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Thread: donut replacement

  1. #1

    donut replacement

    Hi Cloyd
    Since we heard that you were thinking of replacing your
    donuts, we thought it might be of interest to report on how we did
    ours. At the same time we are also replacing the flexible brake lines
    in the undercarriage legs and one master cylinder so we can include
    that process too.
    We had heard all sorts of horror stories about the problems other
    people had encountered while attempting this procedure but these
    proved to be false as I will relate .

    Some tools not in our inventory were needed, and I will deal with
    them as they arise .

    We started out by jacking up the aircraft and supporting the wing on
    a pallet ( covered with carpet ) just inboard of the tie down point .
    Then we lowered the gaiter to expose the Jobolts and removed the
    wheel and solid brake lines ,one tip here is to use a small ziplock
    bag to catch the brake fluid that will drip form the brake line where
    it protrudes from the wing .I found that safety wire holds the bag in
    place quite nicely and allows you to get on doing other things while
    it drains , otherwise you will end up with one hell of a mess .
    Use an angle grinder to grind off the heads of the Jobolts . I found
    it impossible not to leave some grind marks on the leg stub but
    covered these with primer .Having ground off both heads, we put one
    of those rubber cushioned floor mats beneath the trailing arm should
    gravity overcome our efforts to support the leg. With Ashley
    supporting the leg I punched out what remained of the Jobolts , a
    slight twist and the leg came out easily and was lowered to the floor.
    The next step was to remove the pins that hold the pivots .Remove the
    split pin and punch out the cotter pin for the shock absorber rod..
    Remove the nut at the top of the rod ( the first of the tools not in
    our inventory ) . It is a 1 7/16 and was only available in inch
    drive ( so we borrowed one ) .Then punch out the pivot at the bottom
    to allow the trailing arm to swing forward.. Repeat the process for
    the trailing arm pivot taking care to retain the thin spacers that
    are present.
    Despite having heard of a press being needed to remove these pivots
    ours came free with just a mild push no doubt because they had been
    correctly greased over the years.
    Remove the shock absorber rod and discard the old donuts. At this
    point we removed the old flexible brake lines from the leg and
    caliper.
    We found that minerals spirits cleaned the parts easiest of all the
    solvents we tried.
    We had made a couple of jigs to pre compress the donuts out of a
    length of threaded rod and a couple of post supports (these are
    available to any club member who needs them for the cost of the
    postage ).
    Regarding the compressed length of the donuts .We had heard that they
    should be compressed to 6 inches ( good luck- it`s damn near
    impossible ) . We found that compressing to an overall length of 7
    inches was more than adequate ( and about as much as I could do
    without giving myself a hernia ). We allowed 4 days on the jig to
    allow the donuts to settle .
    Use new cross pins to reassemble (they are cheap )
    Reassembly was straight forward. Two tips here, with a sharpie mark
    on the face of the pivot pin the alignment of the cross pin (it's a
    bitch to find when the pivot is in place . and grind an old pin to a
    point ( helps realign the holes )
    Assemble the shock absorber rod to the swinging arm. Insert the
    cotter pin and split pin .
    We had heard that you had to be quick when assembling the donut
    assembly back into the leg because the donuts expand as they relax,
    not the case at all .We had plenty of time and found no need to rush.
    Shove the assembly up into the leg and start the nut (having the
    trailing arm in place helps resist the torque).
    Then fit the trailing arm pivot .Take extreme care not to distort the
    shim washers ( they are very thin ) and align the cotter pin and
    install the split pin ( takes some manual dexterity but not too
    difficult ) .
    Final adjustment of the ride height is measured between the lower
    edge of the leg casting and the center of the shock absorber rod
    pivot point and should be 1.31 inches ( not easy to measure
    accurately ) but in our case this means that we had about inch of
    threads showing above the adjustment nut ( much easier to measure ).
    That's it really. reinstall the leg to the stub , insert the
    jobolts , replace the wheel , go do the other side . We did both
    mains in an easy days work.
    Now step back and take a look , I was surprised at how much
    difference there was.
    DO NOT try to step up on the wing directly without using the step (
    as I used to ). From first hand experience I can tell you " it
    hurts " ( damn near dislocated a hip )

    We are still awaiting some parts so we will tell about the nose leg
    next week







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  2. #2
    Guest
    Guest

    donut replacement

    Great description! At this point, someone is going t ask: "Did you
    take pictures?"
    Your step-by-step certainly takes a lot of the uncertainty out of
    undertaking this procedure.
    Thanks
    David
    81N


