joined to PartRed-14-1b with a Slide-JointRed-14-3. The Joint uses the CAD-Line in the two Parts.

PartRed-14-2 is joined to PartRed-14-4 with a Pin-JointRed-14-5 .

PartRed-14-4 is joined to the Base-Part with a Pin-Joint.

KinematicChain-PinSlot3

Configuration 3 (See Step 2.6)

This is a Rocker and an R-P-P Dyad

Join PartRed-14-1b to the Base-Part with a Slide-Joint

Add a Line to PartRed-14-1b. Use the new Line to join PartRed-14-2 to PartRed-14-1b with a Slide-JointRed-14-3.

Join PartRed-14-2 to PartRed-14-4 with a Pin-JointRed-14-5

Join PartRed-14-4 to Base-Part with a Pin-Joint.

(A Motion-Dimension FB identifies PartRed-14-4 as the Part we will move with a specified motion.

The motion-values at the input-connector to the Motion-Dimension give the rotation to the PartRed-14-4)

KinematicChain-PinSlot4

Configuration 4

This is a Slider and an R-R-P Dyad (or a P-R-R if you prefer to start from the Driven Joint)

Join PartRed-14-1b to the Base-Part with a Slide-Joint

(A Motion-Dimension FB identifies PartRed-14-1b as the Part we will move with a specified motion.

The motion-values at the input-connector to the Motion-Dimension give the displacement to the PartRed-14-1b)

Add a Line to PartRed-14-1b. Use the new Line to join PartRed-14-2 to PartRed-14-1b with a Slide-JointRed-14-3.

Join PartRed-14-2 to PartRed-14-4 with a Pin-JointRed-14-5

Join PartRed-14-4 to the Base-Part with a Pin-Joint.

KinematicChain-PinSlot5

Configuration 5

This is a Slider and an P-R-P Dyad

Join PartRed-14-1b to the Base-Part with a Slide-Joint

(A Motion-Dimension FB identifies PartRed-14-1b as the Part we will move with a specified motion.

The motion-values at the input-connector to the Motion-Dimension give the displacement to the PartRed-14-1b)

Add a Line to PartRed-14-1b. Use the new Line to join PartRed-14-2 to PartRed-14-1b with a Slide-JointRed-14-3.

Join PartRed-14-2 to PartRed-14-4 with a Pin-JointRed-14-5

Join PartRed-14-4 to the Base-Part with a Slide-Joint. This Slide-Joint is at a fixed angle of approximately 60º

KinematicChain-PinSlot6

Configuration 6

This is a Rocker and an P-R-P Dyad

Join PartRed-14-1b to the Base-Part with a Pin-Joint

(A Motion-Dimension FB identifies PartRed-14-1b as the Part we will move with a specified motion.

The motion-values at the input-connector to the Motion-Dimension give the rotation to the PartRed-14-1b)

Add a Line to PartRed-14-1b. Use the new Line to join PartRed-14-2 to PartRed-14-1b with a Slide-JointRed-14-3.

Join PartRed-14-2 to PartRed-14-4 with a Pin-JointRed-14-5

Join PartRed-14-4 to the Base-Part with a Slide-Joint. The Slide-Joint is at fixed angle of approximately 60º

KinematicChain-PinSlot7

Configuration 7

This is a Slider and an R-P-R Dyad

Join PartRed-14-1b to the Base-Part with a Pin-Joint

Add a Line to PartRed-14-1b. Use the new Line to join PartRed-14-2 to PartRed-14-1b with a Slide-JointRed-14-3.

Join PartRed-14-2 to PartRed-14-4 with a Pin-JointRed-14-5

Join PartRed-14-4 to the Base-Part with a Slide-Joint. The Slide-Joint is at a fixed angle of approximately 60º

(A Motion-Dimension FB identifies PartRed-14-4 as the Part we will move with a specified motion.

The motion-values at the input-connector to the Motion-Dimension give the displacement to the PartRed-14-4)

KinematicChain-PinSlot8

Configuration 8

This is a Slider and an R-P-P Dyad

Join PartRed-14-1b to the Base-Part with a Slide-Joint

Add a Line to PartRed-14-1b. Use the new Line to join PartRed-14-2 to PartRed-14-1b with a Slide-JointRed-14-3.

Join PartRed-14-2 to PartRed-14-4 with a Pin-JointRed-14-5

Join PartRed-14-4 to the Base-Part with a Slide-Joint. The Slide-Joint is at a fixed angle of approximately 60º

(A Motion-Dimension FB identifies PartRed-14-4 as the Part we will move with a specified motion.

The motion-values at the input-connector to the Motion-Dimension give the displacement to the PartRed-14-4)