Introduction: Air Engine
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.
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.
- PSI Vs RPM graph
Step 1: Students Work
Here are two typical examples of a students work.....remember these kids are only 13!
Step 2: Fly Wheel - Making the Mould
- 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
- 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
- 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
- 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
- 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
- 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
- Carefully clamp the flywheel onto the pillar drill and drill the centre to Ø10mm and deburr edges
Step 9: Cylinder - Facing & Drilling
- 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
- 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 level....you get a tapering cut on the surface
Step 11: 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
- 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
- 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
- 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
- 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
- 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
• 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
- 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
- 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
- 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 threadlock...note....do 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
If you have any questions about this please ask.