Stirling engines Ball bearings

From what Ive read, shiny wire does a better job of being a bearing on a tin can Stirling engine, but I want to see just how much extra friction a proper ball bearing race or two would add to the mix.

The friction levels are very low on these little engines.

They have to be or they just dont work.

But I want to try to make a more robust version, and perhaps even make one that is capable of doing some work.

Perhaps.

But probably not.

Any attempt to make a bigger tin can Stirling engine would also involve a lot more weight. And more weight means more wear and friction. Ball bearings will be the solution, as long as there is enough power left over to overcome the extra friction that bearings have.

That sounds a little contradictory, but bearings are really good at dealing with extra load on the rotating surfaces, but they involve a little extra friction than say... hovering in space.

So, with this in mind, I looked into small bearings.

They cost a lot.

A 12mm (internal) ball bearing race is a very standard thing that industry makes. They cost around $2 each retail, and are a weighty, very strong thing you might find in a motor bike, or in the centre of a bicycle wheel. They carry a lot of weight, and last for ever. But they have way too much friction.

The little bearings I want that are only around 1.5mm in diameter (internal) all seem to cost around $20 each. They are nothing like the robust 12mm ball bearing races I looked at.

Tiny.

Fragile. (actually not really, but compared to the 12mm version...)

Fragile.

And expensive.

But my fishing real has a dozen of the things. They cant really cost that much. It must just be that there is no real retail trade in them. I need three or four, so I thought of buying a $20 K-mart fishing reel, and pulling it to bits, and thats probably what Ill end up doing. But in the mean time, I really want to know if a bearing will be too costly in terms of friction.

I found a little computer cooling fan in my electronics junk drawer. I figured that should have at least one bearing.

These little fans dont put a lot of stress on their little bearings, but they last for ever and spin really fast, with little friction.

Last for ever, fast.

Perfect.

I started by removing all the bits that didnt look like a bearing.

How hard could it be.

Very, it turns out.

Thats the little bearing inside the small brass tube.




I spent a lot of time and energy trying to get it out.

I started by trying to knock out the pin by gently placing a centre punch (made of thick wire) on the centre axle, and smacking it with a hammer as hard as I could.

That didnt work so well.

Actually that didnt work at all.

I finally got it to give some ground by taking a hacksaw to it, and cutting through all the hard plastic surrounds that held the coils to the little motor.

This left me with a much more manageable bit of kit, that even looked like it might finally surrender its bearings.

In fact, this would be perfect if I could just get the pin out of the centre, so I could put the Stirling engines wire crank through the centre.

Centre.

Difficult

I put one end in over the opening of a little socket so the punch could get through and hit it hard.

Nothing happened, so I turned it over and hit it again.

Thats my trusty hammer at the top of the frame.

Camera shy hammer.

This time it worked.

Theres a little flange on one end of the pin that was making it impossible to tap out.

An amazingly strong little flange.

I hit it hard.

A lot.



Now that the shaft was out, I needed to knock out the bearings. I tried inverting the socket so its outside fit inside the brass sleeve, and rested against the bearing. I hit it again.

And again.

And some more.

In the end I just kept cutting.

The hacksaw was the only thing making any progress.

Who would think there would be a time where a hammer failed me.

Theres no real danger of damaging the little bearings here, as the brass sleeve is soft and bearings are made of insanely tough... stuff.

The bearings came out with ease, once the brass was cut through.

It turns out that the brass sleeve is really a brass sleeve with a divider in the middle.

No amount of hammering was ever going to get the bearings out.





Oddly, after all that hammering, the bearings still roll reasonably.

Reasonably.

The reason the little fan was part of my electronics junk drawer in the first place, was because it no longer turned. I think it was the cooling fan that I replaced on my rectifier, so it was never going to work perfectly.

The bearings spun freely enough after rotating them for a while with my drill. but there was a little bump in each revolution.

This pic is of the new ball bearing raced tin can Stirling engine running on my stove-top at around 200rpm.






