Monday, May 14, 2018

Runaway

Starter motors are not designed for continuous service - they are not provided with any cooling capabilities.  This is because the design expectation is that they will see only intermittent service.  They are high-current, high-power devices however, especially the ones that are expected to crank diesel high-compression engines.  Now hold that thought...

A recent discussion on The Retirement Project bears review here.  It seems that when TJ went to start his engine, the engine start push button stuck, leaving the starter motor running continuously after the diesel had started.  Because of the lack of cooling, a runaway starter motor is a serious problem - aside from destroying the starter, a fire could result.

I recall an incident where a young woman pulled into a gas station where I was refueling my car, and proceeded to fuel hers.  Her starter motor was running, after she shut down her engine (presumably it had been running since she started her car...).  Running, but running poorly - the heat buildup had caused the armature to swell and it was dragging on the field poles, creating more demand for electricity and even more heat.  I opened her hood and found the battery lead to be red hot, smoking, with all the insulation burned off.  Remember, this was at a gas station, where this car (and mine!) were actively taking on fuel.  I shut off the fuel feeds to both cars and then used a tire iron to break the red-hot wire (easy - copper is soft when it is red hot).  The cause?  Welded contacts in the starter solenoid.

One time when driving (I was 17 at the time) my father's 1959 Oldsmobile, the same thing happened to me.  Again, the tool of choice was a tire iron, and I used it to try to pry the battery connection off of the battery.  And failed.  Instead, the post and part of the battery plates came out of the top of the battery, complete with plenty of sparks and acid.  In retrospect, it is lucky I didn't get to experience a hydrogen explosion.  Again:  the cause was welded starter solenoid contacts.

I guess it is not surprising that this happens - these contacts carry prodigious current - 75 - 100 amps in a car engine and more for a diesel, and are connected to a very inductive load.  When they are asked to open, the magnetic field in the starter collapses, boosting the voltage at the contacts, keeping the current flowing for an instant even tho the contacts are open: an arc occurs.  Most of the time, the contacts continue to open, extinguishing the arc.  But if the contacts are already damaged from arcing, the arc gets a head start because the contacts are already hot...

In TJ's case above, the cause was not welded contacts in the starter solenoid, but rather a stuck starter button.  But in my experience, this is much rarer than welded contacts in the starter solenoid.  Regardless of the cause however, the remedy to a runaway starter is the same:  Disconnect the battery.

Easier said than done.

All cars, and almost all boats have a hard-wired connection between the battery and the starter.  In boats, the usual case is that that "Off-1-Both-2" battery switch is only carrying the house loads - the starter is hard-wired.

I believe that this is a pretty serious safety hazard.

Blue Seas M-Series Mini Selector Battery Switch
Those big battery switches can easily carry the starter current load.  Even the smallest ones have tremendous current carrying capabilities. Here's a mini Blue Seas one:
  • Cranking Rating: 10 sec. 1,500 Amps
  • Intermittent Rating: 5 min. 500 Amps
  • Continuous Rating: 300 Amps
For comparison, cranking Eolian's starter (Perkins 4-236 diesel) draws 200 amps - I know this because everything on Eolian goes thru the shunt for our Link2000 monitor. And everything also goes thru the battery switch on the power panel. Including the starter.  I can't take credit for this - Downeast (Eolian's manufacturer) built her this way.

If the starter on your boat does not go thru a battery switch (or THE battery switch), I'd sure try to find a way to make it so...





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Monday, May 7, 2018

Expansion & Bubbles

Everything gets bigger when you heat it.  Fact of the universe.
Water is one of "everything", so when your engine warms up, the cooling water in it gets bigger - it expands.

In older cars, space was left at the top of the radiator for the water to expand into.  In newer cars, the radiator is filled to the brim, and there is an external expansion tank.  There is always one somewhere in the system - there has to be.

Expansion tank on Eolian's engine
It is no different for boat engines.  But.  No radiator, no expansion space in the radiator.  But there has to be an expansion space somewhere in the system.  Right?

OK, now second thought:  air bubbles.  Where do they collect?  Yup, you got it in one - at the highest point in the system, eventually.  In a car, we're back to that space in the radiator.  It's easy to replace the air bubbles in the system with more coolant if they collect in the expansion tank.  It's a good combination of uses.  And in any modern car, the expansion tank or exit to the external reservoir is at the highest point in the system.

Ah, but in a boat.  In a boat, the "radiator" (there isn't one - it's a heat exchanger instead) is unlikely to be the highest point in the system...  Do you have a water heater that gets its heat from engine cooling water?  I'll bet it is mounted considerably higher than the engine.  How about a Red Dot heater (Eolian has both)?  Same question.  So where do the inevitable air bubbles accumulate?

Well, at the highest point in the system.  Always.  On Eolian, that was the water heater.  So, guess how effective the heater was, given that the hot water coils were filled mostly with air?  Yeah, not so much.

Expansion tank, above the water heater


It's been years now, but I installed an auxiliary expansion tank/reservoir at the inlet for the engine cooling water at the water heater.  And collected a lot of air in it.  The expansion tank on the engine simply got filled completely with water - an ineffective and irrelevant (and now removed) bulge in the system.  I put a 14 lb radiator cap on the engine expansion tank, and moved the original 7 lb cap to the auxiliary expansion tank by the water heater.  That way the cap on the engine would never release, and the one on the auxiliary tank would.

