|Orville Douglas Denison’s design for a transportable rescue conveyor would operate off a trailer and be capable of reaching the top of a 113-foot aerial ladder in 50 seconds. (Photo courtesy of Denison Inventions.)|
Besides the aerial platforms commonly used in the United States, other systems exist that can bring firefighters to the top of aerial ladders without climbing. Such systems include the European lift system of a basket or folding platform that can be raised and lowered, carrying firefighters or civilians. However, such systems have not found much favor among U.S. fire departments or aerial manufacturers.
A New Concept
A California inventor has come up with an idea to increase the number of firefighters that can be brought to the top of a ladder, or rescued civilians to the bottom, in less time than it takes to raise or lower an aerial platform or European lift device.
Orville Douglas Denison, of Denison Inventions, has patented a transportable rescue conveyor that can be mounted on a truck, trailer, or mobile device; taken to a fire; and deployed at the scene. He says it also can be put aboard a ship for ship-to-ship recovery efforts.
“My design is to have a rung every 14 inches on the ladder attached to a belt which is attached to a double chain drive, one on each side of the ladder rails,” Denison says. A firefighter would step onto a ladder rung and would rise as the chains and belt bring the rungs toward the ladder’s tip, he says. Denison estimates the system could transport several firefighters to the top of a ladder at the same time. The rungs can be moved either forward or backward and can be controlled by the aerial’s operator on the ground or through a hand-held remote control unit.
Denison’s design is for a 113-foot aerial ladder that’s supported by four criss-cross outriggers and a counterbalance on a cantilevered platform that allows the belt to travel around a take-up mechanism and then be fed back out to the ladder.
Denison says the design will support a 500-pound tip load using the criss-cross outriggers and a tip load of 1,500 pounds if two strut supports are placed under the first section of the aerial ladder.
He has met with fire apparatus manufacturers, but “because it would take substantial amounts of money to develop, they were not willing to risk it.” He adds that he’s had good response from fire chiefs who thought the idea was a good concept yet were concerned that price would be critical in such an application.
Denison says an engineering firm estimated the cost of putting a conveyor unit on a trailer or retrofitting it to an existing vehicle at more than $100,000, while Denison estimates the retail cost at between $150,000 and $250,000, depending on the design and what the conveyor would be placed on.
Conveyor vs. European Concept
The European concept of a lifter system, says Jim Salmi, chief operating officer of Crimson Fire, never caught on in the fire service in North America.
A typical lifter system would be built into an aerial ladder with a T- or L-shaped track on the top of each ladder section handrail, Salmi points out. An elevator or lifter that grabs onto the track with rollers and guide fingers is then pulled to the top by a winch under the ladder.
“A lifter can go to the top of a 150-foot ladder in about 50 seconds and typically can handle 400 kilograms or approximately 1,000 pounds,” Salmi says, although some versions handle smaller amounts of weight. The advantage to an elevator, he adds, is that it is fast.
“Going from the ground to 150 feet in 50 seconds—you can’t move a bucket that fast,” he says. “A platform might take a couple of minutes instead of 50 seconds each way.”
The drawback to a lifter or elevator is that so much space on the vehicle is consumed by the ladder to the extent that the equipment area of the apparatus is limited.
“In the United States, you have to look at what a truck company does,” Salmi observes. “Often it’s an equipment carrier and the aerial isn’t deployed.”
Salmi thinks there’s a lot of clever thought in the Denison concept but that it lacks wide-ranging functionality. “It’s essentially good for one purpose—evacuation,” he says. “It’s not a good equipment hauler and not a master stream device with a waterway. As an engineer, I’m intrigued by the technology but am hard-pressed to see how a fire department might incorporate it into its fleet.”
Mike Harstad, aerial products manager for Rosenbauer, agrees that Denison’s design “looks like an interesting concept” but wonders about how the final product might comply with National Fire Protection Association (NFPA) standards.
“I’m struggling to see how it could comply with NFPA,” Harstad says, “especially in terms of weight disbursement and tip loads. There’s also the question of how much weight it would require to maneuver something of that size when some state weight limits might not allow that vehicle to be on the road.”
David Gurrola, chief operating officer of GROWit, the California engineering and rapid prototyping firm that provided Denison with an engineering design of the unit, says that although his company has not designed fire department aerials before, it has wide experience in the automotive industry, including designing cranes.
“We designed it to be a working project and it meets all the fire codes,” Gurrola says. “We got documentation from NFPA and worked with them.” Gurrola says his company also met with “quite a few fire captains nationally to review relevant codes particular to the needs of an aerial ladder.”
GROWit produced animations of the transportable rescue conveyor to show its features and also made a scale model of the unit.
Joe Hedges, product manager of aerials and chassis for E-ONE, says that, although his company hasn’t worked with a concept like Denison’s, he likes the fact that such ideas get others in the fire industry thinking. “These kinds of ideas help influence change and innovation in the fire service,” Hedges notes. “Years ago, putting 250 pounds at the tip of a ladder and elevating it vertically was unheard of, as was power retraction. So, interesting ideas like this get people thinking of alternatives to what they’re doing now.”
Hedges points out that the transportable rescue conveyor might have design challenges or NFPA concerns in terms of the weight of the vehicle, its rated tip load, and the length of the aerial. He notes that the drawing he saw had at least six axles, which leads him to wonder how much the vehicle would weigh. Placement of the outriggers also could be critical to the overall design, he says.
“A lot of things would have to be researched to come up with a viable design that meets NFPA standards,” Hedges observes. “Thousands of hours of engineering and custom building would go into something like this, which means it might cost more than a traditional aerial.”
Hedges continues, “This would be a big city type of vehicle. But, in today’s market, big cities are looking for something tried and true, so the timing might not be the best for something like this. But, it’s a very creative idea, and pieces of it might be adapted in the future.”
ALAN M. PETRILLO is a Tucson, Arizona-based freelance writer and is a member of the Fire Apparatus & Emergency Equipment editorial advisory board. He served 22 years with the Verdoy (NY) Fire Department, including in the position of chief.