200rpm is around the same speed on the same heat setting as it ran before, but it no longer runs from the heat of a single candle at only 36rpm, so the bearings have increased friction a little.

The brass sleeve was replaced with a cable tie for each bearing, and it turns out that cable ties fit nicely into my adjustable screw in bearing mounts.

Having the adjustable wire crankshaft I made turned out to be worthwhile, as I would never have been able to make just this one change. The smallest change in the crank shaft, in either the displacer crank, or the power piston crank makes a lot of difference as to how well my little Stirling engine runs, so it would be very hard to tell if it didnt work because of the bearings, or because of the different crank I would have been forced to make.

So.

A success as far as this little engine up goes. The bearings are small, but should be more reliable than the a plain wire on wire bearing. And it seems the friction loss is only around a quarter of a candle.

An interesting addition to this learning thing.





120 Things in 20 years measures the amount of friction in a tin can Stirling engine in "candles". I think I just invented a new metric.

Read More..

Entomology A bee!

All last summer there were no bees, and I had to polinate everything by hand.

The closest thing to a bee in the last year Ive seen, was a dead one at my mums house 10 minutes drive away from my house.

No bees.

They are all dying out everywhere on the planet.

Colony collapse disorder I think its called.

But I saw one, alive and kicking in my backyard today.

After chasing it around for half an hour as it frantically tried to escape my shade cloth I finally got a pic of it.

Thanks rapid fire camera maker.

Tis a poor pic, but it does prove a bee still lives.







120 Things in 20 years - Entomology - Yay BEE!

Read More..

Photography New to me Canon EOS 20D camera

My new camera is a lot like my old camera in so far as they both take pictures, and they are both 8 megapixel cameras.

But after that they diverge a bit.

The Sanyo Xacti that Ive been using for the last 1300 photos Ive taken was gifted at me by someone (Thanks anonymous company) when I really needed a replacement because all the point and shoot digital cameras Ive bought to make this blog (I think its 3 now) fall over just after 5000 happy snaps.

5000 seems like a lot when I put it in print, but in terms of time, that equates to less than a year per camera.  Sure they cost less than AU$100, but I still want more than a year out of anything I buy.

This one that Ive been using is still going strong, and does a pretty good job of it I suppose, but I found the interface very heavy going.

It has quite a few options and features, but all of them have to be accessed via a clunky multi-level menu system. That means that every time you want to do anything other than what its set to do now, you have to explore a stack of menus to finally find what you need, and by the time youve found it, the ladybird has finished eating its aphid, and flown away.

My new camera on the other hand is a zillion times better to work with. Ive only had it for around 10 hours, but it already feels comfortable.

Its taken around 1200 pictures so far in its life.

I have very greasy fingers.

Im eating zucchini and haloumi fritters.

Delicious.


The new camera is a Canon 20D. It was originally sold for around AU$1500 (Australian dollar) in 2004, and was described as a "semi-professional" or "prosumer" camera at the time, which of course means substantially more than other imaginary words and their associated imaginary metrics.

But on the whole, the camera rocks.

Thats my official rating out of 5.

It has a 4 GB CF memory card, which is the size of a bulky circa 2012 64GB mp3 player, and that cost around the same as a bulky circa 2012 64GB mp3 player. It takes a while to transfer photos, but it has very nice functionality, and best of all has an interface that works.

It also comes with some nice lumps of glass in the lens. It seems to be the lens that lets down lots of little point and shoot cameras. The quality of the photos taken by my new 8 megapixel camera is a lot better than those Ive taken with an 8 megapixel point and shoot style camera.

The second lens feels a bit like it might blow away, but at $10 its a very nice thing to have around.

The camera came with a Canon 18-55mm f3.5 image lens, with image stabalizer. Ive just discovered I love image stabalizing. Image stabalizing allows you to be a bit shakey, and have the lens do some stuff to fix it.

As I understand it, there are exactly two ways to do image stabilizing.

