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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Monday, April 16, 2018

Ricotta, Again.

Milk is one of those strange products...  apparently they really, REALLY want you to buy it in gallon jugs.  Oh, they'll sell it to you in 1/2 gallon jugs, but for only a few cents less than the gallon jug.

So, being the frugal person that I am, I always buy the gallon jug,  even tho Jane and I frequently don't make it thru the gallon before it starts to get "strong".  Maybe "stubborn" is a better description for a person who refuses to buy the smaller container even tho it fits his purposes perfectly.

And then recently I had a thought, "I wonder if 'old' milk would make acceptable ricotta?"

And delightfully, the answer is a resounding YES!

So, now instead of it being a rare event, I make ricotta at the end of nearly every jug of milk, adding enough from the new jug to make up the difference, because usually there is not enough for a full batch left in the old jug.

And this frequency has led to some experimentation.  First, while ricotta can be made with just about any food acid (lemon juice, vinegar, etc), we like the flavor and texture of that made using buttermilk best.

Second, always add some salt to the curds as you are scooping them out into the cheesecloth to drain.  A little salt really improves the flavor.

Third, try using garlic salt instead of plain salt - it is a delightful addition to the ricotta.

Or try adding finely chopped fresh herbs to the ricotta for another delightful variation.



And since Jane always seems to have a container of heavy cream in the refrigerator, I tried substituting cream for some of the milk.  And here's where I learned something else...  Jane usually buys the "Ultra Pasteurized" variety because it keeps so well.  But as it turns out, the ultra-pasteurization process heats the dairy product to a higher temperature than regular pasteurization, making it unsuitable for cheese making:  it will not form curds.  At all.

My first attempt at cream-enhanced ricotta, substituting a full cup of cream,  produced a cheese that was way too "moist".  In fact, you couldn't really spread it on a cracker - more like you needed to use a spoon.

But problems are often a boon in disguise.  I have found that the ultra-pasteurized cream can be used in making ricotta - as a moistening agent.  But just not so much.  At a level of 1/4 cup in a batch, it produces a ricotta that is delightfully moist and rich.


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Monday, April 9, 2018

Easter Egg Hunt

Perkins 4-236 Expansion Tank

Eolian has a diesel engine, a Perkins 4-236.   Because this is a marine installation, there is no radiator (instead there is a heat exchanger), and therefore no expansion space in the radiator.  For the marine installation, Perkins created a cast aluminum tank to provide the expansion space.

Tho the engine is still in its prime, the tank is failing (galvanic corrosion because it is in contact with steel?  Probably.)

One more lead-in:  An expansion tank should be the high point in the system, so that bubbles and air trapped in the system accumulate there.  But Eolian has an engine-heated water heater which is mounted above the engine, making it the high point in the system.  Long ago I added an after market expansion tank at the water heater engine cooling water inlet, so that we would not accumulate a big air bubble in the water heater, drastically reducing its heating capacity.  Eolian does not need the expansion tank on the engine.

So the fix to the failing expansion tank is simple, right?  Just remove the tank.

Not so fast.  The expansion tank traps the engine thermostat against the casting it is mounted to.  With the tank removed, we will need something else to hold the thermostat in place, and provide a connection for the 1.5" hose that carries the water from the engine to the heat exchanger.

My first thought was to contact our local diesel engine supply house, looking for a Perkins part to bolt on in place of the tank to do just that.  No luck.  Apparently Perkins made that special water outlet casting (which bolts onto the front of the head making a right angle turn upward and providing a four-bolt mounting for the thermostat and the tank), just for use with the expansion tank.  It seems that all other non-marine installations have only a two-bolt mounting pad for a standard water neck/radiator hose connection.

I considered just making a flat plate that gets bolted onto the platform to trap the thermostat, and then drilling it to accept a standard small block Chevy water neck.  I am still considering this option.

But wait...  What do you mean non-marine Perkins installations?  Where else are Perkins 4-236 engines used?  Very little research revealed that the Perkins 4-236 may have been the almost-universal industrial small diesel:

  • Taxi cabs
  • Fork lifts (Hyster)
  • Towed air compressors
  • Towed welders (Lincoln)
  • Industrial tow vehicles, eg luggage tow trucks on runway ramps (Clark)
  • Farm tractors (Massey)
  • ... and more
Water outlet casting, thermostat, and water neck
For all these other installations, it turns out that Perkins made a whole host of water outlet casting and water neck combinations, with the resulting water flow directed to the left hand side of the engine, straight ahead, straight up, to the right, and several angles in between.

Wonderful!  A whole new universe of possibilities has opened up!

