mountable power motors

AIR MOTOR SELECTION
To assist in the selection oi an air motor, we need any two of the following three items of information:
1.	Horsepower required.
2.	Speed CRPM) required againse load.
3.	Work load expressed in foot pounds or inch pounds of dynamic torque Crnoving torque load).

As air motors are dependent upon input air pressure for performance, these factors must also be considered.

1.	Air pressure (psig or bars) at motor location.
2.	Pipe size of air supply system to assure adequate volume (cfm or m³/min) so as to minimize line loss (air pressure drop during motor operation).
3.	Plant air system pressure may vary during the day due to use by other equipment; therefore, base the selection of the air motor on t~ lowest psig or bars that can be cxpected. Then, by using a pressure regulator in the line at the motor, a uniform air supply is assured.

In applications of intermittent short service, Cooper Power Tools' air motors can be operated over the complete range indicated for each without harm or significant wear. In applications involving sustained continuous operation for long periods, however, some guidelines are suggested. Do not operate piston and MR motors at more than 75% of free speed. Consult the factory for applications requiring continuous operation of rotary vane motors at maximum HP or for any applications requiring vertical operation of these motors. Review service manuals carefully. For two known and one unknown, the following formulas can be used:

Ft. lbs. Torque =	1000 x HP 0.19 X RPM

Horsepower (HP) =	0.19 XTorque (ft. lbs.) X RPM 1000

Speed (RPM) =	1000 X HP 0.19 X Torque (ft. lbs.)

When working with Newton meters (Nm), substitute .0258 in place of 0.19 in the formula. Use the performance charts provided for each motor size and type of obtaining this same date procedure:

1.	Select operating pressure.
2.	Select torque required from the left hand scale.
3.	Extend that point position across chart until it intersects with torque performance curve of the selected pressure.
4.	Draw a vertical line from the above mentioned intersection to the corresponding motor scale at the bottom of the chart to determine the operating speed at the required torque and psig pressure.
5.	Extend the vertical line until it intersects the horsepower curve of selected operating pressure and read horsepower from the motor scale on the right side of the chart.

Torque and horsepower curves may be interpreted for approximate performance at other psi pressure.

PISTON AIR MOTOR APPLICATION DATA For all reversible air motors, a four-way control vavle is recomended for forward and reverse operations. One direction rotation only, an on-off vavle may be used. When air is admitted to one port on reversible tools, the other port becomes an exhaust port; if it is plugged, it will produce a sever "back pressure" and greatly reduce speed and power of the motor. Do not plug exhaust ports of motor or control valve, use mufflers. COMPUTING OVERHUNG SHAFT LOADS When planning to equip a motor with a pinion gear, sprocket, drive wheel, etc., the amount of radial load or overhung load must be considered before making a selection. Two formulas are available to establish application bad limit requirements. The first one deals with the effect of the drive wheel or pinion on the shaft. The second, with torque effect on radial or overhung load.
	A = C Where B D

A.	Rated load point dimension from catalog.
B.	Dimension of desired point of load from motor face.
C.	Load to be found.
D.	Rated overhung load irom catalog.
EXAMPLE: Find maximum overhung load 3' from mounting face of 73308AA8 (AB series motor). Refer to catalog. Apply formula.
	2.25 = C C = 2.25X1000 3 1000 3
	C =750 lbs. (new overhung load rating)
To establish the amount of the overhung load for a given torque performance of any motor:
1.	Establish known static air pressure.
2.	Determine starting torque load from application, or stall torque from catalog and known air pressure.
To convert units of stall torque to actual pounds of load at surface of output shaft, use the following formula.
Load =	Torque (inch pounds) Radius of output shaft in millimeters
	or
Load =	Torque (Newton meters) X 1000 Radius of output shaft in millimeters
EXAMPLE: Using the same example, we determine from the catalog that 73308AA8 has a stall torque of 11 ft. lbs. at 90 psig air pressure. To find shaft load:
Load =	(11) ft. lbs. X (12) in. lbs. per ft. lb. 9/16' or (.562) radius of output shaft
Load =	132 in. lbs. .562'
Load =	235 lbs. (overhung shalt load)

By applying this formula to some of the geared motors, you will note that the output performance of the motor will frequently exceed the maximum overhung load rating established for the motor. It the amount is minimal, consider mounting the drive wheel or pinion gear closer to the motor face. This will increase the overhung load rating. If this is not adequate, consider larger motor or outboard bearing support of shaft. Consult factory. If overhung load and torque act in opposite directions, their difference applies.