MODEL BUTTER BOX.

Waikato Times, Volume 100, Issue 16813, 3 June 1926, Page 10

MODEL BUTTER BOX.

STRONGER FOURTEEN FOLD—YET CHEAPER. RESTNED NAILS—N.Z. TIMBER WINS. ECONOMIC IMPORTANCE TO DAIRY INDUSTRY. Willi Iho object of improving Iho service nliilily of huller-boxos used in the export trade Jll <• l-'oresl Service iiindc a series of tests, and lias now developed, as a result of these tests, an attractive metal-strapped box fourteen times stronger than the present unstrapped box, occupying 3 per cent, room and costing from Jd to lid less. A detailed specification for its manufacture is submitted. The tests further indicate the superiority of cementcoaled nails over smooth wire nails, and of the white pine and beech boxes over the imported spruce, packages, whether from North America or Scandinavia.

The current issue or the New Zealand journal of Agriculture contains an article on butlef-hox tests and studies by Mr W. C. Ward, of the l-'oresl Products branch Of the Forest Service. The studies were directed to llu: development of balanced construction lo minimise breakage during transit. The writer states —

"The laboratory studies here described combine practical experience—which is a knowledge of the designs in use, of what limber is available', and of box-factory practice—with accurate scientific tests made on the package ilself, packed as in actual service and subjected to strains that approximate actual transport conditions. Essential Needs. "The main purpose of the study was to develop a balanced and economical construction —that is a box which has enough slranglh in each part for the purpose for which .it is intended, and no more strength in any part I ban is necessary lo balance, the average strength in every other pari. The essential qualifications for an export butler package are (.1) that it be strong enough lo stand up under exceptionally rough handling; (2) that it be able to resist punctures from the corners or edges of other containers; (3) that it occupy the minimum of space; and (i; that it be difficult to open and reclose without special tools —a preventive of concealed pilfering. It was necessary to secure these four qualifications without a burdensome cost.

"Although the immediate purpose was to formulate a specification for a standard box for the export trade the scope of the work was extended lo include a study of the various types of containers now in common use, and lo provide data for the general instruction of box manufacturers and users regarding certain fundamentals of box design. The study may be still further extended at a later date to investigate other types of butter containers which appear to promise improvement upon existing practices." After setitng out the specification worked to and other matters the article describes the tests by the revolvingdrum box-testing machine. Revolving-drum Test. "The most practical method yet devised for testing packing-boxes is the revolving-drum test. For this purpose a replica of the machine shown in Fig. 3 was installed by the Forest Service at its timber-testing station maintained at the School off Engineering, Canterbury University College, Christchurch. The drum is a hexagonsided machine, and revolves slowly at a rate of 1 5-0 revolutions per minute. "The box to be tested is packed with 561 b butter, as in commercial service, and placed in this drum. In the drum is arranged a series of hazards, which cause the box to follow a regular cycle of drops, falling upon sides, top, bottom, ends, edges, corners, and flatwise upon a projection similar to the corner of another box. These drops simulate the usual hazards of transportation. Each face of the drum is counted as one drop. "To facilitate the recording of the locations and character of the failures the faces and edges of the box are numbered as shown in Fig. 4. As the box moves on from one drop to the next the observer notes the beginning of the failure of the weakest point in the construction, and follows its development and that of other weaknesses until the box entirely fails and lets its contents out. The weak features of the box may be 100 few or too short nails, or too thin sides or ends. Such weaknesses arc studied until' the observer is able to build up a box having equal strength in every feature and capable of delivering its contents in the same condition as when first shipped. "The mechanical tests ol the bindings and fastenings were made at the Forest Service timber-testing station maintained at the School of Engineering, Auckland University College." Cement-coated Nails Necessary. After giving technical details Mr Ward summarises bis conclusions, which arc important to timber-curers and sawinillers, as well as boxmakers and users of boxes —■ 1. The use of cement-coaled nails is essential if an economical and balanced package is to be designed. 2. Adequate nailing is of the utmost importance in box construction. 3. Silver beech ranks first, white pine second, and spruce last in suitability for butter boxes when carrying qualities arc considered. 4. The one-piece-side box Is markedly superior lo the two-piece-side box. 5. Flat strapping or wire binding of unanncalcd metal is of great value as a reinforcement on all boxes. 0.- Resistance lo loss ci' contents increases with the number of straps used. Two straps applied in two directions gave better results than two straps applied parallel. 7. Decreasing the thickness of sides, top ,and bottom of white pine boxes below 3-Sin results in marked reductions in strength. 8. Wire bindings of annealed metal increases the resistance of a box to loss of contents, but are inferior to Hal strap or wire binding off unanncalcd metal. 9. Sides less Ihan 5-1 Gin in thickness puncture easily. The drying of thin boards by arlillcial heal, should be carefully controlled lo prevent brittleness. Secrot Formula of "Cement." • Many people will ask, "What is a cement-coated nail?" .If is not a Portland cement-coated nail. The cement is a resin obtained by a formula which apparently the American researchers (or the buyers of their idea) have, kept secret. This is wfial Mr Ward says about it "Cemcnl-conteil nails arc used almost universally by box manufaclurers in Canada and Hie foiled Slab--, j as they have a much higher resistance j

to withdrawal than plain uncoated nails. The cement coaling of the nail consists of various resinous gums mixed by a secret formula and put on the nails by a baking process. Though the makers do not claim that the nails are absolutely rust proof, they do claim that nails thus treated will resist the effects of moisture from 20 to 50 per cent, belter than Ibe uncoated wire, nail. But it is when in use that the non-rusting quality is most evident. There is more coaling on the nails Ihan is actually necessary for holding power. The heal caused by the friction in driving the nail softens Ibe coaling, and the surplus is forced towards the head, completely closing any opening; Ibis prevents the admission of moisture between the wood and the nail. Under similar conditions of use the life of a cement-coaled nail will be about twice as long as that of an uncoated one. They are claimed to require less force to drive, as the softened coating forms a lubricant.

"Any slight difficulties attached to their handling in the box factory do not outweigh the advantages gained, and it is very desirable that the cementcoated nail should be adopted for boxing work throughout New Zealand. Whereas a 2in cement-coated nail driven 1 5-Bin into the side grain of a piece of American pine required a force of 2201 b to withdraw it, a common nail under the same conditions was withdrawn with a force of only lOGlb. . . ."

Chart 2 shows the relative resislance to loss of contents between the three kinds of boxes in common use in New Zealand. The results arc borne out by practical experience. The white pine box resisted loss of contents more than four times better, and the beech box more than eight times better, than the spruce box. The poor nail-holding quality of the spruce wood and its tendency lo split easily are features which do not produce a box of first-class carrying qualities." "The'following organisations (writes Mr Ward) have co-operated with the Forest Service in the work here described: Dairy Division, Department of Agriculture—general; School of Engineering, Canterbury University College —box tests; School of Engineering, Auckland University College—binding tests; Messrs .1. F. Hargreaves and Co., Ltd., Wellington, New Zealand agents for Acme, strapping; Papanui Cool Stores, Ltd., Christchurch—general; Johnson, Clapham and Norris, Ltd., Wellington, and United States Steel Products Company, New York—-cement-coated nails.

"Special acknowledgment is due to the .Madison Forest Products Laboratory of the United Stales Forest Service for its many reports upon box design. These have enabled the present work to be carried to a concllusion without the laborious investigation of many features of design already studied by the American laboratory. "The planning, supervision and presentation of the study have been made under the charge of Mr A. 11. Enlrican, Engineer in Forest Products, State Forest Service."