pg.4
the feature industry this month is....
Rubber Recyclers
The latest in the long list of places I've worked as a construction millwright is rubber tire recyclers. Interestingly, it ties in with wax manufacturers (discussed a few months ago) because tire makers are a consumer of wax makers' products! (Wax is used to keep the tire from sticking in its mold.) So it starts to look like the wide variety of jobsites and factories are really all just many parts of one big picture.
This month's lesson may appear to be simple stuff that almost everyone learned way back in high school. However, it may be that nobody has used it since high school, and it's all been forgotten. If you are a construction millwright, you might need to know it off the top of your head at any time, on any job. Trigonometry!
It's all about right angle triangles. The rule goes like this: the sum of the three angles in triangles is 180 degrees, regardless of the length of the sides. The ratio of two sides is a measure of the angle between them, which ratio can be converted into a degree measurement using sine tables or calculations. Calculating sines, cosines, and tangents in your head is usually a little beyond everyday jobsite math, but if you carry a table in your toolbox (right there with your tap drill chart, maybe!) you can easily work out trigonometric problems if you remember "SOHCAHTOA".
SOHCAHTOA is the mnemonic for these functions:
Sine of angle = opposite side/hypoteneuse (s=o/h)
Cosine of angle = adjacent side/hypoteneuse (c=a/h)
Tangent of angle = opposite side/adjacent side (t=o/a)
Quiz Question:
You are working at a rubber recycling plant, and your job is to fabricate a fume hood for a press. The press isn't there yet, and the press manufacturer has only given you some rough fabrication diagrams showing that the area to be hooded is higher at one end than the other. You are not given the difference in height from the low to the high part of the press side, but the angular distance of contact between the press and the hood is 10'4"; the horizontal length of your fume hood is going to be 8'7"; and the width of the area to be enclosed is 13'. The client says they want the fume hood to be a minimum of 6'5" tall. Therefore, as you lay out the sides of the fume hood, what are their 4 measurements?
Tires are made of rubber, and rubber comes from trees, right? Well, there's more than one kind of rubber, and tires are actually made from a mostly synthetic rubber. The thing is, tires don't last forever and it's not good for the environment to just burn the old ones in incinerators. So like many other products, there is a good business in recycling them. A tire recycling plant begins by shredding the old tires. The chunks are then often frozen so that they become brittle and can be shattered into smaller pieces, or they may just be ground up at normal temperatures. This stuff is next sifted and passed under magnets to remove all non-rubber parts such as steel belts and rocks. The rubber is then more finely ground, cleaned, and packaged for sale as "crumb" or "granules". Crumb rubber is useful as an ingredient in rubberized asphalt, railroad crossing pads, cushioning material in livestock bedding, and can be remoulded into products like mud flaps, roll roofing material, and the like.
Here are a few links to sites related to rubber factories:
The Tire Recyclers of Calgary web site includes information on the process of recycling and products made from the crumb: http://www.recycle.net/trc/index.html
This Recycler's World page will tell you about scrap tire disposals, shedded tire dealers, products for sale, and used rubber recycling equipment: http://www.recycle.net/recycle/Rubber/granule/index.html
The Machinery Dealers National Association page is for buyers of used machinery, and is interesting from a millwright standpoint (we may have installed or removed the stuff!): http://www.mdna.org/
Rebound Rubber Recycling is a company that recycles tires, and their page explains the philosophy: http://www.reboundrubber.com/
Here is an elementary school student's paper on "How is rubber made?" which is actually a good basic overview of the subject: http://www.fcps.k12.va.us/OakViewES/smith/97-98/sixthhome/katep.html
Recovery Technologies' site explains their "Reclaprocessor*" system with a great diagram: http://www.recoverytechnologies.com/eb.html
You make the side in the shape of a trapezoid. To start easy, the short side of the trapezoid is 6'5", the height measurement given by the client. The top side of the trapezoid is 8'7", as given by the press manufacturer. So what is the long side of the trapezoid?
If you select the bottom angle of the trapezoid, you know you have that angle's opposite and hypoteneuse measurements. Therefore,
sin(angle) = 8'7" / 10'4"
= 103"/124"
= 0.831
You can check a sine chart to see that this means the angle is approximately 56 degrees.
Now you want to work out the length of the "adjacent" side.
tan(56) = 8'7" / adjacent
adjacent = 8'7" / tan (56)
= 103 / 1.483
= 69.45" or, to convert to what you might see on your tape measure, 5'9 and 1/2"
(There is more than one way to arrive at this result. Using the other angle, or other trig ratios, will end up with the same result as long as done correctly!)
This measurement represents the amount that the long side is longer than the short side of your trapezoid. Therefore, the long side will be a total of 69.45"+6'5". This equals 146.45", or again, about 12'2 1/2" on your tape measure. This gives you enough measurements to lay out the two sides of the fume hood. The ends of the fume hood will then be two rectangles, one 13' x 12'2 1/2, and the other 13' x 6'5". Now get cutting!
See you on the next update of the Construction Millwright Feature Page!
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