|
|
|
|
|
The two principal systems of measurement in current use in the world are the metric and imperial systems. Nine-tenths of the world's population, that is most of Africa, Asia, Europe, Central and South America, use the metric system as the legally accepted form of measurement. The imperial system, or a variant of it, is used in the British Commonwealth and the United States.
The metric system, in the form known as the "Systeme International d'Unites" (SI), was adopted in 1960 at the eleventh International General Conference on Weights and Measures. This system was accepted by most countries in the world as the international standard for trade, communication and scientific research. There is little doubt that the metric system is an easier and more effective system than its imperial counterpart.
At the present time over twenty countries, including Australia, Canada, Ireland, New Zealand, South Africa and the United Kingdom, are in the process of changing to the metric system. The United States is the only major country still retaining the imperial system, but Congress and other bodies are currently investigating the effects of conversion. Metrication, the process of changing from imperial to metric units, involves in general a well planned, co-ordinated programme of voluntary conversion, industry by industry. In New Zealand this programme commenced in 1969 with the establishment of the Metric Advisory Board, and it is intended that this conversion process will be substantially completed by 1976. Many industries in New Zealand, Australia and the United Kingdom have already completed the changeover and, for most of them, metrication has provided an opportunity to rationalize and standardize the range of sizes of products. Manufacturers faced with re-tooling and3e-setting of equipment have made a critical examination of their methods and materials of construction. Many manufacturers have adopted a completely new range of measurements rather than accept a direct translation of imperial sizes into exact metric equivalents or "rounded-off" values. Beekeepers should familiarize themselves with the likely effects of metrication. In general the total replacement of old imperial items with new metric sizes will cause few problems, but greater attention will be required when modifying, extending or adapting existing equipment. Beekeepers will have little influence over the conversion of general commodities; for instance, sizes of nails, nuts, bolts, timber and containers will be converted at the will of the manufacturing industries. However, the beekeeping industry (beekeepers and hive manufacturers) has a significant voice in the metric specifications for beekeeping equipment.
Figures for metric Langstroth hives are taken from the following:
France: DEXANT, P. S. (1951) Construisez vous-meme votre materiel apicole. Toulouse: Editions Aldex
Mexico: WULFRATH, A. & SPECK, J. J. (1960) Pequena guia para el apicultor principiante Mexico, D.F.: Edifora Agricola Mexicana
Greece: STEPHEN, W. A, (1973) personal communication
Other figures are taken from the references cited: a dash () indicates that no figure was found, not that none exists.
Of the many hive designs in the world, the Langstroth hive has undoubtedly proved to be the most popular. It dominates the beekeeping scene in North and Central America, Australia and New Zealand, and is present in South America; it is much less used in Britain and in Europe.
Bees have a remarkable ability to adapt to almost any type of nesting cavity, whether it is a drain-pipe or a hive of the most elaborate design. L. L. Langstroth developed a satisfactory movable-frame hive in 1851; as a result of his successful promotion of it (including publication of his book The hive and the honeybee), it became the first commercial movable-frame hive to gain wide popularity. Langstroth may have used champagne crates for his original hives; if so, his retention of the basic dimensions of these crates during subsequent modifications of his hives* could explain why he adopted so many fractional measurements (e.g. frames 17 5/8 x 9 1/8 inches). Over a period of 125 years the Langstroth hive has proved to be a most practical unit, meeting the requirements of both amateur and commercial beekeepers, and under proper management, and with excellent nectar flows, honey yields in excess of 250 kg per colony have been obtained.
Considering the widespread popularity of the Langstroth hive, it might be expected that there would be one international metric standard, but there is not. Most of the Langstroth users are in the non-metric countries, particularly the United States, Canada, Australia and New Zealand. In countries where metric Langstroth hives are used, for instance Argentina, France, Greece and Mexico, considerable diversity in specification is evident (see Table 1). Even in countries with imperial Langstroth hives, slight dimensional differences occur between countries, states or counties, manufacturers and advisers.
The New Zealand Langstroth hive (21) differs in a number of ways from the North American version. The hive body has an inner width 3/8 inch (9.5 mm) narrower than the United States Department of Agriculture standard (11). New Zealanders have favoured "bottom bee space" equipment, the frames riding high in the hive body. In North America, Australia and the United Kingdom, Langstroth hives have a "top bee space" a 1/4 inch (6.4 mm) bee space above the top-bars and below the upper rim of the hive body. These and other differences have required special consideration in the formulation of appropriate metric measurements for the New Zealand Langstroth hive.
