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


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

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.

It can also be run as a steam engine
since writing this I have tried to re-create the steam driven version without success. One of the problems is simply generating enough steam: a motor like this uses about one litre of steam every ten seconds. So you have to make a boiler which can vapourise about one cubic centimeter of water every ten seconds, which is quite difficult. Also the rate of steam formation tends to be intermittent, this will stop the engine rotating. Until I've sorted this out the following information should be regarded as suspect.
Latest update is it works a lot better if you use one finger from a latex glove instead of a balloon.

It is using steam from one of Jeff Bindon's light bulb steam boilers.
This can be made into a loco, but I don't really recommend it


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

It is enclosed in a firebox, like the lightbulb boiler


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

hardware steam engine
another hardware steam engine
deceptively simple burner
making a piston from neodymium magnet + oil + iron filings
engine animations
elijah galloway rotary steam engine
some new engines
stirling engines
rc toy traction engine
jeff bindon's toy steam turbine car
whacky working fluids
using steam as a balloon lifting gas
wood chips
read about steam bicycles
nicholas cugnot
ctesibius of alexandria
some problems of modern boilermaking
very interesting but highly controversial page about early development of thermodynamics
cutout model of stephenson's rocket
henry ford's first engine

newcomen engine

some history

pistonless reciprocating airmotor

fan-driven reciprocating blowmotor: early version with baffle that obstructs airflow

later version without baffle works by blowing through straw

further simplification: this will also run on steam if paddle is made from small bit of corriflute

bent wire crank works in palm of hand; drinking-straw con rod is sellotaped to thumbnail

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