What is 5252? What does it mean and why did we name this site Club5252?

Why we named it Club5252 is very simple. Those numbers represent the most important mathematical formula behind horsepower since the year 1775. Since we all here at Club5252 love horsepower and all it has to bring us, we named the club after this formula.

Awhile back, in 1775 the inventor of the steam engine, a gentleman by the name of James Watt made some observations, and concluded that the average horse of the time could lift a 550 pound weight one foot in one second, thereby performing work at the rate of 550 foot pounds per second, or 33,000 foot pounds per minute, for an eight hour shift, more or less. He then published those observations, and stated that 33,000 foot pounds per minute of work was equivalent to the power of one horse, or, one horsepower.

Everybody else said OK. We have no idea why most formulas were agreed to like this :-)

Let's start with horsepower. Now, it's important to understand that nobody on the planet ever actually measures horsepower from a running engine. What we actually measure (on a dynomometer) is torque, expressed in foot pounds (in the U.S.), and then we *calculate* actual horsepower by converting the twisting force of torque into the work units of horsepower following James Watt's theory. If you calculate torque x rpm / 5252 it will always equal your horsepower.

Because horsepower is only a calculation of torque x rpm (highest observed during your run - redline) divided by 5252 rpm....your horsepower and torque will ALWAYS be the same at that rpm. This is called a constant. Now if we are measuring torque and RPM how can we calculate horsepower? Where does the equation HP=TORQUE * RPM / 5252 come from? We will use Watts observation of one horsepower as 150 pounds, 220 feet in one minute. First we need express 150 pounds of force as foot pounds torque.

* Pretend the force of 150 pounds is "applied" tangentially to a one foot radius circle. This would be 150 foot pounds torque.

Next we need to express 220 feet in one minute as RPM.

* The circumference of a one foot radius circle is 6.283186 feet. ft. (Pi x diameter 3.141593 * 2 feet)
* The distance of 220 feet, divided by 6.283185 feet, gives us a RPM of 35.014.

We are then talking about 150 pounds of force (150 foot pounds torque), 35 RPM, and one horsepower.

Constant (X) = 150 ft.lbs. * 35.014 RPM / 1hp

35.014 * 150 / 1 = 5252.1

5252 is the constant.

So then hp = torque * RPM / 5252

If you look at any dyno graph, the two always meet at that rpm.
We at Club5252 have always found this fascinating, since we spend most of our days at the dyno.....lol. That's where we got the idea for the name.



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