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Putt Putt/Pop Pop Think Tech Tank.
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Daryl Canada


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PostPosted: Sat May 15, 2010 7:58 am    Post subject: Putt Putt/Pop Pop Think Tech Tank. Reply with quote

Welcome to the Putt Putt /Pop Pop Tech Think Tank where comments and answers are only an opinion. Should any of my answers prove to be correct answers, credit is shared with Guus Flogel, a putt putt builder in the Netherlands, Jean-Yves Renaud, engineer and builder in France and many others. Should the answers prove to be incorrect then clearly you asked the wrong question.

I hope that you will join in and watch this thread and post your questions and answers. Putt putt building is not an exact science. That is part of the fun.

--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Question.
" In the second to last picture,(sailboat Putt The Magic Dragon) is the copper coil inside the copper pipe, or are the pipes just soldered on a sealed copper pipe?"

The sealed copper pipe is the boiler just as the coil is the boiler on a coil design. There are three main types of engines:- Coil, Diaphragm and other. Other being any enclosed container that isn't a coil and doesn't have a diaphragm. Common shapes for other are drum, barrel and tube to name a few of many shapes tried and possible. The diaphragm type is the same as other but with a flexible membrane that is usually on top. Testing indicates that a diaphragm does not add power to an engine but rather takes away power. Sort of like putting a cushion on a hammer.

Tech tip:-On the intake stroke water is not sucked in. It is forced in by the ambient air pressure on the water surface. If this were not so the boat would sit in place alternately blowing and sucking and going nowhere.
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Roly Williams


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PostPosted: Sat May 15, 2010 9:07 am    Post subject: Re: Putt Putt/Pop Pop Think Tech Tank. Reply with quote

Daryl Canada wrote:
...
Tech tip:-On the intake stroke water is not sucked in. It is forced in by the ambient air pressure on the water surface. If this were not so the boat would sit in place alternately blowing and sucking and going nowhere.


Thanks for starting this thread; it's a great idea. I hope it will help dispell some of the mystery of these wonderful boats. I certainly intend to learn something as well as (hopefully) pass on some of my extremely limited scientific knowledge.

I must start off with a disagreement. "Sucked in" and "forced in by the ambient air pressure" are one and the same thing. That's what the word suck means.

As for the final part; I've often wondered why this doesn't happen. It's one of the mysteries of the pop-pop boat. My own explanation (which may be wrong) is that the water being blown out remains in a straight line for a while before dispursing but the water being sucked in (or pushed in by the atmosphere) comes from all directions. Also, the outgoing water is mixed with steam and so is travelling at higher speed.
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PostPosted: Sat May 15, 2010 9:12 am    Post subject: Reply with quote

I have a question. Why do pop-pop boats need two pipes? Is it simply to make it easier to fill with water at the start or is there some technical reason? I realise that, in a coil type boiler, a pipe has two ends and so it makes sense to make them both work, but that doesn't apply to other types of boiler.
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PostPosted: Sat May 15, 2010 6:12 pm    Post subject: Reply with quote

I always thought that the intake was accomplished due to a vacuum being created in the boiler, with water rushing in to fill the void. The boat moves forward because the vaporized water is at a higher pressure than the water flowing into the intake. Just been my impression.
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Daryl Canada


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PostPosted: Sat May 15, 2010 7:58 pm    Post subject: Reply with quote

Roly, Thanks for the input. I hope you will continue to question and comment. I'm not a scientist so your type of input is needed to keep me honest and provide more detailed information to those who want it.

Quote
"I must start off with a disagreement. "Sucked in" and "forced in by the ambient air pressure" are one and the same thing. That's what the word suck means."

You are correct of course but many do make the connection that suck does not stand alone as a force. A test that connects to this is to use a straw to blow out a candle and then try to blow out the candle by sucking on the straw.

Quote
"As for the final part; I've often wondered why this doesn't happen. It's one of the mysteries of the pop-pop boat. My own explanation (which may be wrong) is that the water being blown out remains in a straight line for a while before dispursing but the water being sucked in (or pushed in by the atmosphere) comes from all directions. Also, the outgoing water is mixed with steam and so is travelling at higher speed."

