BULLETIN 379, U. S. DEPABTMENT OF AGRICULTURE. 



HOT BOXES. 



The frequent occurrence of hot boxes around the machine also was 

 assigned as a cause for many of the explosions. It was asserted that 

 the boxes were allowed to become hot and helped to set fire to the 

 machine. 



The investigators endeavored to obtain information relative to 

 the presence of hot boxes, but the difficulties encountered along this 

 line were increased by the fact that the average operator was not 

 willing to admit that hot boxes occurred frequently in his machine. 

 At the time of the investigation it was difficult to determine definitely 

 whether a boxing had been melted by the fire or had been heated to 

 the melting point before the fire started. During the conduct of the 

 field investigations personal observation of machines while running 

 indicated that a large number of boxings run hot all the time. In 

 some cases the " oiler " could be seen carrying water from the engine 

 and pouring it on the boxes. The results of 113 investigations based 

 on statements of separator men can be summarized as follows : 



One to three each day 2 



One to two each day 1 



No hot boxes 72 



Occasional 33 



One each day 5 



Although difficulty was encountered in obtaining data which were 

 considered authentic, the investigations show conclusively that the 

 presence of a hot box is not essential in order that an explosion may 

 take place. This does not mean that a hot box may not be a con- 

 tributory cause to an explosion if the heat generated is of sufficient 

 intensity and so located as tO' cause ignition. 



DAMAGE TO SEPARATOR. 



The damage to the separators varied from very slight damage to 

 total destruction. In cases where fire-fighting equipment had been 

 provided the damage was much smaller than in the machines where 

 no precautions had been taken. In 146 explosions and fires the 

 results can be summarized as follows : 



No. cases. Per cent. 



Complete loss .40 27. 4 



Partial loss 49 33. 6 



No. cases. Per cent. 



Slight damage 20 13. 7 



No damage 37 25.3 



The total damage reported for all machines was about $60,000. In 

 many cases after complete loss the owner was compelled to dis- 

 continue threshing for the season, and a serious situation was threat- 

 ened unless some remedy was found. 



DAMAGE TO GRAIN. 



In almost all cases the flame from the explosion and fire was blown 

 into the straw pile, and in man}' instances spread to the stacked 

 grain and also to the unthreshed grain in the field. As a result sev- 



