Jof Arnold | Entrepreneur, engineer

Cofounder and VP Product at Timecounts. Previous internet stuff includes cofounder and CEO of YC W11 FitFu and London-based boutique agency BrainBakery with @Benjie. You can find me at @JofArnold on Twitter and on Linkedin and GitHub. I live in London with my girlfriend and a cat and a rabbit.

My career takes me from nuclear robotics and Russian spacecraft, through to motorsport and fuel injection systems. I’m on my third internet startup; my previous two startups, BlogFriends and FitFu, were not financially successful but at least FitFu/GymFu had a huge impact on the wellness of many people. If you’re interested here’s more about what I’ve been up to the past 15 years.


Before starting university, aged 17, I found a job working for Magnox PLC designing and developing software for robots to inspect and repair off-load nuclear reactors. Our projects were so successful at spotting cracks in welds in reactor pressure vessels that we shut down two magnox nuclear reactors.


After starting university - studying Mechanical Engineering MEng at Imperial College London - I managed to find myself working at Moscow Aviation Institute optimizing re-entry vehicle heat shields. In Russian. In Fortran 77. In DOS. It was pretty difficult but my professor seemed to be happy with the results.

More Robots

Following MAI, I raised funds to visit Japan to pursue my interest in robotics. Through broken Japanese and pure hustle I met with Toshio Fukuda (Nagoya University), Shuji Hashimoto (Waseda) and Yoshiuki Sankai - all of which are now legends. What amazes me is that in 2012 – some 12 years since my visit – the technology I saw there still seems futuristic.


Towards the end of my Masters I shifted my attention to motorsport, designing and making hybrid aluminum CFRP composite drivetrain component’s for the faculty’s racing car as well as acting as chief engineer for a small private racing team. After finishing university I had a chance meeting at Silverstone which in just a couple of weeks saw me raise funding to move to South Africa and work on optimizing a V8 sports car for a small manufacturer.

Fuel Injection Systems

The motorsport projects were great fun, but ultimately I needed to find a stable job and eventually found myself working at Delphi Diesel systems designing high-pressure fuel injections systems. Operating at over 2,500 times atmospheric pressure, these components are placed under exceptionally demanding stresses. I soon found I had a knack for balancing stress analysis, manufacturing, material science and testing and was promoted rapidly to lead engineer. This work culminated in the development of critical trade secrets as well as a disruptive new manufacturing process that improved fatigue life by 2x – something for which I received my first patent.

Internet Startups

After hitting a glass ceiling at Delphi, I quit engineering and started a small software agency with Benjie. At the time we didn’t know about things like VCs and Angels, so we structured our work to self-fund side projects. It was through the agency work we met and then joined BlogFriends - probably the first social news filtering startup. The app, built entirely within Facebook, attracted 80% of the Technorati Top 100 top influential bloggers in the world.

After BlogFriends closed, we saw an opportunity with the new "iPhone" and its "App Store". Using the accelerometer we creating motion-sensing fitness apps that trained people by counting reps. The apps, initially called GymFu were quite successful, and eventually merged into FitFu after receiving funding from 4iP, Y Combinator and Start Fund. Despite selling over 250,000 copies and having a core of enthusiastic and dedicated users we decided to close the project in October 2012. I figured I was too old to work on small projects; it was time for something much bigger.

Copyright Jonathan "Jof" Arnold 2013