Introduction: Air Engine

Picture of Air Engine
Inspire the next generation of engineers, challenge their ability and push the boundaries of what they thought a 13year old can make and challenge what you think a teacher can teach!

This is a project I run in my after school engineering club, normally air/steam engines are difficult to make and even harder to get running, I studied various plans and developed this relatively easy build..........even a poorly made example will run. It is a proud moment for both the student and the teacher when they complete and run one of these. Check the video to see one in action.

Learning Objective

Students will apply a series of fundamental engineering skills using a variety of equipment and machinery to work with precision, this includes lathes and milling machines. They have the opportunity to either work independently from a step by step guide or if unsure about a process can ask a friend or teacher for guidance enabling them to learn a new skill. Students aim to recall previously learnt skills and apply in a more challenging situation, they have to use a metal lathe to drill to a precise depth, parallel turn to a specific tolerance,  and......... they will also learn how to cast aluminium. This project is a skills challenge and a massive confidence builder.

Future learning objective

I am intending on expanding this next year to include scientific calculations.
  • F=MA
  • PSI Vs RPM graph
  • Efficiency

Step 1: Students Work

Picture of Students Work

Here are two typical examples of a students work.....remember these kids are only 13!

Step 2: Fly Wheel - Making the Mould

Picture of Fly Wheel - Making the Mould
Materials; Styrofoam 75 x 75 x 20mm + 30 x 20 x 60
  • Scribe a Ø70mm circle on the Styrofoam using a divider or compass
  • Cut out with a coping saw then use the disk sander until round
  • Collect a 'runner' and cut a V groove in the top then flatten the other end on a disk sander
  • See teacher to stick together with superglue.

Step 3: Fly Wheel - Casting

Picture of Fly Wheel - Casting
I am fortunate enough to have access to a crucible in my school workshop if you dont build your own by searching instructables for 'back yard foundry' 
  • Take a metal container and add 20mm of sand in the base
  • Add the mould and bury in sand so top of the runner is sticking out roughly 10mm
  • Get teacher to pour aluminium into mould

Step 4: Fly Wheel - Preparing the Casting

Picture of Fly Wheel - Preparing the Casting
  • Cut runner off casting
  • Clamp and drill Ø6.8mm hole through the centre of the casting then tap a thread at M8
  • Take a large diameter aluminium or steel rod (Ø25mm or above). Centre drill it and then drill a Ø6.8mm x 30mm hole
  • Cut the head off a M8 x 50mm bolt, file the sawn edge and put into the rod

Step 5: Machining the Casting

Picture of Machining the Casting
  • Screw casting onto the machining arbour
  • Parallel turn down the sides until its round round
  • Face off the front of the casting

Step 6: Fly Wheel - Machining the Recess

Picture of Fly Wheel - Machining the Recess
  • Set up the cutting tool to cut the recess 3mm deep into the side, leave approximately 9mm from the outside and middle
  • Set the parting off tool to 450 and chamfer edge
  • Remove the casting from the arbour and flip it around to repeat the machining on the other side.

Step 7: Fly Wheel - Drilling the Holes

Picture of Fly Wheel - Drilling the Holes
  • Using the Digital calliper accurately measure the inner and outer circles then create the 5 centre holes to lighten the flywheel using 2D Design to make a template.
  • Drill a small pilot hole Ø4mm
  • Drill a Ø8mm hole
  • Using the deburing tool tidy the holes you have drilled.

Step 8: Fly Wheel - Drilling the Centre

Picture of Fly Wheel - Drilling the Centre
  • Carefully clamp the flywheel onto the pillar drill and drill the centre to Ø10mm and deburr edges

Step 9: Cylinder - Facing & Drilling

Picture of Cylinder - Facing & Drilling
Materials; Aluminium rod Ø25mm x 55mm long
  • Face off both ends and chamfer.
  • centre drill and drill at Ø10mm to an accurate depth of 45mm.
  • Use the digital calliper to check depth and re-drill if necessary.

Step 10: Cylinder - Machining the Flat

Picture of Cylinder - Machining the Flat
  • Set up work in milling machine to create a flat edge approx 4mm wide
  • Level the work piece using a fixed scribe
  • Use a digital calliper to check the width of each end. if its parallel your work is level
  • Now keep milling until the flat is 15mm wide.
  • The image above shows what happens if its not get a tapering cut on the surface

Step 11: Cylinder - Drilling Holes in Flat

Picture of Cylinder - Drilling Holes in Flat
  • Measure and mark the holes as per the working drawing, holding your work in a V-Block, centre punch, centre drill and drill the holes into the flat.
  • Put the cylinder back into the lathe and re-drill at Ø10mm but be carefull not to make the hole any deeper (this removes any burrs from drilling the small holes into the flat..
  • Use a countersink to deburr the edges of the hole.
  • Sand the cylinder to create a good surface finish.

