Cookie tin banjo

I was browsing through some old Firefox books a while back when I came across some folks talking about making banjos and dulcimers.  In particular, one fella talked about making a cookie tin banjo.  I had 4 cookie tins in my office that I saved after we emptied them last Christmas which seemed perfect for the job.  So, since I had one insignificant piece of junk I needed, I felt compelled to find the rest and build a banjo!

For the neck of the banjo, I used an old piece of bamboo flooring which I glued to a pine 1×4.  The floorboard by itself was not thick enough to provide support where it enters into the cookie tin.  I am not exactly sure that it’s the right thickness now but it seems to fit in my hand ok.   I left the bamboo top squared off but I rounded the back (the pine part) off smooth so I could hold it easily.  Now, I know you are curious how I came up with the shape for the peg head…I traced two Mt Dew cans.  This part is important…you have to use Mt Dew to get the thing just right. 

The tail piece is a chunk of an extra slat from plantation blinds we installed last Summer.  I think there must be a proper way to do this but it seems that the only measurements that really matter are the distance from the bridge to the nut (basically, from the wooden peg on the face of the banjo to the point where the neck joins the peg head.  My length is 25 inches though there is some flexibility in that size.  The distance from the bridge to the 5th string which attaches to the side of the neck is 18 1/2 inches.  Just about everything else negotiable as far as I can tell from reading in Firefox 3.

The hardest thing for me to do was carve the tuning pegs.  I tried using steel thumsbcrew and eye bolts and regular screws but none of those things would hold the string tight enough to tune.  That left me with carving wooden pegs which hold their position by friction.    I bought square 1/4 poplar dowel rods and cut off 2.5 inch sections to carve the pegs.  I rouded the bottom 2/3 of the peg to fit in the hole.  The top part I left square so I could get a better grip on it for tuning.  It seems simple enough but it was a real drag to carve them round.  My hands are killing me from messing with those tiny pegs.  Anyhow, I drilled a small hole in each to catch the string and they seemed to tune and hold pretty well.

I have a chromatic tuner that I got to tune my violin.  I messed around a bit to get the tuning right for the banjo.  I think it is pretty close although the 4th string doesn’t sound right to me.  We’ll see.  It definitely has a banjo sound. 

So, the $6 Martin banjo strings are about the only money I have in this thing.  Gosh, if only I had any idea how to play a banjo!

Solar Furnace - Results

We finally had a sunny day yesterday and I was able to get some real results from my solar furnace.  I had to make a few changes for success though…

First of all, I discovered that the mercury switch was not sensitive enough to really work.    The cold air outside was messing up the way it functioned.  I could not insulate the part of the air box where the switch was since the switch has to be able to move (if you’ve never seen the setup, a mercury switch is placed on a temperature sensitive metal coil which moves and allows the mercury to open or close the switch).  I decided to experiment with wiring the solar panel straight to the fan which actually worked very well.  The fan only came on when the sun was out and shining pretty brightly which was precisely when the best heat was being made.

The pipes that run from the furnace to the house were white originally but it seems that enough cooling took place in the pipes to make the system not work as well as I had hoped.  I painted them flat black like the rest of the system and it worked like a charm.  The pipes absorbed heat from the sun while transferring the heat through the system, thus helping with the whole “hot air rises” thing.

I also discovered that I had a few air leaks around the pipes and in the holes for the air pipes in the furnace.  I used silicone caulking (which will actually cure in about any temp regardless of what the instructions say) to patch all of the holes/gaps/leaks.

Once I made those three changes, I took temperature measurements of the cool air pipe from my family room floor and the warm air pipe from the furnace.  My floor air was 63 deg F and my warmed air was 84 deg F!  Hee-haw!  Eureka! Ding Dang, y’all!

