Stirling engines - Slow motion balloon power piston

I made a few adjustments to my little tin can Stirling engine. It now spins twice as fast, at a rate of around 210rpm. Not that that means much because the more flame you put under it the faster it goes. But it's around twice as fast as it was originally. Quite a success as far as bettering a terribly inefficient Stirling engine goes.

If you ask me.

The main adjustment I made was to replace the two sections of shaft that make contact with the supports. The original shafts and bearing surfaces were made of galvanised fencing wire.

I replaced them with a thinner grade of stainless wire. Actually it's welding wire, and is the same stuff I use whenever I mention stainless wire in the construction of my fishing lures or anything else on the blog.

Pictured here in this uncomfortably framed, but interestingly red image, is the new wire, the old wire, and a match.

The thin stainless wire makes a huge difference. It even runs without the 8g counter weight now.

The counter-weight is there to mirror the weight of the displacer, so without it, the power piston has to lift all that weight on it's own.

With the counter-weight and a minimum sized flame, it can now tick along as slowly as only 32 rpm.


To run as slowly as 32 rpm, I found it also needed a small drop of very light lubricant (fishing reel/sewing machine oil). But it's important to note that the shaft for the displacer - the one that goes through the small hole in the can, should not be oiled. The oil burns, and leaves a sticky residue which will stop the engine.  As seen by the improvement by the slight reduction in friction, the smallest extra friction will kill these little engines. Use graphite, or just leave it with nothing.

If you did lubricate the displacer shaft, it's also possible that oil or Vaseline could get into the displacer container, and being flammable, might eventually find it's way to igniting if everything was just right.

Everything is very rarely just right, and a Stirling engine is a very safe thing to make and use because there are no pressurised containers. The making involves some sharp bits of tin can, and should probably not be built by kids, but as a finished item, it's as safe as any small candle is, so probably qualifies as relatively child friendly.

Lets say... As child friendly as a birthday cake.

Anyway, it looks like this in slow motion (sorry for the poor picture quality)...

[edit from the future - Opps, for some reason the video wasnt dropped into place.] Here it is...

Even more stately.

It's currently clunking away on my desk, running at around 60rpm on these two little flames, and has been doing so for an hour. One flame is about the size a birthday candle, and the other is around half the size of a birthday candle.

My point is it isn't using much heat compared to the last version.

I find it's sounds...

oddly soothing.

K-chunk K-chunk

120 Things in 20 years thinks that if ever I disappear, it might be because I'm off on a Stirling engined bike trip around Australia... in slow motion.

Aquaponics - Tomato

It's cold and rainy here in South Australia, and I keep picking tomatoes.

Winter isn't a good time for tomatoes, but mine seem to be having fun anyway.

My four tomato plants that are growing so their roots are suspended in the fishtank water seem to be fruiting a lot later in the season than they should be. The plants are out in the cold, but their roots are inside the fishtank which is inside a little growhouse.

The plants look like this.

And they are still doing a lot of flowering.

And there are plenty of fruit all over the vines.

And the fruit are still ripening.

These were today's pickings.

Not many today, but there are always some. And a few didn't make it inside.

And there are a lot more on the vines that are nearly ripe. Ripe enough to eat.

All these pics were taken today. It's winter in the southern hemisphere, so the tomatoes should have stopped fruiting a while ago.

It's strange that they are still growing and fruiting this late. Strange enough that I thought I'd contact someone from one of our universities. I remember someone from my research into bees, who was working on growing native bees to pollinate tomatoes. I'm not sure if there were a bee person or a tomato person, but I emailed them in the hope that if they don't care, they might know someone who does.

It might save the industry a bit of money if it turned out the entire plant didn't need to be kept warm to keep them fruiting.

120 Things in 20 years says to be on the lookout for tiny hot houses with tomatoes growing out of PVC tubes, coming to a winter tomato farm near you. Or not.

Aquaponics - Self cleaning swirl filter revisited

One of the many people named Anonymous took the time to comment on my self cleaning swirl filter, so I thought I'd revisit the topic with some thoughts I've been having.

