Monday, November 19, 2012

Alaska Kodiak coal stove

 I use an Alaska Stove Co. "Kodiak" model stove for my primary source of heat.  This solidly built stove is made from 1/4 inch steel plate and cast iron hardware.  I believe these were made beginning in 1977, the year Alaska Stove was founded. Unfortunately, Alaska Stove no longer makes this model, or anything similar to it.  Their new stoves are all stoker-fed rice coal burning stoves, while this is a hand fired stove that will take nut coal or larger, as well as burn wood.  Unlike rice coal stoves, which need electricity for both the stoker and a draft fan, this simple stove requires no electricity.  Yet, it will run 12 hours unattended, giving it nearly the same convenience as a stoker stove.  And it is remarkably uniform in temperature over that time period.  The stack temperature typically stays within a range of 300F to 600F, and the hot air produced within a range of 150F to 200F.
 I received the stove without documentation or an outer shell.  However, it was clearly designed to have an outer shell, for the 1/4 inch plate on the top and rear have cutouts along the edges to create air passages.  I made a shell out of 4 inch concrete block.  The block shell creates an airspace around the outside of the stove which efficiently heats the air circulating through it while also making the stove much safer, for the block rarely gets hot enough to burn someone.  Two 8 inch ducts are connected to the shell.  The inlet has a fan to help circulate the air throughout the house.  It is a small fan which moves about 600 cubic feet of air a minute, but it runs continuously.  This way the house temperature is always uniform. The above picture shows the top of the stove and the air ducts. When the picture was taken, the air was exiting at 145 degrees.

To measure the flue temperature, I use an antique Wheelco thermocouple galvanometer.
This solidly made precision instrument is probably 75 years old and was used in an oil refinery.  It, and thousands of other valuable old items were slated for destruction in order to reduce the refinery's taxes.  This one escaped destruction, but still wears the yellow paint of death.   I cannot find any record of Wheelco.  It is unfortunate that this fine example of American engineering is nearly forgotten, due at least in part to tax laws that encourage the destruction of assets.

 After using the stove a few times, I realized that while it is a very good stove, it also had some serious shortcomings.  When shaking the grates, it was impossible to shake them without having coal jam in between them.  It was also too easy to go too far and dump the coal.  I lengthened the link between the grates until it hit the sides if the grates were rotated more than 15 degrees.  This has proven extremely effective.  The shock of the link hitting the sides loosens the ash and makes it fall readily, while it is impossible for coal to drop down and jam in between.

  Then there was no ash drawer.  This was a serious shortcoming in a stove that is over 2 feet deep.  Also, the ash door is surprisingly small.  I couldn't do anything about that, but I did make a drawer as big as I possibly could.  It has about 1/4 inch clearance all around.  This was a huge help, but there remained one problem.  Because the drawer was narrow, some ash fell along the sides.  This had to be shoveled out.  I took the stove apart and removed the supports for the firebrick. I drilled and tapped holes into them and bolted sheet metal ash guides to them. This gets about 80% of the ash that missed the drawer. 

 One problem with coal is that it takes a lot of air and a very hot fire to get it going, but once it is going, it needs only a small amount of air. In fact, I only open the main air door when starting, and then close it.  The stove then gets all the air it needs through the small openings in the ash drawer, and even these I have open only about 1/4 of the way.  I should point out that I have a very strong draft up my 25 foot chimney.  Since the coal burns so uniformly for 8-12 hours, an automatic control is not necessary.

Recently I added a safety feature: An automatic closer for the main air door.  Without that, I had to say close to the stove when starting, a process that may take more than a half hour.  Coal can surprise you, for it may smolder at a low burn for a while, until it reaches critical mass.  Then you can see stack temperatures approaching 1000 degrees F in a matter of minutes. Not a safe situation.  My safety system consists of an electromagnet which holds the door open, and a thermocouple controlled alarm with relay contacts.  When the alarm trips, the alarm cuts power to the electromagnet and the door drops by gravity.  I like this because it is fail safe. If the power fails, the door will drop.  If the thermocouple fails, the controller will alarm and the door will drop.  Still, I  consider this a safety backup only and would not intentionally leave the house and depend on the alarm. However, I could someday forget and this little thing just might save my house.  Here are some pictures:

