ON THE RESISTANCE OF ROAD VEHICLES TO TRACTION. 34,3 

 Taule \1.— Tractive Remtanco of Level Pavements. 



Description of Pavement. 



Asphalte.— Clean, smooth, no cracks, 52° F 



^ „ „ 84° F 



" I, „ „ 42° F 



Brick.— 3" x 9" bricks on concrete, corners rounded, sand filler, not 

 worn. . 



3" X 9" bricks on concrete, but newer and covered with 



V'dust. 

 3" X 9" bricks on concrete, but cement filler; just completed 



"„ 2i-'' X 8" brick on concrete, pitch filler; new 



" 3" X 8" brick on gravel and cinders; sand filler, corners 

 not round. 

 2i" X 8" brick on sand and old macadam, tar filler; new 

 Granite block,— Smoothly dressed 3" x 9" blocks on concrete joints 

 ^" tar filler ; not worn. 

 „ Smoothly dressed, on concrete, pitch filler ; new 



,', Ordinary granite, 10 years' wear . 



Macadam. — Granite top, no dust, no mud .... 



Plank road.— Oak rilank, 3" X 12" ; nearly new 



Same as above, after wcrn down \" in many places 

 clean. 

 „ As above, covered with \" fine loose dirt . 



Steel wheelway.— 8". ll^b- channel, on 2" x 8" pine, on macadam 

 covered with I' ' powdered stone. 

 „ Same as above, scraped clean with a shovel 



,, „ covered with I" fine dust . 



Wood block.— Rectatigular blocks, 3" x 12", considerably worn 



Round cedar block, covered with i" silica pea gravel 

 „ ,, I" crushed gravel 



" I', 'I „ clean, blocks slightly convex on top 



" ", Round cedar block, 2" plank, 2" sand, clean, not 



worn. 

 „ „ Same as above, clean, slightly worn . . . . 



„ considerably worn , 



lb. 

 per ton of 

 2.000 lb. 



37 

 70 

 34 



17 



31 



22 

 24 

 37 



25 

 29 



30 

 36 

 18 

 32 

 38 



40 

 40 



19 



28 

 36 

 90 

 50 

 53 

 37 



51 

 54 



3, 4 and 5 with wheels averaging 424" diameter, the remainder 47". 



XIT. Summary of the Ojnnions of Various Writers on the Effects on 

 Traction on the Level of the. Independent Elements of Koad Resistance. 



Tractive Force. 



Diameter i Width 

 of Wheels of Tyres 



Inversely 

 as the 

 cube root 

 of the 

 square. 



Inversely 

 as the 

 square 

 root. 



Nature of 

 Tyres 



