The damping characteristics under three conditions of packing are illustrated in the lowest graphs, and again in these, we see typical effects of fluid or plastic friction.

Figure 32 shows the results observed with grease on the pivots and bearings of a 5-ton capacity self-contained type scale. The lever system was of the conventional A-lever type, with shelf lever and weighbeam. A reading scale graduated in millimeters was used, in connection with a pointer, to register accurately the balance and rest

points. The scale was kept loaded to full capacity throughout the entire series of observations. Special grease No. 349 was the only material used on this scale.

It will be seen that the SR increased from 1.5 to 2.3 pounds as grease was packed in the pivot bearings, beginning with the main levers and concluding with the tip pivot of the shelf lever; it should be noted that no significant increase developed until packing of the shelf lever bearings was begun.

Special attention is directed to the damping behavior of the scale under condition of maximum packing. The two graphs illustrate that the deceleration of the weighbeam motion was quite rapid. It may be observed that when the beam was released from the two opposite extremes of its travel there was a difference of approximately one division in the rest point; that is to say, with all bearings, up to the weighbeam, packed there was a "lag" or "hysteresis" effect similar to that which characterizes the performance of some automatic-indicating scales with moving parts having considerable angular motion.

The fourth and final study (see fig. 33) was conducted with special grease No. 349 on a motor-truck scale of 20-ton capacity.

To summarize the information developed by these studies it may be said that the data indicate:

1. That the effect of packing the pivots and bearings of scales with grease is to reduce the sensitiveness and to produce a damping or decelerating effect on the weighbeam vibration.

2. That the SR effects, in a lever system, are in proportion to the angular motion of the levers treated, being very slight for the main levers, which have little anguar movement, and increasing as packing progresses toward the weigh beam and shelf lever, which have, relatively, a considerable angular movement.

3. That the effects are somewhat greater in the case of loop bearings, where the pivots are entirely surrounded by grease, than in the case of plane or merely concave bearings.

4. That the effects are greater with greases of heavier consistency and, for a given grease, are greater at lower temperatures.

5. That if packing is carried too far toward the weighbeam, a lag or hysteresis effect causes minor inconsistencies in performance. The practical conclusions to be drawn are the following:

1. That the practice of packing scale pivots and bearings with grease to prevent their corrosion, an essential principle of maintenance for many types of large-capacity scales, need not materially affect the performance of the scales if the packing is performed by a competent scale mechanic or other person familiar with the requirements. 2. That the grade and consistency of the grease used should be determined according to the temperatures prevailing in the scale pit and according to the angular motion of the levers treated and the form of the bearings in which it is packed. In this connection it may be said that certain greases having a lime-soap base are said to contain a certain amount of free moisture and that others are said to have some acid content, which increases with exposure to air. One manufacturer, it is understood, has developed a grease containing rustinhibiting ingredients and, while the Bureau has developed no information as to its efficacy, it would seem that such a product would be a more positive rust-preventing agent than a grease containing free moisture or acid.

To conclude these remarks, it will be said that since, in any event, the incidental frictional effects introduced by grease are far less serious than those contributed by rusting of the vital scale parts, and since protective treatment with grease insures a longer period of satisfactory weighing performance and a material reduction in maintenance or renewal costs, it is recommended that the practice be adopted by large-capacity scale owners generally, and that it be advocated and encouraged by weights and measures officials and by scale manufacturers and scale repair agencies.

The ACTING CHAIRMAN. The balance of today's scheduled program, items 17 and 18, will go over until tomorrow morning. Mr. Smith has an announcement to make.

Mr. R. W. SMITH. Arrangements have been completed for the informal meeting requested by a number of officials yesterday afternoon; this will be held this afternoon at 2:30 o'clock, in the Chinese Room at the hotel.

