http://www.instructables.com/id/How-Not-to-Build-A-Valved-Pop-Pop-Boat/

Home   Sign Up!   Browse   Community   Submit

   All     Art     Craft     Food     Games     Green     Home     Kids     Life     Music     Offbeat     Outdoors     Pets     Photo     Ride     Science     Tech

How Not to Build A Valved Pop-Pop Boatby LetsBuildOne on January 12, 2011

Table of Contents

How Not to Build A Valved Pop-Pop Boat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Intro:   How Not to Build A Valved Pop-Pop Boat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Step 1:   The Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Step 2:   Making the valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Step 3:   Making the boiler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Step 4:   The Intake/Exhause Manifold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Step 5:   Make the Hull . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Step 6:   Put it all together . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Step 7:   Test It! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Step 8:   Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Related Instructables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

http://www.instructables.com/id/How-Not-to-Build-A-Valved-Pop-Pop-Boat/

Author:LetsBuildOne    Let's Build OneI'm a Masters Engineering Student. I build things because I want to and because I enjoy the design, fabrication and development.

Intro:  How Not to Build A Valved Pop-Pop BoatThe ProblemPop-Pop Boats are notoriously inefficient for many reasons but the main problem is the action by which it moves forward.

The  ExplanationExhaustWhen the engine pops it squirts water out of the exhaust. This water travels almost straight out with little divergence.

IntakeWhen the engine sucks in fresh water it sucks from all around the inlet. The water sucked in from the sides should be symmetrical so they sum to zerobut approximately a third of the water in taken comes from the same vector as the exhaust squirted which cancels out say a third or more of the forward thrust when thenet product is found.

The SolutionPut valves on the engine so that it sucks from the front and blows out the back potentially quadrupling the forward net thrust!

Step 1: The PlanWith the concept set the principles of operation are simple. All that remains is to design an appropriate way of implementation.

ValvesThese only have to be one way and should require no return so should take little force to open. I went straight for the shuttle valve. I found the smallest reasonably sizedball bearings I could and designed the valves around them so they would close from one side and free flow the other. Then, they would be mounted to allow free suckingfrom the front, no blow and free blow on the back, no suck. The ball bearings where 6mm steel.

Exhaust and IntakeI know through my research that the number of tubes is essentially irrelevant. One tube can work as effectively as two or more. The aspect to be considered is surfacefriction. As the output of the engine has an optimum cross sectional area the way to attain the least losses is to have one tube of the required diameter. Since I want tosplit the input and output I needed two tubes, one in the front for intake, one out the back for exhaust. I decided to have them both of the same diameter copper pipe ofaround 6mm internal diameter (1/4") To fit my valves. 

calculated from working engines boiler size to tube cross sectional area ratios.

Engine TypeHere I have two choices, the simple coil boat or the difficult to seal pop pop boat.

Coil EngineThere is a minimum radius to which you can bend a pipe without flattening or crimping it. My quarter inch copper pipe dictated that the coil would be rather large indiameter and hence hard to package in a boat hull of the size I was envisioning. I also know through research that pop-pop boats don't work well at larger volumes as theinertia of the water displaced with each cycle limits the frequency of operation to a point where there is little if any or the motion can be rather sporadic. This meant theinternal volume of the coil that would form my boiler may be too large. Classic Pop-pop EngineThese are simplest when constructed out of steel beverage cans. Instructions on how to do this are on the internet and I dare say here on Instructables. If you havetrouble finding them, send me a message or e-mail and I'll either add a link here or send you the link. This would be good but the boiler needs to be at a fairly horizontalangle to catch the heat from the heat source. A vertical boiler would receive little to no heat as heat rises. This would mean that complex bends would be required to getthe engine in the middle of these two pipes going on opposite directions. Fluid dynamics say that corners are bad as far as resistance and efficiency goes so this wouldnot be optimal.