Ok, so I was pretty happy with the results.  The fan kicks on and off with the sun which manages the heat pretty well.  I still need to boost the power to the fan to get a little more air flow.  I did some experimenting and was able to get a better temperature rise with a bit more air flow.  I will probably add another cheap-o solar panel to run the fan better.  I also need to find a better way to prevent backflow.  I really don’t like hanging a piece of plastic in front of the vent.  For now, it is working but I don’t like it as a long term solution.   I have glass to build one more furnace so I will probably build it out then figure out some way to deal with both systems.  Anyhow, for now, I am pleased with the solar furnace!

Solar furnace installation

I last posted a week or so ago about my solar furnace.  I mentioned that I needed to install the system in my window and get the fan/thermostat working.  Well, my friends, wait no longer!  This weekend I finished the installation of the solar furnace and even powered it with a small solar panel…but I am getting ahead of myself. 

My downstairs family room has 5 windows, 3 of which face southward.  A south facing panel is optimum because it gets sun almost all day as the sun progresses across the sky.  I read that 20 degrees from due south results in a 5% decrease in performance.  Luckily I have south windows but if I didn’t have due south, I would still try the furnace.  A 5% decrease would still make things interesting.   In addition to the direction, you have to consider the angle from horizontal of the panel so that it gets optimum sunlight in the winter when the sun is lower in the sky.  I have read various thoughts on the optium angle but the easy one for me to remember is “latitude + 10″.  Here in Charleston, our latitude is 38 degrees.  According to this calculation then, the optimum angle from horizontal is 48 degrees.  Using my trusty eyeball, I leaned the solar panel along the south wall of my house and tilted it at precisely 48 degrees.  To be more exact, you should consider doing a site survey to make sure you really have things right. I will probably just mess with it until it gets the best sun. In a more permanent installation, you would want this to be much more precise. Mine is easily movable. 

Anyhow, I built a box (which I insulated) to run a warm pipe and a cool pipe through my window.  The thermostat and fan are inside the warm pipe inlet so the warm air should automatically rise and slowly flow across the thermostat.  The rise in temperature should kick on the thermostat/fan and move the air a little better through the system.  As the warm air evacuates, it will cool the thermostat and turn off the fan. 

I mentioned in the last post on this topic that I could not drive the fan with a super cheap solar cell.  I was rumaging through the junk bin at the office when I found a pair of fans (actually, quite a few fans) that were lower amperage than my original one.  Anyhow, my new fan is rated at 12 volts and  0.16 amps.  I know it will run at 9 volts so I figured I needed a solar panel that would produce 1.44 watts (i.e. 9 * 0.16).  Harbor Freight sells a solar panel used for trickle charging auto batteries for $19.99.  Actually, the website has it for $14.99 but in the store it is more.  If I would have taken the printout to the store, they would have reduced the price.  Apparently the store and website are somewhat independent.  I didn’t have a printout and it wasn’t worth driving back for it so I paid $19.99.  Ok, back to the story - it will produce 1.5 watts which will run my new fan.  I don’t know if it always just produces 12 volts and the amps vary (because it produces differently depending on the strength of the sun) or if it produces 0-12 volts and constant amps, etc.  All that is to say, I don’t know exactly what wattage is driving my fan but it turns it.  It occurs to me as I write this that I should measure the output with my mulitmeter…but really, for now, I don’t care.  The fan turns fine in sun and that is my main goal.  Unfortunately, the fan will not blow the dryer vent louver open. I had planned to use a dryer vent to close the inflow when not in use.  I will have to resort to the “plastic over the hole” method I mentioned in the earlier post, to prevent back-syphoning.  And let me tell you, back-syphoning is real and a problem if you don’t deal with it…I quickly learned a lesson on that topic!

Ok, lots of words to describe all this.  The only problem is, I have not had a sunny day since I got this thing installed.  I wanted to post about this progress but I don’t have any real results yet.  I will have to post again with results.  I know it will make a difference, but I don’t know the extent.  Stay tuned!