The ACTING CHAIRMAN. Please do not let our meeting this afternoon interfere with the trip through the Bureau; we urge you to make that trip if you have not done so before, because it is very, very important. I would like to ask that as many others as possible attend the meeting, including those representing manufacturers of retail scales, because questions relating to the proper display and manufacture of those scales will be discussed.

(At this point, at 1:15 p. m., the Conference took a recess until 2 p. m.)

FOURTH SESSION-AFTERNOON OF WEDNESDAY,

JUNE 5, 1940

TOUR OF THE LABORATORIES OF THE NATIONAL BUREAU OF

STANDARDS

(The afternoon session of the Conference consisted of a visit to various laboratories of the Bureau, with particular attention to the laboratories of the Weights and Measures Division. The National Standards of Length and Mass were viewed in the vault where these standards are preserved. Visits were also made to the completed Vehicle-Scale House and to the new High Voltage Laboratory, a building of unique construction nearing completion. Those participating in the tour were divided into small groups, each in charge of a member of the Bureau staff who served as a guide.)

(There was also held on this afternoon the informal meeting of a group of weights and measures officials and others, agreeable to the request of a number of officials. This meeting was held at the Mayflower Hotel.)

SECRETARY'S NOTE.-On the evening of Wednesday, June 5, an informal party was held in the Italian Garden at the Mayflower Hotel, for the entertainment of those attending the Conference. Through the courtesy of the United States Secret Service there was shown a sound-motion-picture film, "Know Your Money." Dancing and other entertainment followed. Light refreshments were served.

95

280936-41-8

FIFTH SESSION-MORNING OF THURSDAY,

JUNE 6, 1940

(The Conference reassembled at 9:45 a. m., at the Mayflower Hotel, James O'Keefe, Vice President of the Conference, in the chair.)

REPORT OF COMMITTEE ON SPECIFICATIONS AND TOLERANCES, PRESENTED BY JOHN P. MCBRIDE, CHAIRMAN, AND DISCUSSION THEREON

The Committee on Specifications and Tolerances recommends to the National Conference on Weights and Measures the adoption of the Additions and Amendments to the Specifications, Tolerances, and Regulations for Commercial Weighing and Measuring Devices, copies of which bave already been made available to the Conference. As these recommendations are read, explanatory comments will be interpolated from time to time.

Committee on Specifications and Tolerances.

Mr. MCBRIDE. A new code, as follows, is recommended for tentative adoption. [Reading:]

TENTATIVE SPECIFICATIONS AND TOLERANCES FOR SINGLESERVICE MEASURE-CONTAINERS (EXCEPT MILK BOTTLES)

Note. The following specifications and tolerances are not to be construed to apply to measure-containers used for milk, cream, and buttermilk, these being covered by the code for milk bottles.

DEFINITION

A single-service measure-container, hereinafter referred to as a measurecontainer, is a container intended to be used once only, to determine at the time of sale the quantity of commodity comprising a retail sale made on the basis of liquid measure and to serve as the container for the delivery of the commodity to the customer.

SPECIFICATIONS

1. Capacity.-Measure-containers shall not be subdivided and shall be of one of the following capacities only: 1 gallon, 1⁄2 gallon, 1 quart, 1 pint, 1⁄2 pint, and 1 gill standard liquid measure.

2. Proportions.-The over-all inside height of a measure-container shall not be more than twice (a) the mean inside diameter (if conical or cylindrical) or (b) the length of the short side of a midsection (if of rectangular cross section).

3. Filling point. The capacity of a measure-container shall be determined to a definite filling point, which shall be (a) the top edge, (b) a graduation near the top edge, or (c) the lowest portion of a shoulder, cap seat, or indentation near the top edge, of the measure-container. The filling point shall be sharply defined and it shall extend at least halfway around the circumference or across two opposite sides.

4. Marking. A measure-container shall have its capacity conspicuously marked on the side in combination with the word "liquid" or the letters "liq" when the word "quart" or "pint" occurs. If the filling point is below the top edge, there