## Monday, January 21, 2019

### How much can draft animals pull?

Approximate force required in pounds per square inch to pull a moldboard plow at 2 mph in normal conditions are:
sandy soil 2.5 PSI
corn stubble 3 PSI
wheat stubble 4 PSI
blue grass sod 6 PSI
clover sod 7 PSI
clay soil 8 PSI
prairie sod 15 PSI
virgin soil 15 PSI
gumbo 20 PSI   (Source)

One of my coffee drinking buddies tells me that they used a two-mule team to pull a single bottom, 14" plow six inches deep and used three mules to pull two 14" bottom plows.

Figuring clay soil and the two mule team, 14" * 6" * 8 PSI = 672 pounds pulling force or 330 pounds on the draw-bar per mule. And the mules would do that all day long.

Figuring clay soil and the three mule team, 2*14" * 6" * 8 PSI = 1344 pounds pulling force or 450 pounds per mule.

Another source claims draft horses can pull six times their weight when it is a carriage (pavement). It must be clear that this is not the tension they are putting on the draw-bar but the weight of the carriage.

A third source claims three-to-five times a draft horse's weight is a ball-park figure but highly dependent on surface and how fast you want to pull. Again, this is not the tension in the drawbar but the weight of the wagon + passengers + freight.

Stage coaches weighed about 2500 pounds and could carry nine people inside + six on top and freight. A more typical load might be six inside, two driving and fifty pounds of freight per passenger. At a buck-fifty per person, that is 2500 + 1200 in passengers + 400 in freight for a gross of 4100lbs.  Teams of four or six horses would pull them at five miles per hour and get changed out every four-to-six hours. The roads were terrible.

Triangulating:
If you can believe what you read on the internet, a horse bred for pulling can cart 1X-to-4X it weight provided it is pulling a smooth rolling cart along graded dirt roads or across dry, cut hay-fields. It can pull them at walking speed for as long as you want to sit on the seat and drive them.

That is a tremendous multiplier. A horse might easily pack 20% of its weight and can pull 2X. That is ten times as much payload!

Greatest invention since the wheel. Oh! Wait a minute.....

1. Ona good road, 6 times his weight is a pretty good number. Bricks or pavement. Less on gravel or hard dirt. Even less on soft ground. Also, wheel width makes a difference.

Put a horse to pulling a wagon on steel rails (think "railroad" and he can pull, on level ground, about 9 times his weight (at a walking pace).

I have seen a 6 team hitch of percherons shear a 1/2 inch bolt.

YMMV

1. Mr B:

Thank-you! You are a font of useful information.

2. Not sure how useful, but it is data.

Readers who are willing to comment make this a better blog. Civil dialog is a valuable thing.