1921.] 



315 



dry clay, or 21 chains of 3 ft. in. mains in similar clay, or 

 12 chains of 3 ft. 6 in. mains in wet clay. 



Mechanical Considerations. — The excellence of the engine 

 and mechanism was remarked upon by all en^^ineers w^ho 

 examined the drainer, and there is no doubt that the machine 

 is well designed for cutting trenches in all classes of land. 

 The engine was designed to burn petrol, which certainly 

 seemed uneconomical in this type of heavy-duty motor. 

 Undoubtedly the cost of fuel could have been reduced by 

 30 per cent, if an efficient form of vaporiser had been fitted 

 to burn paraffin. The machine was intended primarily for 

 use in America, where distillate is cheap, and probably the 

 manufacturers had not considered the fuel question for 

 England. During the trial second grade petrol and benzol 

 were the fuels used. 



The safety device previously described only acted on two 

 or three occasions, for on striking an obstruction the driving 

 chains usually broke (or jumped their pinions) befoi-e the 

 clutch slipped. This clutch was undoubtedly out of adjust- 

 ment, and if it had been attended to there would have been 

 less trouble w^ith the chains, and a fruitful source of minor 

 delays would have been removed. 



The width of the trenches dug for the 2 in. tiles was 

 criticised by practical men. It was pointed out that there w^as 

 too much lateral play in a drain 11 in. w^ide at the bottom. To 

 remedy this Mr. Thompson Close, the Ministry's inspector, 

 arranged for an iron tile-mould to be fixed to the bottom of 

 the sole of the machine, its function being to make a groove 

 in the floor of the trench of the exact size to take the' 

 2 in. tiles. This was an improvement. In any case, some 

 unnecessary earth is excavated when digging for small pipes, 

 and if the digging w^idth could be reduced to, say, 8 in., which 

 should offer no mechanical difficulties, economies should be 

 effected. On the other hand, very narrow drains, if deep, 

 are difficult for men to work in, should such drains subse- 

 quently need deepening or grading before the tiles are laid; 

 again, if wider trenches are dug, a relativolv largo amount of 

 earth is disturbed, which may ^rive a quicker ])er('olation and 

 render the drains more effective. 



The machine was provided with a large assortment of spares, 

 but two breakdowns involving ca'^tings necessitated workshop 

 repairs. On four occasions minor jobs had to be taken to the 

 local smithy. In noting these stoppages, however, it should 



