ON THE RESISTANCE OF ROAD VEHICLES TO TRACTION. 

 Ace rage for tlie lohole of the Runs. 



331 



From the above and fig. 2 the advantage of the pneumatic is evident. 



It is considerably augmented with the speed and the load. 



General average obtained for all roads, at all speeds and loadings : — 



For iron-shod wheels 

 ,, pneumatic ,, 



22-07 kg. 

 15-63 kg. 



Michelin found that even upon hard and smooth ground, pneumatic 

 tyres gave a greater economy, amounting to about one-third. 



Fia. 2.— Second Series of Trials (August 1895). 



/KOM - RUBeCR 



. PNEUM 



Third Series of Tests, November ISOo. 



More variety in the nature of the roads. 

 Three trials over each kind of road : — 



(A) Total length, 40 m. ; gradient, 1-5 per cent. ; macadam, fairly 

 good, less sound than second series. 



{B) Total length, 110 m. ; good regular pavement ; gi'adient, 1-2 per 

 cent. 



(C) Badly paved, irregular ; gradient, 1-9 per cent. ; length, 50 m. 



{D) Steep gradient, 5-8 per cent.; macadam, in good condition ; length, 

 80 m. 



(E) Road through vineyards very badly maintained ; length, 50 m. 



Experiments made at the trot, (fee. 



Now, if we take the average of all these speeds over the three Courses 

 A, B, and C, we have' 



