Predict Before You Build

Hardware tests are valuable. Blind hardware tests are expensive.

Before building a drivetrain or arm, create a prediction. The prediction does not need to be perfect. It gives the test something to challenge.

A minimal mechanical prediction

For a wheeled robot, you might estimate:

• wheel speed;
• linear speed;
• force at the floor;
• time to travel a known distance.

For an arm:

• static load torque;
• output speed;
• time to rotate through a target angle.

Then compare those estimates with simulated or measured behavior.

Example: two candidate drivetrains

Suppose the same motor and wheel can use either a 6:1 or 12:1 reduction.

Now add constraints.

If the robot must climb a ramp, pushing force may matter more. If it must cross an open field quickly with little load, top speed may matter more.

The correct ratio depends on the mission.

Failure mode: one-number design

A mechanism chosen from one number is fragile.

Examples:

• selecting a motor only from no-load rpm;
• selecting an arm gearbox only from stall torque;
• selecting a wheel only from diameter;
• selecting a structural member only from weight.

A system operates across several conditions. Your design should name at least the conditions that could change the result.

Build a prediction table

Create a table with this structure for a robot mechanism:

If you do not have hardware, use a spreadsheet, calculator, or simple simulation for the second column and vary one assumption.

Examples:

• increase load by 25%;
• reduce available motor speed;
• increase wheel radius;
• change the gear ratio.

The goal is not to make the prediction match. The goal is to learn which assumptions control the design.

Dossier checkpoint

Add one paragraph:

The mechanism is most sensitive to ______ because ______.

That sentence forces you to identify the variable that deserves the most attention during later testing.