For the last few weeks I've been thinking of getting some more fish.

And I've also been thinking about developing the self cleaning swirl filter a little more.

My original design was to tap off a small amount of clean water for NFT tubes employing the self cleaning filter to keep the roots from collecting solids and blocking the NFT tubes. In the end I got around that by just taking my water from the sump, where there were no solids, but that required a better pump to get water to the top of the tubes. .

If this were ever to be implemented as a system to remove solids from a system rather than returning them to the grow beds it would need some adjustment.

It's easy to set up a container so that it is right at the point of tripping a siphon, but will never actually get there unless someone suddenly dumps water into it. With this in mind, one option I thought of  when I was playing with this idea, was to use a deer scarer...

Set a dripping tap, so it slowly filled a deer scarer. The deer scarer should tip only once or twice a day, and should dump the same amount of water that the self cleaning swirl filter takes from the system each time it's triggered.

I'm going to build a deer scarer, and see how it works, then see if it really would take care of dosing the self cleaning filter with the correct amount of water to make it do it's thing.

You can see my previous work on my self cleaning swirl filter here.

Photography - My new macro-bot

I built a thing today.

It moves stuff in small increments using a small electric motor, in response to a users input.

I guess that means I've built my first robot.

Actually, probably my second.


My device looks like this

It also looks like this.

The bit with the "1" next to it is my previously built power supply that delivers 5 volts to my project.

The bit with a "2" next to it is the previously made PICAXE Proto Board that connects some input/output pins to my breadboard.

The "3" is the transistor bit, that powers the motor when the chip sends a signal to do so.

And the "4" isn't really visible. If you could see the "4", it would be next to the the switch that the user presses to make the subject move a tiny bit.

The point of this exercise is to attempt to make a device that carries an empty box of mints along a steady track, to carry a subject to different focal distances, in order to make a series of photos to create a focus stack, and thus create an image with a greater depth of field than might otherwise be achieved.

This absurdly simple solution, represents my first successful attempt at creating an electronic something without external help from someone, somewhere on the planet.

All the software does is wait for someone to press the button, then move the subject a tiny bit closer to the camera. This changes which bit of the subject is in focus, and enables the user to take a "stack" of pics, each one having a different plane in sharp focus. The user can then knit them all together using some free software, creating a photo with an otherwise impossible depth of depth of field.

The 11 lines of code that makes it work look like this (the very small amount of black text is the actual software, the green text is just my description of it)


; Macro Mover ver 2013 06 10 0200
        ;moves a small platform holding a photographic macro subject a tiny amount closer to the camera         '            each time a button is pressed, helping to create a "focus stack"
;no rights reserved
;use at your own risk

;For picaxe 08M2

#No_Data 'saves a few seconds when uploading the code to the chip, because it doesn't have to check for data

main:' begin the main program loop

if pinC.1 = 1 then gosub Move    'if someone is pressing the button, jump to the bit of code called "Move"

goto main ' if it gets this far, go back to the start and check for a button press again

Move: 'the bit of code that moves the platform with the subject on it

do until pinc.1 = 0 :loop ' hang here until the button is released

high 2 'turn on the motorconnected to pin 2
pause 2 ' wait for 2 milliseconds
low 2 ' turn off the motor connected to pin 2
pause 100 ' pause for 100 milliseconds

      return 'go back to the gosub that called the "Move" code


I started with an old CD ROM drive that I ripped all the interesting bits out of.

I think this is the original motor because it fits perfectly. This is the motor that made the laser head move from the centre to the rim. Now it's the motor that moves the photographic subject towards the lens, changing which bit is in focus.

The blu-tac is there as a weight to keep the linear cog in contact with the gear that the motor connects to.

So the motor makes the black bit move from this extreme...

(see the black bit)

to this extreme, but in tiny increments each time the button is pressed.

Each button press causes a a quarter of a millimetre migration.

.25 mm = 0.0098 inches

A tiny amount each button press.

The camera sits on the large grey platform to the right.

The software controls how much the motor moves at any given moment. This way we control how much we increment the slice of our subject that is in crisp focus.

