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Apparatus Purchasing: Custom Cabs, Part 3

Issue 4 and Volume 22.

By Bill Adams

Part 1 described the development of custom fire apparatus cabs.

Part 2 described how safety standards developed for the commercial trucking industry were adopted by reference in National Fire Protection Association (NFPA) 1901, Standard for Automotive Fire Apparatus. All fire apparatus manufacturers that build their own cabs and chassis were invited to explain how their products are constructed. Their responses follow my questions.

1 Cab skins, including doors, are constructed from 3⁄16-inch aluminum plate. Also shown is the engine tunnel sidewall, which is constructed from ¼-inch aluminum plate and welded to the front wall, floor, and vertical roof support posts. (Photos 1-5 courtesy of E-ONE.)
1 Cab skins, including doors, are constructed from 3⁄16-inch aluminum plate. Also shown is the engine tunnel sidewall, which is constructed from ¼-inch aluminum plate and welded to the front wall, floor, and vertical roof support posts. (Photos 1-5 courtesy of E-ONE.)

Describe your Cab Substructure.

Mark Bartlett, engineering manager, Spartan Motors: “Cab designs are an extruded aluminum substructure platform, using a dual-roll-cage design with aluminum flat panel outer skins.”

Dave Reichmann, national sales manager, Rosenbauer: “Extruded aluminum design, using 6061-T6 extrusions. Our 3⁄16-inch-thick extruded design creates an extremely safe environment for our customers.”

Yoseph Setiadi, operations manager, Sutphen Hilliard, Ohio, facility (cab and chassis plant): “The Sutphen cab is designed similar to a roll-cage design. While strength is a very important design factor, weight is also a great design consideration. We want to design a cab that results in a lower center of gravity for the overall truck. We have chosen aluminum as the primary material used in the construction. The frame construction all around the cab uses extruded 6061-T6 aluminum, which is stronger than the 5052-H2 aluminum we typically see on a sheet metal part.”

2 The 3⁄16-inch cab sidewalls and cab roof are welded to the perimeter roof extrusions. Slots are CNC-machined into extrusions for wiring.
2 The 3⁄16-inch cab sidewalls and cab roof are welded to the perimeter roof extrusions. Slots are CNC-machined into extrusions for wiring.

Joe Hedges, product manager, E-ONE: “E-ONE cabs use a combination of 6061-T6 and 6063-T6 high-strength aluminum extrusions and 0.188-inch 3003-H14 aluminum plate to create an extremely durable structure. The cab foundation features a wishbone style floor substructure that measures 3.0 inches × 2.25 inches with a substantial 0.435-inch wall thickness. The cab also features two centrally located 3.0-inch × 3.0-inch × 0.188-inch wall vertical posts that support a 3.0-inch × 3.0-inch × 0.375-inch wall roof crossbeam. The vertical posts are also welded to the 0.25-inch engine tunnel side plates that extend all the way forward to the front cab wall. At the rear of the cab are two 6.0-inch × 1.438-inch rear wall extrusions that are also welded between the floor substructure and roof extrusions. The roof structure consists of a perimeter extrusion measuring 4.125 inches high × 7.5 inches wide with an internal grid of 1.5-inch × 3.0-inch x 0.188-inch wall rectangular tubes to support the roof plate. The extrusions and plate are all engineered to work in conjunction with each other to give the cab its roll-cage-type design that provides increased personal safety by supporting more than five times the NFPA/Society of Automotive Engineers (SAE) roof load requirements.”

3 Two 3.0-inch × 3.0-inch posts with a 3⁄16-inch wall thickness and a 3.0-inch × 3.0-inch horizontal crossbeam with 3⁄8-inch wall thickness contribute to the cab’s ability to exceed the SAE roof load requirement by more than five times.
3 Two 3.0-inch × 3.0-inch posts with a 3⁄16-inch wall thickness and a 3.0-inch × 3.0-inch horizontal crossbeam with 3⁄8-inch wall thickness contribute to the cab’s ability to exceed the SAE roof load requirement by more than five times.

