Space Electronics - MW40KF Tri Axis Moment Weight Scale

For measuring large blades, including jet engine fan blades, Space Electronics' MW40KF three axis moment weight scales provide the most accurate measurement combined with the most ergonomic loading and unloading.

This remarkable instrument is at least 20 times more accurate than conventional 3-axis moment weight scales. It has a sensitivity of 0.02 oz-inch and can measure moment weight up to 30,000 oz-inch. This represents a sensitivity of 1 part in a million! This extraordinary performance is achieved by using the same technology which we use to measure satellite moments. The MW40KF machine automatically measures all three moment weight values (radial, axial, and tangential) without the need for the operator to manually rotate an interface plate or add range weights. A Windows based computer automates the measurement process and displays the measured moment weight.

These 3 axis moment weight scales are mainly used by both the OEM manufacturers and maintenance and repair operations (MRO) providers for jet engine fan blades and power turbine buckets.

1. Central pivot uses spherical air bearing Conventional moment weight scales use a pair of knife edges which are oriented at right angles. We use a spherical gas bearing which floats the moment arm on a thin film of air. This frictionless pivot has a center of rotation which only varies a few millionths of an inch, even if the scale is severely overloaded while the blade is being inserted in the adapter. There is no wear in this pivot. It retains its full accuracy for 30 years or more, and requires no maintenance.

2. Force restoration technology Conventional moment weight scales use strain gage load cells to measure moment. We use force restoration technology. A laser senses the deflection of the moment arms and electromagnetic actuators apply an equal and opposite force to each moment arm to restore the scale to its original position before the blade was inserted in the adapter. This eliminates mechanical non-linearity and results in a signal to noise ratio which is 1000 times better than a strain gage load cell. The error in comparing blades to a master blade is 0.0003% of full scale.

3. No sliding range weights Unlike conventional moment weight scales, it is not necessary to add weights to a hanger or slide weights along a shaft in order to measure the range of moments from 0 to 30,000 oz-inch. A binary range weight system within the scale automatically lowers the correct weight on the moment beam, resulting in greatly increased dynamic range. It is not necessary to counterbalance the adapter before making a measurement. The scale first measures the moment due to the adapter, and then measures the moment with the blade installed.

4. Automatic blade rotation It is not necessary for the operator to rotate the blade 90 degrees in order to measure the 3^rd axis of the blade. This is accomplished automatically by the scale.

5. Many blades can be measured with the same adapter It is not necessary to use a separate adapter for different blades. As long as the root dimensions are the same, then a single adapter is usually sufficient. An optional pan weight scale can be supplied which measures blade weight with an accuracy of better than 0.0001% of full scale. The on-line computer then converts the measured moment to the value at the correct Z-plane radius. This results in a major saving in system cost and eliminates the need for the operator to repeatedly change adapters.

6. Blades are loaded vertically On conventional moment weight scales, the blade is loaded horizontally in the adapter and hangs down below the machine centerline. When the clamping mechanism is actuated, the blade rocks upward, altering the position of the blade root. On our scale, a hinged adapter allows the blade to be inserted while it is in a vertical position. The blade then hangs straight down, allowing gravity to press the blade root against the adapter. When the blade is clamped, it retains its correct position.

7. Blade is clamped automatically The adapter clamp is actuated by air, rather than using hydraulic cylinders. The air is supplied to the clamp through a flexible coupling inside the machine. There is no need to attach a hydraulic hose to the adapter, and there is no oil within the adapter. This eliminates the mass shift error which occurs with hydraulic systems when the blade is rotated from a vertical to a horizontal position.

Specification	Value
Maximum weight (including tooling)	150 lb.
Range of radial blade moment that can be measured w/ specified accuracy *	0 to 30,000 oz-inch
Maximum transverse moment that can be measured	+/- 1,000 oz-inch
Range of radial moment indication	+/- 1,000 oz-inch
Readout sensitivity	0.02 oz-inch
Readout resolution	0.01 oz-inch
Moment linearity	0.1 oz-inch
Total radial moment measuring error ***	0.2 oz-inch
Total axial/tangential moment measuring error ***	0.2 oz-inch
Nominal mounting plate radius**.	7.8745 inch
Mounting plate dimensions	ARP4773
* Combined moment of blade plus adapter Nominal distance from fulcrum to vertical adapter mounting surface * Tooling error is not included Accuracy limits assume an environment which is free from drafts, excessive vibration and has a stable temperature.

Optional SE90060 Total Calibration System (for model MW40KF) - With this calibration system, the user can perform both "relative" and "absolute" calibrations for the model MW40KF Moment Weight Scale. This system includes the following items:

- Relative Moment Calibration System - This track and ball calibration system bolts directly to the interface of the MW40KF moment weighing system and provides an 800 oz-in calibration moment which accommodates the "relative" moment measuring range of the MW40KF. Calibration factors for the MW40KF force transducers are determined and recorded automatically by use of incorporated calibration software (included). Accuracy of this calibration system is at least 5 times better than the accuracy specifications for the moment weight system. Mass and distance values are traceable to NIST.

- Absolute Moment Calibration System - This weight hanger provides up to 19,000 oz-in of calibration moment which yields a total "absolute" calibration of the moment weight system.

A storage container is supplied - This container is equipped with recessed clasps and metal reinforced edges and corners. It is suitable for shipping as well as storing the calibration system.