The camera is securely set in place because there is a tight fit due to my bending some tags in order to hug the camera. There is also two lumps of blu-tac securing the camera to the base.

This arrangement feels totally secure, and I haven't had any problems with the camera moving.

Last, but far from least, I added a subject platform  and a light source. The subject sits on a platform made form an empty tic-tac (small mint confectionery) box,

The light source is the thing on three zebra legs.

It's best to move the light source with the subject as it moves toward, or away from the camera, to avoid photos with different exposures, so a light that moves with the subject is best.

Once you have a "stack" of photos with different bits in focus, you can knit them all together with a program like "MacroFusion" (free, open source program I run on my linux computer)

To use this Macro-bot device, you press down once or more times, on a button to move the subject a tiny bit closer to the camera. After each button press (or two or three) you take a photo. Each time you press the button, the subject moves a fraction of a millimetre. I found pressing the button once was suitable for macro shots where the lens was at full zoom, and pressing three times when the lens was at minimum zoom.

Some experimentation is required, but as soon as I made this, I immediately solved all the problems I was having with poor alignment of my photos in a focus stack.

Successful results to follow...

120 Things in 20 years - Sometimes, all you have to do to make a robot, is to replace all the bits from the robot you salvaged last week.

Photography - Maybe bee

I was playing around with my new, home made macro lens, and found this interesting little dead thing to act as a model.

I thinks it's maybe a bee.

Or a wasp.

Or an ant.

I think it's a bee.

If it's a bee, it's probably a native Australian bee. Perhaps a Megachile or "Resin bee".

Or a wasp.

Either way, this is what you find if you mentally mark out a square foot of ground on my lawn, and search it as if it were a crime scene.

A very interesting looking little critter.

It's perhaps 5mm long.

The background is a dark woollen glove

Dark subject against a dark background.

Still learning.

120 Things in 20 years wonders how it's going to get a bee to wink in a planned portrait when bees don't have eyelids.

Home made cheese - Haloumi and zucchini fritters

Here's an excellent thing you can do with your home made haloumi.

Grate 300g of zucchini, and squish out as much liquid as you can.

Drop it into a bowl with a grated onion, 250g of grated home made haloumi, 1/2 cup of plain flour, 2 teaspoons of grated lemon rind, 2 eggs, and a tablespoon of fresh dill.

Add salt and pepper to taste, and roll into balls.

It's a good idea to chill them in the fridge for an hour to make them hold together, but that's optional.

Shallow fry them in some olive oil pressing them flat once they hit the pan, flipping to get even golden-ness.

Let them sit for a bit on some paper towels, and serve them with aioli for a truly awesome taste that will be very popular with young and old.

They're great hot or cold, and originally the recipe came from

Totally worthwhile.

120 Things in 20 years - Representing an excellent reason to get into making some home made haloumi.

Aquaponics - Sweet Remano peppers

I harvested the first of my very late capsicums today.

This is my all time favourite variety called Sweet Remano pepper.

They are very late to fruit as I like them red, and they went in very late.

These things are so delicious, that I think they are too valuable to eat.

For some strange reason, I cant buy them from any of my local fruit and veg shops, or supermarkets.


120 Things in 20 years - I really need to learn how to use my new camera when trying to take pictures of the Sweet Remano peppers from my aquaponics system.

Stirling engines - Balloon Power pistons

My original balloon power piston looked like this.

It had a connecting rod glued to the centre, and the other end of that rod connected to the cam shaft. The result was that as the air was heated in the chamber with the displacer, it expanded, filled this balloon, and pushed up the connecting rod.

I think it also pulls as the air cools and contracts, but that isn't very obvious either way. In that video (see link in first sentence) you can see the balloon inflating and giving the connecting rod a little push.

I'm amazed that the air can expand and contract at such a high frequency. I'm amazed these things work at all.

My power piston design was a little rough, and to be honest I was lucky that it worked at all.

The balloon kept slipping around under it's rubber bands, making the connecting rod feel some resistance as the balloon reached it's limits of free movement. The result was some extra friction where it wasn't necessary.