Bruce A. Nalesnik, KME chassis group product manager: “KME designs each Predator™ cab model using the latest versions of 3-D modeling engineering software and finite element analysis (FEA) to ensure structural integrity under all loading and operating conditions. After the initial design work is completed, LS-Dyna crashworthiness simulation is performed to verify that the crashworthiness exceeds federal motor vehicle safety standards (FMVSS) and SAE requirements. Actual vehicle crash testing is performed to validate the simulation and FEA models and to verify that the occupant zones of our cab can withstand impacts as high as five times the required load, providing the occupants the maximum protection available. All cab models start with the same cab substructure made from specifically engineered 6061-T6 and 6063-T52 aluminum extrusions. These extrusions, along with an integrated panel system, provide the structural framework that allows it to be the strongest cab in our market. KME does not bolt together cab structure components; all cab structural areas are welded or bonded with structural-grade adhesives. The combination of thick walled extrusions and the use of up to 3⁄16-inch aluminum sheet materials gives our cab weldment superior longevity and test-proven structural integrity.”

4 The 1.5-inch × 3.0-inch rectangular extrusions with a 3⁄16-inch wall thickness are welded into a grid pattern to support the fully welded 3⁄16-inch roof plates.
4 The 1.5-inch × 3.0-inch rectangular extrusions with a 3⁄16-inch wall thickness are welded into a grid pattern to support the fully welded 3⁄16-inch roof plates.

Describe your cab sheet metal and why it is used.

Reichmann: “Rosenbauer uses 3⁄16-inch 5052-H32 aluminum sheet metal because we feel that the additional thickness and strength benefits for safety and durability outweigh any cost savings from using 1⁄8-inch material.”

Hedges: “E-ONE cabs use 0.188-inch 3003-H14 aluminum plate for the cab front, side, and rear walls as well as the roof, floor, and doors. This material was chosen because it has good forming capability and is less likely to exhibit stress cracks than 6000 series material. The 0.188-inch thickness provides added strength when compared to thinner materials as well as more resistance to deflection. All the cab skin material is fully welded (not glued) to the cab extrusions.”

5 The highlighted extrusions indicate the components providing the E-ONE roll-cage construction
5 The highlighted extrusions indicate the components providing the E-ONE roll-cage construction.

Setiadi: “Sutphen uses different thicknesses of aluminum sheet, ranging from 1⁄8-inch to ¼-inch thick. Most of the aluminum sheet parts are made out of 1⁄8-inch-thick aluminum to minimize the weight. The side window and the back of the Sutphen cabs are made out of 3⁄16-inch aluminum to minimize the welding visual impact, and ¼-inch-thick aluminum is used on rear floor for support.”

Bartlett: “All Spartan cab sheet metal is aluminum (5052-H32) ranging from 0.09 inch thick to 0.187 inch thick. Material thickness is selected primarily based on structural design requirements and secondly on weight considerations.”

Nalesnik: “Cab doors are manufactured with 6061-T6 and 6063-T52 aluminum extrusions and then they are covered with 3⁄16-inch-thick 5052-H32 aluminum plate. KME cab doors are mounted to the cab shell with a 3⁄8-inch-diameter continuous stainless steel piano hinge. Strength doesn’t stop with the cab. The cab-to-chassis attachment includes two rear latch assemblies and two pivot assemblies. Each pivot assembly features two plates that are welded into the cab main structural supports along with high-strength steel pivot brackets attached to the frame with grade 8 fasteners. This attention to detail has allowed the Predator™ cab and chassis to exceed frontal impact testing with an impact load greater than 2.1 times the specified load.”

6 These photos show the sequence of cab construction from the initial buildup on a jig to prepaint. (Photos 6-10 courtesy of Sutphen
6 These photos show the sequence of cab construction from the initial buildup on a jig to prepaint. (Photos 6-10 courtesy of Sutphen.)