Your explanation is mostly correct. The power stroke is unidirectional while the intake is multidirectional.

In your last sentence a bit more information could help down the road a bit. Hopefully steam will not be mixed with the water on the power stroke. This can indicate that the interface between steam and water is breaking down or the tubes are too short to support the stroke length of the water "piston". Dissolved gasses will usually appear as bubbles during the warmup phase but once fully stabilized (10min. to 2 hrs depending on the volume of the engine) only a very few bubbles should appear. If steam is constantly being exhausted the engine will burn out. Burn out is the term used when the boiler becomes dry because the water column has moved too far down the tubes. ie too much gas in the upper part and little or no water vapor /steam. Bubbles from the wake can be confused with exhausted bubbles.

Comment
"I have a question. Why do pop-pop boats need two pipes? Is it simply to make it easier to fill with water at the start or is there some technical reason? I realise that, in a coil type boiler, a pipe has two ends and so it makes sense to make them both work, but that doesn't apply to other types of boiler."

More than one pipe is not required. A piece of pipe with one end sealed and without even a rudimentary boiler will work, however, multipipe engines so far have proved to be superior. Why this is so is only partialy understood, at least by me.

AzRob,  Does the above answer your comment?

Inevitably answers provoke more questions and hopefully this is how this thread will work best. I could add more related information to the above but perhaps if we keep this discussion somewhat linear it will be better understood by all.

Roly and others with scientific backgrounds,.. ..I expect you have at least a couple of new questions already. When you have some time on your hands look up Payne's work on these engines. He ran a lengthily government financed laboratory study on these engines. He discovered a lot of things that don't work,
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Roly Williams


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PostPosted: Sat May 15, 2010 8:14 pm    Post subject: Reply with quote

Daryl Canada wrote:
...
He discovered a lot of things that don't work,

I know that experience only too well
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Stoker


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PostPosted: Sat May 15, 2010 10:41 pm    Post subject: Reply with quote

Roly Williams wrote:
Daryl Canada wrote:
...
He discovered a lot of things that don't work,

I know that experience only too well


I believe it is reasonable for me to claim professional status in the field of discovering things that don't work!

Meanwhile, I think (hope) that I can further clarify a point that has already been made, so that it might be better understood. If not, then I will be obfuscating it still further, but here we go anyway.

The Pop-pop / Putt-putt engine works on pressure differentials, such that on the feed "stroke" where the engine is "sucking" water in, it is powered by a maximum pressure differential of one atmosphere of pressure (roughly 14.7 psi or 1013.3 mbar or 101.3 kPa or 29.9 inches [760 mm] of mercury or about 33 feet of water), which by the way means it is impossible to suck water up a straw more than 33 feet, and then only under condition of a perfect vacuum created at sea level. You may do a bit better if you can arrange to perform the experiment at a location that is below sea level! It should also be noted that ideal conditions are never encountered in reality, such that the intake "stroke" on a Putt type engine is more likely to be powered by an approximate 1/2 to 2/3 atmospheric differential.

It should be further noted that the intake of water during the feed "stroke" is a bit random, pulling water in from every direction approximately equally, and thus pretty well cancelling any directional effects being cause by this event.

On the other hand, the power "stroke" is very directional, in line with the axis of the exhaust tube, and depending on the efficiency of the heat exchange being realized between the heat source and the water, can offer a pressure differential of several atmospheres of pressure, due to the rapid expansion of the steam and the subsequent expulsion of the water column previously "sucked" up. Therefore, a repeated "jet" of water exiting the Putt-putt engines tubes with a force greater than that of the resistance offered to the surface area of the vessels hull, by the water it is floating in, will result in a net forward motion of said vessel, or so it is hoped!

I hope this helps detail the process in a comprehensible manner. If not, I'll take my flogging and return to my seat!
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Last edited by Stoker on Sat May 15, 2010 11:40 pm; edited 2 times in total
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mogogear


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PostPosted: Sat May 15, 2010 10:46 pm    Post subject: Reply with quote

Well, the Pop Pop vortex looks to have started!!