What I need is a bit more room for error.

With that in mind, I did some research and found what I think might be a useful design, and also came up with one myself that might work pretty well.

I found this one in use already and mine was made from a balloon neck, and a plastic bottle top.

To start with I created a plastic disk around 25mm in diameter by trimming off the sides of a plastic bottle cap. 

It was pretty easy to do with scissors, and a cut that went in a spiral gradually cutting away the side.

I also have a copper elbow that will be the power piston's basic form.

This will take the place of the ungainly plastic bottle with the hole hacked into the side as seen in the top-most picture on this post.
I cut the neck off a balloon and inserted the plastic disk. The connecting rod would be glued to the centre of this disk at the top.

The cut end of the neck is stretched over the copper elbow so that it looks like this when at it's highest. (this would be the end of the power stroke)

And like this at it's lowest.

It looks quite neat, and this is probably the design I'll use unless it proves to require too much air expansion to fill it.

My design includes the same section of balloon neck, and a cable tie to secure the top.

I tightened the cable tie with pliers  and then cut the rest of the balloon away with scissors.

It looks like this at it's lowest. Or near it's lowest.

It might be the case that this design will prove useful when used entirely at the low end. It requires much lass change in air volume to move 10mm up or down from it's pictured position.

I have no idea if it will be of any benefit to use this (green) design, but It should be easy enough to try both with my adjustable cam shaft.

120 Things in 20 years - When it comes to balloon power pistons for Stirling engines, I have standards above which, I will not go.

Making smoked foods - Soldering iron cold smoker

I bought some very inexpensive cuts of chicken labelled "Breast roasts for two" from my local supermarket.

They appeared to me to be a prime candidate for value adding.

I brined them in a solution of water, salt, sugar, pepper, and some lemon juice. I also threw in a couple of bay leaves. I have no accurate record of the measurements used.

Measurements are a tricky thing, because you cant rely on one batch being the same as the next. The amount of meat, and it's existing water and salt content create differences. You can probably ignore the existing levels, but the amount of meat being brined changes things a lot. The result is you cant just say x amount of water needs y amount of salt.

As I understand it, the process of absorbing the salt and sugar is done by osmosis. Salt is removed from the water, so the amount of meat in the brine changes how much salt is left in the brine. The result is the solution might need to be stronger to brine more meat. Irregular shaped meat like my chicken breast still on the bone, requires a bigger amount of water to cover it.

The good thing is, it will probably work well no matter what you do, but it does make a recipe a bit pointless.

That being said I used about 6 litres of water and a bit over half a cup of both salt, and sugar.

Brine your food in cold water, in the fridge.

After an hour and a half, I removed the chicken, pat it dry, and placed it into my lidded BBQ.

A 12 or 24 hour brine would have been better but I was pressed for time.

I also placed my trusty tin can full of holes inside, and jammed a 60watt soldering iron* into it at the base.

Perfect, cold smoke in minutes.

A total success.

The wood chips were from a store bought pack of smoking wood chips.

I'm pretty sure this would ruin the soldering iron for soldering, but this was one I've never used as it was way too powerful for anything I might do.

Previously I used my tin can full of holes with burning heat beads to keep it going, so I needed quite a few holes to support the combustion required to keep it alight. With the soldering iron, I can choke it down a lot more because it will never go out. I think I'll make a new tin can with less holes, and a large adjustable hole in the top by way of two lids with large holes that I can rotate to make whatever size hole I need. This should allow total control over how much smoke is made, and with some marks on the lids, I should be able to keep a record of what setting it was on, and what worked and what didn't.

But it does seem that everything works, no matter what you do so don't be too stressed over recipes and instructions. Just have a go, and you wont be disappointed.

120 Things in 20 years - Should have done a bit more research before trying to make a cold smoker because a soldering iron works really well.

*using a soldering iron for a cold smoker is NOT an original 120 things idea

Photography - Hack a macro lens from a zoom lens

I decided to make a more permanent macro lens.

The improvised one here was just too crazy to use. Everything had to be held together with tape, string, and luck.

