Links To Other Pages
Home  About Me The Engines  Bessie  Steamers  Events  Odds & Ends

Useful And/Or Interesting Data

(More will be added from time to time)


Horsepower is a unit used to express the power (rate of doing work)
of an engine in the imperial system of measurements.  The term horsepower was first used
by the Scottish engineer James Watt.  He used it to compare the power of steam engines to the power of horses.
The term was later used to express the power of such devices as car engines, jet engines, electric motors, and nuclear reactors.
One horsepower is defined as 550 foot-pounds of work per second, or 33,000 foot-pounds of work per minute.
One foot-pound is the work needed to lift one pound one foot.  The metric unit of power is the watt.
One horsepower equals 745.7 watts 

If an engine lifts a 550-pound object to a height of 2 feet in 1 second,
it is working at a rate of 1,100 foot-pounds per second (550 X 2 divided by 1 = 1,100).
This engine is delivering 2 horsepower (1,100 divided by 550 = 2).  If a 150-pound man climbs
to a height of 88 feet, he does 13,200 foot-pounds of work (150 X 88 = 13,200).  If the man makes this
climb in 1 minute (60 seconds), he is working at a rate of 4/10 horsepower (13,200 divided by 60 = 220; 220 divided by 550 = 4/10).
A person who is accustomed to hard work can work at a rate between 1/10 and 1/8 horsepower continuously during an 8-hour day. 

The power of an engine was measured in indicated horsepower, or brake horsepower.  It is now usually measured in watts. 

Indicated horsepower is a measurement of the power produced inside the cylinders of an engine.
The power in foot-pounds per minute is first calculated by multiplying together the average pressure on the pistons,
the area of each piston, the length of the piston's stroke, the number of power strokes per minute,
and the number of cylinders in the engine.  This power must be divided by 33,000 to
give the engine's indicated horsepower. 

Brake horsepower is sometimes called effective horsepower, because it is the amount of power available at the engine's shaft.
Brake horsepower is measured by a dynamometer.  This instrument measures the engine's speed and the torque
(amount of twist) exerted by its shaft.  It is lower than indicated horsepower because friction in the
engine wastes part of the power produced in the cylinders.

Thread Types

There are many different types and sizes of threads.  Listed here are a few you may have heard of.

Nowadays the most common threads are metric.  When our stationary engines were
made the old British threads were used.  Without doubt the most useful
spanner I have in my toolbox is a very old 1/2" AF (Across Flats).


BSW British Standard Whitworth - This was the first standardised thread form.  Sir Joseph Whitworth proposed this thread in 1841.
BSF British Standard Fine - Since 1908 this thread, in conjunction with BSW has been the mainstay of British Engineering, and was used when finer pitches were required.
BSB British Standard Brass - Because brass tubing has a uniform wall thickness, irrespective of the tube diameter, any thread cut on  it, would have to have the same depth, so 26 tpi is standard on all diameters.
BA British Association - In the 1890's, the British Association for Advancement of Science (BA) realised there were no English screw thread standards for small electrical and scientific equipment, so they proposed the BA system loosely based on the Thury threads already in use in Europe (hence the metric sizes).
UNC Unified Course - This thread was standardised in 1918.
UNF Unified Fine- This thread was also standardised in 1918.
UNEF Unified Extra Fine - This thread was used for special purposes.
ISO Metric ISO screw threads are the world-wide most commonly used type of general-purpose thread. They were one of the first international standards agreed when the International Organisation For Standardisation was set up in 1947.


12 volt Regulator Details

I drive a 12 volt car dynamo from my Lister D, which in turn supplies the electricity for the lighting display board.
In order to control the voltage output from the dynamo a regulator is required.  I have seen many car dynamos being driven
from stationary engines on the rally field, and so I thought it may be useful to include some details here.  The following details are for
the very familiar Lucas type voltage regulator.  Note that we are talking about the old fashioned DC dynamo, not the more modern AC alternator.

Obviously the first picture here is shown with the black regulator cover removed.

12v Regulator Details.JPG (35313 bytes)

If you click on the pictures on the left you will see a better sized image.
The car voltage regulator consists of two parts - the "voltage regulator" (the left coil) and the "cut-out" (the right coil).
Lets deal with the cut-out first.  This acts like a switch which operates at a given dynamo output voltage.  When it switches in, as the dynamo speed increases, it connects the car battery to the dynamo via the regulator, and hence charging can commence.  When the output voltage is too low (at low dynamo speeds) the cut-out drops out to prevent the battery trying to run the dynamo like a motor, which would quickly drain the battery.  From this you can see that the cut-out is of no use to us if we are just using the dynamo to run some lights from our stationary engine.  I've included it's explanation for interest, as it's an integral part of the whole regulator box.

Regulator Air Gap Settings.JPG (25116 bytes) The part that we are interested in is the left hand coil, the regulator.
This is the part that controls the maximum output voltage from the spinning dynamo.  It's important that we control this voltage otherwise any lights we connect could quickly fail.  You can see from the detailed view on the left that the adjustment screw is number 2. (Important! Note that it is shown as screw number 1 in the overall view above).  Using a volt meter connected to the output terminals to the lights, adjust the screw with the engine and dynamo running at normal speed..  I tend to run my dynamo at about 10 volts which helps to extend the lamp life, although it does reduce the light intensity a little.
  Looking at the above will give you an idea of how it works.  Below you will find out how to actually connect the parts together.
A1 A F D E

A1 Connect this terminal to the positive (+) side of the lights, ideally through a fuse.  If you are using several lights then a good sized cable should be used.
A  This terminal is left blank.  (It would normally be connected to the car battery. positive (+) terminal).
F  Connect this terminal to the field winding on the dynamo.  This is the small terminal on the back of the dynamo.
D  Connect this terminal to the large one on the rear of the dynamo.  This cable takes all the load and so use good sized wiring.
E  This is the earth terminal.  Connect this to the main body (metal casing) of the dynamo using good sized wiring again.  Also connect this terminal to the negative (-) side of the lights

An old 12volt car dynamo looks pretty harmless, but it is capable of generating quite a few amps.
It is therefore important to ensure all your connections are tight and the proper sized cable is used in order to avoid overheating and damage.

I have tried to make the above as clear as possible.  If you need any more details just ask.


Top of page    Home page