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Short Shaft vs. Long Shaft Motors

Short shaft motors can easily be identified by a "TS" after the frame number and are typically used for direct coupled loads. A flexible coupling is used between the motor and the driven load. These motors are not designed for radial loads which would be imposed by belt, or chain applications. They have smaller bearings and the output shaft extensions are smaller in diameter.

Except for rotor weight and magnetic side pull there is little radial loading on the bearings. The 284TS is the smallest short shaft motor in the U.S. MOTORS® line.

Long shaft motors, identified by a "T" after the frame number are used where radial or overhung loads are present. Examples are belts, chains or gears. Ball bearings are the standard.

Horizontal Motor Shaft Summary

Shaft dimensions and designations for frame sizes up through 440 shall be in accordance with NEMA.

Shaft dimensions and designations for frame sizes 5000 and up are noted below:

SS = Small Short Shaft (Recommended for 2 pole application)
S = Standard Short Shaft
MS = Medium Shaft
G = Automotive Duty Delco Shaft GM-7EQ, 7EHQ
ML = Medium Long Shaft
(Blank) Large Long Shaft
Z = Special Shaft Extension (Per Customer's Dimensions)

Basic Frame

U

V

N-W

S x ES Keyseat

5000 SS 2 - 3/8 4 - 1/2 4 - 3/4 5/8 x 3 - 1/8
5000 S 2 - 7/8 5 - 1/2 5 - 3/4 3/4 x 4 - 1/8
5000 3 - 7/8 11 - 1/4 11 - 5/8 1" x 10
5000 G 3 - 1/2 10 - 3/16 10 - 1/2 7/8 x 9
5800 SS 2 - 7/8 5 - 1/2 5 - 3/4 3/4 x 4 - 1/8
5800 S 3-3/8 6 - 1/2 6 - 3/4 7/8 x 5 - 1/4
5800 MS 3 - 7/8 7 - 1/2 7 - 3/4 1" x 5 - 5/8
5800 ML 3 - 7/8 11 - 1/4 11 - 5/8 1" x 10"
*5800 4 - 7/8 14 - 1/4 14 - 5/8 1 - 1/4 x 12 - 7/8
6800 SS 3-3/8 6 - 1/2 6 - 3/4 7/8 x 5 - 1/4
6800 S 3 - 7/8 7 - 1/2 7 - 3/4 1" x 5 - 5/8
6800 MS 4 - 3/8 7 - 1/2 7 - 3/4 1" x 5 - 5/8
6800 5 - 1/8 15 - 1/8 15 - 3/8 1 - 1/4 x 13 - 3/8
7000 SS 3 - 7/8 7 - 1/2 7 - 3/4 1" x 5 - 5/8
7000 S 5 - 3/8 10 - 1/2 10 - 3/4 1 -1/4 x 8 - 5/8
8000 SS 4 - 3/8 8 - 1/2 8 - 3/4 1" x 6 - 5/8
8000 - S 5 - 7/8 11 - 1/2 11 - 3/4 1 - 1/2 x 9 - 1/8

* Not Available on TEFC Frame.

Note: Shaft letter dimensions are per NEMA MG1 - 4.01