Any comments on J2420 and your products?

Nalesnik: “KME recognizes that despite excellent engineering and design practices in conjunction with proven construction methods, testing is still a critical phase for ensuring safety of custom cabs for the fire service. Working in conjunction with industry-leading third-party safety specialists, our cabs and chassis have met and exceeded all crash and crush test standards for frontal and side impact and roof crush tests in compliance with SAE-J2420, SAE-J2422, and ECE-R29. Through extensive third-party testing at an independent laboratory, KME cabs and chassis were subjected to the most rigorous and thorough battery of tests available in the industry. The independent leading third-party tester performed all front and side impact testing. Frontal impact testing was done at 2.1 times the industry requirements.”

Hedges: “E-ONE cabs were third-party tested for front impact resistance (SAE J2420). They not only passed the requirement, but the cab’s robust construction resulted in it exceeding the SAE requirements by more than two times.”

Bartlett: “All existing Spartan cab offerings have been base model tested by an accredited third-party testing facility and met the SAE J2420 criteria.”

Reichmann: “The requirement for the front strength dynamic load test is 44.13 kilojoules (kJ). Rosenbauer exceeded the requirement by more than two times by testing at 100 kJ.”

Any comments on J2422 and your products?

Reichmann: “The requirement for the cab roof is 24,130 pounds. The Rosenbauer cab was tested to 120,000 pounds, almost five times this standard.”

Bartlett: “All existing Spartan cab offerings have been base model tested by an accredited third-party testing facility and met the SAE J2422 criteria.”

Hedges: This test has two parts: straight roof loading and side impact load. The E-ONE cab was tested by a third party and easily passed both. In addition, once the cab was tested using the SAE-required weight, we increased the roof load to more than five times the SAE requirement, and it still passed.”

Any comments on ECE29 and your products?

Nalesnik: “KME’s independent leading third-party tester performed all required roof and side crush testing. Weights exceed the industry requirements by 100,000 pounds.”

Bartlett: “All existing Spartan cab offerings have been base model tested by an accredited third-party testing facility and exceeded the minimum requirements for ECE29 roof crush.”

Reichmann: “Rosenbauer meets all ECE29 requirements.”

Hedges: “NFPA 1901 14.3.2 requires cabs to meet SAE J2420 and 2422 or ECE Regulation number 29. E-ONE chose to comply with the SAE requirements.”

Any comments about the J2420, J2422, or ECE-29 regulatory criteria?

Setiadi: “The Sutphen cab was tested based on those three standards. We pride ourselves on building the safest and strongest cab in the industry. We believe we further strengthen our place in the marketplace by passing those standards.”

Hedges: “E-ONE strongly agrees with NFPA 1901 having a cab strength requirement to ensure firefighter safety while responding to or returning from a call. Cab strength, in addition to proper use of seat belts, contributes greatly to occupant safety in the event of a crash. In addition, safety features such as electronic stability control and OnGuard collision mitigation can help prevent an accident from happening in the first place.”

Nalesnik: “KME believes the three test criteria are sound benchmarks for the fire service to ensure a minimum level of protection to all occupants.”

Reichmann: “Occupant safety is of the utmost importance to Rosenbauer, and we believe that, to ensure certain safety standards are met, having these standards as a benchmark is important to the industry as a whole.”

Bartlett: I believe the implementation of these three requirements within NFPA 1901 is good. This gives all custom cab manufacturers a guideline for cab structural integrity, resulting in end user confidence for product safety. The one negative I see in this regulation is that vehicles [with] less than 26,000-pound gross vehicle weight ratings (typically commercial chassis) are not required to comply with the regulation. Industry safety guidelines should be equal whether or not you are building a custom or commercial chassis.