• 1. Project an image onto the censor, so that the image is a little larger than the censor, and the image has some extra image in the margins. Then have the camera track your shakey projection, and then use magic or software or something to knit together a nice crisp image.

• 2. Track some points on the image, and move the lens around a bit so that any given point on the censor always sees the same bit of the image, or move the censor to achieve the same thing.

• 3. Use gyroscopes mounted on at least two axes to resist the movement of the entire camera. Things spinning around like to keep doing it. If you take the tire off your bike (stop first) and hold the axle while someone else spins it as fast as they can, it becomes difficult to change the angle its on. This is why a spinning top (do they still have those?) stays upright, and is simply due to the universe being an amazing place.

Amazing!

The camera shows its age through its 8 megapixelness, as at the time of writing, thats about 16 megapixels short of where it should be.

I bought it from a second hand camera store in Japan for $150 with the Canon 18-55mm zoom, and I got the second lens, a Tamron 100-300 zoom, for $10 from the bargain bin.

Thanks Tom.

Toms a friend of mine.

Hes really good at buying way too much camera gear from junk bins. His hobby includes buying those instamatic film cameras that were big in the 70s. He likes to buy them when they have rolls of film still in them so he can process the film. In some subtle way, thats slightly different from buying some old photos.

Which is nice.

For him.

Hes kind of a time traveller, but he only gets to look, and doesnt get to choose what he looks at.

Mostly he gets to look at darkness.

Sometimes darkness, but with slightly mouldy edges.

Luckily, I dont suffer from collecting things other than my collection of odd people I know.

Toms one of my favourites.

Thanks Tom.




120 Things in 20 years - One of the best parts about getting my new, second hand Canon 20D camera, was getting to look at the Japanese supermarket junkmail it was packed in. Its been 20 years since I was in Japan, and the junkmail paper is now of even better quality.

Read More..

Fire Quicker more durable ethanol stove

A while back I made a pretty convincing ethanol camp stove out of a coke can.

It worked well and looked like this when it was running.

Ive used it a bit since then and its definitely a practical addition to any backpack.

The problem is its starting to show signs of aging. The can expands and contracts, and there is now a crease where extra gas flows giving an uneven flame.




In my model (also not my design) I used an inner sleeve with holes at the top to let the gas out. The result is that the trapped ethanol (spirit/alcohol/methanol) between the outside wall, and the inner wall boils the spirit, and creates a gas jet that looks a lot like a normal BBQ burner.

One of the problems was trying to get the top of a coke can to fit into the bottom of a coke can. Its tricky because (of course) they are the same size. It can be done, but involves gently stretching the outside one and it takes a lot of messing about.

Now Im being pretty fussy here. The little burner works really well, but it did tend to leak fuel around creases that formed in the join between the top and the bottom sections.

Someone on a Stirling engine forum pointed me towards a different method of making one. This method involves no holes, but it just encourages those creases that mine developed by itself, and I think it might be a winner.

Theirs also used a drink can, but I think it might make a more robust version if I used a tinned food can.

So, to start with, I peeled a normal, every day food tin.

The first step was to trim it to size.

I needed the top to fit into the bottom, so the first thing to do was punch a hole in it to enable a cutting tool to get in there.

I used that mystery tool that pocket knives have.

Probably a leather working tool or something.

Who knows, just punch a hole in the can.

Next jam in some tin snips or something to make a nice cut to separate top from bottom.

My tin snips are stupid, so I ended up using scissors.

This isnt the best way to use scissors, so dont do this at home unless you actually own the scissors.





One very good method of cutting a tin can, is to just tear it by grabbing a ragged tail of tin with a pair of pliers and twist. If theres a groove to follow, it actually makes a pretty straight cut.

As I said, I ended up using scissors to trip everything to it was nice and neat.

I made the inside sleeve (the one on the left), slightly taller than the other so the pot could sit on the rim and let the gas escape from the gap between the outside sleeve.

