Tag Archives: horse

Of horses, trucks, and horsepower

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Horsepower is a unit of work production rate, about 3/4 of a kW, for those who like standard international units. It is also the pulling force of a work horse of the 1700s times its speed when pulling, perhaps 5 mph. A standard truck will develop 200 hp but only while accelerating at about 60 mph; to develop those same 200 horsepower at 1 mph it would have to pull with 200 times more force. That is impossible for a truck, both because of traction limitations and because of the nature of a gasoline engine when attached to typical gearing. At low speed, 1 mph, a truck will barely develop as much force as 4-5 horses, suggesting a work output about 1 hp. This is especially true for a truck pulling in the snow, as shown in the video below.

Here, a semi-truck (of milk) is being pulled out of the snow by a team of horses going perhaps 1 mph. The majority of work is done by the horse on the left — the others seem to be slipping. Assuming that the four horses manage to develop 1 hp each (4 hp total), the pull force is four times a truck at 1 mph, or as great as a 200 hp truck accelerating at 50 mph. That’s why the horse succeed where the truck does not.

You will find other videos on the internet showing that horses produce more force or hp than trucks or tractors. They always do so at low speeds. A horse will also beat a truck or car in acceleration to about the 1/4 mile mark. That’s because acceleration =force /mass: a = F/m.

I should mention that DC electric motors also, like horses, produce their highest force at very low speeds, but unlike horses, their efficiency is very low there. Electric engine efficiency is high only at speeds quite near the maximum and their horse-power output (force times speed) is at a maximum at about 1/2 the maximum speed.

Steam engines (I like steam engines) produce about the same force at all speeds, and more-or-less the same efficiency at all speeds. That efficiency is typically only about 20%, about that of a horse, but the feed cost and maintenance cost is far lower. A steam engine will eat coal, while a horse must eat oats.

March 4, 2016. Robert Buxbaum, an engineer, runs REB Research, and is running for water commissioner.

Theodore Roosevelt jumps fence, rides moose

Perhaps my favorite president is Theodore Roosevelt, a liberal Republican with a strong America first agenda, and an ability to work on the world stage. He was a friend to immigrants and to the poor, but not opposed to prosperity either. Though some thought he might be crazy, none thought he was a wuss, and none messed with him or with the USA when he was in office. Yes, that’s the president riding a moose, jumping a fence, and camping on a cliff with John Muir. In his spare time, he wrote books (very good books) rode in an airplane, and visited Panama.

theodore-roosevelt-mooseTheodore Roosevelt Jumps Fence on Horsetheodore-roosevelt-yosemite

He had many pets and children in the Whitehouse, by the way, spoke several languages the conversing with guests, and kept a boxing instructor on staff so he could stay in shape. For a fun read, try his biography of Thomas Hart Benton, or his Naval war of 1812. His personal defense pistol of choice was a .32 caliber, semi-automatic, gold inlaid.

January 16, 2013 R.E. Buxbaum. If you liked this, you might want my insights into a famous incident where Teddy Roosevelt got shot on the way to giving a speech. Instead of treatment, he gave the 2 hour speech and survived after asking that the bullet be allowed to remain in place. Why did he do this? How did he survive it?