Hand held, temperature compensated railroad bearing bore gage
Albion Devices, Inc., has developed a hand held, temperature compensated bore gage. The initial design is intended for the rail road industry, with specific application to railroad bearing cone bores and, with an optional adapter, wheel bores, but the gage is adaptable to many internal measurement uses.
Thermal effects on critical dimensional measurements become more significant as tolerances have continued to tighten in response to quality demands. Albion’s new bore gage compensates for most of these thermally induced errors in such measurements.
Using separate, user programmable coefficients of thermal expansion for each of the materials that make up the work piece, the gage itself and its calibrating master, (the “elements of the measuring system”) the gage corrects dimensional readings so that dimensions are displayed as if all the elements of the measurement system were at the International Reference Temperature of 20°C / 68°F. To do this the gage uses Albion’s well tried and tested TComp II controller, familiar to railroad and auto industry personnel, which is mounted in an adjustable orientation on the gage handle.
Easy, menu driven, touch screen user friendliness.
The introductory model of this gage has an adjustable range of 5.1 inches (129 mm) to 6.2 inches (158 mm), to accommodate the most common railroad bearing sizes. It is available with either of two adapters (or both) to adjust its size over that range. One adapter is threaded and can be manually rotated to arrive at a desired setting. The other has specific locators for standard bearing sizes.
The bore gage has a spring loaded gage head with a “wing” which retracts as it is pressed against the far wall as it is placed in the bore. For best results the gage contact points and the bore should always be clean and the workpiece (bearing) should be placed on a flat, horizontal surface (bench top). The gage head should be allowed to rest, flat at the base of the bore, on the bench top. This will result in measurements being made within the 3/8 inch to 1/2 inch range of the edge of the bearing as per AAR guidelines. Turn the bearing over to take the measurement on the other end, or use a flat spacer to accurately measure other heights.
In usage, if there is a noticeable difference between the temperatures of the gage and the work piece then allow a few seconds for the built-in temperature sensors to stabilize. The gage uses two temperature sensors. One is mounted behind the circular disc on the front of the measuring contact point. This picks up the temperature of the master during zeroing. The micro computer in TComp is programmed to then assume that it is measuring a work piece temperature after that. The other sensor is built into the gage head to monitor the gage temperature and adjust for any changes. An LVDT within the measuring head detects movement electronically which is converted by TComp into a dimensional measurement and displayed.
Measurement range/LVDT travel: ± .02 inch (± 0.5mm)
Resolution: 0 .00005 inch, 0.00125 mm
Repeatability: ±.0 .0001 inch, 0.0025 mm
Storage for up to 19 part/feature definitions
Environmental: 32°F(0°C) - 125°F(51°C)
Workpiece: 32°F(0°C) - 150°F(65°C)
Humidity range: Maximum 95% relative non condensing.
10°F change ‑ 3.5 secs
30°F change ‑ 5.5 secs
Electrostatic discharge: Tested to + 15kv (I.E.C. spec. 801-2, 1984)
Communications output: RS-232
Touch screen liquid crystal digital display, rechargeable 9v battery or A/C powered; user programmable tolerances and much more.
Gage was zeroed on master. Then gage was heated and cooled while measurements were taken.
The following sample data illustrates the effectiveness of this gage in reducing measurement errors caused by temperature. Note that the temperature compensated measurements remain within +/- 0.0001 inch throughout: