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Step 5: Specify the Lovejoy Model 501 Torque Arm Bracket to prevent rotation of the manual pulley handwheel so that it can be adjusted while the motor is running. This item is NOT required for MLA or HLA driver pulleys. Step 6: For remote control or linear actuation of the manual pulley, refer to the appropriate section in the Econoline (MLA), Hi-Ratio, or Hexadrive (HEC, HLA) section of this catalog.

Variable Speed Drives - 7199 Variable Speed Drives Adjustable Center Example

Selection Process

IMPORTANT: Be sure to specify the correct driven pulley for the mounting arrangement. For example, you need to specify an “R” suffix (for reverse mount) with the Econoline Series spring-loaded pulley if it is a “C” mount. Also check to be sure the driven pulley is available in the bore size that will fit the driven shaft. Step 4: Using the shaft center-to-center distance from “d”, select the correct drive belt from the Selection Chart. The center distance between the shafts must be held to the correct distance for the drive belt that is used in order to attain the published speed range. Drive belts are available only in certain lengths, so the center distance may need to be altered from the original design in order to suit the best available belt. If you have a center distance that is not shown in the chart, refer to the formulas in the Variable Speed Engineering Data on page VSD-68, or call Lovejoy Engineering for assistance in calculating the correct center distance. Step 1: The WB series is chosen to fit into existing motor belt guards and motor mounts (see page VSD-30). Step 2:

Selection Examples: Adjustable Center Drives

For 1 HP @ 1,150 RPM, the Model 301E variable speed driver pulley with a 7/8 inch bore (to fit the motor shaft) is selected.

WB Series Selection Example

Step 4: From the Belt Selection chart, under the column headed by the 1922G8SK sheave, read down to find the center distance, then follow to the left to find the appropriate drive belt. The center distance nearest to 15 inch in the chart is 15.4 inches. Notice that the motor travel for full speed range with the 301E pulley is 3.5 inches, so the maximum center distance will be about 19 inches. A belt conveyor application requires a drive with a 2.8 to 1 speed ratio. The drive will consist of a variable speed belt drive, a speed reducer, and a chain drive from the reducer to the conveyor head pulley. The input speed range to the reducer must range from 370 to 1,050 RPM. The motor is 1 HP @ 1,150 RPM, with a NEMA 145T frame and 7/8 inch shaft. The torque into the reducer must be 50 in-lb. Center distance between the motor shaft and the reducer input shaft is about 15 inches. Step 3: From the Driven Sheave Selection chart for the Model 301E pulley, the 1922G8SK should be used because it offers a driven speed range of 360 to 1,075 RPM, which covers the requirement for this drive. Note that the torque rating for this drive 58 in-lb. This is a constant torque output throughout the driven speed range. An SK bushing is needed to attach the companion sheave to the driven shaft.
Step 5: Select a suitable motor base based on the NEMA motor frame size. For a 145T frame, there are two choices: the Model 301 cast iron base, or the Model SMB-184 steel base. After assembling a complete drive package, you will end up five components: a 301E x 7/8 inch variable speed pulley; a 1922G8SK companion sheave; an SK bushing with a bore to fit the driven shaft; a 1922V544 belt; and a 301 or SMB-184 motor base. Step 2: Both the Models 160 and 170 variable speed pulley are rated for 3/4 HP, which is closest to the drive load of 0.65. In our example, the motor shaft is 5/8 inches, so we can use the Model 160. Step 3: The Driven Sheave Selection chart for the Model 160 variable speed driver pulley (see page VSD-26) shows that a 6-inch pitch diameter companion sheave will provide a driven speed range of 615 to 1,675 RPM when used with a 1,750 RPM motor. This covers the required driven speed range. Step 1: Referring to the Service Factor chart on page VSD-68, a service factor of 1.3 is recommended for pulsating loads. Motor horsepower multiplied by the service factor equals a drive load of 0.65 HP. Either the Econoline of Aluminoline series could be used with an “A” or “B” section belt, but in this case the Aluminoline is better because it is two-side moveable and will maintain better belt alignment with a short center distance.

Aluminoline Selection Example

VSD A variable speed pulley is needed for use on a plastic cut-off machine that indexes material through a guillotine-type shear once every second. Inertia of the shear is not high, but the load is pulsating up to 25% over the motor torque. The motor is rated 1/2 HP @ 1,750 RPM with a NEMA 56 frame (5/8 inch shaft), and a stock (“A” or “B” section) belt is preferred. Good alignment and short center distance is a concern. The driven speed range requirement is 800 to 1,600 RPM. Continued

VSD-10

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