11 This sequence shows Rosenbauer cabs in prepaint, after paint, and during trim-out. (Photos 11-13 courtesy of Rosenbauer.)
11 This sequence shows Rosenbauer cabs in prepaint, after paint, and during trim-out. (Photos 11-13 courtesy of Rosenbauer.)

If you offer more than one internal cab width, what are they?

Setiadi: “Sutphen offers one cab width. However, our cab varies in length – 56, 62, and 73 inches – and roof heights of flat or 10-, 15-, and 20-inch raised roofs.”

Reichmann: “Yes, we have two widths. The Commander is 99 inches skin to skin with an interior width of 91.5 inches fully trimmed. The Warrior is 96 inches skin to skin with an interior width of 88.5 inches fully trimmed.”

Nalesnik: “KME offers a 100-inch and 96-inch exterior cab width and offers standard-width and narrow-width engine enclosure options in the 100-inch-wide cab.

Hedges: “E-ONE offers two cab designs. The Cyclone and Typhoon cabs have an internal door panel to door panel width of 90 inches and a wall to wall dimension of 87.5 inches. The Quest door panel to door panel width is 93.25 inches and has a wall to wall dimension of 91 inches. The Cyclone and Typhoon cabs have an outside width of 94 inches and use overlap-style doors that provide additional interior space. The Quest is a 100-inch-wide cab with flush-style doors.”

Bartlett: “Spartan offers two cab widths. The narrowest interior cab width is 87 inches, and the widest is 92 inches.”

Do you offer different materials for cab construction?

Bartlett: “All Spartan cabs are constructed with aluminum materials as described above.”

Nalesnik: “It really is up to the customer to determine what type of cab material works best for them. Factors such as cost, weight, and testing criteria are part of the discussion KME has to ensure all the facts are explained thoroughly.”

Hedges: “E-ONE cabs are all constructed out of aluminum. We believe this material is advantageous for this application because of it being lighter than other materials, providing more carrying capacity for personnel and equipment. And, aluminum does not mean a reduction in strength as proven by third-party testing of our cabs. In addition, aluminum lends itself well to the high degree of customizations fire departments require to meet their individual needs.”

Do you have any comments on safety gurus pushing for more leg and hip room in cabs?

Reichmann: “Specific to the hip width, we had the opportunity to research this during the development stage for the Commander cab. We solicited and received a great deal of customer feedback during this process. The feedback overwhelmingly guided Rosenbauer to concentrate on increased hip room and improved ergonomics, which have been integrated into all of our cabs. Rosenbauer meets the proposed width standards today.”

14 Prepaint sanding and priming. (Photos 14-17 courtesy of Spartan Motors.)
14 Prepaint sanding and priming. (Photos 14-17 courtesy of Spartan Motors.)

Setiadi: “Per our customers’ requests and engine configurations, Sutphen can accommodate lengthening the leg room by shortening the engine hood compartment.”

Nalesnik: “KME is always striving for more leg, hip, and elbow space. As long as expectations can be realistic and not imposed without a thorough vetting, the competitive process will continue to provide results in this area.”

Bartlett: “Typically, increased leg room has not been an issue with Spartan’s cab designs. Increased hip room has, however, been a hot topic of discussion of late. There seems to be a push toward multipurpose vehicle applications, which is driving the need for departments to carry more equipment. This increased equipment requirement will drive many departments to the big block engines. In doing so, this will increase engine compartment widths. With the increased engine compartment widths and department of transportation (DOT) maximum vehicle widths, significant increases to seating hip room are going to be extremely difficult for custom cab manufacturers but not so for manufacturers of commercial cabs with engine-forward configurations.”