�

Junk vibrobot

There is a category of electric critters called vibrobots.  I hesitate to call them robots , but I guess they are autonomous moving things.  Anyhow, as usual, I have bits of junk laying around that tend to rear up and get in the way now and then.  I have an old motor I salvaged out of a vcr or something.  I also had wire insulation hangers from my crawlspace insulation project.  That’s about all you need to build a junk vibrobot.  I bent a paperclip in an L-shape and taped a screw to one end of it.  The screw attached off center of the motor shaft throws the balance of the motor off so it vibrates.  Since it is attached to rigid, skinny wire feet, the vibrations through those feet on a hard surface translate into motion…random motion!  So, I zip-tied the end of the paperclip without the screw to the shaft of the motor.  I then bent the insulation hangers in an arc and zip-tied the 2 sets of legs around the motor.  I hooked a 9-volt battery to the motor contacts and away it went.   I tried putting little rubber feet on it but the bare wire on hardwood jittered the best.

 Mo, our silly cat had to get in on the fun.  The kids had a blast running the v-bot around Mo.  They had it timed perfectly so he would jump in the air when it started spinning.  For a cheap toy, it was quite a bit of fun!  Just a word of warning though…if you do this on your dining room table, be sure the cat is not around.  Also, be sure your wife is not around as she will not be impressed with the cat on the table or with the little scratches the v-bot feet leave.  Of course, this is certainly not the first time I have scratched the dining room table…but that’s another story.

Click the image for a short video

Here are some other vibrobots that other people have made.  I have seen some that are solar powered, some that look just like bugs, and some that are made or worse junk than mine. 

Itty bitty vibrobot
Bristlebot
Minty vibrobot

Solar Furnace - thermostat

Earlier this week, I posted about my solar furnace project.  I can’t take all the credit for the idea of a solar furnace as they have been around for a long time.  Most of them seem to be passive - relying on natural motion from the warm air rising through the system.  This sort of air flow is not typically very strong (though it can be), so cannot open a louver or check valve.  Just leaving the hot air pipe open is an option though physics will bite back at night or when it is not sunny outside.  Just as hot air rises, cool air sinks so at night, warm air will syphon from the house backwards through the system.  Some folks drape a piece of plastic over the warm air output so that the warm flow blows the plastic open a little.   Cool air cannot flow back through the plastic, supposedly. 

All that sounds nice, but I cannot be satisfied with simplicity when I can further complicate things with technology.  Being interested in saving a buck and doing the right thing energy-wise, I replaced our old thermostat with a digital programmable one a couple of years ago.  I noticed that the old thermostat had a mercury switch so I didn’t want to just throw it in the trash - instead I kept it in my stash of junk…and lucky I did.  This project is prime for my sort of junk.  I stripped the mercury switch and the bi-metallic temperature wire from the thermostat and connected it to an old computer fan.  I am building a box that will contain the thermostat and the computer fan.  The fan will pull warm air from the furnace across the thermostat.  While the air is warm, the mercury switch will turn on the fan which will blow open the dryer vent (that will prevent cold-air backflow) and send warm air into my room. 

Initially, I had planned to power all of this with a solar panel.  My fan is a 12 volt, 0.62 amp fan (though I ran it just fine with a 9-volt battery).  To drive the fan directly from the solar panel (at 9 volts), I would need a 5.58 watt panel (watts = volts * amps).  I may be able to get away with a little less but the cost of a 4-6 watt solar cell would still cost somewhere around $50.  I have various 9 volt wall-wart transformers from old gadgets that I no longer need.  For now, I will just drive this system from wall power.  At 9 volts, when the fan is on, it will draw around 4-5 watts - about the same as a nightlight.  I can live with that. 

My plan is to get all of this hooked up and running this weekend.  I will post again with the final project.  It is supposed to be cool this weekend so I guess the timing will be right!

