146 



MOUNTED INSTRUCTION 



Good Draft 



PRINCIPLES OF DRAFT 



(Acknowledgment is made to Colonel Wm. P. Ennis, F. A.) 



In the discussion of the principles of draft as applied to the artillery 

 team, it is necessary to consider: (First) the construction of the Artil- 

 lery Carriage: (Second) the physical conformation of the horse as a 

 mechanical device. 



THE CONSTRUCTION OF THE ARTILLERY CARRIAGE 



In the construction of field gun carriages it is considered that seven 

 hundred pounds dead weight is the maximum load each horse can pull 

 under severe conditions, that two hundred and fifty pounds horizontal 

 pull is the greatest average that can be obtained from each horse in a 

 six horse team. 



Within limits the higher the wheel the easier the draft. The width 

 of the tire also has an appreciable eiTect in the resistance offered to 

 different kinds of roadbed. 



The length of recoil of the gun and the stability of the carriage during 

 firing are also very important considerations. 



After a series of experiments covering all these subjects the Ord- 

 nance Department has decided on a fifty-six inch wheel with a 3-inch 

 tire as the most advantageous for the 3-inch field carriage. 



In rolling friction the force applied should be parallel to the direction 

 of motion. With the 56-inch wheel, the wheel trace by itself makes an 

 angle of about 8° with the horizontal but the pull of the lead horses 

 ahead decrease this angle to about 6°. 



