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1. 12:30 PM - Flap Actuator Motor (Albert)
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| Subject: | Flap Actuator Motor |
Had an issue with my flaps not moving on occasion. Was going to replace
the unit (approx $450) but found a paper on Vans site
(Support|Contstruction FAQ|Flap Motor Maintenance) called Flaky Flap
Motors. It said that in 2002 they switched suppliers and the new units
used a motor made by Pittman. It said the problem appeared to be in the
previous units using a Motion Systems motor.
Mine was the newer unit (Pittman) but the reported problem apparently
was caused by grease from the gearbox getting into the motor causing
failure. Even though mine was the newer motor I followed the procedure
and it seems to have solved the problem. Since this was a little hard to
find I'll copy the procedure below. The original has several highly
useful pictures.
Note: there some washers on the end shaft. Keep track of the order in
which they were installed. also a couple of small o rings.
Albert Gardner
RV-10 N991RV
Yuma, AZ (Home of the Arizona Territorial Prison) (Not a current or
former inmate)
FLAKY FLAP MOTORS Over the years, we=99ve received the occasional
report of intermittent flap motor operation. We never found a consistent
problem. Sometimes it was poor wiring or a bad ground, a couple times it
was a switch giving up, occasionally the problem would be with the motor
itself. But problems were rare, and the flap motors in our demonstrator
airplanes worked day in, day out, for years. In 2002, we switched
suppliers, replacing the units we=99d received from Motion Systems
with a custom made unit powered by a Pittman brand motor. The new units
can identified by the Van=99s logo incised on the aluminum gear
box housing. Not long after the change was made we got a significant
number of complaints about motors failing after just a few hours.
Naturally, we suspected the new motorsbut as it turns out, the
newer =9CVan=99s=9D units were not the culprit.
Instead, the problem seems to appear in one of the last batches of
Motion Systems units. These we received about three years ago and they
are now starting to appear in finished airplanes. The problem is usually
caused by an excess of grease in the gearbox (that=99s the almost
cubical casting where the flap actuator tube and the motor meet at right
angles). As the unit spins, hydraulic pressure pushes grease back into
the motor unit and coats the windings, commutator and brushes. Grease is
an insulator, and when the brushes are insulated from the commutator,
yo=99 motor don=99 motate no mo=99. Cleanliness is
next towell, it makes your flap motor work better too. You can
remove the cap on the end of the motor and wipe the commutator shaft
clean and your motor will work for a while. But to really solve the
problem, all the grease must be removed from the flap motor or the whole
cycle will just repeat. Remove the actuator unit from the aircraft and
take it a clean, well-lighted bench. Assemble a small jar of clean
lacquer thinner, some cotton swabs, a Phillips screwdriver, an allen key
set, tweezers and some of those very thin wire ties that come on loaves
of bread. If you=99re of an age and have a magnifying visor, bring
it. Remove the Phillips screws from the motor assembly and gently,
carefully, remove the steel cap from the end of the motor. Inside is a
black plastic horseshoe wrapped around a shaft. Notice the three small
holes in the heel of the horseshoe. Turn over the cap and look inside
=93 see the little index pin? See where it goes =93 that
hole in the horseshoe? Remember that. There are several washers on the
shaft. These must be reinstalled in the order they came out, so
carefully note and preserve their orientation as you remove them. Slide
the horseshoe gently off the motor shaft. A couple of little copper
colored things are going to jump out (those are the brushes). They are
retained by very thin wire springs. Now use the allen key to remove the
bolts holding the motor to the gear box. Pull the motor winding/shaft
assembly out of the cylindrical housing (the magnets will resist, but it
will come out) and inspect it for grease and corruption. Clean the motor
and brush assembly with lacquer thinner or some other clean solvent.
Scoop any excess grease out of the gearbox. There should be enough to
lubricate the gears, but the whole cavity does not need to be full of
grease. Be careful not to disturb the tiny o-ring in the recess of the
gearbox. Clean the commutator (the shiny part of the shaft that the
brushes ride on) with the cotton swabs or even a bit of scotchbrite.
Reassembling the motor can be more difficult than getting it apart.
Begin by teasing the little springs that go behind the brushes back into
their recess and tie them back with the wire ties. This may take some
patience When the springs are held back, use the tweezers to
re-insert the brushes, taking care that curve worn on their contact
surface matches the curve of the motor shaft. Tie the brushes back.
Insert the gear end of the motor shaft back into the gearbox and check
to see the baseplate is down tight. Put the cylinder/magnet back around
the motor =93 the little notch in the rim should be on end away
from the gearbox. Gently, carefully put the horseshoe back around the
shaft and slide the wire ties out. The springs should force the brushes
up against the commutator. Reinstall the washers. Reinstall the cap with
the long Phillips screws. Find a 12-v battery and test the motor by
holding the wires against the posts. Reversing the wires should make the
motor run the other direction. The motor unit and screws securing the
housing to the gearbox. The long phillips-head and short allen-head
screws have been removed or backed off and the motor separated from the
gear box. The motor cap and the horseshoe shaped brush housing have been
removed. The brushes have popped out of the housing, and if you look
closely, you can see the tiny spring that must be behind the brush when
it is re-inserted. The springs keep the brushes up against the motor
armature. The motor armature has been removed from within the motor
housing and the washers removed from the motor shaft. Tucking the
springs and brushes back into their cubbyholes is the toughest part of
the exercise. Be careful not to bend the springs. A small spacer made of
any non-magnetic scrap, that keeps the brushes pushed back will help get
the =9Chorseshoe=9D back on the shaft.
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