Toilet Paper Engine
7 Steps
Simple, easy to make, and fun, this model engine is made from cheap easy-to-find materials. It runs on compressed air supplied by your lungs as you blow the piston down and then suck it back up!  It demonstrates principles of motion and engine operation, and allows students to learn the main parts of any engine:  Crankcase, Crankshaft, Connecting Rod, Piston, Cylinder, and Flywheels.

I can't take credit for "inventing" this cool project but I've adapted this to make it a lot easier to build, and it can be done very quickly.  This is an activity I do with my 7th and 8th grade students in a Small Engines Repair class, but it could be used for many other activities like drafting, measuring, studying the laws of motion, or even a history project, as it closely remembers an old hit and miss engine.

Content Learning Objective:

By building a Toilet Paper Engine, students will understand the basic principles of operation in an Internal Combustion Engine.

Language Learning Objective:

By building a Toilet Paper Engine, students will identify engine parts using their correct names; i.e.- a ping pong ball is not a ping pong ball, it is a Piston.

Please find included below an Instructions Booklet .pdf, a Template .pdf, and a Measurements Worksheet .pdf.  Also included is a Google Sketchup model of the completed engine

Other Resources:

I have had a few people ask about other resources relating to engines that could be used when teaching, so here are a few!

http://www.animatedengines.com/  Excellent website that shows cutaway animations of just about every type of engine you could imagine!

http://en.wikipedia.org/wiki/Four-stroke_engine  Wikipedia's take- a couple of great animations, TONS of information, and lots of other links to more websites.

http://www.animatedpiston.com/Home.htm  A couple of animations of different motorcycle engines- neat because you can hide different parts of the engine while the animation is running.

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## Step 1: Gather Materials and Tools

Lets start by getting everything we need together.

Tools Needed:

Hot Glue Gun
Scissors
Wire Cutters
Pliers
Ruler
Pencil
Drill or Drill press and Drill bit

Supplies:

Approx. 2 sq feet of cardboard
Toilet paper roll or paper towel roll cut in half
8" of wire (a wire hanger would be perfect)
Piece of wood dowel ( just over 4" long and about 3/8" dia)
Ping Pong Ball
2 used or worthless cd's
Duct tape (you never know, right?)
Glue sticks for the hot glue gun
Small piece of sandpaper or file

Additional items that come in handy (especially if building with large groups):

Trace-able templates for the cardboard parts made in step 2.
Several crankshaft bending templates
Instructions book
Pre-cut and drilled dowels for the connecting rods.

COST:  I estimate each engine has roughly \$1.00 worth of materials.  The only things I had to buy was the Ping Pong ball (40 cents), the dowel (\$1.00 was enough to make at least 6), and the wire (large role cost me \$4.00).  I had sandpaper, tape, hot glue sticks, and everything else laying around.
vwtm2006 says: Mar 1, 2013. 1:40 AM
hi , look to make things easier just make the template of the crank and cylinder supports with degrees, thats it !!!!!!!!!!!!
vwtm2006 says: Feb 28, 2013. 11:36 PM
i really dont know how to thank you are the best !!!!

waiting patterns
vwtm2006 says: Feb 28, 2013. 1:00 AM
hi bro can you make templates for the v4 engine , it will be very very helpful.
I agree with others its the best idea and the best project , thanks

dorkpunch (author) says: Feb 28, 2013. 9:34 PM
I will see what I can do!
dorkpunch (author) says: Mar 12, 2012. 11:13 AM
Just an update- I've had a few people ask about other resources, so I have added a few websites to the first step you might want to check out.
biochemtronics says: Feb 16, 2012. 7:42 AM
This is so simple it is amazing. Thanks so much for sharing it.
dorkpunch (author) says: Dec 16, 2011. 9:10 PM
UPDATE!!!

I built a V4 model, and it works! There is a new step at the end called Variations 2 with more information on the V4.

I also added a picture there of all three engines together AND a picture of the 20 or so engines my class just finished building.

Teaser pics for ya'll.
Ugifer says: Jan 17, 2012. 7:01 AM
I love these!

