x L x rpm
x W) / 33000 where W is the net force
on the lever: that is, the scale reading minus the weight of the lever
by itself.
pg.4
the feature industry this month is....
Chewing Gum Makers
Sometimes construction millwrights work in fun places. Places that make things which you don't have to be a construction millwright to know what the product is for. Of course, we get to see and work on the machines which produce them, and that's even more fun! This month let's look at a factory for something very common: chewing gum.
Speaking of machines and things we all know, a familiar term in describing some machines is horsepower. What does that really mean? Well, to start with, "work" is the force you exert to move something a distance, and "power" is the rate at which the work is done. Work can be measured in foot-pounds, 1 ft-lb meanining you have moved one pound a distance of one foot. Power can then be measured in foot-pounds per minute. One horsepower equals 33,000 ft-lb per minute, which once upon a time was considered the amount of power you could actually get from a real live workhorse. A nice even number, right?!
Of course, when you look at your car, it doesn't seem like it would be all that easy--or even objective!--to measure how fast it can pull a weight a distance; and in fact that's not the formula they use to calculate the rated horsepower of gas engines. There are many different formulae, actually, and a problem with a car is that the engine is producing rotary power, and horsepower is a linear measurement. One simple formula given by the Society of Automotive Engineers (SAE) is that linear rated horsepower of a gas engine equals the diameter of the cylinders squared (in inches), times the number of cylinders, times 0.4. That is,
hp=D2 x N x 0.4
"Brake horsepower" is different again, and measures the power of an engine delivered at its flywheel. This is really a more meaningful number, since much of an engine's "rated" horsepower may also be lost in its own operation, and not really available for use. They measure brake horsepower by attaching a brake to the flywheel pulley, and measuring the force the engine can apply to it. One such setup is called the Prony Brake, in which the brake is connected to a lever that exerts force on a scale. The formula then becomes
bhp= (2 x L x rpm
x W) / 33000 where W is the net force
on the lever: that is, the scale reading minus the weight of the lever
by itself.
Quiz Questions:
1. You lift a 85 pound weight 5 feet in the air in 3 seconds. What horsepower are you producing to do that?
2. You've got a 6-cylinder gas engine with cylinders of 4.5" bore. What is the SAE rated horsepower for this engine?
3. When an engine was tested with the Prony Brake, while running at 3000 rpm it produced a reading of 153 pounds with a 4' long, 25 pound lever. What is its brake horsepower?
Although way back, people were known to chew the resin from certain trees directly, these days there's usually a little more to gum than that. Chewing gum is made from gum base, sweeteners, softeners, and flavourings. Sweeteners and flavourings speak for themselves. Gum base can still be a natural resin from certain trees, or (more often these days) it can be a synthetic base. Softeners keep the gum flexible by retaining moisture; glycerin is often used for this.
When they set about making gum, they grind the base materials, then melt it and purify it in centrifuges and filters. The hot gum base is then put into mixers, basically a bowl with rotating blades like your home mixers, except these are more likely the size of a large water tank. The other ingredients are added here. The gum dough will then be placed under decreasingly spaced rollers until the final thickness of the gum is reached, and then it is cut into single sticks, or pellets for candy-coating. It is "conditioned" in specific temperature and humidity conditions. Gum for candy-coating will then be put into revolving pans with the sugar coat ingredients, and shaken and dried several times until the coating is the right thickness. Stick gum will be dusted with powdered sugar to keep it from sticking together. At last it is packaged in very precise wrapping machines, and shipped to distributors.
Lots of great machinery for a millwright to maintain!
Here are a few links to sites related to chewing gum:
The National Association of Chewing Gum Manufacturers has a variety of interesting pages, from the evolution and story of gum to how it's made and fun facts: http://www.nacgm.org/consumer/consumer.html
The Wrigley company site will tell you the story of chewing gum and explain the ingredients: http://www.wrigley.com
The Pfizer company owns Adams Brands, makers of Clorets, Trident, and Chiclets among others, and has an interesting page on the history of gum: http://www.gum-mints.com/
The "Useless Knowledge" site has an in-depth answer to 'How is chewing gum made?': http://www.uselessknowledge.com/explain/gum.shtml
Here's a page showing you the interior workings of the Ford gum machine, seen in supermarket entrances everywhere: http://www.fordgum.com/
And this page will give you more information on horsepower, if the quiz has piqued your interest: http://www.howstuffworks.com/horsepower.htm
1. work = 85 lb x 3 ft
= 255 ft-lb
3 seconds equals 0.05 of a minute
power= 255 / (33000 x 0.05)
= 0.15 hp
Roughly one-seventh of a horsepower!
2. hp=D2 x N x 0.4
=(4.5)2 x 6 x 0.4
= 48.6 hp
3. bhp= (2
x L x rpm x W) / 33000
=
[2 x 4 x 3000 x (153-25)]
/ 33000
= 292.5 bhp
See you on the next update of the Construction Millwright Feature Page!
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