NOTES ON UFE-SAVING APPLIANCES. 149 



The stationary tie-rod is fitted with a brass sleeve on which the nut is sKding. 



Mr. Norton placed undue importance on the bending effect in the nut due to 

 the fact that the screw and the supporting tie-rod do not have the same centers. 



Among the models shown at the meeting was one that had a screw in the center 

 of the support; this design is adopted in appliances where great stress is laid on keep- 

 ing the resistance as small as possible. It is not done on ordinary davits, however, 

 because it has been found unnecessary by actual tests. The arm is guided by the 

 nut and rolls on the quadrant flange in the groove ; the nut is supported by the tie- 

 rod so that it cannot bend; but only slide. 



In all types of davits, ample clearance must be given, owing to the rigid and 

 solid construction. This can be done in the quadrant type but, on the other hand, 

 in the Norton davit such clearances must increase wear and tear, owing to its less 

 rigid construction. 



The diagrams of Mr. Forbes' paper were figured under absolutely the same con- 

 ditions for both types of davits; the same swing, the same boat weight, the same 

 crank radius, the same screw center-Hne and the same screw. The latter is very 

 important, everything being figured on the dimensions of the standard Wehn davit. 



It has to be remembered that when this Norton davit is swung out the length 

 of the connecting screw and sleeve is about 8 feet, and it is not supported in any way 

 except at the ends. 



The objection Mr. Norton made to the open construction of the screw, tie-rod 

 and rack on the Welin davit is one that was made while it was practically unknown ; 

 is no longer criticized, but is considered a great advantage. 



A glance shows whether everything is in running order on the Wehn davits; 

 in the Norton davit it is impossible to see the condition without unscrewing the 

 entire davit for inspection. It would, however, require a great deal of paint to 

 obstruct working of the screw as Mr. Norton suggests, with the ample clearance 

 given in the Welin davit. 



The Welin patented chocks are very simple and make a substantial bed for 

 any boat. The gripes that hold the boat are connected to the chocks and are 

 released automatically when the outside chock-block is folded down. It must be 

 remembered that in swinging the boat out neither the Welin nor Norton davits give 

 a straight upward lift only, but an outboard swing also, therefore stationary chocks 

 of sufficient height would be in the way. 



The Welin compensating arrangement was not mentioned by Mr. Norton. 

 This arrangement gives the boat a straighter path of travel than does the Norton 

 davit. In the latter the boat has almost the same path of travel as the top of the 

 davit. Both davits at the start give a rising curve, but with the Welin compensa- 

 ting arrangement this is not higher than is required to clear the chocks and then 

 the path of travel slopes gradually downward and outboard. With the Norton 

 davit it is more of a jump. This compensation is of great assistance when taking 

 the boat in, and it is on this account that the power needed for swinging in a boat 

 on the Welin davit is only 75 per cent of that needed with Mr. Norton's davit. 

 The Norton has about one-third more working parts than the Welin davit, minor 