The bee space is of major importance in all hive construction. It is the spacing between adjacent frames, or between the frames and the hive body, which the bees generally keep free of propolis or comb (Fig. 1). L. L. Langstroth in 1851 exploited the principle of the bee space, which had been known in Greece in the 1600s (5) but probably not in Ancient Greece (3).
The Langstroth bee space of 1/4 - 3/8 inch (6.4 - 9.5 mm) has remained the standard in most countries, although some variations exist e.g. 3/16 - 5/16 (4.8 - 7.9 mm) in Britain (9). In New Zealand the metric bee space has been accepted as 7.5 plus or minus accepted as1.5 mm.
Langstroth, in developing his 10-frame hive, did not have at his command the scientific principles and procedures now used in establishing and evaluating new processes. Despite this, his hive measurements have generally stood the test of time. Many studies have confirmed the size of the bee space as 1/4 - 3/8 inches, although recent evidence suggests that bees may accept greater tolerances. Using a micrometer, measurements on the distance between naturally built combs gave a bee space varying between 6.4 mm and 19 mm (15).
The width of the end-bar of the self-spacing brood frame is one measurement open to debate. The width of Hoffman's end-bar (1 3/8 inches, 34.9 mm) ensured that worker brood combs are spaced no less than 1 3/8 inches midrib to midrib. Recent work (1) demonstrated that a spacing of 32 - 33 mm between brood combs was best for Italian hybrid and Carniolan bees; with only a few strains of honeybee did the spacing approach the Hoffman 35 mm. Research into colony founding and initial nest design showed that the bee space plus comb thickness increased with increasing population from 31.8 mm to 38.1 mm. The latter measurement included drone and honey storage combs, which in nature are spaced at greater midrib-to-midrib distances than worker brood comb.
The internationally accepted end-bar width of 1 3/8 inch (34.9 mm) thus appears to be slightly greater than the natural spacing used by bees. Metrication may provide an opportunity to re-specify this. New Zealand has adopted 33 mm as the metric end-bar width of a Hoffman self-spacing frame.
The New Zealand Ministry of Agriculture and Fisheries, in its advisory capacity, has attempted to assist agricultural industries in their adoption of the metric system. The timber industry's conversion to the metric system in January 1975 was considered as the deadline for the selection of an appropriate metric specification for hive equipment. After preliminary investigations into the scope, extent and effects of metrication of hive equipment, the Ministry of Agriculture and Fisheries published a 30-page study paper (18) "Background to metrication of beekeeping equipment". This paper was designed to generate discussion and awareness among beekeepers, equipment manufacturers and advisers. Feedback, in the form of criticism, comments and alternative proposals, was collated and evaluated. Concurrently, during the 1973/74 honey season, hives and hive parts manufactured to metric dimensions were tested in the field.
By May 1974 the Ministry of Agriculture and Fisheries had completed its review of metric hive measurements, and presented to the industry its report (19) "Proposals for the metric Langstroth hive". This took place at two meetings, to which the National Beekeepers' Association of New Zealand sent its nominees, representing bulk honey producers, section comb honey producers, and equipment manufacturers. The Ministry's proposals served as a basis for discussion. Arising out of these meetings metric measurements were adopted that standardized the length, breadth and depth of hive bodies and frames. The adopted measurements were then promoted at meetings and in published articles (20). The Ministry of Agriculture and Fisheries now proposes to publish a revised plan for the construction of the 10-frame Langstroth hive, based on these adopted metric measurements.
In any conversion of hive measurements from imperial to metric units special attention must be paid to the bee space and to the effects of equipment interchange.
When more than one hive pattern is in existence, difficulties may occur in attempting to convert to the nearest whole millimetre. In many countries, the government agricultural body sets a standard for the benefit of the industry. This standard may be accepted, modified or rejected by state or county beekeeping advisers, hive manufacturers and by beekeepers. As a result, the average hive in the field may depart somewhat from the national standard.