I bent a series of grooves in the base of the inner sleeve so that they would allow the flow of gas, and also allow the inside sleeve to fit inside the outside sleeve.

This was simply a case of grasping with pliers, and twisting them to the left, and slightly down toward the centre.

Next I inverted the inside sleeve and carefully positioned the outside sleeve over it so that I might press the two together by stamping down with my foot.

Which failed completely.

Read More..

Stirling engine ver 2

I made a few changes to My little home made Stirling Engine.

Change is always required when your engine seizes after only 55 seconds.

This one ran until the plastic bits caught fire.

Much better...

The original displacer popped itself to bits when it got hot enough, so this new version has a different design thats open to air travelling through it.

The autopsy also shows why my little engine stopped so suddenly. There is only around a quarter of an inch of air above and below the displacer when its at its extremities, and the bottom popping off made the displacer touch the bottom of the can it was in.



I replaced the can surrounding the displacer because I had to use a can opener to get the displacer out, and reattached the power piston balloon.

In the process of building the new displacer can, I discovered a new way to drill a hole that suits my personality perfectly.

You punch a hole with a nail, then rip a circular hole with pointy nose pliers in much the same way as opening an old style tin can of fish that the eater would open with a key.





If you arent old enough to know what Im talking about it, count yourself lucky and get on with it. You havent missed a thing.

I drilled a few large holes in the top and bottom of the displacer, and packed it full of stainless steel, kitchen scrubber pad.

Apparently this works, and acts as a thing called a regenerator.

A regenerator can often be found on a Stirling engine and acts to store heat between the hot and cold sections as the air moves between the two.



The regenerator material collects heat from the freshly heated air inside the can the displacer is in. As the heat is displaced from the hot section to the cold section, some heat is removed and stored in the material. This is a good thing, because we want the cold side of the equation to be as cooled as possible. When the cooled air returns to the hot end, it picks up the heat it dropped into the regenerator on the way through, making it heat up more rapidly.

Its not by magic that the heat knows when to sit and when to be picked up, just that the air is hotter on the way up from the heated section, and has cooled a bit at the top before coming back through the regenerator.

I put the new displacer in its tin can, and threaded its wire through the bottom of the top can that holds the crank shaft.










In the process of de-constructing the first version, I bent the shaft a little, and it never ran quite as smoothly again. The little Stirling engine took a lot more heat to get it going this time, but Im not sure if it was due to the new design of the displacer, or just due to the fact that every thing was a bit warped.

Friction really kills these things, so making sure the shaft is straight is a must.

It does run, and its going a lot faster than the first version, but I suspect that has to do with all the extra heat from using a gas burner rather than a candle, and not some gain in efficiency.

I think I now know a little more about these interesting engines, and a little more about the universe in general, and I think Ill have another go at building a better one. Id really like to make one efficient enough to run on the waste heat from my wireless router so it could just jig around all day for free.



120 Things in 20 years is finding the universe yet more interesting as a result of building this version 2 of my first, working, home made Stirling engine.

Read More..

Stirling Engines My first Stirling engine build

In spite of my video camera running out of battery during filming, I managed to get the first (and only) moments of my first Stirling engine running.

Tis a funny kind of beast running so slowly and deliberately.

I officially like Stirling engines. Mine looked like this...

It ran for a total of about a minute before the displacer fell to bits. It was sealed airtight, and as it got hot it just popped. It turns out there isnt really any need to make it air tight.

I think.

My displacer started life as a soft drink can.

I marked out a straight line to cut it down to size.

I took a guess as to what size it should be.

I scratched a series of arcs with a bent piece of sharp wire, each at different points, to find the centre, then punctured it with a drawing pin. 

I marked out another can, but this time much shorter.

Then squashed the big one over the little one after turning the little one upside down.

This gave me a sealed can again.

I glued it with super glue.

The gluing was what killed my brand new Stirling  engine after only 60 seconds. As the heat increased, so did the pressure inside the sealed displacer, and eventually it popped open.

