﻿22 



BULLETIN 17, U. S. DEPARTMENT OP AGRICULTURE. 



layer of C and D, the difference in side-wall insulation does not seem 

 sufficient to account for the difference in efficiency. The striking 

 difference in the four types of cars is in the roof insulation. Types 

 A and B, with the low efficiency, have but 1 inch of insulation, and 

 that is divided into two layers with intervening air space. Type 

 C has 1$ inches of solid insulation, and D has two layers, each 

 1 inch thick. There are undoubtedly several factors which govern 

 the efficiency of a car, but it is worthy of note that the indices of 

 efficiency of Table 5 seem to vary in about the same way as the 



A44//V ploop 

 P&PBP? 

 'A/P .SP^CB 



'/-MObel.7- 

 sub-ploop 



>?//? SP4CB 



't/A/OPELT 



SOB-PCOOP 



ma/as ploop 



^/PAPBP 



yS^/ "/Ysl/P PBZ.T 



^.papes? 

 ^sce -pz-oop/a/g- 

 v=7//p spac-b 



B4PBP 

 SUB -BZOOPYA/6 



puoop 



-r.t/ P&PEP 

 ; /^Sl/B-BLOOP 



i/p specs' 

 S "mm? pez. t 

 bc/b-ploop 

 -a/p spacb 



--g "b^/P BELT 

 Si/B-BLOOP 

 VJ//P SPACB 

 ' /-//VO^eZ-T- 

 SUB-PLOO/? 



A7>7//V PZ.OOP 

 P'UBBBPO/D 

 /4/P> BPACB 



b&pep 



Si/B-PZ. OOP/MG 

 A/P SBACB 

 Y" L/A/OrBlT- 

 SOB -PLOOP/A/G 

 A/P SPACE 



^"z/a/obblt 



P&PEP 

 'Si/B-Pi-OOB/A/G 



■/VV4/A/ PLOOP 



PAPEP 

 ■A/P SPACE" 

 P&PEP 

 SOB-Bi-OOB 



BAPBP 



/"BA/PBBLT 

 •PWPBB 

 SCB-PLOOA? 



-Pi-OOP 

 ■SOB-PLOOP 

 /4/B BP&CE 

 •/ "BA/P BBLT 

 .SC0-P2.OOA? 

 A/P SPACE 

 SUB-BL.OOB 

 Al/P SPACE 



^\ SOB-BLOOB 



^^ < — PBIPBf? 



Fig. 7. — Cross sections showing floor insulation of different types of refrigerator cars: a, Type A; 6, type B; 

 c, type 0; d, type D; e, floor insulation separated into three layers;/, 1-inch layer of hair felt with two 

 uninsulated subfloors. 



roof insulation. The floor insulations of the four types are about 

 the same and are very similar in thickness to the walls. 



ICE BUNKERS. 



Each of the types A, B, C, and D is equipped with a characteristic 

 ice bunker. Type A uses the siphon bunker shown in figure 8. 

 Type B has the galvanized-iron box shown in figure 9, the box being 

 perforated to allow the air to come in contact with the ice. Type 

 C has two large, reenforced wire baskets (fig. 10), which permit free 

 contact with the air. In front of the basket ice holder there is an 

 insulated wall, with an open space at the top of the car for the admis- 

 sion of warm air and a similar space at the bottom for the escape of 

 the cold air. Type D uses the iron tanks shown in figure 1 1 . With 

 such tanks the ice can be crushed very fine, permitting a uniform 



