boscacci / piston-balancing

Match connecting rods, piston pins, and pistons to make optimally uniform weights

Piston Balancing

A practical problem in automobile mechanics.

Problem Statement

In a combustion motor, it's best if the masses of the different piston assemblies are roughly the same.

Each piston assembly consist of three components:

• Piston
• Connecting Rod
• Pin

A car motor may have somewhere between 4 and 16 cylinders (for piston assemblies). Call this n.

Given [n] sets of (pin, rod, piston): How can we mix and match these components such that the variance (in grams) between assembled sets is minimized?

One might alternatively seek to minimize the difference between the heaviest and the lightest assembly.

Methods

A brute-force approach is demonstrated in Pistons.ipynb.

The nasty nested for-loop does not scale beyond 4 cylinders on a consumer laptop.

In pistons_multithreaded.py, the same ugly approach is thrown at more cores. It took me 17 minutes to solve for 6 cylinders on an 8-core macbook air.

RFP

Now it's your turn to find a smarter approach to this problem. How can this be computed for a 16-cylinder engine?