For most items of Langstroth equipment the old imperial recommendation of the Ministry of Agriculture and Fisheries (21) would represent the preferred measurement for hives in New Zealand apiaries. However a few notable exceptions occur. For instance the length of the bottom-bar was recommended as 17 13/16 inches (452.4 mm) by the Ministry of Agriculture and Fisheries, whereas New Zealand's largest equipment manufacturer offered two types of bottom-bar, one 17 3/4 inches (450.9 mm) long and the other 17 5/8 inches (447.7 mm). All three bottom-bars are in common use. A compromise measurement of 450 mm has been accepted as the metric standard.
The situation is more complex in Britain, where a number of hive types are used, including the National, Smith, Modified Commerical, Langstroth, Modified Dadant, and double-walled WBC hives. It may be decided that a metric specification is required for each hive type. On the other hand metrication could provide a useful opportunity to reduce the number of recommended hives. Hive standardization has long been a topic of vigorous discussion in Britain. Two recent contributors (2, 17) have advocated that the Langstroth hive should be accepted as the standard British hive.
The economic consequence of any change in specification is of vital concern to most beekeepers, and in particular to commercial beekeepers. The value of beekeeping equipment in many countries represents a multi-million dollar investment. If metrication rendered existing equipment obsolete, it is highly unlikely that beekeepers would accept a newly dictated dimension at least until such time as the three-foot ruler breaks.
In New Zealand it was accepted as a basic principle that metric equipment should be freely interchangeable with non-metric equipment. In general most hive parts are constructed to a standard specification. However on occasions some manufacturers introduce slight changes that acquire wide popularity, and this type of variation from the original specification should be recognized. The metric specification adopted in New Zealand (Table 1) departs little from the non-metric specification, and lies well within the wide range of equipment variations in use.
Of all the dimensions affected by the interchange of metric and imperial equipment, the most critical is the top-bar "play" - the clearance between the end of the top- bar and the inner rebated surface of the hive body (Fig. 1). The metric top-bar play should not be less than 1 mm nor greater than 2 mm, otherwise the frames would be held too tightly or too loosely within the hive body. An imperial top-bar length of 19 inches (482.6 mm) and an inner rebated length of 19 1/8 inches (485.8 mm) for the Langstroth hive gives a top-bar play of 1/16 inch (1.6 mm). The newly adopted metric dimensions in New Zealand specify a 482 mm top-bar, 485 mm inner rebated length, and a 1.5 mm top-bar play.
The change-over will include a slow phasing-in and phasing-out period. It will be many years before full conversion is finally achieved. Frames may last more than 20 years, and well preserved imperial hive bodies and roofs could still be in existence in 50 years' time. A thorough mixing of metric and non-metric frames and hive bodies is anticipated.
During the change-over period, full consideration must be given to the space between the frames of one hive body and those of the hive body above. Four arrangements of frames within hive bodies are possible: imperial frames in an imperial hive body, imperial frames in a metric hive body, metric frames in an imperial hive body, and metric frames in a metric hive body. One of these units placed upon another offers a total of 16 combinations of bee space between the two hive bodies. Interchange difficulties may occur if the metric depth measurements for the hive body, rebate, frame, and top-bar lug depart significantly from the imperial measurements for these depths.
It is possible to replicate existing hive specifications in metric terms simply by converting the imperial measurements to the nearest millimetre. This procedure would seem to be the easiest approach to hive metrication; it has been recommended by F. G. Smith (12), who has much knowledge of hive design, and adopted (10) by Pender Limited, an Australian hive manufacturing company. In New Zealand, conversion to the nearest millimetre was considered to be neither essential nor desirable, for a number of reasons which are discussed in the following sections.
Metrication presents an opportunity to ease or eliminate undesirable measurements. If direct conversion to the nearest millimetre were adopted, any weaknesses in the imperial specification would only be readvocated. Very few changes have been considered necessary to Langstroth's hive. Many experiments and trials have sup- ported the validity of the original specifications. However, if evidence clearly established that optimal colony conditions could be achieved by minor changes to the existing measurements, then these changes should be evaluated.
One particularly inappropriate measurement in New Zealand has been the 7/32 plus or minus 3/32 inch (5.6 plus or minus 2.4 mm) bee space between the end-bar and the hive body. The general measurement represents the degree of play in the top-bar. This unfortunately small spacing has often resulted in frame immobilization. With metrication a new spacing has now been accepted, 7.5 plus or minus 1.5 mm, very similar to the North American bee space of 5/16 plus or minus 1/16 inch (7.9 plus or minus 1.6 mm).
