air motor
This is a very early version; they only have an exhaust valve, no inlet valve. Although this causes them to be very inefficient they are fairly simple to make.
It works by blowing into a paper cup. This inflates a polythene diaphragm which in turn pushes on a crank. The crank pulls a thread which opens & closes an exhaust valve. The valve is made from the neck of a party balloon, it has a small piece of slightly curved card super-glued to it's upper side, this helps the valve to open & close properly. A bit of drinking straw radiuses the valve support and allows the tube to fold round it without creasing although in later versions I abandoned this idea.
detail of valve, this one without the slip of card. The valve gives endless trouble, the most common problem is that it glues itself shut when it dries out.
This is a much better version
Movie
It is much easier to make & more efficient, it will run on the air stored in a second balloon, this opens up the possibility of making a self-propelled vehicle
Movie
In fact it is much more satisfactory to use it as a cable car: a bit of fishing line is strung across the room and a turn taken round the crankshaft pulley, two bent wire guides are necessary to keep the fishing line clear of the flywheel.
Movie
It can also be run as a steam engine
It is using steam from one of Jeff Bindon's light bulb steam boilers.
link to movie
This can be made into a loco, but I don't really recommend it
Movie
I found the lightbulbs kept breaking, so even though they make very efficient boilers I started using miniature coke cans instead
To make it work I had to put the balloon directly on top of the boiler rather than using a steam pipe
Movie
It is enclosed in a firebox, like the lightbulb boiler
Movie
This is a detail of the firebox
In a desperate attempt to make it produce a bit more power I added a counterweight to the string hanger, this improved the valve closing quite a lot
It makes a satisfying 'chuff-chuff' noise
Movie
engine animations
stirling engines
rc toy traction engine
jeff bindon's toy steam turbine car
wood chips
read about steam bicycles
nicholas cugnot
ctesibius of alexandria
very interesting but highly controversial page about early development of
thermodynamics
cutout model of stephenson's rocket
newcomen engine
some history
back to main site
my email is davidvwilliamson@hotmail.com
Back in the good old days people used to make things properly. Not out of coke cans and sellotape.
