Trailer Travel

by
James Rooney, D.V.M.

While this subject is somewhat at odds with others on this site, the question of how a horse should or could travel in a trailer or a truck comes up often enough that I should like to make a few observations.

The horse, or any other object or animal for that matter, in a moving vehicle is subjected to three motions caused by three forces: yaw, pitch, and roll.

Yaw is the motion parallel to the surface. It the horse were standing on a revolving platform, alternately spun back and forth, it would be experiencing yaw.

Pitch is the back and forth motion like that of a hobby horse. In a truck or trailer this motion is most apparent when the vehicle begins to move - accelerates - and when it comes to a stop - decelerates.

Roll is the motion from side to side, like the movement of the pacing horse. Whenever the vehicle goes around a turn, for example, a rolling force is applied to the horse.

Yaw is normally very small and would be experienced only if the trailer were swaying rather wildly from side to side. This would happen if the trailer were attached to the towing vehicle by a tongue, for example. The two motions which the horse must routinely deal with, then, are pitch and roll.

The horse can best deal with pitch if it stands in line with the forward (or reverse) motion of the vehicle. As the vehicle accelerates, picks up speed, the horse would tend to fall backward and props itself with the hind feet to resist this. When the vehicle decelerates, slows down, the horse tends to move forward and resists this by propping primarily with the fore feet.

In order to deal with roll the horse would be best off if it stood sideways in the vehicle, so that it could use the legs to brace against the side to side motion just as it used its legs to brace against the to and fro motion.

Now it is obvious that the horse cannot stand to and fro and side to side at the same time. What it does, then, just as we humans do and other animals do, is to take that position which best resists - deals with - both pitch and roll. That it, the animal moves to a position at 45^o to the line of motion of the vehicle, the pitch, and to the direction of the roll, side to side.

I assume, fairly reasonably I hope, that the horse or cow, or goat, or whatever does not consciously figure all this out. The animal simply moves to that compromise position which most effectively resists the forces and motions imparted by the motion of the vehicle.

That is a rather pretty piece of theoretical mechanics, I think, but really not necessary. All one has to do is turn a horse loose in a good size trailer, such as a western-type cattle trailer, and observe the position the animal assumes when the trailer moves off. The horse knows its theoretical mechanics quite well!

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