My diaphragm piston air engine with rotary valve
Fri 8 November 2024
I made an air engine with a diaphragm piston and a rotary valve. It was inspired by
a video from Robert Murray-Smith,
but improves on the design. Read more
Interesting features of John Harrison's sea clocks
Sun 12 November 2023
I recently got to see John Harrison's sea clocks at the Royal Observatory at Greenwich.
I recommend visiting if you get the chance. This post is about some of the interesting things
I observed. Read more
Incongruous technologies redux
Sun 5 November 2023
Good news: I have worked out why my incongruous technologies are
incongruous: it's because of software! Read more
The Douzieme gauge
Mon 2 October 2023
In this post I'm going to explain what a Douzieme gauge is, show you how I made one myself,
and propose some alternative designs for higher precision. Read more
Five interesting things from the Science Museum
Wed 23 August 2023
I enjoyed a quick visit to the Science Museum at the weekend, and here are a few of the interesting things
I saw. Read more
Incongruous technologies
Sun 2 July 2023
Take saws, for example. We have saws for cutting wood, saws for cutting metals, saws optimised for cutting curved shapes,
electric saws, computer-controlled saws, and so on. Saws are pretty well explored. Saws are general-purpose.
You probably won't discover a new use for saws. Read more
The crank position sensor works
Sat 6 May 2023
I have now used the 3d-printed light gate as a crank
position sensor on the Wig-Wag, and the first impression is
that it works well. Read more
Revisiting oscillating engine loss calibration
Mon 1 May 2023
Since my Wig-Wag has run in a bit now, I have revisited
the loss calibration. Read more
More inlet pressure measurements
Tue 18 April 2023
I'm not completely sure what has changed, but I'm now getting more convincing-looking inlet pressure data. Read more
Measuring Wig-Wag inlet pressure fluctuations
Mon 17 April 2023
I have connected an electronic pressure sensor near the inlet of my Wig-Wag so that
I can test the hypothesis that the actual pressure available at the inlet changes throughout the cycle of the engine. Read more
Calibrating losses in the oscillating engine simulator
Thu 13 April 2023
The biggest unknown variable in the oscillating engine simulator
is the amount of friction loss that an engine is likely to experience. To calibrate the simulation I have measured the speed of my engine at various supply pressures
and then simulated the same conditions, adjusting the simulated loss until the speed matches. Read more
Oscillating Engine Simulator
Sun 19 March 2023
I've been working on an oscillating engine
simulator. It's a type of steam engine where instead of valve gear, the cylinder swings back and forth, exposing a hole
in the cylinder to an inlet port for the power stroke, and to an exhaust port for the exhaust stroke. Very simple.
(I've also been working on building one, in the form of a Wig-Wag,
but I haven't got very far with that). Read more
Optimal eccentric-weighted coins
Thu 12 January 2023
If you wanted to make a hole in a coin so that the centre of mass is moved as far away from the
original centre as possible, how big a hole would you make and where would you put it? Read more
Measuring motorcycle lean angle with a single accelerometer
Mon 10 January 2022
The naive method of measuring motorcycle lean angle with accelerometers is to put a 2-axis accelerometer on the bike and measure
the angle between the x acceleration and the y acceleration. This only works at a standstill. When the bike
is moving, the measured angle would be 0. The purpose of the lean angle is to position the resultant acceleration vector so that it
points from the centre of mass to the contact patch of the tyres, otherwise you will fall over. So how can we measure the lean angle? Read more
Towards a high-resolution grid of tiny electromagnets
Tue 21 September 2021
I'd like to build a high-resolution grid of tiny electromagnets. It would work a lot like an LED matrix display, except instead
of the pixels emitting light, they emit magnetic fields. I have made a small proof-of-concept, but I need help
to learn more physics to improve the strength of the field and the density of the pixels. Read more
A short pendulum with a long period
Sat 8 May 2021
The period of a pendulum is proportional to the square root of its length: to double the period,
the pendulum needs to become 4x as long. But actually physics has no idea how long your pendulum is,
the thing that really matters is the radius of the arc that the centre of mass travels
through. There's no inherent reason that we wouldn't be able to increase the radius of this arc
without increasing the height of the pendulum. Read more
Chassis Design with Finite Element Analysis in FreeCAD
Tue 7 January 2020
Finite Element Analysis is a way to calculate the stresses and strains on an
object in various load conditions. The object is modelled as a series of "finite elements" (in our case triangles), and then we specify the locations
of points that can't move (fixed points), and the locations, magnitudes, and directions of forces that are present. Read more
Home 3d metal printing: first results
Mon 12 August 2019
A couple of weeks ago I learnt about an interesting 3d metal printing process,
from a company selling it for $100k USD, and speculated that it might be DIY-able for much less. Well I now have some
promising first results. Read more
Towards a Better Pythagorean Cup
Fri 4 January 2019
There was an article on Hacker News the other day by David Richeson entitled
Make Your Own Pythagorean Cup.
A Pythagorean cup is a cup with a built-in siphon. Supposedly invented by Pythagoras, the cup functions just
like an ordinary cup as long as it is only filled to a certain level. If anyone gets greedy and tries to take
too much wine, the level rises above the top of the siphon, which causes the siphon to self-start, and the
greedy person is punished by having the entire contents of the cup dumped into their lap. Read more
Flat Earth and the Coriolis Force
Sun 9 December 2018
I've been learning about "flat-Earthers" recently. They're a fascinating group of people who genuinely believe
that the Earth is flat and that governments, scientists, and industry are in on a big conspiracy to trick
everyone into thinking the Earth is round. Read more
On the design of a herb jar lid
Mon 27 June 2016
My herb jar lid has two operating modes:
one has small holes which allow you to shake the herb out slowly, and the other
is a single large hole which allows you to shake the herb out quickly. Read more