Good stuff..Daryl please let me or any of the moderators know if your understanding of the "picture posting" etc fights with you and help is needed to lower the learning curve.

You can easily contact a moderator offer a handy link to answer a difficulty if it arises by just clicking on any of the moderators names at the top of each section of the forum.

As this type of technical discussion will be immensely aided by pictures as it progresses.

Once again- Thanks for sharing your passion with the group! Thumbs up!
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PostPosted: Mon May 17, 2010 3:17 pm    Post subject: Reply with quote

Just a thought, but if this thread takes off and starts becoming heavy with important information, perhaps it would be good to make a "stickie" out of it at the head of the Steam Launch forum, or here on the Tech forum!
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wesgoos


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PostPosted: Mon May 17, 2010 4:52 pm    Post subject: diaphrams and others Reply with quote

OK then Daryl, when I put water into my modified Science Toy boilers by turning them over and pouring water in one tube till it comes out the other tube (lower) ...I'm converting it from a diaphragm engine into an "other" engine. ( ...hmmm ..thats probably why it requires more heat to get it going... ) more water ...more heat. ...but if I want
"pop" , I have to figure out how much water is too much and how much is enough (or "just right")
Now... about tube lengths...is there (are there) "optimums "?...limits ?
maybe different for different motors (boilers)?
BTW and IMHO , I think (and consider ) we are all scientists ...even though I've spent most of my working life as a shipfitter-welder /draftsman
Thanks so much for starting this thread Daryl ,
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Daryl Canada


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PostPosted: Mon May 17, 2010 7:23 pm    Post subject: Reply with quote

I will very soon post an engine build project. Your questions are answered I think by that post.

Two points are worth further mention. Both Slater's engine and the "made in India" engine are examples of well designed engines that always work well when built properly and not damaged.
I know Slater built hundreds of engines to get his design right. However, putt putt engines do not scale up proportionally. Modifying either is unlikely to bring improvement but don't let me discourage you from trying. Innovation is needed and can lead to improvements.

Let me know if I have missed anything in your question.

Putt Putting is still far from an exact science.
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Daryl Canada


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PostPosted: Tue May 18, 2010 7:46 am    Post subject: Reply with quote

This is an engine design for those who want to build a more powerful putt putt engine. At the very least this engine will produce power equal to 10 of the "made in India" diaphragm engines. It will be silent. If you want that pop pop sound later on I can tell you a simple way to do it. It would be great if several of you built this engine . Later, a race?

You can build this with the boiler described or with a copper coil using approximately the same ID tube. I would change to brass tube close to either side of the high point if using a coil but that is not absolutely necessary. Silver brazing is required as common low temperature solder will melt at the required running temperature.

I think the photos are self explanatory except maybe for nipples and tilt height and tilt angle.  I braze short sections of pipe into the boiler one size larger than the main pipe size. This saves a lot of trouble with having to build a jig to hold the long tubes in place when they are installed and, you can align the tubes very close to how you want them by bending the nipples if necessary after they are brazed. Tilt height is the vertical distance from the top of the exhaust tips to the highest point of the tubes. For this engine it should be between 3" and 3 1/2". When you run it you can experiment to find the best height for your engine.This is usually a 10 to 15 degee tilt angle.  

You can blow the photo up so that the overall length actually measures 16" long. This gives a full scale plan.to work from. The tube OD is 1/4" and the ID is 7/32. This is common dimension thin wall brass (.014) pipe that you should be able to find at hobby stores. It is not necessary to be absolutely exact. Cut each tube 17" long. With 3/4" nipples the length should work out when the tubes are bent.

The boiler is 3" of common copper 1/2" ID water pipe usually .030 to .040 wall. Either will do as will a bit less or a bit more. You may plug the ends with pipe caps or fabricate inserts. I fabricate to keep the weight down. Butt welded end plates can be a weak point. OK to make the boiler longer but I would not go smaller.

