Pop-pop or Put-put Steamboat Made Easy for Children

Children, from about 6 years old on, can make this real steam propelled boat under adult supervision. This pop-pop or put-put steam boat requires neither soldering nor gluing. No drilling or puncturing is needed. It does involve an easy to make bending tool.

I wanted to make a construction manual for a simple pop-pop kit I am making for some friends and colleagues. So I thought: why not make my first instructable?

This instructable is aimed at adults wanting to help children make a pop-pop boat at school, at home or wherever you like. Do take your responsibility in dealing fire and steam and in assessing if and how the children can deal with it safely.

I will not explain how pop-pop steamboats work, as you can find an extensive explanation on The Science Toymaker. Original inspiration for the coil engine came from the Pop-Pop Pages. In the following steps I will explain how to build one real easy.

I have been giving creative workshops for children since several years now, mainly at the school my daughter is attending: Leefschool Klavertje Vier. My workshops almost always involve a scientific or rather technical topic, most often something that rides, sails, flies or at least moves: rockets, mousetrap cars, solar powered vehicles, hovercrafts... If you understand Dutch you can check out my website: http://users.telenet.be/masynmachien

These workshops are open to children from 6 to 12 years old, but as the average age tends to be around seven, I learned to simplify things. My aim is to allow young children to build working things by themselves, with as little help as possible. Very often that involves a good preparation making templates and such. The pop-pop boat I present here is a culmination of that.

The essential materials for the boat and engine are:
- a brass or copper tube 3mm or 1/8 inch outside diameter, 2mm inside diameter, 50 cm length. For sources see (1) below;
- a narrow aluminium cake baking form (disposable). I prefer to use a size a type about 19 cm long, 6 cm wide and 5 cm high, easily giving the right shape;
- a binder clip with a base of about 2 cm;
- a small aluminium cup, as from a candle light (or you can make something similar from aluminium foil);
- about 1 square cm of double sided adhesive tape (the type without foam, because I am not sure the foam type is heat resistant enough. The foamless kind is, when one side is cooled by the water).

For the bending tool or coiling mandrel you need:
- a sturdy cylinder shape (e.g. piece of wooden dowel), about 2 cm diameter and 3 cm length;
- a piece of scrap wood minimum 4 cm x 15 cm x 1 cm;
- one screw with a length about equal to the thickness of your piece of wood and one screw 2 to 3 cm longer (for each you will need a matching screwdriver, not shown).
- a piece of sturdy tube with a loose fit over the brass or copper tube and minimum about 20 cm long;

For the optional rudder, you need about one third of an extra aluminium form. For this rudder you can print and cut out a helpfull template from the drawing added to step 6.

For the optional decorating you can use permanent markers, common aluminium foil and some more double sided tape.

(1) You can buy the brass tube at modeling shops or at OPITEC. The article number at OPITEC is 813.716. OPITEC serves Germany, France, United Kingdom, Italy, Switzerland, The Netherlands, Austria, Belgium, Spain and Hungary. You can experiment with shorter lengths (e.g. 12 inch), but lesser coils gives a larger chance the pop-pop cycle stops after a while. To my experience any copper or brass tubing with this diameter is bendable with the mandrel and technique described further. I never found the need to soften the material commonly available.

Of course, for live steam you need water and fire (or heat at least).

The water heated in steam is taken from the water the boat sails in. So you need clean water to sail in. You only need about 2 to 3 cm depth. As these boats are very light you can only use them outside when there is no wind. Avoid borders or anything else hanging low over the water surface, because they might be exposed to the flame. As long as they are not leaning over towards the water, I never had any trouble with fragile border materials, like a vinyl inflatable pool, but do not blame me.

The heat comes from a flame. I do not use candles, for several reasons. One is that with the coil engines a simple candle seems to miss somewhat on heat (or rather heat transfer), resulting in the pop-pop cycle to stop after a while. Putting a double wick in the candle helps quite a lot but not completely. Another reason is the smoke the candle gives and the sooth deposited on the coil, both with one wick or two wicks. This is not only messy, but also diminishes the heat transfer to the coil.

Instead I use Esbit fuel tablets. These are sold as fuel for camping cookers, but also used to be popular for steam toys and models. You can get these Esbit tablet at camping shops and also at OPITEC (artikel number 439.161). These tablets burn very clean. These tablets faintly smell like petroleum , so I guess that is what they are based uppon. The odor is quite faint, the package is not even air tight (apparantly there is no need to).

The packaging of the Esbit fuel tablets mentions inhalation and contact with the skin should be avoided, but I never had any reaction although I am quite sensitive to such things. You will find similar warnings on lamp oil. Any way, it is good practice to fuel charge your boat with pliers or tweezers, also avoiding burning your fingers when hot charging.

One tablet burns about 10 minutes. Half a tablet gives a little more than 5 minutes. Two tablets is a waste in this kind of boats, not giving a proportionally longer burning time. To my experience, the influence of the amount of fuel on the speed of the boat is negligable.

This tool is best made in advance by an adult. Checking out how the tool is used in the video in the next step can help illustrate how it should be set up.

The short screw and the cylinder shape are put near one end of the piece of wood. The gap between both should be equal to the diamater of the brass or copper tube. The position of the screw along the circumference of the cylinder is not critical. However, if you do it as in the second picture, you will be able to mark out the "starting position" for the bending on the long end of the piece of the wood (see last picture).