    --- In musketeermail@yahoogroups.com, "ajpcps" <ajpcps@...> wrote:
    >
    > Hi Cloyd
    > Since we heard that you were thinking of replacing your
    > donuts, we thought it might be of interest to report on how we did
    > ours. At the same time we are also replacing the flexible brake
    lines
    > in the undercarriage legs and one master cylinder so we can include
    > that process too.
    > We had heard all sorts of horror stories about the problems other
    > people had encountered while attempting this procedure but these
    > proved to be false as I will relate .
    >
    > Some tools not in our inventory were needed, and I will deal with
    > them as they arise .
    >
    > We started out by jacking up the aircraft and supporting the wing
    on
    > a pallet ( covered with carpet ) just inboard of the tie down point
    .
    > Then we lowered the gaiter to expose the Jobolts and removed the
    > wheel and solid brake lines ,one tip here is to use a small ziplock
    > bag to catch the brake fluid that will drip form the brake line
    where
    > it protrudes from the wing .I found that safety wire holds the bag
    in
    > place quite nicely and allows you to get on doing other things
    while
    > it drains , otherwise you will end up with one hell of a mess .
    > Use an angle grinder to grind off the heads of the Jobolts . I
    found
    > it impossible not to leave some grind marks on the leg stub but
    > covered these with primer .Having ground off both heads, we put one
    > of those rubber cushioned floor mats beneath the trailing arm
    should
    > gravity overcome our efforts to support the leg. With Ashley
    > supporting the leg I punched out what remained of the Jobolts , a
    > slight twist and the leg came out easily and was lowered to the
    floor.
    > The next step was to remove the pins that hold the pivots .Remove
    the
    > split pin and punch out the cotter pin for the shock absorber rod..
    > Remove the nut at the top of the rod ( the first of the tools not
    in
    > our inventory ) . It is a 1 7/16 and was only available in inch
    > drive ( so we borrowed one ) .Then punch out the pivot at the
    bottom
    > to allow the trailing arm to swing forward.. Repeat the process for
    > the trailing arm pivot taking care to retain the thin spacers that
    > are present.
    > Despite having heard of a press being needed to remove these
    pivots
    > ours came free with just a mild push no doubt because they had been
    > correctly greased over the years.
    > Remove the shock absorber rod and discard the old donuts. At this
    > point we removed the old flexible brake lines from the leg and
    > caliper.
    > We found that minerals spirits cleaned the parts easiest of all the
    > solvents we tried.
    > We had made a couple of jigs to pre compress the donuts out of a
    > length of threaded rod and a couple of post supports (these are
    > available to any club member who needs them for the cost of the
    > postage ).
    > Regarding the compressed length of the donuts .We had heard that
    they
    > should be compressed to 6 inches ( good luck- it`s damn near
    > impossible ) . We found that compressing to an overall length of 7
    > inches was more than adequate ( and about as much as I could do
    > without giving myself a hernia ). We allowed 4 days on the jig to
    > allow the donuts to settle .
    > Use new cross pins to reassemble (they are cheap )
    > Reassembly was straight forward. Two tips here, with a sharpie mark
    > on the face of the pivot pin the alignment of the cross pin (it's a
    > bitch to find when the pivot is in place . and grind an old pin to
    a
    > point ( helps realign the holes )
    > Assemble the shock absorber rod to the swinging arm. Insert the
    > cotter pin and split pin .
    > We had heard that you had to be quick when assembling the donut
    > assembly back into the leg because the donuts expand as they relax,
    > not the case at all .We had plenty of time and found no need to
    rush.
    > Shove the assembly up into the leg and start the nut (having the
    > trailing arm in place helps resist the torque).
    > Then fit the trailing arm pivot .Take extreme care not to distort
    the
    > shim washers ( they are very thin ) and align the cotter pin and
    > install the split pin ( takes some manual dexterity but not too
    > difficult ) .
    > Final adjustment of the ride height is measured between the lower
    > edge of the leg casting and the center of the shock absorber rod
    > pivot point and should be 1.31 inches ( not easy to measure
    > accurately ) but in our case this means that we had about inch of
    > threads showing above the adjustment nut ( much easier to measure ).
    > That's it really. reinstall the leg to the stub , insert the
    > jobolts , replace the wheel , go do the other side . We did both
    > mains in an easy days work.
    > Now step back and take a look , I was surprised at how much
    > difference there was.
    > DO NOT try to step up on the wing directly without using the step (
    > as I used to ). From first hand experience I can tell you " it
    > hurts " ( damn near dislocated a hip )
    >
    > We are still awaiting some parts so we will tell about the nose leg
    > next week
    >






    Join BAC today and be a part of the ONLY Type Club for the Musketeer series!

    www.beechaeroclub.org


    Yahoo! Groups Links

    <*> To visit your group on the web, go to:
    http://groups.yahoo.com/group/musketeermail/

    <*> Your email settings:
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    <*> To change settings online go to:
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    <*> To change settings via email:
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