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.

Stately.

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.

Read More

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.

Read More

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...

http://en.wikipedia.org/wiki/Shishi-odoshi

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.

Read More

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.

Anyway...

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"
;120thingsIn20Years.blogspot.com
;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.

Read More

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 taste.com.au

Totally worthwhile.







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

Read More

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.

Read More

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.

Delicious.















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.

Read More