A.C. Gilbert introduced the smoke-in-tender (SIT) unit in 1946, along with the introduction of the new 2-rail S-gauge American Flyer train line, and continued it in 1947. After that, re3verse units were moved to the tender, and the smoke units moved to the front end of the boiler. But even though SIT units only existed for two years, 1946 and 1947 units were different. Here are the most notable differences:

  a) BRUSH-BRACKET ASSEMBLIES----the 1946 brush brackets were a flat piece of black bakelite, spaced away from the SIT field by two steel tubes through which the two brush-bracket screws passed. Presumably, these brush brackets were too fragile and easily broken, because in 1947, they were replaced by black bakelite plates with molded vertical sides which strengthened the plate and also replaced the need for the hollow steel tubes.



   b) ARMATURES---- The 1946 and 1947 armatures are easily identified, and they are not interchangeable in the SIT units. In 1946, the three commutator plates were riveted to the backing, and fabric insulation can usually be seen around the edges, behind the plates. The rivets can be seen in the surfaces of the three plates. In 1947, the plates were no longer riveted, but were cemented to a thick bakelite backing plate, and no fabric insulator is present. Viewed from the side, this black bakelite backing is easily seen.

c) FIELDS---- Visually, the only way to differentiate the fields is to measure the total thickness of all the stacked plates of the field. The 1946 field (and armature) have fewer plates, and measure 8/32" thick. The 1947 field and armature have more plates, and measure 10/32" thick.

d) RESISTANCE READINGS: If you have an ohmmeter, good fields and armatures should result in different values:
       1946 FIELD: 3.1 - 3.3 ohms
       1947 FIELD: 3.6 - 3.8 ohms
       1946 ARMATURE:  3.3 - 3.5 ohms
       1947 ARMATURE:  3.4 ohms

Remember that you should not mix-&-match 1946 and 1947 components.

Machine rewinding of your damaged components, to original specs, is available.

We can also convert your SIT unit to a can-motor, with either bellows or cylinder operation !