The temperature controller:  An old Omega controller from my junk box.  Also in the box is a Sonalert audible alarm and a 9 volt "wall wart" power supply from some long ago discarded electronic gadget.
 The electromagnet holding the door open.  The electromagnet is another "wall wart" transformer, but this one has had one side cut off to turn it into an electromagnet.  Transformers make decent, and cheap electromagnets, for nearly everybody has some of these laying around somewhere.  This one was from a US Robotics 33k modem.  Remember those?  They were popular when nearly everybody was using dial up America Online.  As an electromagnet, this transformer uses only 63 milliamps at 9 volts.

 The electromagnet has de-energized, and the door dropped.  While the power is restored to the electromagnet as soon as the stove cools and the alarm stops, the magnet is far too weak to raise the door.  In fact, it has barely enough power to hold the door up.  Better that way.  Any disturbance would cause the door to break free and drop. 
 The arm that holds the magnet is attached to the stove bracket by a single bolt which is aligned with the air door hinge pin.  This way the magnet can be set to hold the door at any position, or even swung up and out of the way.

I believe Alaska Stove still sells replacement grates for these stoves. At least they did 6 years ago, when I replaced mine after acquiring the stove.  This stove was badly abused and seriously over-fired, warping the grates and the firebrick supports along the sides.  The front was warped too, and  the door would not close properly.  Since Alaska Stove did not sell the firebrick supports anymore, I had a local foundry cast new ones for me, using the old ones as a pattern.  I straightened out the front by intentionally over-firing it without firebrick in the front.  Then I pounded the warped front with a sledgehammer while the steel was soft.  That worked well, and the door closes properly now.

I built a 6 foot x 18 foot coal bin that holds approximately 10 tons.  Later I covered the bin with solar panels, in the process creating what may be the worlds only coal bin with solar panels.

I burn between 3 and 4 tons of coal each winter, at a cost here of $200/ton.  That is like getting heating oil for less than $1/gallon, or propane for maybe 75 cents.   However, the money I'm saving by burning coal is only part of the story.  My house is much warmer with coal heat.  My high efficiency propane heater delivered all it's heat upstairs to the living spaces, as it was designed to do.  This however, left me with a frigid basement which was unpleasant to be in during the winter months. By contrast, the coal stove heats the basement to 80 degrees F.  This heat eventually works its way upstairs, supplementing the heat arriving through the ducts.  Because of the stored heat in the basement, the stove can be out many hours before the house feels cold.  By contrast, when heating with propane, the house only felt warm when the heater was running.  Yet, even when running the propane heater for maximum efficiency by turning the heat down whenever possible, I still had some January propane bills that were larger than my entire season when heating with coal.

Wednesday, August 29, 2012

1970 Evinrude 6hp Outboard Motor

 I bought a 1970 Evinrude 6hp outboard to power my Sunbird to and from the ramp, and for when there is no wind.  I chose this motor because the price was right:  A few hundred $$ vs. $1,000- $1,400 for a new one.   Also, it was in very good condition.  In addition, it weighs only 43 pounds, while newer ones I looked at were from 53 to 85 pounds.   The weight advantage comes not from flimsy construction - in fact the Evinrude is impressively built - but from the fact that it is a simple 2 stroke design, unlike the modern 4 strokes.  The Evinrude is not as clean burning as newer designs, but this is a motor that will see maybe 10 hours use a season.  In addition, the motor needs to be removed for trailering. The far more expensive, and far heavier newer motors simply do not make sense for me, even if they are cleaner burning. The Evinrude has other advantages, too.  As a 2 cylinder 2 stroke, it has 2 power pulses for each crankshaft revolution, vs. only 1 power pulse for 2 revolutions in a single cylinder 4 stroke.  It produces it's rated power at lower RPM's than the 4 strokes, and is very smooth at all speeds.