In New Zealand the millimetre has been used as the unit in preference to the centimetre, to conform with the terminology set by the building industry. Conversion to the nearest whole millimetre would result in a number of "awkward" sizes that are difficult to memorize, e.g. 483 mm as the metric length of a 19-inch (482.6 mm) top-bar, and 241 mm as the depth of the 9 1/2 inch (241.3 mm) Langstroth hive body. There are several metric options for most hive measurements, and these could be used as alternatives while still preserving the appropriate bee space and permitting an interchange of metric and non-metric equipment. For the sake of future generations convenient measurements are to be preferred. Multiples of 5 mm are practical saw-bench measurements. Otherwise, even numbers are preferable to odd numbers; 1 mm is about the finest measurement that can be obtained with accuracy in milling and refining timber.
All New Zealand hive dimensions have been specified in whole millimetres, and a subdivision of a millimetre occurs only in bee space measurements, e.g. 7.5 plus or minus 1.5 mm.
Although in metrication we endeavour to make "metrics fit hives", not to make "hives fit metrics", some thought must be given to the raw material of the hive timber. In countries facing a metric changeover, the timber industry will adopt new standard sizes for timber. In so far as metric sizes depart significantly from present sizes, the hive manufacturer may be forced to re-examine his manufacturing methods. He will be looking for the most efficient and economical way of making hive components, without undue wastage of timber; the purchase of non-standard, specially cut, timber would greatly increase hive equipment costs.
In New Zealand the timber industry has adopted metric units that are, in general, multiples of 25 mm. The 250 x 25 mm board replaces the imperial 10 x 1 inch (254 x 25.4 mm) used as basic stock by hive manufacturers. The 9 1/2 inch (241.3 mm) depth of the Langstroth "full-depth" hive body can be obtained from 10-inch green-sawn Pinus sp timber. Unfortunately the new green-sawn width of 250 mm will not allow sufficient margin for a metric equivalent of the old 9 1/2 inch depth after weathering, shrinkage and distortion. As a result, 238 mm (approximately 9 3/8 inches) has been accepted as the depth of the hive body. Where the breadth or thickness dimensions of hive components are not critical, it is desirable that these measurements conform to other measurements used in hive body construction. For instance, if the decking for the floor board or hive lid is the same thickness as that of the hive body, standard timber can be efficiently used.
The internal dimensions of the hive body (Fig. 2) are more important than the external dimensions, because (along with the frame measurements) they determine the bee space between hive parts. Although 7/8 inch (22.2 mm) is accepted widely as the standard wall thickness of the hive body, this may vary from manufacturer to manufacturer, or from one run of milled timber to the next. As a consequence, slight changes in external dimensions may be required to maintain the standard internal dimensions.
The internal length of the imperial Langstroth hive is 18 1/4 inches (463.6 mm). This provides an adequate 5/16 inch (7.9 mm) bee space between the end-bar of a 17 5/8 inch (447.7 mm) frame and the wall of the hive. New Zealand has adopted 465 mm as the internal hive body length and 450 mm as the bottom-bar length. These convenient metric measurements are within 1 - 2 mm of existing measurements, and provide a bee space of 7.5 mm.
Hive bodies usually hold 8-12 frames, the 10-frame Langstroth hive body being the most common. The internal width of this hive body varies considerably from country to country. It is 14 1/4 inches (362.0 mm) in Australia (13) and New Zealand (21) 14 1/2 inches (368.3 mm) in Britain (9); 14 5/8 inches (371.5 mm) in the USA (11); and 14 7/8 inches (377.8 mm) in Canada (16). Differences also occur between states, provinces and counties. In practice the maintenance of a bee space between the outer frames and the hive wall has been forsaken in favour of improved frame mobility. Beekeepers often reduce the frame number to 9 for the brood chamber and to 8 for the honey super. New Zealand has adopted 365 mm as the internal hive body width. This slightly wider hive body, together with the 33 mm Hoffman end-bar, improves frame clearance when there are 10 frames in the brood chamber.
