AN AMERICAN FLYER® REPAIR CLINIC
From Port Lines Hobbies
AN AMERICAN FLYER® REPAIR CLINIC
From Port Lines Hobbies
There are several weak points in the Gilbert SIT units. These existed in some
AF S-gauge engines from 1946-1947.
Brushes and springs are very small, and subject to breakage, wear, and heat
breakdown.
The bakelite brush brackets on the back of the motor also tend to be quite
fragile, and frequently crack. Bakelite is not easily repairable.
SIT armatures and fields were wound with very fine enameled wire, and are easily
damaged.
Early SIT units used a rubberized cloth bellows. It's not unusual for the
rubberized coating to dry out, crack, and become ineffective.
Later units, and repaired units, used a diecast metal cylinder and piston in
place of the bellows, but the cylinders typically deteriorate and crumble.
And, of course, the internal wick and heating element can be either burned out
or hardened.
Brushes, brush springs, bellows material, and cylinders are available as replacement parts. The bakelite brush brackets are not. Armatures and fields are not available as replacement parts, but can be rewound if not otherwise damaged.
In addition, SIT units can be updated with can-motor drives which operate much more smoothly, quietly, and efficiently than the original motors.
A. BELLOWS REPAIR:
The square fiber board on each end of the bellows is easily removed. Remove all
old bellows material. Then clean the edges of all residue, and lightly sand them
with fine emery paper.
Replacement bellows material is wrapped tightly around all four edges of one
fiber board, after a thin bead of fast-setting glue is applied to the board's
edges. I have done this successfully with "superglue", but if you're not
comfortable using that, try rubber-cement.
Once it sets up, apply a thin bead of cement to the edge of the second fiber
board (be aware of orientation of the tab for later attachment to the gear).
Then carefully insert the fiber board into the bellows, and be sure it is firmly
wrapped tight around it. Set it aside to set.
Finally, apply a thin bead of glue along the seam, and pinch it closed to set.
Once all glued joints are dry and tight, re-assemble the unit and test.
A Bellows Jig is available that makes this rebuilding much simpler. The jig
clamps both fiber boards in place parallel to each other, and the proper
distance apart.
Glue is them applied to all edges, and the bellows is wrapped around both boards
at once. The seam is glued, and allowed to set before the bellows assembly is
removed and re-installed.
B. CYLINDER REPLACEMENT:
A 5-piece cylinder kit is available which replaces the bellows assembly. The kit
consists of a smoke piston, cylinder, attachment clip; piston pin, piston lever,
and full instructions. Assembly is quite easy.
This converts the SIT unit into a piston unit similar to the standard smoke
units found in most later engines.
C. SMOKE WICK REPLACEMENT:
Replacing a SIT wick and element is very little different from replacing one in
a later smoke unit. Our instructions for doing so are found in Repair Clinic #1,
so we won't repeat it here.
PARTS AVAILABILITY: You should be able to locate all parts referenced in this clinic as "available" in our online AF PARTS CATALOG, under "SMOKE UNITS".
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