Big change in water heater efficiency!

So where do the air bubbles in your engine cooling system accumulate?




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Monday, April 30, 2018

Fresh Homemade Pasta

You like pasta?

Well, you'll like fresh homemade pasta even more.

Is it hard?  NO!

Marcato Atlas pasta machine
You will need a pasta machine - if you're on a boat, a hand cranked one is ideal.

Then all you need is flour, water, eggs, and salt.

Makes approximately 1 lb of pasta:
  • 365 grams flour
  • 8 grams salt
  • 2 eggs + water to make 181 grams of liquid
Why am I weighing things instead of following the more usual (American) standard of volume measure?  Well, because flour packs considerably, so the actual amount of flour you dump into your mixing bowl depends dramatically on how you packed it into the measuring cup.  And this is a recipe that is very sensitive to moisture content:  Too much and the pasta sticks to the rollers and cannot be successfully slit.  Too little and you simply cannot roll it.  So, get a scale and weigh the ingredients.

Mix with a fork, then by hand, and finally kneading on the counter until all the flour is incorporated.

Roll out into a log of roughly uniform diameter and cut into 6 equal pieces.

The initial passes thru the pasta machine are simply a continuation of the mixing, but in a shear regime that you cannot reach by hand.  Roll at position 1, fold, roll again.  Do this until all the unevenness in texture is gone.

Fold and roll again at position 3 (yeah, you can skip 2)

Roll again at position 4 (do not fold)

Roll again at position 5 (do not fold)

Hang each of the resulting pasta sheets on a rack to dry slightly.

Move the crank to the slitter portion of the pasta machine.  Slit each pasta sheet and hang the resulting noodles back on the rack, using a long spoon handle to capture and transfer the noodles.

Take the time to separate the noodles on the rack so that they don't stick together.

You can cook the noodles immediately in boiling water, or let them dry over night, or split the batch and do both.  The dry noodles will keep more or less indefinitely, but take considerably longer to cook than the fresh ones.

Trust me, it is so easy and so tasty that you'll never go back to store-bought pasta!





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Monday, April 23, 2018

Only One Expansion Tank Now

(Part one of this story is here.)

Like with so many things,the preparation for this task far outweighed its actual execution.

Corroding cast aluminum expansion tank

There are only 4 bolts that hold the expansion tank on the engine, and they do not protrude into the water passage.  This means that they were not rusted or corroded - they were easily removed.  Loosening the hose clamp attaching the tank to the heat exchanger, and the tank was easily lifted out of position.  Far less work than I anticipated.

It's out!


...and the corrosion is worse than I knew

It turns out that the worst of the corrosion was at the hose attachment spud.  It was so bad here that I fear that I could knock off that spud with a sharp blow.  Good to get this failure point off the boat.

In an earlier post, I detailed the time and effort spent in trying to find a replacement fitting that would serve as a thermostat housing and provide a connection to the heat exchanger.  That search satisfied, I thought I was out of the woods.

Not so much.

Since I was in there, I know that my son would chide me if I did not replace the 40-year old thermostat.  So I started a search for a thermostat for a Perkins 4-236, 160°F.  Well it turns out that none of the diesel supply houses in Anacortes could provide one corresponding to the part number in my engine manual.  Or even in a cross-reference manual.

I thought that the thermostat looked very familiar. The one oddball thing was this little device:

Jiggle pin

I told you I did deep research...  In typically British fashion, it is called a "Jiggle Pin."  Its function is to allow air bubbles trapped below the thermostat to pass thru it when the engine is not running.  When there is water flow, the jiggle pin moves up and blocks the hole, stopping water from bypassing the thermostat.  A nice feature, but not strictly necessary, since once the thermostat opens, there is free passage for bubbles, which will then accumulate in the highest point in the cooling system.

I did find some Perkins thermostats.  In England.  For $50, not including shipping.

So I went to my local NAPA store.  I LOVE NAPA!!  No pimply-faced kid behind the counter that can't do anything without the computer (you should see their faces when I answer their question, "What kind of car is this from?" with "It's a Downeast 45 sailboat with a Perkins 4-236 diesel...  they are paralyzed) - experienced countermen who know engines.  I showed the thermostat to the counterman, and allowed as how it sure looked like one for a small block Chevy engine...  he went and got one off the shelf and with his calipers we compared the Perkins and Chevy thermostats.  Yup, the $8 Chevy thermostat is a drop-in replacement, tho without the (not strictly necessary) jiggle pin.

And then the second, and harder problem:  I needed a 1.5" hose that had one end expanded to 1.75" to fit over my new fitting.  And it had to have a right angle bend right past the expansion.  And a straight section at least 8" long to reach the heat exchanger.  Try searching for that on line!  The NAPA counterman took me into the hose room and gave me his calipers and left me to search.  It took me two minutes to find a suitable hose, a NAPA 8349.

What's left of the hose after I cut off the part I needed.  There are still a couple of useful bends there...

So, thanks to NAPA, in the space of 15 minutes I had solved both the thermostat and hose problems and was on my way back to the boat.  Can I say it again?  I LOVE NAPA!!

Done!

I ran the engine until it was hot, the thermostat opened, and the bubbles had accumulated in the expansion tank.  Job done!

Expansion tank, higher than the water heater

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