I poked a straight length of fencing wire through both holes, then bent and super glued one end to stop it slipping through.

My wire originally had a slight loop at the other end, but I had to cut it off to remake the thing after I glued myself to it.

Dont do that.

And if you want to be really scared, use super glue, then adjust the dials and buttons on your new camera with the same fingers.

Anyway, the main thing is stick some wire through the displacer.

Next I took a tin can and smacked a hole in it with my familys trusty meat mallet.

This meat mallet used to be my mothers (it probably still is), and was used as the household hammer for as long as I can remember.

Here we see the entire family history of hammering.

Actually thats half the family history of hammering. The other half is of course, on the other side.







So then, I took the length of wire sticking out of the displacer (soft drink can thing), and threaded it through the bottom of the tin can.











Like this.

Its a bit difficult to see, but thats the soft drink can displacer thinggy under the tin can.









Next, I took another tin can and drilled a big hole in the side.










And sanded down a small plastic bottle so that its contour matched the tin cans.










Then cut a really big hole in the side of the small plastic bottle.

Something like a pill bottle would work.

All this, so I could glue the small plastic bottle on the side of the tin can with a big hole in the side. 

Next, I stretched a balloon over the entire little plastic bottle, and pulled the slack so that it was tight everywhere but the top.

I also glued a length of wire to the centre of the slack bit.

This, believe it or not, is something called a "power piston".

Ill explain what all this stuff does later.


Next I bent a crank shaft, and some mounting points for the wires coming from the displacer (through the bottom of the tin can), and the wire glued to the balloon (power piston)

The crankshaft has one offset bit (offset by around 8mm) to attach the displacers wire, and another to attach the power piston wire to.

The two offset, (bent out) bits, are at 90 degrees to each other.

So from the left...

straight, then down, then straight, then back up to the original.

That makes the first cranky bit.

Then continuing straight, then back, then straight, then forward back to the original plane.

That makes the next cranky bit.

If you look at the crankshaft end on, if one crank was at 12 oclock, the other would be at 3 oclock (or 9)

I found this almost impossible to get on camera (or to explain), but it looks like this.

Its probably best seen on the video.

The crankshaft is lightly held in place with two inverted U shaped bits of wire taped to the sides. (just visible near the top, left rim of the device)

I stuck a cardboard disk about the size of a CD onto the end of the shaft to act as a flywheel, and then added nuts and bolts with blu-tac until the thing was balanced.

To get them in the right spot, I put the disk in a random place, and if it rolled back to a different position, Id stick on a weight so it wouldnt.

I should have been able to do this with just one weight of the correct size, but for some reason it was beyond me.

So...

• The displacer is the soft drink can thing inside the bottom can. 
• The bottom can is sealed ([buy - EDIT  - note from the future-  Who makes errors like this?] by the top tin can) except for the small hole in its top that has the displacers wire poking through.
• The displacer travels up and down inside the bottom tin can with a total travel of around 1cm.
• The displacer gets very close to the top and bottom of its tin can container, but never actually touches.
• The displacers wire is connected to the crankshaft (between pink beads)
• The power piston (pink balloon) is floopy, and connects to the crankshaft 90 degrees offset from the displacers crank.
• The top tin can is there to hold up all the other kit, and as the top seal for the chamber holding the displacer (soft drink can thing)
• When the air inside the bottom tin can heats up it expands, forcing the power piston up. This turns the crank and gives the device its power.
• As the device rotates, and the displacer moves down, forcing the air up and away from the heat, so it cools and contracts. 
• When it contracts, the power piston is sucked down.

Thats pretty much it. Repeat as desired, or until something breaks. 

Some light oil can be added to any surfaces that have friction. (where the displacer wire moves up and down into the bottom tin is a high friction area)

==============>>> IMPORTANT!!! Note from the future - It turns out you probably shouldnt add oil to the point where the wire slides through the can. Theres a chance of explosion as the oil is heated to a gas. <<<================

120 things in 20 years - I made a Stirling engine!

Read More..