       It is a good idea to check the water pump on these motors, and I found my impeller to be worn out, and the pump housing corroded.  Impellers are cheap enough, but housings are not.  I decided to save some money and bore my housing out, using my Harbor Freight Mini Mill.  I made a stainless steel liner from my scrapped Craftsman air compressor.  By lucky coincidence, their inside diameters were the same.  At right is a picture of the bored out housing and new liner.

 Here is the liner installed.  It is a press fit, and secured with J-B Weld.  Will it last another 42 years?  I'm not sure about that, but it will likely last long enough.  I believe this housing, and most other parts are original on this low-time engine.
 The inside of the lower end was in very good condition.  I snapped the two rear bolts while removing them, for corrosion held them fast.  Once again, I saw no sign that these were ever removed since new.  I was able to extract them, and found that the holes are 1/4" deeper than the 1" bolts used.  Since these threads were weakened by the corrosion, I replaced the bolts with new 1-1/4" stainless bolts, taking advantage of the extra threads at the bottom of the hole.  Since I plan to inspect the lower end annually, I don't expect the new bolts to have time to seize in the holes.

One other problem I had with this engine was a very stiff throttle.  I traced this to the bottom bearing of the vertical throttle shaft. Here they used a nylon bushing which had very close clearances to both the engine frame and the bevel gear.  Some aluminum corrosion built up between the bushing and frame, nearly seizing it completely.  It took a lot of effort to wiggle it free. Once clear of corrosion, I lubricated it with silicon grease, and it operates smoothly once again.

If you have this problem, be sure this hole is clear of corrosion, or it will come back.  I rolled up sandpaper and drew it through a few times.
Here is the vertical shaft.  The stainless clip goes on the top end, and the nylon link connects it to the bevel gear.  The bevel gear on the horizontal shaft is shown below right, and the shaft is below left.  The shaft is solid brass, and is in much better condition that it appears.  The bevel gear is aluminum, and also in great shape.  The screw pinches it to the shaft, but even if it is loose, it will not turn because both the gear and shaft have a flat side

The next thing I looked at was the tilt mechanism. Initially very stiff, it soon loosened to the point where the motor would fall back down.   I disassembled it to see how it worked.  It uses a plastic cone for friction and a very thick spring to put compressive force on the cone.  

Not shown in this picture is a flat fiberglass washer that is on the spring side of the tilt mechanism.  It is a thrust washer that prevents the aluminum pieces from rubbing against each other. The spring and bolt were originally aluminized.  I treated the rusted areas with rust converter, and then painted them.  I put silicon grease on the plastic cone when I reassembled it.

Taking the flywheel off proved to be a challenge.  Like nearly everything else on this motor, it appeared to be undisturbed for the last 42 years.  I bolted on my Harbor Freight puller, and it did not budge, even though the 1/4-20 stainless bolts I screwed into the flywheel were bending under the load.  I tried a few gentle taps, and nothing. I heated the flywheel, still nothing.  Finally, I supported the flywheel with 2 metal bars supported by sawhorses. Now I could safely whack the top of the puller without worrying about shock loads on the crank and bearings.  That worked. and I didn't have to hit it very hard. 

Removing the flywheel exposed an ignition system in pristine condition.  Everything looked original.  I replaced the condensers, but being cheap, I filed the points.  They are working well, and may last many hours.

 The points are set at 0.020", and care should be taken to be precise, for the point gap affects the ignition timing. Even better, use a timing light. If the Set Points mark is between the two marks on the engine, it is correct.  Time the top plug with the Set Points T and the bottom with the Set Points B.  1,000 RPM is recommended, but is not critical as the timing does not advance with RPM relative to the timing marks. 

The timing does advance with throttle setting, but since the timing marks move with the throttle, the timing light is accurate at any throttle setting.   Low speed operation RPM is primarily controlled by the timing.  The carburetor's throttle plate is at it's idle setting throughout the low speed range, while the timing varies.  At higher speeds, the timing and throttle plate move together.

Some pictures of the powerhead. A few screw heads are rusty, but that's about it.
This motor is remarkably easy to start, and runs very well throughout it's speed range.  It may be 42 years old, but it runs like new.  It was a good choice for my application, and it's age doesn't worry me a bit.