It turns out it's pretty easy to hack a macro lens, if you already have a short zoom lens you don't need.

There are a lot of canon kit lenses that came with the cameras floating around out there for only a few dollars. The best price I saw was $3.98 US.

The lens I'm using is a canon EF 35-80mm zoom. I got it for free from someone who paid around $5 for it in Japan.

 The first step is to find some screws that might let you get inside.

The object here is to remove the front lens element.

My screws were found under a sticker, but different lenses hide the screws in different places.

Removing the sticker revealed 3 screws.

The sticker is useless after you remove it, so don't try this unless you want the change to be permanent.

That's the wrinkled corpse of the sticker in the background.

Undo the screws.

This allows the top lens element to be removed.

This lens cluster does the focusing as far as I can tell.

At this point you can take a macro shot, but the lens will leak a lot of light onto your censor. The black plastic surround covers a gap between the outer lens casing, and the inner sleeve that controls the zoom.

In my lens, it wasn't possible to remove the lens from the plastic surround, so I had to cut it off.

If you were trying to do this as a temporary thing, and wanted to try it before you commit, all you need to do is cover the lens front with something light proof with a hole around 2cm in diameter in the centre.

I'm guessing gaffer tape would work well.

The main thing is to create a cover for the gap between the outer casing and the inner zoom sleeve.

The lenses are of no use, but the plastic surround is very useful, because it has a screw thread to take filters.

A clear glass filter, or a UV filter will be the thing that keeps dust out of the lens.

The large black plastic thing is the bit we are keeping.

There was an extra hole that I filled with a screw to keep everything light tight.

A clear glass filter, and it's all done.

The results are pleasantly surprising. The original lens could zoom into around 6cm in width. This is closer to 1cm.

The focus ring no longer does anything, but the zoom still zooms. 

There are two ways to focus. 

Moving the camera or the subject until the scene is in focus is where you start. The distance from the lens that the subject needs to be is only around 5cm. Once you have the subject roughly in place, you can use the zoom to change the point that's in sharp focus. 

The zoom also works as a zoom, and changes the field of view between 12mm and 25mm from one extreme to the other. ie at full zoom (as per the shot of the pencil, you can fill the frame with a 12mm object)

All in all, not quite as functional as a proper zoom lens, but for $5 it represents a pretty good compromise, and something I'd call a total success.

120 Things in 20 years - If canon just made the front lens element removable, I wouldn't have needed to do this lens hack to convert a zoom lens to a macro. 

Photography - Seeing what's inside a canon auto focus lens

Opening up my old camera in an attempt to fix a stuck lens didn't end well, but it did make me want to open other stuff.

A mouldy $5 canon EF 35-80mm zoom seems like a good candidate.

I actually made it work better than it did when I started.

That's officially a successful repair.

We don't see many of those around here.

Odd feeling.

It turns out I wasn't being all that original when I used a lens cleaning cloth to make my macro lens hack light tight. It seems canon does something similar with a rubber band.

I attacked the rubber grip of the lens by lifting it up with a small flat head screwdriver, and sliding it up to reveal the three screws that control the zoom function.

Once that was done, the lens started falling apart. All it took was finding where the screws were in the first place. All the places I was told to start by the Internet were all false leads. I'm guessing things like lenses are made by the lowest bidder at the time, so these things probably change design all the time.

The only real stumbling block was this very fragile looking plug.

Luckily I had uncounted them when I pulled apart my point and shoot canon digital, and discovered they weren't really all that fragile.

I covered it with a folded bit of paper so the pliers wouldn't scratch the circuit off and pulled.

I also tried to avoid touching anything that looked like it might be copper. I have a feeling that touching stuff might lead to corrosion.

Probably just being paranoid, but it wasn't any really effort to avoid it. I should buy some cotton gloves for this kind of thing.

The little plug looks like this when it's unplugged.

Robot's are probably better at putting stuff like this back together, so I took a lot of photos as I was unbuilding it, so that I might have a chance of putting it back together.

That's a tip.

Take lots of photos of things as you pull them apart.

One part that was really fragile was this little bit of kit.