 Spammers have been attacking this page so I have turned off comments.  If you would like to have a discussion, please post on one of the other solar furnace posts or send me an email message.  My contact info is in the “about/contact page”.  Sorry for the inconvenience.

�

A salty bunch

We gathered a jug of salt water from the ocean 2 years ago on a trip to Tybee Island near Savannah, GA.  I had in mind when I collected it to do an experiment to show the kids how to separate the salt from the water, how crystals formed, how to research stuff, etc.  I finally got around to it last weekend.  We did several experiments which have had mixed success.  First, we looked at various things under the microscope including epsom salts, table salt, and sugar.  In our first experiment, we suspended a string in a cup full of ocean water.  No crystals formed on their own so we are waiting on evaporation to expose the salt.  We also mixed epsom salts and water to form crystals.  This was sort of cool but not as dramatic as I had hoped.

Next, we supersaturated water with table salt.  Crystals have definitely formed on a suspended string.  Crystals have also formed on the side of the jar in which we are doing our experiment.  We put a bunch of salt in that jar so the effect is pretty dramatic.  This was closer to the effect for which I was hoping.

Both of these experiments were pretty slow to show much effect for kids though.  Being anxious for my kids to ohh and ahh at my scientific knowledge and ability, I found a recipe for making crystals from salt, liquid bluing, and ammonia.  As a base, we tried to use a piece of cardboard rolled up in a tube.  My expectation was that the cardboard would wick up the water and make a little crystal tree.  For some reason, the cardboard did not wick any moisture. 

I guess it was too dense (or maybe I was?) so the crystal tree turned into more of a crystal shrub.  Still, the effect started within a day or so.

 Anyhow, here are some additional methods to make crystals.  The kids were in to it for awhile and had a good time checking on the progress.  I’d recommend it for your own edification as well!
http://britton.disted.camosun.bc.ca/snow/boraxsnowflake.html

 http://www.squidoo.com/groweasycrystals

http://silken-didyouknow.blogspot.com/search?q=crystal 

http://www.science-projects-resources.com/crystal-science-projects.html

�

Solar furnace

Being a cheap-skate, I am incredibly excited about doing anything I can to put a little extra green in my pocket.  I have been looking online and thinking a lot about making a solar furnace to supplement our home heating.  We happen to have replaced 2 screen doors with full-length windows so I was presented with a couple of large pieces of tempered glass.

You can look around online for solar furnace or passive solar heat and find tons of additional information, but basically, these things work by capturing heat and using the principle that hot air rises.  I snaked clothes dryer exhaust tube side-to-side through an insulated (with sheets of styrofoam insulation) wooden box.  I covered the insulation with roofing felt to make the inside of the box black (plus I knew roofing felt would live through high heat).  I painted the box and the dryer hose with flat black paint so it absorbs heat very well. 

Cool air from my family room floor is pulled in to the bottom of the system.  The sun heats it as it sits in the tube.  The heating causes it to move upward eventually running back into my family room at about waist-high level.

This version does not show a blower on it yet so air flow depends purely on the principle of hot air rising.  I am working on a version that uses a small fan powered by a solar panel to move the air.  I’ll post more on that later as I get the details worked out.

Anyhow, for the results…I set this in the sun at about 4:30 one afternoon.  The input temp was stable at 62.8 degrees F.  I then measured the output temp. 

I could not believe it but my digital thermometer maxed out when the temperature got over 160 deg F.  The last picture I took before it maxed out was at 157.3 deg F.  I have no idea what the temperature actually got to but I saw at least a 100 deg F temperature differential! 

I have some more info to post on this but it will have to wait until later this week…

�

This sucks

I talked a little about drying beans the other day but I didn’t tell you what we do with the beans once they are dried.  Actually, we dehydrate and dry all sorts of things actually and this applies to everything we do.  As I have said before, I get hair-brained ideas fairly regularly.  I wanted to be able to vacuum seal stuff in jars but I couldn’t see spending the money to get one of the fancy vacuum sealers.  Foodsaver makes attachments for their powered products to evacuate the air from mason jars so I decided to give that a try with a modification of how the air gets removed.  I needed something that sucks! 

