Testing machine that operates without any lubrication of the machine elements within the vacuum chamber measures static friction and sliding friction at very low speeds. Moving parts are held to a minimum to simplify operation in the vacuum chamber

Skyrus, J.

Wilkinson, C.

English

NASA Technical Reports Server

October 1967	
-	 Brief 67-10379 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Machine Tests Slow-Speed Sliding Friction in High Vacuum 
Strain Gage Leads 
Strain Gage
Vacuum Chamber Door 
Load Beam
Frame 
Pin Holder
	 Bellows Seal 
Drive Screw 
Lubricated
 
Plate	 Movable 
Platform
Jj Differential 
Ribbon II Transformer	 Transducer 
Suspension// Transducer
	 Leads 
The problem: 
To design a machine to measure the effectiveness 
of solid lubricants (e.g., molybdenum disulfide) be-
tween slow-speed sliding members at various frictional 
loads in ultrahigh vacuum. 
The solution: 
A testing machine that operates without any lubri-
cation of the machine elements within the vacuum 
chamber. The machine measures static, or starting 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
friction as well as kinetic, or sliding friction at very 
low speeds. Moving parts are held to a minimum to 
simplify operation in the vacuum chamber. 
How it's done: 
The friction pair (sliding surfaces) to be measured 
consists of three spherically tipped, equidistant pins, 
and a plate specimen. Pins and plate, or the plate 
alone, are coated with the lubricant to be evaluated. 
When only the plate is lubricated, the pins are pol-
ished to a 400 grit metallographic finish.
(continued overleaf) 
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19670000379 2020-03-11T21:07:31+00:00Z
The movable platform, which carries the plate 
specimen, is suspended from the frame by four flexible 
steel ribbons A shaft attached to one end of the plat- 
form passes through a bellows seal in the door of the 
vacuum chamber to an exterior drive mechanism. The 
pin holder supports weights which press the pins 
against the plate. The force measuring system consists 
of two beams with four bonded strain gages. These 
gages are connected in a conventional Wheatstone 
bridge arrangement, with leads passing through a seal 
in the chamber door to an external amplifier—recorder 
circuit. 
As the platform is driven back and forth in a linear 
motion by the drive mechanism, friction between the 
attached plate specimen and the contacting pins tends 
to move the pin assembly along with the platform and 
plate. However, the linkage between the pin holder 
and load beams restrains the pin holder, so that the 
pins slide against the plate. Because of the- frictional 
force, the load beams bend slightly and correspond-
ingly deform the strain gages. The resultant unbal- 
ancing of the bridge circuit provides an electrical 
signal which is proportional to the frictional force.
This signal is amplified by a two-channel strain gage 
amplifier—recorder and appears as an ink pattern on 
one channel of the recorder chart. The position of the 
pins relative to . the plate is determined from the out-
put of the differential transformer transducer attached 
to the shaft drive mechanism. This output signal ap-
pears simultaneously on the second channel of the 
chart.	 -	 -	 -	 - 
Note:	 - 
Details concerning the design and operation of the 
machine as well as the results of experiments with 
typical solid lubricants may be obtained from: 
Technology Utilization Officer 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: B67-10379 
Patent status:	 - 
No patent action is contemplated by NASA. 
Source: C. Wilkinson and J. Skyrus 
- of Douglas Aircraft Co., Inc. 
-	 under contract to 
Marshall Space Flight Center 
(MFS-12341) 
Brief 67-10379	 Category 05


Machine tests slow-speed sliding friction in high vacuum

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