The Problem
I work in HVAC Test & Balance (TAB). A big part of the job is identifying specific pulleys (sheaves) on rooftop units to adjust fan speeds.
The old way involved carrying a physical catalog, measuring the part with calipers, and then manually flipping through pages to find a match. If the measurement was slightly off, or the catalog was missing a page, you were stuck guessing.
I realized I could speed this up significantly if I just had a digital database I could search from my phone.
The Build: The "Browning" Engine
I built TestAndBalance.xyz, a simple web app that replaces the catalog.
Here’s how I broke it down:
The Database: I needed the data first. I digitized the specs for over 2,000 Browning sheaves, mapping the physical dimensions (Outside Diameter, Pitch) to the actual Part Numbers and Bore sizes. Now, instead of a book, I have a queryable dataset.
The Search Logic: Field measurements are rarely perfect. A sheave might be rusted, or the angle might be awkward. I set up the search to handle a bit of variance.
If I input 3.4, the logic searches a range (like 3.35 to 3.45) to find the closest valid part number. It acts as a "fuzzy search" for hardware.
- The Hardware Interface (Calipers) Since this tool relies on physical inputs, I still need to carry calipers. The software is only as good as the measurement I type in. It helps confirm I'm looking at a "3V" belt profile vs an "A" profile, which is hard to tell by eye but obvious when you measure it.
The Physics Layer
To make it more than just a lookup tool, I added the Fan Laws (fluid dynamics formulas) into the frontend.
When I select a new sheave size, the app automatically calculates the resulting Brake Horsepower (BHP). Since power increases with the cube of speed, a small change can ramp up power usage fast. The app flags the new BHP so I can verify it’s safe for the motor before I even order the part.
Summary
I built this because I wanted a tool that fit my specific workflow. It’s a PWA, so it loads instantly on a job site, and it saves me a few hours of manual lookup time every week.
If you’re interested in automation for the trades or just want to see how it works, you can check it out here: TestAndBalance.xyz
I’m Dyami Connell, an HVAC TAB Technician.
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