A depth of 9 1/2 inches (241.3 mm) has been widely accepted for the standard Langstroth full-depth body. Variants of the imperial hive body depth in use in English-speaking countries include the Modified Dadant, or jumbo, at 11 5/8 inches (295.3 mm); WSP at 7 1/2 inches (190.5 mm); the New Zealand 3/4 depth Langstroth at 7 1/4 inches (184.2 mm); the Manley honey super at 6 5/8 inches (168.3 mm); the Ideal or shallow super at 5 3/4 inches (146.1 mm); the New Zealand half-depth Langstroth at 5 1/4 inches (133.4 mm); and the section-comb super at 4 3/4 inches (120.7 mm).
In converting to the metric system, certain convenient, rounded measurements are possible; for instance, 240 mm, 170 mm and 120 mm may be appropriate in most countries for the depth of the standard, Manley and section comb hive body respectively.
Many sizes and types of frame are in use throughout the world. To provide the correct bee space above and below the frames, the frame depth is usually 5/16 - 3/8 inch (7.9 - 9.5 mm) less than the depth of the hive body containing the frames. If properly dried timber, free from distortion, is used in hive construction, it is suggested that a bee space of 8 mm should be left above and below frames.
The Hoffman brood frame has achieved international popularity, and it has been adapted for most depths of hive body. The Hoffman frame is frequently used in the honey super, although its self-spacing end-bar is designed specifically for the brood nest. The so-called Manley self-spacing frame is designed for the storage and extraction of honey. It too has proved popular in many countries, particularly in recent years. Mr. R. O. B. Manley first described this frame in 1946 (7); he acknowledges that the credit for its manufacture should be given to Mr. E. W. D. Madoc (8). The Manley frame is usually associated with a hive body 6 5/8 inch (168.3 mm) deep.
Once the basic metric dimensions for length, breadth and depth have been determined for the hive body and frames, it becomes possible to specify the dimensions of other hive components. Floor boards, inner covers, hive lids, division boards, excluders and pallets: all these reflect the length and width measurements of the metric hive body.
The 10-frame Langstroth hive body has proved to be the most popular unit for comb honey production. It contains seven section holders, each with four 4a-inch (108-0 mm) square sections, and eight separators. This large number of small components requires detailed accuracy in construction. Very few options are available in the selection of equivalent dimensions. To prevent difficulties with the realignment of timber-cutting equipment, the section should retain its present size and shape.
If changes have occurred to the inner dimensions of the frame, some modification in the size of the comb foundation sheet may be required. The Langstroth-size foundation sheet is 16 3/4 x 8 inches (425.5 x 203.2 mm). A foundation sheet 425 x 200 mm has been proposed for the slightly shallower New Zealand metric frame. The dies used in embossing the hexagonal pattern on foundation wax are unaffected by metrication. They usually emboss 857 cells per square decimetre for worker brood comb, and 520 cells per square decimetre for drone comb (4). Recent work in USA (15) has suggested that 813.8 and 540 cells per square decimetre respectively are more appropriate measurements.
For those countries intending to convert to the metric system a national team approach is required. Metrication should not be an occasion for manufacturers and advisers to go it alone and impose their "standards" on others. This would result in an even greater variety and incompatability of hive equipment than exists at present. Implications of the change-over must be fully considered. This involves a re-appraisal of existing equipment in common usage, and the specification of acceptable metric standards deemed necessary to meet the present and future needs of the industry. Difficulties in resolving a standard must be anticipated, particularly when hive differences occur between manufacturers, states or counties.
A national or regional meeting of all affected parties should consider the implications of metrication, and resolve on a satisfactory standard. A decision to round-off all imperial measurements to the nearest millimetre may prove to be the most acceptable national approach to metric standardization. The use of unsatisfactory dimensions may, however, be perpetuated by such a decision, and a valuable chance to improve them may be missed. The real danger lies in metrication by default, when no decision is taken by the industry.
Metrication has presented New Zealanders with an opportunity to reassess and rationalize hive measurements, while preserving continuity in the change-over from existing equipment. The process of selecting metric measurements has been aided by many factors, including the relatively small size of the beekeeping industry (210,000 hives), a single hive type, one major manufacturer of equipment, and a willingness on the part of the industry and ancillary groups to co-operate as a team.
Home NZ Bkpg Bee Diseases Organisation Information Contacts
Email to Nick Wallingford, webmaster of the site...