I sometimes do holiday projects with my 6-year old and a few of her friends. This may well be featuring!

You could make valves using more toilet roll tubes and ping-pong balls.

This time, you would attach a ball to the shaft, so it spun with the engine inside a toilet roll. It would want an "inlet" hole in the front (away from the engine) and an outlet hole (well, groove) in the side that matched a hole in the side of the tube. Then, as the engine turns, the valve opens on the power stroke (outlet hole lines up with groove in ball) but then once the ball turns so the groove is past the hole, the hole is blocked and no more air blows in. A tube would take air to the calendar head and another valve on the other end of the shaft would have the opposite timing as an outlet.

Two cylinders could run off one pair of valves by having their inlet holes on opposite sides of the tube.

Not sure if that makes any sense but it works in my head!
Gydoko says: Dec 20, 2011. 12:58 AM
how do you blow on all 4 cylinders with good timing?
dorkpunch (author) says: Dec 20, 2011. 7:15 AM
You don't have to, one person running one cylinder will spin the other 3 over, so basically you only have one power cylinder, the rest are for show. You can, however, use any of the 4 cylinders as the power cylinder!
Gydoko says: Dec 21, 2011. 3:15 AM
powerful thing, for an toilet paper engine!
earlyflyer says: Jan 2, 2012. 4:37 PM
Great instructable. Putting this on the winter-project-with-the-kids list!
vedant says: Dec 19, 2011. 11:30 AM
will it matter if i don't add the flywheels ?
where does the air you blow in escape from and how does the piston come back ?
dorkpunch (author) says: Dec 19, 2011. 11:36 AM
Yes, it will matter. You can make the piston go up and down without flywheels, but its very jerky and it will not continue to "run". I have had students make them out of cardboard when they forgot cd's, and it seemed to work okay. You may have to double layer the cardboard to get enough weight to make the engine run smooth.

The air that was blown in is sucked back out when you inhale. If the engine is built well, you can just time your breaths out- but you have to take your mouth of the engine a little to let the air inside come back out.
vedant says: Dec 20, 2011. 1:42 AM
I have an idea but it will work with 2 cylinder engine only.
If you make an air out let on both the cylinders and then blow air into it
you wont have to coordinate the breathing hopefully.
The placement is very important.
I am not sure if it will work or not.
What do you think ? + I really liked the work you have done
dorkpunch (author) says: Dec 20, 2011. 7:14 AM
I've been toying with that idea- basically making a port at the bottom of the cylinder kind of like a 2 stroke engine would have. Not sure how well it would work- you would still have to stop blowing so the piston would come back up. You don't need two people to run the 2 cylinder- it will run on one cylinder just fine! Still need to upload video of it and the V4 running.
pop88 says: Dec 17, 2011. 8:46 AM
Creatively
thank you
rondacosta says: Dec 15, 2011. 4:26 PM
Big test to be tried?: could it work just by spot-blowing into de piston ball and when it comes back from inertia another blow will send it back away again? The demostration by a young "engineer" would be perhaps more successful,,,,
dorkpunch (author) says: Dec 16, 2011. 2:41 PM
It does, and actually quite well. I do think it would be pretty easy to cut a port at the bottom of the cylinder sorta like a 2 stroke, and build only an "intake" valve system on top to time the pulses of air. Still working on it though, got side tracked and built a V4 model... Pics to follow!
absolutekold says: Dec 16, 2011. 7:37 AM
Yeah it's possible but would require more weight to be added to the flywheel (for added inertia to keep the piston traveling during the return stroke) and either a careful eye or some sort of timing making the project far more complicated than the original design intended. If it were me modeling it after a 2 stroke with a port near the bottom of the stroke for exhaust and just giving it a blast when it passes TDC (top dead center) like a hit or miss engine should do nicely. Compressed air or computer duster would be good then let it run a few cycles and when it slows enough for you to time it give it another blast. also with added weight, balancing the flywheel becomes an issue but keeping it speeds low and using something like pre-molded door trim to keep the weight close i don't see why it wouldn't work.
Carleyy says: Dec 15, 2011. 10:53 AM
This is a great resource for teachers! Thanks for documenting it so thoroughly!
axiesdad says: Dec 15, 2011. 9:20 AM
What a great classroom project! Have you shared this through any professional journals (NEA or whatever)? You should; Junior high science classes would love this.
Green Silver says: Dec 15, 2011. 8:30 AM
All you need to do now is hook it up to a hair dryer or the air outlet of a vacuum cleaner. 10/10 idble.. :D
dorkpunch (author) says: Dec 14, 2011. 4:51 PM
For anyone thats interested, I added one more step, "Variations", showing the two cylinder engine I built with a little more information. Heres a quick pic for you though:
ride on toy dude says: Dec 13, 2011. 7:23 PM
Do you think it would be possible to add more cylinders
dorkpunch (author) says: Dec 13, 2011. 8:09 PM
It would be very simple to make this into a two cylinder opposed or "boxer" engine- just add another connecting rod and piston to the same crankshaft but point it out the opposite direction. It would be hard to get it "powered"- two people controlling their breathing at the same time enough to spin it would take some practice. I'm sure you could build a v8 as well, but again, tough to power it!
ride on toy dude says: Dec 14, 2011. 6:55 AM
AWESOME
dorkpunch (author) says: Dec 14, 2011. 1:32 PM
So... I couldn't stop thinking about it. I built a 2 cylinder opposed boxer-style engine and it worked great- the other piston just goes back and forth, no power, but it still works. I'll add some pics to the final step later tonight.
Dream Dragon says: Dec 13, 2011. 7:59 PM
That's REALLY clever!

