THE TROTTER’S WIND SHIELD.

New Zealand Illustrated Sporting & Dramatic Review, Volume XII, Issue 736, 14 April 1904, Page 10

THE TROTTER’S WIND SHIELD.

The advent of the two minute trotter and the faster pacer was received during the past season with much jubilation by horsemen all over the land. Many an old timer’s prediction was fulfilled, and many there were who acknowledged the error of their judgment as to the impossibility of the feat, but a calmer consideration of these sensational records has resulted in discrediting or throwing out the same by harness horse authorities, and the decision thus rendered has started a bitter controversy on all sides among horsemen. Let us throw aside all sentiment in matter and attempt a mathematical solution of the problem as to the benefit rendered a perform, ing horse by the wind or dirt shield pacemaker. On a perfect still day a horse going around two minutes is breasting a wind of 30 miles an hour created by his motion. Overcome this force which is opposing bis speed, either completely or partially, and you will materially accelerate his motion by preventing a distressing waste of energy to the performer We will now find what the pressure of the air amounts to when no shield is employed. For several centuries machines have been invented to determine the pressure of wind of various velocities. The sails of a vessel under a breeze of 30 mile an hour stands a pressure of over six pounds per square foot. Windmill experiments show four ana a-half pounds pressure per square foot for a 30-mile-an-hour wind, while perhaps the most reliable instrument, the anemometer of Dr. Lind, gives five pounds per square foot for a 30-mile wind This we will abide by as a conservative figure. The United States Weather Bureau uses Smeaton’s rule, which gives four and a-half pounds pressure per square foot on a flat surface. Observations in England showed 14 pounds per square foot for a 38-mile wind and 42 pounds pressure forj a 70-mile wind, or about twice as great as Smeaton’s rule would give. Now the surface presented hy a harness horse when rushing through the atmosphere, is made up by the front part of the horse, his legs, part of the driver, part of the sulky and the forepart of the wheels, all of which, measured on a present time champion, amount to about twelve square feet; however, the surfaces whose section is tu elve square feet, are not flat, hut rather spherical or cylindrical; hence the pressure on such surfaces is different from that on flat surfaces, or is equal to one-half, according to Troutwine and other experimenters. Thus the two-minute horse on a dead calm day, facing a 30-mile wind created by himself, me its an opposing force of one-half of five pounds per square foot, or two and one half pounds; and the section of the cylindrical surfaces in this case being 12 square feet, we find by multiplying twelve by two and a-half, a pressure of thirty pounds against the unshielded trotter. , , , Behind the shield, the horse benefits most when close up, but benefits some if within any reasonable distance The partial vacuum and suction, so called, behind the pacemaker certainly withdraw a large part of the 30 pounds pressure that would otherwise oppose the horse. The dirt shield pacemaker shields the horse behind in the same wav that the Reliance in windward position effectually blanketed the Shamrock, though the two were more than twenty lengths apart, and yet some horsemen claim that only when the pace follower is less than one length behind is he assisted to any extent . When the champions of the past year go their miles unshielded this coming season we will better appreciate the damaging effect of atmosphere pressure on their wonderful records. „ Hugh E. McLaughlin in the “ New York Sun.