Thursday, July 26, 2012

AMF Alcort Sunbird sailboat

My latest project is a 1979 Sunbird sailboat.  This picture is as purchased.  Astute observers will immediately notice a couple of major problems!   First, the mast is being carried in a very poorly supported and unstable manner.  The second is that the trailer is absurdly short for this boat.

I decided I wasn't going anywhere with this setup, so I concentrated my initial efforts on the trailer.  Step one was to lengthen the trailer.  I was able to add 24" to the frame, and 36" to the wooden bunks.  Since the Sunbird manual recommends 4 keel rollers, I added them, using brackets made from Unistrut.  They make sturdy brackets, and were much cheaper, especially since I had the Unistrut on hand.

An inspection of the trailer wiring revealed that nothing was worth salvaging, so I replaced everything and installed LED tail lights.  The lights I bought claimed to be submersible, but they were submersible in the same way an inverted cup is submersible.  There were openings in the bottom for the wires, and the lenses were sealed with simple foam gaskets.  I made them truly waterproof by sealing all the holes and seams with hot melt glue.
  Now to tackle the mast support problem.  My goal was to have something that is sturdy, easily removable, and lockable.  I also decided to add a center stop light to reduce the risk of getting rear ended in traffic.  In addition, the mast protrudes about 4 feet past the trailer lights, which is a bit too far.  By adding lights to the mast support, this distance is reduced to 2 feet.  The support is a bar of aluminum 1/2" x 1 1/2", and the mast holder is made from 1/8" aluminum. The support has pockets on the back side that the rudder hinges go into. Then a 5/16" rod drops into the top rudder hinge, locking to it securely.  When the mast is installed, the rod cannot be backed out.  The mast is secured with a padlock, securing everything in place.

The lights plug into a receptacle next to one of the trailer lights.  The lights are bright and hard to miss.

The boom block's plastic pulleys were degraded from 30 years of exposure to the elements.  Since I have a 3D printer, I decided to put it to use, and print my own replacement pulleys in ABS.
I began by milling of the head of the rivets holding the block together. I milled as little as possible off, for I plan on reusing the rivet.

I reassembled the block using stacks of washers to prevent the block from spreading now that the rivet's head is gone.  This works well, and below is the rebuilt block.

I practiced rigging it in my back yard. Note the mouse-eaten sails. 

The Sunbird's maiden voyage was a success.  There are no leaks, and we didn't have any mishaps.  The Sunbird is a great boat.  Stable (for an un-ballasted boat) and easy to handle, she moves along nicely in gentle 5 knot winds.  A nice (and inexpensive!) way to spend a Sunday afternoon.
However, it is not very nice when the wind drops to zero!  The Sunbird took a surprising amount of effort to paddle in.  That experience made it clear that an auxiliary motor was essential.  The Sunbird manual recommends a long shaft motor, max 6 HP.   Unfortunately, long shafts are not common on the used market, and new motors are prohibitively expensive.  I found a 1970 6HP short shaft Evinrude in very good condition, so I bought it and then got to work designing a motor mount to enable me to use it.  This gave me the opportunity to solve a second problem.  Where to put the gas tank?  There isn't much room in the cockpit, especially when one is scrambling around adjusting the sails and switching sides to balance the boat.  Therefore, I designed a mount which both lowers the motor and holds a gas tank.  As a bonus, the motor is moved 10 inches off the stern, completely removing it from the cockpit area.  I made the mount from 1/8" aluminum sheet and 1" x 1 1/2" bar stock and bolted everything together with 47
10-32 stainless screws.   I wanted this mount to survive the worst possible conditions while protecting the gas tank and remaining securely attached to the boat and motor.  The mount can hold a 1 1/2 gallon tank, which is all I need.

I machined an aluminum cap with tubing fittings for the fuel and vent lines.  It is spill proof and impervious to water splashing in.

 These pictures are of the original concept.  I have since trimmed the top twice and raised the mount 3 inches.  The pictures above are of the original design while the picture below is of the second generation.

