ANGULAR CRANK. 



vertical, and the downward pressure of the 

 foot at C is directly transmitted in full to the 

 point B, where it acts in turning the arm A B 

 just as powerfully as if the pedal itself were 

 fixed at B. Thus the foot at C gets the benefit, 

 for the most effective part of the stroke, of the 

 greater leverage at the greater distance A B, 

 while actually moving round a circle with the 

 smaller radius A C. 



To those who have a little mechanical in- 

 stinct, or a little practical acquaintance with 

 the facts of mechanical work, the fallacy of 

 this claim is too obvious to need any explana- 

 tion. To most others the following considera- 

 tion will show that it is not in accordance with 

 common-sense. 



The one essential which determines the 

 leverage of a crank is its length that is, the 

 distance between the crank axle and the pedal, 

 and it makes no difference to the power result 

 what is the shape of the metal connection 

 between the two ends so long as it is strong 

 enough to be rigid. 



It may be quite straight, like an ordinary 

 bicycle crank. It may be S shaped, like the 

 grindstone cranks in the carts of travelling 

 knife-grinders ; or it may be solid right round 

 the circle, in the form of a disc, as is often seen 

 in the donkey-engines used for raising luggage 

 on board ship. But the shape is of no conse- 

 quence whatever for the power-leverage, for 



107 