I can’t take sole credit for these ideas but I can’t remember where I saw a similar discussion on the idea.  Anyhow, a brake bleeder sucks just fine and, in fact, even has a vacuum guage on it to tell how much it sucks.  My first plan was to integrate the brake bleeder with the mason jar sealer.  Although I wouldn’t want to hand pump a brake bleeder all day long, I can pull a vacuum of 20 inches of Hg in about 30 seconds.  The mason jar sealer works perfectly for that.

Moving on to bigger and better, Harbor Freight (a cheap tool supplier) has a vacuum pump for evacuating hvac systems.  You simply hook it up to your air compressor and it will draw around 28 inches of Hg.  I couldn’t make it work as well with the jar sealer for some reason though I didn’t try too hard either.  You can (as I did) fashion some sort of a cup-like end for a piece of hose.  You could use a stout film canister or a small piece of tupperware or somehting similar. 

Punch a hole in the lid of the jar and put a piece of duct sealing tape (the shiny silver stuff, not regular duct tape) on the lid leaving the hole exposed.  Hold the cup over the hole and tape and start the vacuum.  When you are finished, slide the cup off across the tape sealing the hole.  The vacuum will further hold the tape in place providing a great seal. 

With a little effort, you could probably use the hvac pump with the jar sealer too so it is worth a try.  My “cup” solution works for things like large pickle jars or other containers that aren’t mason jar sized.

A traditional vacuum cleaner will not pull sufficient vacuum for this to work by the way.  You’ll need something designed to draw (from what I have read) somewhere around 15-25 inches of Hg to be sufficient.  Also, this is not a replacement for canning stuff that should be canned.  We only store dehydrated stuff this way.  Anyhow, it’s a pretty cool option for storing garden stuff and it can be pretty cheap depending on the junk you have laying around your workshop.

My first time…

They say you never forget your first time…knitting.  This weekend will forever be in my memory.  This special time of my life was beyond my expectation.  Why do people have such a hard time talking to the kids about…knitting? 

So I was inspired by the folks at Children in the Corn to try this form of loom knitting.  I have never been one to have enough patience to sit down and do stuff like this so their mention of knocking out a hat in an evening was appealing.  I have never heard of Knifty Knitter looms so I wandered out to our local junk retailer and bought the cheapest one they had.  There are a variety of looms for making all sorts of things but I wanted to ease into this.  My wife accuses me of too often jumping into things with both feet so I decided to honor her and only spend $4 on this newest hobby (if it becomes that).  So, the cheapest loom that the junk retailer had was the flower loom.  The package assured me that I could make all sorts of things besides flowers so I figured I was set for life.  Never mind the pink loom or the purple hook.  I was about to be a knitter. 

What I didn’t know was that the only pattern that came with the loom was for flowers.  A quick internet search turned up the only other pattern for that loom - the friendze scarf.  Cool…I have a daughter…she’ll dig a friendze scarf knitted by her Dad on a pink loom.  This isn’t wierd at all.  Sure enough, Abigail loved the first scarf I knitted.  She danced around as I worked on the first one.  She sang and laughted and giggled and hung around while I worked.  She even said she loved me for knitting her a scarf.  She took it to school to show her friends and teacher.  I really like knitting now…that’s the easiest $4 I ever spent!

I learned a few things along the way…superglue every other peg into the loom if you never plan to make flowers.  The pegs are designed to pull out for flowers but are a real pain for scarves.

Work around the loom clockwise but wrap the thread around individual pegs counter clockwise. If you don’t, you’ll gnaw off your own arm and beat yourself senseless with it…trust me on this one lefty.

Single color yarn is more difficult to work with than variegated.  Both are cool though.

