It started with a reactor simulator
The idea behind the site.
I needed a nuclear reactor simulator — something to teach and demonstrate with, where you could move a control rod or trip a pump and watch what the machine actually does.
Nothing suitable existed. Full-scope training simulators are licensed, costly, tied to one plant and one control room, and assume you can already operate one. At the other end were toys: a slider and a cartoon with no physics worth discussing. Nothing in between, and nothing I could open in a browser and hand to someone as a link.
So I wrote my own — and that is what turned one simulator into a site. A reactor is not a nuclear problem. Making it behave needs the neutronics, but also heat transfer, fluid flow, the mechanical limits of the components, the electrical system it feeds and the control logic tying them together. Every one of those sent me looking for a calculator to check a number against, and every time I found the same two options: something behind a licence, or something that handed me a figure with no statement of what it assumed. So I wrote those too.
A path that did not look like a plan
Where the range of subjects comes from.
I started in electrical engineering — power systems, machines, networks — which is where the cable, transformer, voltage-drop and grid tools come from. Then nuclear energy engineering in Stockholm: reactor physics, thermal hydraulics, radiation protection, and the simulators and radiation tools that followed from it. Later industrial R&D in mechanical engineering, where things have to be manufacturable and an elegant calculation that cannot be built is worth nothing — the bearing, shaft, beam, gear and pressure-vessel calculators came out of that. And in parallel a doctorate in physics, on radiation and the environment, which forced me to get comfortable with the idea that a result is incomplete until you have said how wrong it might be.
None of it was a strategy. But the effect is that I have had to be a beginner in a new field four or five times, and being repeatedly bad at something teaches you what a good explanation looks like. Most of the tools here are the explanation I wish I had been given.
A calculator should tell you what it assumes
The rule every tool on this site follows.
Most engineering calculators on the open web give you a number and nothing else — no method, no indication of which standard they approximate, no mention of where they quietly stop being right. That is worst precisely when you are new to a subject, because you have no feel for whether the answer is plausible and therefore no defence.
So every tool here states the method, names the standard it approximates, works an example with real numbers, and says where the method stops being valid and what to do instead. Where I am approximating something a code handles more carefully, I show the size of the gap — that gap is what a newcomer cannot see and most needs to know about. None of it replaces a governing standard or a qualified engineer; these are screening and teaching tools, and they say so.
Method, corrections and review dates
How the pages are built and kept.
Every calculator is a single self-contained page. The engineering runs in plain JavaScript in your browser, nothing is sent anywhere, and no account is needed. A tool you cannot inspect is a tool you should not trust with a number you intend to act on.
Each page carries a month and year. That date moves when the content changes — a method corrected, an example added, a limit clarified — not for styling or housekeeping. A review date that advances across a whole site every month tells you nothing.
Every page also has a Report an Error button in its header, which opens a message with the page URL filled in. Include the inputs you used: an error I cannot reproduce is an error I cannot fix.
Getting in touch
Corrections, questions and everything else.
For a specific calculator, the Report an Error button on that page is best — it carries the URL with it. For anything else, including collaboration, write to Support.EngineerHub@gmail.com.
EngineerHub is an independent project, not affiliated with or speaking for any employer, university or standards body.