Stirling engine Success!

I just made an engine!

I even think I got it on video.

It ran for about a minute at around 78 rpm before making a popping sound and seizing up.

Which would have been perfect if it was connected to an old record player...

playing a very short song...

that I only wanted to hear once.

The camera battery went flat during filming, but but the video should be on there. Ill find out tomorrow. If not, Ill just fix it.

Yay me!

More later...



120 Things in 20 years is very pleased with itself       :{)

Read More..

Stirling engines A complete history of Engines

Some time ago, somebody invented the steam engine. The steam engine works by heating water in an airtight container to make steam. The steam is massively expanded water, and the result is lots of pressure.  Once you have lots of pressure you bleed a bit of that pressure intermittently into a piston, and the piston gets pushed. Connect that to a crank, and you have rotational motion, and an industrial revolution. You also have lots of factory workers being blown up in hideous, explosive  accidents, with all the screaming, and loss of productivity that goes with being killed.

Later someone invented the internal combustion engine, and the turbine engine. These run on fossil fuel. They had a pretty good run until somebody discovered it was making us sick and killing everyone.

The turbine engine is a big thing you tend to stick to the ground in a power plant and make electricity. That way the factories could all have much safer working conditions where hardly anyone ever got blown up, but it also kills the earth a bit. Just a little every day. And sometimes some of them explode anyway. Thats not so good, because some use uranium to make the heat, and that never ends well.

Anyway...

The internal combustion engine tends to be used in portable things like cars, because they pack such a lot of punch for such a small weight in fuel. They also kill the world, just a little bit each day, and sometimes explode, and sometimes just mash into each other, and mash into other things that tend to be near roads. They do a lot of mashing.

The main advantage with the turbine, and internal combustion engines, is that they spread out the damage. Just one or two people from any given factory at any given time get killed by them rather than taking out half the factorys workforce all in one go like a steam engine disaster might. The mayhem and disaster is spread out so that each factory takes just a small share of the disruption to productivity. Except perhaps with the uranium stuff. I think thats why Australia is shipping all our uranium to distant countries. To move it as far away as possible.

Anyway...

A Stirling engine on the other hand is a slightly more peaceful beast that doesnt really do a lot, but what it does, it does pretty thoughtfully. Historically it fits between the steam engine and the stuff we use today (2013, just in case someone reads this in 40 years). The Stirling engine is an engine that uses the difference in heat between two of its bits of kit, to make stuff spin around without all the explosions.

There.

Thats the design description out of the way.

Its very safe, because it doesnt have a pressurised container. It needs a source of heat, but that can be solar, or waste heat from something else. Rotting compost, your wireless router, whatever. They are not a very powerful engine, which is why the internal combustion engine took over, and they are not very responsive to sudden changes in desired power output. Thats also why the internal combustion engine took over. And they are not very powerful... Internal combustion engine blah blah blah.

So...

The most beneficial thing as far as Im concerned is that they wont blow up and kill me.

Theyre not very useful. But thats not going to stop me making one.

The kind of thing that will stop me making one, is more likely to be that I have no idea how.

Ive never made an engine before, and have also never met anyone who has, but it turns out they are a pretty simple kind of beast, and with a bit of luck, wire, string, and the total combined wealth of human knowledge stored on the Internet, I might be able to make one.

People are very clever, and there are some really helpful ones out there that are willing to help me.

Ill be trying to make a very small Stirling engine that runs on the power of a small candle, that will do no work, but will hopefully work.



120 Things in 20 years - Stirling engine - It might go round and round.

Read More..

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 isnt 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.

Im amazed that the air can expand and contract at such a high frequency. Im 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 its rubber bands, making the connecting rod feel some resistance as the balloon reached its limits of free movement. The result was some extra friction where it wasnt 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 pistons 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 its highest. (this would be the end of the power stroke)

And like this at its lowest.

It looks quite neat, and this is probably the design Ill 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 its lowest. Or near its 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 its 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.

Read More..