From: Getting the Garbage Out
A History of Experimentation
Ever since tractor-trailer rigs replaced horse-drawn garbage wagons, engineers and entrepreneurs have been exploring ways to unload municipal solid waste from transfer trailers.
“Dump trailers left the horizon because they lacked sufficient capacity and because they were unstable when raised on the uneven face of a landfill,” says Phil Bortz, vice president of sales and marketing for MAC Trailer Manufacturing Inc., in Alliance, OH.
Side-discharge dump trailers never caught on as transfer trailers because most hold a relatively small payload. “With this type of operation, everyone is looking to maximize capacity,” Bortz says.
 |
Photo: Hallco |
Hopper trailers like those used for coal, grain, and sand don’t work with municipal solid waste for two reasons. “Garbage corks,” says Dan Jackson, senior sales executive at Keith Manufacturing Co. in Madras, OR. “It doesn’t flow.”
Also, Bortz points out that hopper bottoms typically discharge into a bin. “They have a free gravity fall into a receiving container underneath. In a landfill, the bottom would be discharging onto the face of the landfill. It wouldn’t be practical.”
By the 1980s, Jackson says, the most popular unloading system was the chainout. “It could unload a trailer in three minutes, but when the chain broke, it was always with a full load and underneath the load, so you had to hand-unload the trailer to make repairs. The chainout had a hydraulic motor, a gear on a shaft, and slides 24 inches long bolted to the chains to pull them. It was like a conveyor belt, except there was no belt. Maintenance was high and cubic capacity low. People have since changed blade designs and configured things differently, but back then a pushout lost about 20% of carrying capacity compared to a live floor.”
Belt trailers also were used for municipal solid waste, but not successfully, Jackson says. “In North America, most belt trailers had a continuous return, requiring a space under the floor for the belt to go back, which reduced capacity. Also, a belt trailer typically didn’t have a full 8-foot-wide belt. It was about 5 feet wide, and the walls sloped into the floor, which also reduced capacity. In freezing conditions it virtually wouldn’t work because the load would freeze to the walls. The belt wasn’t sufficient to break it loose.”
The roll-floor trailer, imported from Europe in the 1980s, had a full-width, non-continuous belt with take-up rolls at the front and back, and hydraulic motors in front and back to move the belt back and forth. “It’s not being used, because it won’t work,” Jackson says. “The belt has to ride on a solid metal surface underneath. If you get water in there, the belt freezes to the pan.
“Also, with garbage typically top-loaded from one side, the heaviest drops on one wall while the fluff floats to the opposite wall. The belt stretches, and you have a big problem. The wider the belt, the worse were the problems with stretching and tracking off to one side. To make matters worse, the operator often would forget to rewind the belt to the front spool before loading it. Then the only way to get the load out was hand-unloading. Roll floors were used in smaller truck bodies in Europe for agricultural and forest products, but not for trash. They never should have gone into the waste market,” Jackson says. “There were problems with coal when it froze, but with garbage, nothing would come out. The operator would try to shake it and drop the car. It wasn’t a reliable technology for solid waste.”
Live-Floor Origins
Live-floor technology originated in the 1970s. Olof Hallstrom, founder of Hallco Manufacturing Co. in Tillamook, OR, invented the concept in 1971. “He’s a dairy farmer,” recounts Don W. Wilton, Hallco’s vice president of sales and marketing. “He had some potholes in a road. He decided to take his old pickup truck with cross-members in back and lay two-by-fours the length of the truck bed. On top of the two-by-fours went a load of river rock. He drove over to a pothole, drilled through the ends of the two-by-fours, put bolts in, and hooked a chain to the bolts. He decided to pull out one two-by-four with a tractor to let the rocks fall through the slats and onto the ground.
“He expected a tough pull because he had 15 tons of river rock in the truck, but the two-by-four came out like butter because the load was being held in place by the other slats. It came out without friction or drag. He thought if something came out that easily, it could go back in the same way.”
Hallstrom is now 75 years old and still inventing. “He’s designing floors for garbage trucks and shredder operations,” Wilton reports.
As early as 1973, Keith Foster (who died in April 2006 at age 83) was making live floors for agricultural use. Keith Manufacturing Co. moved to municipal solid waste in 1980. “We built the entire trailer with our floor,” Jackson recalls. “We sold the first one to Tom Fry, a waste hauler in Sun Valley, California, who came by the World Ag Expo in Tulare where we were displaying trailers with Walking Floors. He had been using chainouts and was looking for lighter weight and lower maintenance. Keith built him a trailer, and Keith’s Walking Floor supplanted chains.”