This left a completely fabricated boiler of my own design which was in the same size ratio as the smaller commercial pop-pop boats that you can buy but with an in lineintake/exhaust orientation which made sense to me for the intake/exhaust placement I was envisioning.

Conclusion

http://www.instructables.com/id/How-Not-to-Build-A-Valved-Pop-Pop-Boat/

Steel shuttle valves with a 1/4" copper pipe intake/exhaust and a conventional boiler with slight modifications.

http://www.instructables.com/id/How-Not-to-Build-A-Valved-Pop-Pop-Boat/

Step 2: Making the valvesI used a lathe to turn a piece of 1/2" brass bar down and a ball nosed drill bit to make the seat the ball bearing will seat into when sealed. I then made a cage to hold theball bearing in the centre of the chamber whilest allowing it free movement and water around the sides.

http://www.instructables.com/id/How-Not-to-Build-A-Valved-Pop-Pop-Boat/

http://www.instructables.com/id/How-Not-to-Build-A-Valved-Pop-Pop-Boat/

http://www.instructables.com/id/How-Not-to-Build-A-Valved-Pop-Pop-Boat/

http://www.instructables.com/id/How-Not-to-Build-A-Valved-Pop-Pop-Boat/

Step 3: Making the boilerThe boiler was made out of 1" copper pipe, almost flattened with the ends crimped and brased. I then drilled a hole out of the bottom for the tubes to be put in and asection out of the top for a steel diaphram.

This was mistake number two! Don't add a diaphram because it makes the engine sound cool, sealing it was almost impossible and it frequently blows a seal!

http://www.instructables.com/id/How-Not-to-Build-A-Valved-Pop-Pop-Boat/

Step 4: The Intake/Exhause ManifoldI took a piece of 1/2" copper tube and two steel rods of the same OD as my 1/4" copper pipe and put a small taper on one end using a Lathe.

I then slightly flattened the 1/2" pipe in a vice and hammered in the two steel rods. I then took two smaller diameter steel rods and placed them between the two steelrods on the outside and squashed them in using a vice.

This was then cut to length and Brased to the boiler.

http://www.instructables.com/id/How-Not-to-Build-A-Valved-Pop-Pop-Boat/

http://www.instructables.com/id/How-Not-to-Build-A-Valved-Pop-Pop-Boat/

http://www.instructables.com/id/How-Not-to-Build-A-Valved-Pop-Pop-Boat/

http://www.instructables.com/id/How-Not-to-Build-A-Valved-Pop-Pop-Boat/

Step 5: Make the HullI used the hull patern from a pop pop boat website that uses the steel from a vegetable oil drum. The drum was opened with a can opener and a flat sheet was extractedusing a pait of metal sheers. The patern was printed and stuck onto the metal with a low tack glue stick and cut out using shears. The patter was then removed and all thefolds made before the hull was sealed with copious amounts of areldite.

http://www.instructables.com/id/How-Not-to-Build-A-Valved-Pop-Pop-Boat/

Step 6: Put it all togetherThe pipes had to be put in place after the hull was constructed as they would be on the underneath of the hull down the length of the boat. Holes are sealed with epoxyresin and it's ready!

http://www.instructables.com/id/How-Not-to-Build-A-Valved-Pop-Pop-Boat/

Step 7: Test It!The engine ran like a normal pop-pop boat but much less power until the inlet/outlet was high enough then the valves kicked in and it worked perfectly!... For one cycle...

After much thought I realised I has been an idiot and there where two fatal flaws to my design.

1. The weight of the ball bearings- The amount of energy it took to open or close a valve was roughly that which was normaly taken to move forwards so there was littleenergy left for propulsion.

2. Here is the real problem- It is a resonant engine. This means it works at a natural frequency which is dependant on the size of the boiler, the length and the diameter ofthe intake/exhaust pipes. As the engine is in operation pressure waves travel up and down the tubes at a relatively high frequency. By adding valves to the arrangment Ihad inadvertantly stopped the engine from consistantly running at its natural frequency as when it reached it, the valves would kick in, and it would cough and stop only tobuild up to another splutter in due course.

