"frozen" pintle pin in alum. rudder cheeks

Discussion in 'Sunfish Talk' started by odegaard, Apr 3, 2017.

  1. odegaard

    odegaard cAPTN oDIE

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    The problem is with a Force 5 pin, but about same as a Sunfish--I have tried soaking in penetrating oil/heat/banging on it--but still NG. I don't want to break the aluminum--any suggestions appreciated.
    Thanks Odie 27777
     
  2. Roller

    Roller Member

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    Even though you've already done it all, I would (again) try serious heat. It is *very* difficult to chemically dissolve aluminum oxide (which is what is binding the pin in the rudder casting).

    • I would first clean as thoroughly as possible the aluminum ears on the rudder casting that hold the stainless steel pin (wire brush, etc). I would pay special attention to the area around the small washer and circlip that the spring on the pin pushes against the bottom ear.

    • I would soak the ears/pin area of the rudder casting at least overnight (or longer) with a good penetrating agent (like PB Blaster or graphite penetrating oil). Wipe off the excess, put the casting in a plastic bag, and put the unit in the freezer for several hours.

    • When the casting is as cold as you think it will get, apply serious heat to the aluminum ears around the pin.
    Aluminum melts at ~660°C (1,221°F).
    A dual temperature 1500 watt heat gun runs at low: ~300°C (575°F) / high: ~600°C (1112°F).
    A propane torch (air only, not Mapp gas) runs as high as 2,000°C (3,623°F) -- !CAN EASILY MELT ALUMINUM!

    I would use a heat gun on high, trying to heat the aluminum ears as hot as possible before the pin heats up too much (perhaps shielding the pin from the heat gun to get max temp differential).
    Then carefully tap (or vigorously rap!) the pin (perhaps from alternating ends) until you see movement. If the pin moves in the ears, you can do it all again and eventually free the pin. Got my fingers crossed....
     
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  3. Alan S. Glos

    Alan S. Glos Active Member

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    Roller's approach is spot on. I have used this or a similar method several times. I would add cleaning the whole assembly with a 6" dia. soft wire wheel mounted in a bench grinder motor/arbor. When you think you have it ready to free, put the casting in a vice and hit the end of the s.s. pin with a mildly firm tap with the flat side of a ball peen hammer. It will free up and then move but you will need to clean off the pin with more oil and steel wool to get it to work properly. If you can get it to work without removing the pin from the casting, so much the better as the little retaining rings and the s.s. spring can be a pain to remove and then reassemble (unless you have all the right tools.)

    Alan Glos
    Cazenovia, NY
     
  4. Light and Variable Winds

    Light and Variable Winds Well-Known Member

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    All the above plus advancing the caution that the stainless-steel pin can break! :eek: I use a small tack hammer—weighing only a few ounces—for difficult removals.

    If none of this works, I'd continue "on the attack" with solvents, even if drilling or grinding a small "mini-inspection-port" into the middle of the aluminum casting is required. It won't hurt to grind through the aluminum to where the grinding wheel reveals the pin. Start with one "mini-inspection-port". Add solvent—tap the pin some more. In addition to PB Blaster, try ATF fluid, and Kroil. Be patient—let solvents work their magic! :)

    This past year, this unorthodox grinding wheel setup pictured below has been my "go-to" ultimate tool for many, many, operations. (Cutting rags, pipe, rebar, sheet metal, castings, forgings, brass, aluminum, zinc, stainless steel, fiberglass, plastic, shortening drill bit shanks, even sharpening pencils!) It'd be perfect for adding such a "mini-inspection-port".

    Use eye protection. :cool:

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    Last edited: Apr 4, 2017
  5. Light and Variable Winds

    Light and Variable Winds Well-Known Member

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    Two more things:

    1) When grinding through the aluminum, you'll have struck the pin when you see a few sparks. (A very few sparks).

    2) Odie, while on the subject of a Force 5, is this round, 9-foot, "foundling" mast section from an early Force 5 sailboat?

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  6. Roller

    Roller Member

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    Cutoff wheels are very handy for a wide range of tasks, but I would be very reluctant to take one to an aluminum Alcort rudder cheek in an attempt to free the pintle pin. The aluminum ears on the cheek are only about 5/8" wide, and there is only about 1/4" of aluminum surrounding the pin. For strength you need every bit of aluminum there is now around the pin. A cutoff wheel (even a mini disk in a Dremel tool) is not a precision instrument. Slotting the ear holding the pin would (IMO) remove way too much material.

    Under heat aluminum expands at approximately twice the rate of stainless steel. We're trying to use this differential + lubricating penetrant to unseize the pin so it can be tapped (or whacked) out.
     
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  7. Light and Variable Winds

    Light and Variable Winds Well-Known Member

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    Your explanation certainly makes sense, and got a "like". :) Could that property of aluminum be used in reverse? Say, dropping the aluminum ears into dry-ice? (My local supermarket may still carry dry-ice for shipping fresh-caught fish).

    What cutting I had in mind was a horizontal cut—as below. At the risk of breaking a small drill-bit, drilling a small hole (off-center) would be better. 'Course, if the selected anti-corrosive substance had crept satisfactorily through the aluminum ears, there would be no need to drill or make a cut.

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  8. beldar boathead

    beldar boathead Well-Known Member

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    So you are saying if aluminum expands under heat, use dry ice to make it contract even tighter on the pin?? Seems making it tighter will make it harder to get the pin out? Plus heating it seems simple and free as opposed to having to track down dry ice.

    BB
     
  9. Light and Variable Winds

    Light and Variable Winds Well-Known Member

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    Heating a seized lug nut is said to crush the rust that is keeping it from turning.

    With dissimilar metals, this "differential" should work both ways—expanding or contracting. The dry ice concept is to crush the corroded oxides against the stainless steel pin. When the aluminum returns to room temperature, the s/s pin should have altered the corrosion within—and offer a "fresh face" to solvents.

    A 12-volt "dead short" across the s/s pin would have the same effect, but might cause the aluminum casting to fracture! :eek:

    Still, even that could work to free the pin, and can be repaired at a lesser cost than buying a replacement. :)

    This just in! :cool:

    https://www.ford-trucks.com/forums/...ff-vs-acetone-atf-poultice-vs-pb-blaster.html
     
    Last edited: Apr 9, 2017
  10. Roller

    Roller Member

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    (Very) long time machinist/mechanic practice has been to expand the part and/or shrink the seized pin or bolt in the part to help free it. Experimentation welcome; report results here.
     

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