As max cleanliness of the metal is important for brazing, in building the boiler I usually drill pilot holes for the tubes 1/32 undersized first. After brazing in the ends you don't have to clean the pipe holes, just drill to the correct size.

Tips:--- Soaking in water will remove most of the flux left over from brazing.
          Use lots of flux. Parts coated with flux are less likely to become oxidized or burned and are therefore easier to clean for the next step.
          When pre heating for brazing try to keep the open flame away from the joints to be brazed until the materiel is very bright red. Then apply the flame and solder to the join. The solder should almost instantly liquefy and suck into the seams. If the solder comes off in chunks the heat is too low. Depending on the thickness of the solder wire you get you can if necessary for fine work or light materials hammer the wire flat to make it thinner and easier to melt.
          Pressure test the boiler before and after installing the tubes. It"s easier to repair a leaking boiler before the tubes are installed, and, leaks can develop after running. Usually a pin hole in the solder that was filled with hardened flux that took time to wash out or scale from heating. Washing the engine inside and out with muriatic acid before installing the long tubes is a good idea. The engine will not run for long if at all if there are leaks.
            Heat. This engine would run on 2 to 5 x 7/32  ID wicks using methyl hydrate. Initial testing could use any heat source. Best running temperature would likely be in the 250 to 400 F range. Over 550 the engine may burnout and if it stops running  turn off the heat and start again.  An infrared thermometer is a good tool to have if you don't have one now. This tool has many uses around the home besides steam engines. And a note on the use of them. They can read very wrong on polished surfaces and even when the surfaces are sooted from running.  The solution I have found to this is painting with flat black.
           Filling. With the boiler down fill through one tube untill it runs out the other.
           It should start to run in 2 to 5 min. depending on the amount of heat applied. A small engine like this can take up to 1/2 hour to achieve it's best performance so don't give up if it is erratic at first.
           Note. Once an engine has run long enough to stabilize there will be little or no liquid water in the boiler, only steam and perhaps some gasses. Most of the bubbles that escape during warmup are gasses dissolved in the water being expelled.  
            Correct tube length is usually about 62 x the tube ID for the "unheated part". This is not exact science. Longer rarely hurts other than a slight reduction in power but too short can cause steam bursts and loss of water in the tubes or failure to start.
             As you can see, I have built this exact engine. I have very similar engines in a 4 tube version and  7 tube versions. Different tube ID/OD and length is beneficial/necessary for the 4 or 7 tube versions.
             You don't have to build a boat to test it. A simple raft will do or clamp it and stick the tubes in a pan of water.
         
I'm assuming you have some if not all of the skills needed to build this engine so some build details are not included. Please ask if anything is not clear.

Credit to Jean-Yves for doing the work to evaluate many engines by several builders to arrive at the (approximate) method of determining tube length and tilt height. Read more at http://www.eclecticspace.net/index2.php?rub=poppop  Click on the flag to translate.



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Last edited by Daryl Canada on Sun May 23, 2010 8:21 am; edited 2 times in total
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mogogear


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PostPosted: Sun May 23, 2010 5:48 am    Post subject: Reply with quote

Daryl

I have needed to read this more than once to discover my questions:
For now I am unsure of your terms- unheated  vs heated sections of the tube.


They look to be backwards to me...

The unheated section is nearest the flame source ( almost at the boiler... the heated seems to be farthest away from said flame??

All else makes sense.... but if I am missing that I may be missing a lot more...
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PostPosted: Sun May 23, 2010 7:36 am    Post subject: Reply with quote

mogogear wrote:
Daryl

I have needed to read this more than once to discover my questions:
For now I am unsure of your terms- unheated  vs heated sections of the tube.


They look to be backwards to me...

The unheated section is nearest the flame source ( almost at the boiler... the heated seems to be farthest away from said flame??

All else makes sense.... but if I am missing that I may be missing a lot more...

I, too, am puzzled by that. I assumed it was a typo.
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PostPosted: Sun May 23, 2010 8:13 am    Post subject: Reply with quote

OOps!  You are correct. Heated and Unheated were reversed. I say were because I will now attempt to edit the message.

Good thing I charge less for incorrect answers.
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