AERONCA Memo M-12

                                               MEMO NO. M-12
                                               OCT. 20th, 1936 RES

AERONCA AIRCRAFT CORPORATION
MIDDLETOWN, OHIO

INSTRUCTIONS FOR "LAPPING THE PROPELLER HUB TO THE CRANKSHAFT ON ALL
AERONCA ENGINES INCLUDING MODELS E-107, E-107-A, E-113, A, B, and C."

The following procedures should be used to "relap" the propeller hub to the
crankshaft:

Remove the propeller hub assembly, using propeller Hub Puller, tool No.
T-11, and examine the hub and crankshaft for any signs of wear.  If a
red dust is present it indicates that the two tapered parts are not
fitting together properly and should be "relapped." Be sure the puller
is screwed on to the hub as far as possible to prevent damage to the
threads.

After cleaning the parts with gasoline, check the taper fit by either
drawing a number of pencil lines horizontally on the taper shank of the 
crankshaft or by using some Prussian Bluing.  Remount the propeller,
oscillating it several times and remove.

CAUTION

Apply a small amount of oil to the taper shank before checking as it is 
possible to gall the surface if they are dry.

To "relap", apply a slight amount of fine grinding and lapping compound,
such as No. 2. Glover Brand, or equivalent, to both the front and rear
bearing surfaces.  Lap the surfaces together by periodically oscillating
the propeller and relieving the load so as to obtain a good fit.

CAUTION

Do not under any circumstances rotate the propeller in one continuous
direction and do not "lap" any longer than is necessary as the hub moves
back along the taper shank quite rapidly as metal is removed.

After "lapping", check the fit, using pencil lines or Prussian Bluing,
as explained above.

When both bearing surfaces show a good fit, apply a very small amount of
the lapping compound to the small front bearing surface on the taper
shank and "lap" a slight amount more, using only oil on the larger rear
bearing surface.

NOTE: This operation is absolutely necessary in order to insure a tight
fit on the rear surface.  Due to the difference in the diameters of the
front and rear bearing surfaces it is necessary to lap the smaller
surface and additional amount so that the hub will fit tightest on the
rear surface.

Clean both surfaces thoroughly, slip on the propeller hub assembly and
washer, tighten the nut and saftey with a cotter pin.

NOTE: If the propeller hub has been lapped a number of times is may be
necessary to counter sunk the small steel washer, as shown below, in order
that the propeller hub will be help under torsion load from the nut.

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M-12

Check the clearance between the head of the propeller bolts and
head of the bolts holding the front cover of the engine.  This clearance
should be at least 3/32".  When mounting the propeller and hub, it is
very important to draw up on the propeller hub nut very tight, using
a socket wrench with an 18" arm, if available.

It is also important that the six bolts holding the wood propeller
to the hub be tight.  It may be necessary to pull up on some of these
bolts more than on the others in order to properly track the propeller
which should be within 1/16" at the tips, however, they should all be
sufficiently tight to prevent any movement between the propeller and hub.

The hub shold be removed, checked, and relapped every 100 hours of flying.

It is usually advisable to install a new propeller hub on a new
CRANKSHAFT, IF THE OLD HUB IS GALLED.