It is bolted to the boat with four  5/16" stainless bolts.  The upper part of the Sunbird's transom is reinforced with wood inside, making it plenty strong to support the motor in this fashion.  The 1970 Evinrude is a nice little motor.  It is extremely well made, and easy to start.  It is also remarkably quite at no-wake speeds, which is the condition that I will be primarily using it in.  At 6HP, it will be loafing most of the time, while a smaller engine would need to be run at higher throttle settings.  It is also not excessively heavy at around 45 pounds.

The motor moved the boat along nicely on my first open water test, going what I estimate was about 12 knots, and burning less than 1 gph. Full throttle was surprisingly quiet.  I was curious about the condition of the water pump when I returned home, and after dismantling, I found the pump housing to be badly corroded and the impeller worn.  Pumps housings, new or used, are expensive.  So, I decided to fix mine with a stainless steel liner.  By lucky coincidence, the inside diameter of the pump was nearly identical to the diameter of my scrapped Craftsman air compressor cylinders, which are stainless steel sleeves. I bored out the pump housing, and installed a section of the Craftsman cylinder as a liner.

Then I once again raised the motor mount to it's third, and final position.  Now the short shaft motor is mounted only 2 inches below the Sunbird's transom, and it is still plenty deep in the water.   It now clears the water when raised by 3 inches.

 Every sailing trip has made me aware of something that needs to be repaired or improved.  The latest is the rudder spring pin.  The hole in the rudder was greatly enlarged, so I made a pair of aluminum bushings to fit in the hole after I drilled it out to restore it to a round shape.
At right, the pin and bushings.  Note ugly hole in rudder.  Below right. Bushings on pin.  When installed in the rudder hole, the bushings meet in the middle.

Bottom:  Installed in rudder.  The larger diameter combined with the flanges should prevent the hole from distorting again.

 Another quick fix.  The bracket at the top of the mast was missing, and the previous owner simply tied the end of the boom cable to the mast.  I made one out of aluminum C channel.

 I quickly realized that raising the mast without assistance was a risky operation.  First, you are standing inside a boat with an uneven deck and obstructions like the boom pulley in the center of the deck.  Second, the boat is likely a bit unstable even though it is on a trailer.  Third, the mast is 20 feet tall, and you are at a huge disadvantage as  you are holding the mast only a few feet from it's bottom.  Lose your balance when you are halfway up and the mast can fall to the side, for the side stays are still slack, or it may fall back on you.  Once you have the mast fully upright, the fun is just beginning!  Now you have to maintain forward pressure on the mast while walking around the cabin and up to the bow to attach the fore stay.  Hopefully you have the fore stay in one hand, and it is not tangled up with the various ropes and rigging.  Now attach the fore stay to the bow fitting while not letting go of the mast.  Yes, it can be done, and has been done by many people for many years.  But it only takes one slip to lose control of the mast and probably break something. Even worse, you will be quite embarrassed if anybody was watching you at the time.   Rather than risk the embarrassment, I devised a safe and simple way to erect and lower the mast solo.  I attached a simple pulley to the bow fitting and then I tied the ends of the jib rope together.  I then tied my mast raising rope to the jib ropes and threaded it through the pulley.  Now I raised the mast in the conventional manner, but while taking slack out of the rope.  The mast is much more stable, with less of a tendency to fall to either side.  Once it is fully raised, simply wrap the rope around the cleats at the base of the mast, and the mast is secure.  You can now go up to the bow fitting at your leisure, without worrying about losing control of the mast.  I have also found it easier to tighten the fore stay since I can put tension on the rope while tightening the turnbuckle.  The pulley is not in the way of the jib, so I just leave it there and attach the jib to the next hole.  To lower the mast, simply reverse the process.  For me, the reduction of accident risk is well worth the few extra minutes it takes to attach and remove the rope.

This picture could have been taken in 1983.    A 100% vintage rig:   A 1983 Ford towing the 1979 Sunbird on a 1979 Dilly trailer.  Observant readers will notice that the sails and boom are removed.  A gusty crosswind was blowing across the ramp that day, so I removed the sails at the dock.