LIBRARY 
 
 TATE PLANT BOARD 
 
 ET-168 December 1940 
 
 United States Department of Agriculture 
 1 Bureau of Entomology and Plant Quarantine 
 
 A MOBILE SAMPLE-CARRYING RACK 
 
 By H. W. Rusk, Division of Insecticide Investigations 
 
 For a number of years fruit samples from apple orchards 
 have been coll<='ct«^d throughout the growing season and brought to 
 the chemical laboratory (for resid\ie-deposit analysis) in inexpen- 
 sive paper bags. This practice has resulted in the physical removal 
 of some of the residues, owing to contact with the bag surface 
 during travel and subsequent handling preparatory to analysis. 
 
 The trailer rack herein described was constructed to carry 
 44 individual samples of 25 fruits each. The fruits are impaled on 
 12-gauge pointed ste^l wire pin!=5 4 inches long. The pins bearing 
 the fruit are placed on the sampling boards and are finally trans- 
 ferred to the sample-carrying boards, which are then slid into their 
 proper place in the rack. 
 
 The method of collecting fruit on wire pins and mounting them 
 on boards or long sticks is not new; as early as 1932 ^ this pro- 
 cedure was used by the Vincennes laboratory of the Division of 
 Fruit Insect Investigations for collecting fruit from field spray 
 plots for artificial infestation under controlled laboratory 
 conditions. At that time the sticks bearing the fruit were placed 
 in slotted drawers of large wooden boxes, which v/ere brought in 
 from the field by truck. From 1936 on, a four-wheeled trailers 
 bearing a specially constructed rack has been in use by the Division 
 of Fruit Insect Investigations for carrying samples for biological 
 testing from the orchard to the laboratory. 
 
 It will be seen, therefore, that the trailer rack herein 
 described is merely an adaptation of a previously devised rack, 
 the alterations in design being made in such a fashion as to make 
 
 1 Lathrop. F. H.. and Sazama. R. F. 1952. A laboratory- 
 field method for the study of the efficiency of codling moth 
 sprays. Jour. Econ. Ent. 25: 83-96. illus. 
 
 2 Steiner. L. F. 1939. The laboratory-field method for 
 testing codling moth insecticides. U. S. Dept . Agr. . Bur. Ent. 
 and Plant Quar., E-48a, 10 pp. (multigraphed) . illus. September 
 1939. 
 
- 2 - 
 
 it more suitable to the sampling for chemical analysis It permits 
 the placing of an entire 25-fruit sample on a single board. The 
 boards are of a size that v/ill allow them to accommodate 25 fruits 
 up to 2| inches in diameter. For larger fruit it will be necessary 
 to space the holes for the wire pins a little differently, and the 
 number of fruits per board will have to be reduced. 
 
 The trailer rack was constructed according to the plans 
 given in figures 1 and 2. Figure 3 shows the truck and trailer 
 ready for travel from the orchard to the laboratory. Figure 4 shows 
 the trailer open and ready to receive the samples. In figure 5 a 
 sample-carrying board has been mounted on the side of the rack to 
 illustrate the way in which each stratum sample is placed in it. 
 Directly below it are shown the sampling boards with their respec- 
 tive fruits ready for transfer to a sample-carrying board. In 
 position from left to right it will be seen that 7 fruits are taken 
 from the top stratum of each tree, 10 from the middle stratum, and 
 8 from the bottom stratum. By this placement it is possible to 
 conduct studies of residue loads on either the entire tree or 
 sections of a tree. Figure 6 shows a view of the rack with some of 
 the boards filled with fruit and in place. 
 
 The trailer itself is a small two-wheeled unit consisting of 
 chassis, springs, axle, roller-bearing 16-inch wheels, and trailer 
 hitch. 
 
 The bottom frame illustrated in figure 1 was bolted directly 
 to the trailer chassis in several places with 3/8-inch carriage 
 bolts of suitable length. Flat washers and lock washers were used 
 in all cases to prevent the nuts from working loose. 
 
 To prevent the sample-carrying boards from jumping out of 
 their grooves during transit, it was necessary to use square-bend 
 screws 2 inches long with ^-inch bends. One screw inserted in each 
 runner about 10 inches from the front of the rack was found to be 
 sufficient to prevent any jumping of the boards. The screws were 
 run down until the projecting bends were about 1/8 inch from the 
 sample-carrying boards. 
 
 The sides of the trailer rack are covered during transit 
 with curtains of automobile topping material. These curtains 
 contain a piece of strap iron -f inch wide and 6] inches long, which 
 is inserted in a hem in the bottom of the curtains to weight them 
 down. The sides of the curtains are folded around the front and 
 the back of the trailer and secured in place with automobile curtain 
 snaps. During the sampling the curtains are rolled up to the top 
 of the rack and held securely by cloth straps. 
 
3 - 
 
 As a safety measure a combination stop light and tail light 
 was mounted at the left rear of the trailer rack. Two-wire cable 
 with a detachable coupling was used, the two circuits being grounded 
 to the trailer chassis, which in turn grounds to the truck chassis 
 through the hitch. 
 
 A list of lumber necessary for the construction of the 
 trailer rack is given below. It should be noted that all dimensions 
 of lumber are full measure, in which case a piece listed as 2 by 
 4 inches is actually that size and not a standard "2 by 4" which in 
 reality is If by 3f inches. 
 
 Lumber List 
 
 2 
 
 1 
 
 2 
 
 10 
 
 2 
 
 3 
 
 2 
 
 6 
 
 5 
 
 24 
 
 20 
 
 10 
 
 4 
 
 88 
 
 1 
 
 1 
 
 2 
 
 44 
 
 2" 
 
 X 
 
 4" 
 
 2" 
 
 X 
 
 4" 
 
 2" 
 
 X 
 
 6" 
 
 2" 
 
 X 
 
 2" 
 
 2" 
 
 X 
 
 4" 
 
 2" 
 
 X 
 
 2" 
 
 1" 
 
 X 
 
 2" 
 
 2" 
 
 X 
 
 2" 
 
 1" 
 
 X 
 
 4" 
 
 1" 
 
 X 
 
 4" 
 
 1" 
 
 X 
 
 10 
 
 1" 
 
 v/ 
 
 8" 
 
 1" 
 
 X 
 
 6" 
 
 1" 
 
 X 
 
 1" 
 
 X 60" Bottom frame 
 X 52" Bottom frame 
 X 42" Bottom frame 
 
 Side posts 
 
 End posts 
 X 60" Side ties, middle ridge tie 
 X 42" End ties 
 
 Cross runner stops 
 
 Cross runner rests 
 
 Runner supports 
 
 X 53 
 X 53 
 
 X 56 
 X 56 
 X 20 
 
 X 10" X 20" Runner supports 
 X 20" Runner supports 
 X 20" Runner supports 
 X 20" Runners 
 42" X 60^" X i" 3-ply veneer top 
 
 42" X 60" X t" 3-ply veneer bottom (notched to fit) 
 42" X 53" X t" 3-ply veneer ends 
 If" X 10" X 20" sample-carrying boards (white pine or other 
 
 soft wood) 
 If" X 7" X 13" sampling boards 
 
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 Figure 5. — Method of placement of fruit. 
 
 Figure 6 — Rack partiallj filled with fruit. 
 
\ 
 
 Figure 3. — Truck and trailer ready for travel. 
 
 ■<r->s~- "Vi. 
 
 Figure 4-' — Trailer open to receive samples. 
 
UNIVERSITY OF FLORIDA 
 
 3 1262 09240 8771