I find the easiest way is to put in the short screw first and the cylinder second. This way it is easier to use the 3mm tube to measure the gap. You can also check the starting position of the tube will be parallel with the piece of wood. You can glue the cylinder provisionary and attach it firmly with a the long screw from the back. If your cylinder shape is hollow you can attach it by pouring hot melt glue inside. You can add a screw from the back, into the glue mass, but that is probably not necessary.

If a point of any of the screws comes out of the wood, do take measures to avoid anyone hurting him or her self at the sharp edge (use a shorter screw or grind down).

Mark a line on the piece of wood 9,5 cm (for 50 cm tubes) from the cylinder as "starting position" foor the bending.

Fixing the tool, for example to a sturdy table surface can help, but can be ommitted.



In addition to the video, here follows a description:
Put the brass or copper tube in the tool as shown in the previous step, with the one end sticking out 9,5 cm (i.e. adjacent to the mark made earlier). Slide a sturdy tube over the other end as a bending assistance, keeping the end at least 1 or 2 cm away from the mandrel/cylinder. KEEPING THIS DISTANCE IS VERY IMPORTANT to get smooth bends and avoid local buckling of the tube. Using the piece of wood and the assisting tube as levers bend the brass or copper tube around the mandrel. It is important to keep the end of the sturdy tube one or two cm away from the cylinder to avoid to much local bending. Try to keep the windings relatively close to each other, but gaps up to about half a cm are still OK. Make four windings, ending up with the two ends of the tube perpendicular to each other (see pictuere). Remove the assisting tube and slide it over the other end, up to about 1 cm from where the tube passes the screw. Bend the tube end 45 degrees towards top end of the tube. Remove the assisting tube and the complete coil. Turn the coil around and slide it back on the mandrel, fitting the other end between the cylinder and the screw. Slide the assisting tube over this end and also bend it 45 degrees, bringing it in parallel the other end. Your steam engine is ready.

I explain what you see in the video:
First stretch both ends of the baking form. One end will form the bow, the other end is folded inwards. Make sure not to push the fold to deep in, to avoid water running in when the boat is in use. About 45 degrees is OK. Widen the sides of the boat a little to provide better access to the inside. Put the engine in the fold with the tube ends touching your working surface. If the two ends of the tube are not of the same length, put the longest one top. This way it will be easier to keep both ends in the water the boat is steaming in later on. Attach the engine tubes with the binder clip, making sure to clamp both sides of the folded aluminium with the tubes in between. Having the opening of the coiled shape directed somewhat vertical (i.e. not sideways) will make charging with fuel and lighting easier later. You can leave the clamp levers upright. This will also make mounting the optional rudder easier.

Once the assembly is securely clamped you might need to bend the aluminium a little to get everything in the right shape. Put the small aluminium cup under the coil, fixing it with a little double sided adhesive tape at the bottom. As the bottom of the boat will be kept cool by the water and the heat is mainly directed upwards, the tape will not burn.

This step involves cutting a disposable aluminium baking form, giving some sharp edges. Some care should be taken not to cut yourselves.

A rudder is not absolutely necessary. However it is required if you want your boot to go straight or make a determined curve. Without it, the boot will unavoidably make a somewhat undetermined curve. It is up to you to decide wether you bother to make rudder. You can always decide later and add a rudder at any time. Just let everything cool down before adding it after running the boat.

Print out the template below. Scale it in such a way that the shapes are 12 cm long. This is the case if you print the drawing fitting to a full A4 sheet. I also added the drawing as a pdf that should automatically print to the correct scale. I have put several shapes in the drawing to save paper when you do this for a larger group.

The shape of the rudder is not very critical. One side should be angled at about 45 degrees to fit in the boat. One long edge must be made straight to correspond to the folded sided of the rudder (see further on). The rest of the shape is chosen to make the rudder easily bendable in the middle. Making the shape symmetrical eliminates the question what way around the rudder should be mounted. Finally everything is rounded to avoid sharp point that can hurt.

Cut out the desired number of paper rudder templates and follw the video and instruction below:



From an extra disposable aluminium baking form cut a flat piece of at least 12 cm x 5 cm. With the baking forms I am using I can get 3 of those pieces out of one form. Fold the piece of aluminium along its long axis. Put a paper template on it, making sure the straight edge is aligned with the fold. Attach it by putting some clear cellotape over it. Cut out the shape. Of course you do not cut the straight side/fold.

Opening the binder clip slightly, slide in the rudder in between the fold in the boat hull, straight side down. Align rudder and tubes.

You can decorate the boat as long as you use materials that resist to water and in some degree to heat. You should not put any decoration close to the flame, but it even then it is best to use materials that do not scorch or burn when they come to close to the heat by accident. You can make puppets and such with ordinary aluminium foil. I often use double sided adhesive tape with aluminium foil stuck to one side, to make a somewhat heat resistant adhesive tape. To decorate the hull I use permanent markers.

Fill the coil engine with water at one end, untill it comes out the other end. You can use a syringe, but you can also do it under the tap (of course only with no fuel in the boat). Put the boat in the water. Charge the little cup with an esbit tablet. Light a match and simply drop it in the cup. It is not necessary to hold the match. I is better to try again if needed, than to hold the match to long and burn your fingers. You can remove the rests of the match once everything has burned and has cooled down.

Allow a little time for the esbit tablet to ignite fully. After a while the prolusion will start. Always keep the two tube ends in the water or it will stop. You can charge a second esbit tablet once the first is almost completely burned. Do this with metal pliers or tweezers to avoid burning your fingers. Do note the esbit tablets can become partly liquid when burning, so be careful with the boat.

Try bending the rudder until the boat follows the path desired.

Enjoy!