15 Cab electrical and wiring harness installation.
15 Cab electrical and wiring harness installation.

Hedges: “When conducting voice of customer work, one of the first things a user typically asks for is more room for the officer and crew. Since cab widths are limited by DOT regulations, and engine requirements are often for 500-horsepower or more, it’s a challenge to provide a substantial increase in driver and officer space with a conventional engine-forward design without raising cab heights. This need for more occupant space was one of the main drivers behind E-ONE developing an all new rear-engine chassis named the Hush Series (HS). Moving the engine entirely out of the cab allows us to provide the space suggested by the National Institute for Occupational Safety and Health firefighter anthropometric study. The HS cabs, both the traditional Cyclone style and the more modern Quest style, have an open interior design that not only provides industry-leading interior space for firefighters and gear but also allows for improved visual and audible communication between crew members. And with the engine mounted at the rear of the chassis, the cab interior is approximately 10 decibels quieter than typical front-engine products.”

If you offer more than one type of cab construction, do you want to comment on the differences?

Bartlett: “Spartan presently offers one cab construction. However, customized variations are virtually unlimited.”

Nalesnik: “KME continues to offer different cab widths and lengths and the associated supportive engineering for these options because of fleet department requests for narrower and shorter WB designs for their environmental operations. Different cab materials are likewise offered (i.e., stainless steel) for those customers who require a specific cab material based on their history with certain cab configurations.”

16 The substation for final prep and road test.
16 The substation for final prep and road test.

Hedges: “The E-ONE Cyclone and Typhoon cabs are built exactly the same. The Quest cab, because of its more modern styling and flush doors, has some unique exterior extrusions. However, the floor subframe, vertical posts, and roof structure are all very similar in design to the Cyclone and Typhoon cabs. The Quest cab’s large windshield is positioned to not only provide optimal forward visibility but allow cab corner-mounted mirrors to be viewed through a wiped area.”

Do you have any comments on the specific development of your cab line(s)?

Reichmann: “While in the development process for the Commander, Rosenbauer did extensive customer research and integrated many of the needs and desires that end users indicated they wanted in a custom cab.”

Bartlett: “No comments at this time on future cab development.”

Nalesnik: “KME has been producing custom chassis since 1986 and is in the midst of its fifth generation of chassis development. We currently offer more 300 custom cab configurations for all types of pumper, aerial, and rescue applications. We continue to strive to improve our design and option portfolio based on customer feedback and industry trends.”

17 Final electric and trim work.
17 Final electric and trim work.

Setiadi: “In recent years, Sutphen redesigned its cab department factory layout to a production flow layout. This allows us to meet an increased market demand and set up a Kanban system to replenish parts.” (Note: Kanban is a scheduling and inventory system for lean manufacturing and just-in-time inventory timetabling. While Kanban relates specifically to a Japanese system, lean engineering and just-in-time inventory control have been practiced in Europe and domestically to improve manufacturing efficiency.)

Hedges: “E-ONE began building an aluminum cab for the fire service over 30 years ago. Since then, we have developed many variations that include the initial fixed midcab engine placement, engine-forward tilt cab, midengine cabs, and rear-engine cabs. In 2007, the Quest cab was introduced that provides modern styling and excellent ergonomics. One thing that remains constant over the years is that E-ONE continues to build its cabs with occupant safety and long-term durability in mind.”

Do you outsource your cabs?

Hedges: “E-ONE cabs are all engineered and built in our production facilities in Ocala, Florida. We are a true single-source manufacturer, producing our own cabs, chassis, bodies, pump modules, and aerial devices.”

18 The beginning of a jig formed cab layout. (Photos 18-20 courtesy of KME.)
18 The beginning of a jig formed cab layout. (Photos 18-20 courtesy of KME.)

Nalesnik: “No. KME designs and produces all of its custom chassis cabs at their main production facility in Nesquehoning, Pennsylvania.”

Setiadi: “Sutphen does not outsource the cab. We build the raw cab in our Hilliard, Ohio, facility and install the interior parts in our Springfield, Ohio, facility.”

Do you have any predictions for the future of custom cab design?

Nalesnik: “Cab designs have changed drastically over the past 10 years as fire department needs have evolved to provide multiuse apparatus. The use of the cab for additional compartment space via emergency medical service compartments and on-scene operations reinforces the need for flexibility by the chassis manufacturers, or they will find it increasingly difficult to compete in the market.”