I contacted my brother-in-law back in Indiana (thanks Tom!) who is an antique tractor collector, and he provided me with several contacts for Massey tractor salvage yards, many of which provided additional contacts...  you know how this goes.  Almost everyone I talked to was very friendly and curious about my problem ("Did you say the engine is mounted in a boat??").  Finally, I found that Massey (tractors) part no. 37762701 would provide me with a water outlet facing forward, and to which I could (hopefully...) bolt a Chevrolet small block water neck.  This part is available new for a cost ranging from £19, $57, to $295 depending on where you look.
Massey 37762701
But I continued the search, this time starting with Lincoln welders, which also used the Perkins 4-236 engine.  In the way of the Internet, that led me hither and yon, but surprisingly, I ended up on a forum where boat owners with 4-236 engines were discussing using JBWeld to repair failing expansion tanks.  And one of the posters mentioned Trans Atlantic Diesels, and that they sold a number of parts that addressed exactly the problem of failing expansion tanks on Perkins diesels.  One of the solutions they sell is a combination expansion tank, exhaust manifold and heat exchanger, made by Bowman.  This was more than I wanted or needed (I've already replaced the heat exchanger with a Monel one, and replaced the exhaust manifold with a stainless steel one), but that forum poster also mentioned that supplied with this kit was a part that bolted directly onto the existing water outlet, trapping the thermostat and providing a hose outlet going to the right side of the engine...

Exactly!
Oh. My. Gosh.  This is exactly what I started out looking for originally!  So I called them.  You'll want to talk to Sherrie - she is by far the most knowledgeable about Perkins engines, and in particular the marine versions, of anyone that I have talked to in this long journey.  Yup, they have such a thing!  But the one they sell with the Bowman  unit is designed for 2" hose, and my setup uses 1.5" hose...  Sherrie said they'd fabricate one for me with the 1.5" outlet for no additional charge!  And when I called back to provide the Perkins part number for my thermostat, she was already downstairs talking to the fabrication shop!

The Easter egg hunt is over.  The second part of the story, the actual removal of the expansion tank and installation of the new water neck/thermostat housing, is here.


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Monday, March 26, 2018

The Hidden, Never-resting Enemy

If your boat has an inboard engine, chances are that it has a shaft log - you know, that place where the prop shaft exits the hull.  This cannot be a mechanically rigid seal because it needs to accommodate movement of the engine on its mounts, and movement of the prop shaft in the cutlass bearing.  Typically then, regardless of the seal type, the shaft log includes a short length of rubber hose, one end of which is clamped onto the rigid hull fitting, and the other end onto the actual seal housing.

OK, so it's below the waterline and therefore needs to have two hose clamps on each end:  four hose clamps in total.  Also, typically, the shaft is slanted down, towards the aft end of the boat.  And it's in a typically hard-to-access location.

Add all this together and what do you have?  An opportunity for the bane of all boaters to work, silently, unobserved, trying to sink your boat.

No seal is perfect; this means that there will be the occasional drop of sea water exiting the seal.  Because the shaft is slanted aft, this lone drop will travel aft, along the bottom of the seal assembly and then the bottom of the hose.  In it's passage, it will travel over the bottom side of all four of those hose clamps. 

The bottom side of the hose clamps.

Where corrosion can work it's evil, undetected.

The NEW hose clamps

Last weekend I changed those four hose clamps on Eolian's shaft log.  All four of them showed corrosion; two were terrible.  And all four hose clamps looked almost new from the top, the only side that you can see.

If both hose clamps fail on one end of the hose (typically the aft end), there is a good chance that the torque applied to the hose via the seal assembly will cause the hose to rotate and eventually come off of the hull fitting.  When this happens, water starts coming into the boat.

How fast?  Well, that depends on your boat's construction.  On Eolian, the cutlass bearing is embedded in the hull, just aft of the hull fitting that the hose attaches to on the inside.  Therefore in our case, the water flow would be minimal - just that little bit that can squeeze past the clearances between the shaft and the cutlass bearing (and its lubrication grooves).

If, on the other hand, your boat has its shaft supported on a strut, then the flow area is huge - the difference between the shaft diameter and the hull fitting diameter - probably not less than a half inch.  There's gonna be a LOT of water coming in!

Due to the seriousness of a failure, and because visual inspection cannot disclose incipient failure, your shaft log hose clamps should be changed on a schedule, regardless of their appearance.

What frequency?  Well I can't tell you that.  If you haven't changed them in a while, go do so.  If they look bad, you waited too long. Cut your maintenance interval in half for the next time.  And if it's been more than 5 years since the last replacement, your should go change them now!


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