Get more looms.  My daughter liked the first two scarves but I think she is ready for something cooler and bigger now.  These things are so simple to use that I will likely buy more and make more stuff.  I need to wear a winter hat in the cold as I have no hair to protect my noggin.  I tend to go through knit hats like I change underwear…at least once a month.  Being able to knit my own in an hour or so sounds pretty good to me.

If you buy a pink loom, don’t let your son catch you using it.  My boy doesn’t know why he teases me but he knows it’s funny.  That’s all I will say about that.

Special times…I will never forget my first time…knitting.  Now that I have done it, I can’t get enough.  I want to knit all the time - in the car, watching tv, outside in the woods, while other people watch.  I am a knit-o-maniac!�

Making Apple Cider - part 2

Yesterday I posted about how we found some apples and mashed them in preparation for pressing out the cider.  I’ll let the pictures do the talking mostly.  I’ll include some lessons learned at the end.

�

�

�

We quickly learned that adding one apple at a time into the crusher is much better than dumping in 10 at a time.  We didn’t empty the bucket for every apple but we made sure one was crushed before adding another.  We also learned that you get a lot more cider if you crush the apples a lot.  We ran several batches of apples through the press with a “poor crush” and got much less cider than when we really crushed the apples.  We only got 2 gallons of cider so we ended up spending $6/gallon which is not cheap, though it is still of value to me since it is fresh and educational.  Anyhow, we’re getting another bag of apples and will crush all of them completely.  I expect at least twice as much cider.  I’ll make a good crusher for next year so this won’t be a problem then.  Some folks completely pulverize apples in a new, only-for-apple-cider dispose-all (like in your kitchen sink).  I didn’t want to spend the money but they do get a great yield per pound of apples.  I’ll likely make some sort of hand cranked grinder.

We learned that yellow jackets and honeybees can smell apples from thousands of miles away and that they can fly at supersonic speeds to get to them.  Cover stuff up whenever possible.

Get a piece of metal to put between the bottle jack and the top of the wooden presing frame.  I thought of it before hand and am glad I did.  The bottle jack would destroy the wood otherwise.  Also, have several blocks of wood around that will fit into the basket.  The bottle jack probably will not fully press all the cider out at its fullest extension without adding blocks at some point to lengthen its extension.

Listen for stress on the wood when you are pressing.  The jack puts the whole system under a lot of pressure and you could tear things up pretty good if you don’t pay attention.  Wood will tell you when it has had enough.  Listen to it!

If the cider pours over the top of the wooden plunger, release the pressure and let it go back down.  Press it again and you’ll get more cider out.  Also, cut a drain hole in your catch pan or empty it often so the cider doesn’t re-absorb into the pomace when you release pressure on the bottle jack.

When you are done pressing, keep pressure on the pomace a bit longer.  Cider will drain for a short while after you stop pressing.

I drilled holes in a single row around the lower side and the very bottom of the stainless steel pot.  I am not sure if more holes would be better or just make for a weaker pot.  I will not likely add more holes.

Run the cider through a coarse strainer.  It just looks better to me without chunks of apples floating in it.

We read that apples sometimes (often?) carry E. coli and that homemade cider should be drunk at one’s own risk or else be pasteurized.  I have read several things but apparently heating it to 160 deg for 1 minute is enough to kill all sorts of stuff.  I also know that heating cider too much ruins the pectin and sort of erases the “cider” taste/texture.  We haven’t gotten sick yet but will likely pasteurize and can most of the cider.  Officially, I’d recommend you do too.  If you choose not to, at the very least, refrigerate it so it doesn’t ferment too quickly (good for 5-10 days).  Of course, you can ferment cider and make adult beverages too.  I’ll leave that for you to research.

All-in-all, this was a good time and I’d recommend building one of these if you have access to apples.  The kids had a good time and the cider is hard to beat!  Holler at me if you want a parts list or more specific/detailed pictures.  I am happy to help!