A ball shaped piston gets around complex linkages at that end, and it's all nice and easy to get parts. One thing that I DO wonder about is the possibility of an "exhaust valve". Obviously lung pressure takes care of inlet valve and ignition timing, but the only engine that has a "suck" on the exhaust stroke is a Newcommen Steam engine where the stem is condensed in the cylinder.

I'm wondering if a "Pallet Valve" might be possible with a trip on the flywheel or something?
dorkpunch (author) says: Dec 13, 2011. 8:12 PM
I have a couple of ideas I should probably get around to trying out, but yes, it would be really cool to have a valve of some sort so you could run it on compressed air instead of having to do it with breath...

I was thinking of having a flapper valve or reed valve that could be tripped open by having an extra bend on the crankshaft that hits a pushrod - sort of an over head valve 2 stroke. Hard to explain, guess I need to build a model and see how it works!
dorkpunch (author) says: Dec 13, 2011. 8:14 PM
AND...

I think in a pinch you could live with out the ball piston- pretty sure if you cut a disk the right size out and glued that to the dowel, it would still work. Theres a LOT of room for error on this engine...
Dream Dragon says: Dec 13, 2011. 8:28 PM
Yes it's got a lot of built in tolerance but with sticky tape and toilet rolls you kinda NEED a lot of leeway.

Valve Wise, that's more or less what I was thinking. I suggested a trip on the fly wheel to get around having to bend the crank shaft in more devious convolutions, and I'm not sure it'd run on compressed air without an INLET valve too. If you have an exhaust valve it'd certainly be POSSIBLE to add an inlet valve, and I imagine it would run adequately fron the air in a baloon if you did, but I like the way that the user has to TIME their breath to get the thing to move correctly. Makes it a more interactive demonstration...

Or put both valves in and make them MANUALLY operated...
wilgubeast says: Dec 13, 2011. 4:16 PM
This is an AWESOME CLASSROOM PROJECT.

A bazillion imaginary internet PBL points. Love the language acquisition objective, too.
janaWolf says: Dec 12, 2011. 11:56 PM
Looks interesting, but are you sure it will work?
dorkpunch (author) says: Dec 13, 2011. 6:14 AM
Yes, it "works"... We've built maybe a hundred of these in my classes over the last 3 years. Some work better than others, just depends on how much time you spend on it and how accurate you are. It doesnt run by itself if thats what you mean- you have to continually suck the piston up and then blow it back down like it shows in the video clip.