May-June 2007
From: Getting the Garbage Out
A History of Experimentation
Ever since tractor-trailer rigs replaced horse-drawn garbage wagons, engineers and entrepreneurs have been exploring ways to unload municipal solid waste from transfer trailers.
“Dump trailers left the horizon because they lacked sufficient capacity and because they were unstable when raised on the uneven face of a landfill,” says Phil Bortz, vice president of sales and marketing for MAC Trailer Manufacturing Inc., in Alliance, OH.
Side-discharge dump trailers never caught on as transfer trailers because most hold a relatively small payload. “With this type of operation, everyone is looking to maximize capacity,” Bortz says.
|
Photo: Hallco |
Hopper trailers like those used for coal, grain, and sand don’t work with municipal solid waste for two reasons. “Garbage corks,” says Dan Jackson, senior sales executive at Keith Manufacturing Co. in Madras, OR. “It doesn’t flow.”
Also, Bortz points out that hopper bottoms typically discharge into a bin. “They have a free gravity fall into a receiving container underneath. In a landfill, the bottom would be discharging onto the face of the landfill. It wouldn’t be practical.”
By the 1980s, Jackson says, the most popular unloading system was the chainout. “It could unload a trailer in three minutes, but when the chain broke, it was always with a full load and underneath the load, so you had to hand-unload the trailer to make repairs. The chainout had a hydraulic motor, a gear on a shaft, and slides 24 inches long bolted to the chains to pull them. It was like a conveyor belt, except there was no belt. Maintenance was high and cubic capacity low. People have since changed blade designs and configured things differently, but back then a pushout lost about 20% of carrying capacity compared to a live floor.”
Belt trailers also were used for municipal solid waste, but not successfully, Jackson says. “In North America, most belt trailers had a continuous return, requiring a space under the floor for the belt to go back, which reduced capacity. Also, a belt trailer typically didn’t have a full 8-foot-wide belt. It was about 5 feet wide, and the walls sloped into the floor, which also reduced capacity. In freezing conditions it virtually wouldn’t work because the load would freeze to the walls. The belt wasn’t sufficient to break it loose.”
The roll-floor trailer, imported from Europe in the 1980s, had a full-width, non-continuous belt with take-up rolls at the front and back, and hydraulic motors in front and back to move the belt back and forth. “It’s not being used, because it won’t work,” Jackson says. “The belt has to ride on a solid metal surface underneath. If you get water in there, the belt freezes to the pan.
“Also, with garbage typically top-loaded from one side, the heaviest drops on one wall while the fluff floats to the opposite wall. The belt stretches, and you have a big problem. The wider the belt, the worse were the problems with stretching and tracking off to one side. To make matters worse, the operator often would forget to rewind the belt to the front spool before loading it. Then the only way to get the load out was hand-unloading. Roll floors were used in smaller truck bodies in Europe for agricultural and forest products, but not for trash. They never should have gone into the waste market,” Jackson says. “There were problems with coal when it froze, but with garbage, nothing would come out. The operator would try to shake it and drop the car. It wasn’t a reliable technology for solid waste.”
Live-Floor Origins
Live-floor technology originated in the 1970s. Olof Hallstrom, founder of Hallco Manufacturing Co. in Tillamook, OR, invented the concept in 1971. “He’s a dairy farmer,” recounts Don W. Wilton, Hallco’s vice president of sales and marketing. “He had some potholes in a road. He decided to take his old pickup truck with cross-members in back and lay two-by-fours the length of the truck bed. On top of the two-by-fours went a load of river rock. He drove over to a pothole, drilled through the ends of the two-by-fours, put bolts in, and hooked a chain to the bolts. He decided to pull out one two-by-four with a tractor to let the rocks fall through the slats and onto the ground.
“He expected a tough pull because he had 15 tons of river rock in the truck, but the two-by-four came out like butter because the load was being held in place by the other slats. It came out without friction or drag. He thought if something came out that easily, it could go back in the same way.”
Hallstrom is now 75 years old and still inventing. “He’s designing floors for garbage trucks and shredder operations,” Wilton reports.
As early as 1973, Keith Foster (who died in April 2006 at age 83) was making live floors for agricultural use. Keith Manufacturing Co. moved to municipal solid waste in 1980. “We built the entire trailer with our floor,” Jackson recalls. “We sold the first one to Tom Fry, a waste hauler in Sun Valley, California, who came by the World Ag Expo in Tulare where we were displaying trailers with Walking Floors. He had been using chainouts and was looking for lighter weight and lower maintenance. Keith built him a trailer, and Keith’s Walking Floor supplanted chains.”