I have also realised that the lengths of the pipes are very different due to the placement of the engine and so this will make the engines harmonics rather unusual andprobably not desirable.

Step 8: ConclusionBack to the drawing board! Mechanical valves won't work! 

Update:Since this boats design and manufacture I have designed and made a working valved Pop-Pop Boat .

http://www.instructables.com/id/How-Not-to-Build-A-Valved-Pop-Pop-Boat/

Related Instructables

How To Build aValved Pop-PopBoat byLetsBuildOne

Pop-pop or put-put steamboatmade easy forchildren bymasynmachien

Buying a boatonline:Adventures ofLil PuttRestoration bystation420

Steam PoweredPotato Pistol 1.0by robbtoberfest Cheap and

Simple SteamEngine byliam2317

Hardware StoreSteam Enginefull instructionsby kcbford1

Comments

7 comments Add Comment

 tobyker says:  Mar 5, 2011. 10:03 AM  REPLYGood to see work on pop pop boats. I have used the valves from car windscreen washers in my boats, mounted inside the boat and connected with high-temp silicone tubing. You can insert concentric tubes into the outlets to increase velocity and encourage intake through the valves

 rickharris says:  Jan 18, 2011. 12:30 AM  REPLYI have been chuntering round a type of water ram jet - using flap valves and a flash boiler (with a bigger burner than a candle) but two side by side to getalternate actions so avoid the issue of slow cycling.Alternatively there seems to be some mileage perhaps in a Stirling type system using a water column as the power piston.

Again cycle time is an issue due to the water column returning under it's own timing, multiple units side by side could get round this - rather like a multi barrelmachine gun.

 LetsBuildOne says:  Jan 18, 2011. 2:27 AM  REPLYYou can dictate the frequency at which the engine operates by the size of the boiler, the diameter of the tubes and the length of the tubes.

The smaller the above, the faster the frequency.

I'm curious as to how you where going to make the engines run alternately? I like your ideas, they sound interesting. It would be good to see how theywork...

 rickharris says:  Jan 18, 2011. 9:18 AM  REPLYOn my list of things to do - so are a lot of other things as well!

 rickharris says:  Jan 18, 2011. 12:31 AM  REPLYYou could of course add a simple flap valve to the system made from little more than a soda straw rather than the mechanically heavy ball valve. Not muchalteration to do either.

 LetsBuildOne says:  Jan 18, 2011. 2:40 AM  REPLYThe problem isn't only the weight of the valves although that is a big problem. The bigger problem is that the engine works like a tuned exhaust on an ICengine and by adding automatically operated valves to the exhaust and intake system you will change the harmonics of the engine.

As the engine operates a pressure wave travels down each pipe, bounces of the effective end of the pipe and back into the boiler.

The first problem is I have pipes of different lengths, this means I've spread my power curve over an area rather that having a high peak power that theengine could sit at using it's own resonance.

The second problem is that when the valves are closed they make the pipe effectually an inch shorter which means that the engine now has a differentnatural frequency and will try to change to run at that frequency, but, When it tries the length of the tubes changes again as the valves open and close.This means that an engine designed to run at a specific frequency is constantly building to a power band instead of achieving it.

If you managed to valve both the inlet and the outlet with super light weight valves that don't change the length of the pipes then it has potential to work. Iwould theorise that there would still be pressure waves as the valves open and close that would mess up the harmonics and it would perform far belowexpectations.

The solution here lies in a form of valve that doesn't vary the length of the pipes and doesn't physically close a pipe to stop the flow of water.

LBO

 rimar2000 says:  Jan 17, 2011. 5:10 PM  REPLYThanks for doing the work for me!!! I was thinking this approach for years. I maked a few pop-pop boats, they have many secrets.