Step 12: Cylinder - Axel

Picture of Cylinder - Axel
  • Cut a Ø6mm steel rod to 30mm long
  • File a chamfer on each end
  • use a M6 die to cut an external thread 20mm long
  • Thread lock into the 6mm hole in the cylinder

Step 13: Piston

Picture of Piston
  • Cut Ø8mm rod to 40mm long
  • Face and chamfer both ends of the 8mm aluminium rod.
  • Mark out and centre punch, then Drill Ø3.2mm hole as per the video and drawing below.
  • Machine some Ø12mm nylon rod as per the diagram above
  • The nylon is hammered onto the aluminium

Step 14: Chassis - Marking Out

Picture of Chassis - Marking Out
Print the working drawing ensuring the CAD software you use does not alter the scale. you can use the printout as a template.
  • Cut out a template
  • Use tape to stick template onto steel plate, ensure the bottom of the template is aligned with the bottom of the plate
  • Scribe around chosen template with a ruler and scriber
  • Ensure the paper is pressed flat against the steel then centre punch the crosses.

Step 15: Chassis - Drilling Holes

Picture of Chassis - Drilling Holes
  • Clamp the steel into a drill vice ensuring it is gripped on the top shelf
  • Use a medium centre drill to drill and the holes approx 2mm deep
  • Use the appropriate drill bit for each hole according the working drawing
  • Remove steel from vice and use the deburing tool to tidy up the edges

Step 16: Chassis - Cutting

Picture of Chassis - Cutting
  • set up the chassis in the milling machine
  • Mill the two longest sides down to the scribed lines
  • Cut the top edge off with soft jaws and a hack saw

Step 17: Crank Ring

Picture of Crank Ring

• Carefully measure distance between piston and chassis
• Face off Ø25mm aluminium rod, centre drill, drill Ø10mm x 10mm deep
• Chamfer the outer edge
• Part off at the correct thickness
• De-burr holes.
• Center punch  4mm in from edge, drill Ø3mm.
• Cut Ø3mm steel to 12mm long and FILE a chamfer on the edges and thread lock it into the crank ring

Step 18: Support Rods

Picture of Support Rods
  • Use Ø12mm aluminium rod and create two pilers as per the working drawing
  • Drill the side hole on a pillar drill
  • Thread all four holes with a M5 tap

Step 19: Base

Picture of Base
  • This is precut for the students as they are not allowed to use a router
  • Students can mark and drill the holes
  • The measurements are taken from the hole centres on the chassis
  • The diameter of the holes is Ø6mm for the clearance and Ø10mm fro the counter bore

Step 20: Assembly

Picture of Assembly
  • The flywheel and crank are attached using a Ø10mm steel rod that is long enough to go through the fly wheel, chassis, and crank ring
  • The axel should be stuck using not get threadlock in the chassis or the wheel will not turn
  • They cylinder is held with a spring and a M6 nut
  • The support pillars are fixed using a M5 bolt cut to size
  • The base is fixed to the engine with 30mm long M5 bolts

Step 21: Enjoy

Picture of Enjoy
This example has a very heavy flywheel so is much slower than the one shown on the fist step.

If you have any questions about this please ask.



weirdharold (author)2017-04-07

Do you sell completed versions?

Dschepp made it! (author)2016-05-31

I made this in my high school shop class

T0BY (author)2015-07-08

Beautifully made! You are a craftsman.

nnandhu (author)2015-06-27

will it work if its made in a larger size

DenverAnne (author)2015-02-02

Hi there. I've been looking for a tutorial on how to build a minni diesel engine for my year 10 science project but haven't found anything that can help me, luckily Google helped me find this tutorial. It's not diesel but I'll enjoy making it either way. Thanks so much from Wynberg Girls High school, South Africa!

bosko90 (author)2013-08-29

Nice air engine! did you try it with steam?