It's like a switch that drags it's contacts along a curved section of circuit board tracks so that the contacts keep in contact when you rotate the lens to zoom.

Or perhaps they adjust the aperture as you zoom, as I've noticed the available aperture range changes from one extreme of zoom to the other.

Who knows what it's really for, but I bent it convincingly out of shape when I was putting the thing back together.

I managed to fix it, but two of the pins will never be the same again.

This is the rear element. (the bit you can see a lens in on the left)

It's a cluster of ... three I think it was... lenses (two at least, but I think one was made of two), that I think also contains the aperture control.

The aperture control stuff must be in there, because there was nothing else with electronics in the lens.

I think this is me taking apart the lens that was really two lenses.

This things all had mould, but the other side of the one you can see in this pic had the most.

This is what I decided was the aperture bit.

I hope this isn't too technical for the reader.

Is bit even a word in this context...

Anyway, the remarkable thing is, after wiping down all the lenses with a lens cloth, it was actually an improvement.

That's the before and after shots with this lens.

Most of the milkiness is gone, but there is still a bit of mould on the front bunch of lenses, but I think I might hack them off and convert this thing to a macro lens.

I've been reading up on lenses, and how to hack bits off lenses that you dont want, and turn them into lenses that you do want.

Anyway, not a bad outcome for a $5, brand name, auto focus, zoom lens.

I cant wait to cut bit's off it.

120 things in 20 years - Where you will still find someone who thinks a lens doing it's auto focus thing is excitingly like having a robot. You also might find someone interested in photography trying to open a lens to see if there really is a man inside who does the focusing. (there's not by the way)

Photography - Improvised macro lens mould study

I got another lens from a junk bin in a camera store.

This one is a canon f 1.4, 35-80mm zoom.

It has an auto focus motor that makes a sound a bit like you might hear if you put a blender in a blender, but the auto focus still works.

The bits that don't work so well, are the lenses.

The problem is mould inside the lens.

Not uprising for a 500 Yen lens sitting in the junk bin of a camera store in the country that invented humidity.

That's a ridiculously close up shot of the mould.

Ridiculously close up.

I don't have any way of doing macro shots with my new camera, so I had to improvise.

I took the shot of the mould with this home made bit of kit.

The blue lens cloth is there to keep the light out of the improvised macro lens, because the small length of toilet roll acting as an extension tube  isn't light tight.

The lens attached (that's a generous description) to the camera is actually on backwards, and is resting against the other end of the toilet roll tube.

The lens resting on the red kitchen scrubber is the new one with the mould garden inside.

The torch is a torch.

The torch is there because the camera's lens has the aperture set as small as it will go (f36) to try to get at least some of the mould in focus.

I didn't really achieve that.

The exposures were around 30 seconds long (many minutes without the torch), and other people were working in the house at the time. My desk is a wobbly kitchen table top heavy with old CRT computer monitors, and all the other junk I like to keep at hand. As as a result it amplifies any movement from people, traffic, and the fridge and freezer compressors.

If you put a glass of water on a desk like mine and look at the reflection, you will see the reflected image dance all over the place. Normally it isn't a problem, because the camera and lens would both move at the same time, but with this contraption, there was nothing of substance connecting the lens and the camera.



The lens has mould in it.

The image on the left was taken with the canon 18-55mm lens that came with the camera.

The image on the right is taken with the mouldy 35-80mm lens.

The camera was set to the same settings for both shots.

Mould is not a friend of the lens.

The point of all this, is to point out that I wont be taking an angle grinder to my lens in some future post  without reason.

Actually I'll try to open it up and clean it, but there is a fair chance it's bits of glass are coated in a very delicate plastic coating, called coating. If that's the case the mould may have become a permanent fixture by etching it's way into the coated bits.

The mould appears to be on only one element, so I might be able to salvage some other bits and make a proper, mould-free macro lens.

120 Things in 20 years warns that when I say "proper" I mean the improvised macro lens might employ slightly fewer toilet paper tubes, and where they are unavoidable, they might be made a bit less wobbly and light leaky.

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