These is my steam engine from student project:

TheParacorder (author)2012-08-08

now make it street legal... and go 60mph

cj8675 (author)2012-06-22

you should make the kids do everything. My grandfather tought me the lathe and vertical milling machine at age six (am 14 now)

apb92 (author)2012-05-28

Can you tell me how the air supply is fitted, is it just a push fit?
Also what length, diameter and strength spring is best to use?


jonnyd55 (author)apb922012-06-12

hi, good questions :) air supply is just push into the hole. a light spring is best, the nut allows adjustment of pressure.

connercrawford2012 (author)2012-04-19

could you please tell me the dimension thickness of the chassis this would be much apreciated

Hi, it doesn't really matter. I have made engines that have had 10mm chassis. However this design uses 5mm

connercrawford2012 (author)2012-04-19

what was the tickness of this plate as i cant seem to find it your help would be much apreciated

Archemedes54 (author)2012-03-11

Any ideas on what else it could be used for?

jonnyd55 (author)Archemedes542012-03-12

anything that uses a low torque revolving motion

tinker234 (author)jonnyd552012-03-13

or use a car alternator and run it off of that to get elctrycyty

jonnyd55 (author)tinker2342012-03-13

unfortunately the alternator would require more torque than the engine could generate + you would get less energy out the alternator than you put into the compressor! if you have any ideas on how to solve that issue you will quickly become the richest person in the world!

tinker234 (author)jonnyd552012-03-14

maybe a series of belts and pulleys

curious youth (author)2012-03-10

this is amazing !
you should design an air powered car ! that thing would run itself. you would become a millionare

jonnyd55 (author)curious youth2012-03-10

especially if it ran of flatulence!

curious youth (author)jonnyd552012-03-10

not if theres a reservoir :)

Ahmed2 (author)2012-03-06

vedry good

steveastrouk (author)2012-03-04

Nice Ible, a teacher needs to run it through a spell-checker though....

jonnyd55 (author)steveastrouk2012-03-04

Not the first time thats been said....a combo of dyslexia and monkey typing results in some dodgy spelingz

steveastrouk (author)jonnyd552012-03-04

Where are you based ? If you're doing this in the UK, it makes great ammunition for me and the head of DT at the school I help in to go for funds. The "school lathe" is a disaster area - there's no lubricant been near it for 20 years.


jonnyd55 (author)steveastrouk2012-03-05

Im based in south cambs / north essex is that anywhere near you? if it is im sure we could arrange a visit to our school to see the awesome stuff we do in graphics, resistive, engineering, textiles, electronics and food.

steveastrouk (author)jonnyd552012-03-05

I'd like to really kick things up in my sons' school. DT is a dead end topic there. It sounds like you're running it the way I would ;-)

I'm up in Lancashire.


colorex (author)2012-03-02

Hey Jonny,

I would say that this could run as a steam engine as well, just connect it to a steam boiler instead of a compressor.

jonnyd55 (author)colorex2012-03-03

it absolutely will :) however home made pressurised steam is not allowed in a school unless the boiler pressure tested by a H&S company :( its a shame H&S is killing any fun we might like to have in life!

steveastrouk (author)jonnyd552012-03-04

In the UK at least, model engineering clubs often have people who can pressure test small boilers with the correct hydraulic equipment.

jonnyd55 (author)steveastrouk2012-03-04

your probably right, i would expect its excluded from all schools. I have never checked as I would not allow my students to make one......just in case they got hurt....... its a shame really :(

REA (author)jonnyd552012-03-04

Also, most schools budget their funds in favor of sports programs, mainly football.apparently little Johny throwing a football 150+ yards is more important than Billy being able to design a high-efficiency steam engine.

colorex (author)REA2012-03-04

That's sooo sarcastically true! I wish it were the other way around!

colorex (author)jonnyd552012-03-03

Nice! Just don't forget to post it!

bloomautomatic (author)2012-03-04

This excellent on many levels. First, it's a great instructable. Second, it's great that you're doing this level of work with kids of that age (or any age in school.) Third, it's a great device by itself. You should be commended. 5 stars.


jonnyd55 (author)bloomautomatic2012-03-04

Hi, thanks for the nice comment and the awesome patch :) i like your kinetic man it made me remember back to when I was 13, as i made one at school! but it was nowhere as cool as yours.... I will investigate the idea further.... watch this space :)

terrapinlogo (author)2012-03-02

these are better done than the work of some 18 year old students at my school

thoraxe (author)terrapinlogo2012-03-02

Well he does have access to materials, mills, lathes, and casting equipment. Your average middle/high school usually doesn't have any of that.

jonnyd55 (author)thoraxe2012-03-03

Its not that a high school is missing equipment...... they are missing the right tech / shop teachers who pester local companies to buy the equip for the school..... just like we do at our school

steveastrouk (author)jonnyd552012-03-04

More like H+S policy excludes it - it does in the school I volunteer in.

About This Instructable




Bio: I love making stuff, I love Instructables, I love tools, I love machines, and I love materials. But most of all I love Arnie.
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