Bartlett: “I predict that future cab designs will begin to look at the means of driving down weight – not just in the cab construction methods but in the components that are installed in it.”

19 A cab weld-up.
19 A cab weld-up.

Reichmann: “Technology will be relevant. Rosenbauer believes that safety and technology will be the main driving forces for all future custom cab designs while still maintaining the ability for customization.”

Hedges: “I believe the trend will continue toward more rugged cab and cab interior designs. Providing more room for the crew as well as increased storage space will continue to be a priority. However, this may require new thinking relative to engine packaging. In addition, with electronics permeating nearly all aspects of our lives, users will more and more demand that apparatus, especially cabs, will become more technologically advanced.”

Nonmanufacturer Views

To get some outside-the-industry opinions on cab construction, I asked Tom Shand, senior partner at Emergency Vehicle Response, and Jim Lyons, owner of J. Lyons Fire Consultants of Glastonbury, Connecticut, for their comments on custom cab construction.

Lyons: “As a consultant, I try to educate the customer on all the aspects of custom cab and chassis design. Many do not know or realize the difference in cab materials available, the material thicknesses available, and what safety or long-term maintenance benefits are afforded by each. An example is 1⁄8-inch-thick aluminum cab material vs. 3⁄16-inch material. I find that most apparatus sales representatives do not talk about cab material thickness or the different materials available if they only offer one type of material and thickness. Those that offer multiple materials and thicknesses tend to offer those as options for consideration.

“Typically, a sales representative sells on features and the name of the manufacturer as opposed to construction details. It’s when we analyze the manufacturer’s specifications that the details are exposed. A simple way I try to assist my customers is to show them a ¼-inch-thick aluminum metal sample and then a 3⁄16-inch metal sample. These are the two most common materials used in the construction of aluminum custom fire cabs. At that point, the lightbulb typically goes off. It’s when they can actually see the difference that they understand the difference.

20 The features of a KME cab
20 The features of a KME cab.

“Another area most customers do not realize they have a choice on is the overall width of the cab, which, in most cases, equates to the room available inside the cab. Many manufacturers have gone back to offering 94-, 96-, or 98-inch-wide cabs, which were very popular in the early 1990s prior to the new emission standards. Those models of cabs could accommodate the heavy-duty large-horsepower engines at one time. When the new Environmental Protection Agency (EPA) standards were implemented, many manufacturers increased the overall width of cabs to 100 inches wide, which allowed for more room inside and to accommodate the larger engines and cooling packages. Now with financial considerations being more of a decision factor in purchasing, many manufacturers have reintroduced the smaller cabs combined with medium-duty engines and drivetrain packages as more affordable options. The smaller-width cabs do not afford as much room inside for the driver or officer position as the 100-inch-wide cabs. So, interior cab width is another area most don’t realize is an option for consideration. The durability and type of material used and the manufacturing process to construct the cab are directly related to overall safety of the cab.”

Shand: “Over the years, the apparatus industry has largely gravitated to all-aluminum cabs for several reasons. Galvanized steel cabs produced during the 1980s and early 1990s proved to be highly susceptible to corrosion and often required a midlife rehabilitation to provide 12 to 15 years of service life. With the requirement for four-door fully enclosed cabs combined with a preference for engine-forward cab designs, most all builders, with the notable exception of Seagrave, migrated to all-aluminum cab construction to reduce the front axle weight loading. Since the NFPA 1901 requirement to have all custom fire service cabs subject to a standardized static crash test, all builders of custom cabs must meet at least the minimum requirement to ensure the safety of occupants. Unfortunately, these tests do not always simulate the types of serious accidents where apparatus are involved. Units with short bumper extensions with limited impact or crush zones along with the standard stainless steel bumpers offer limited protection against cab intrusion when an apparatus contacts large, immovable objects such as trees, buildings, or heavy vehicles.

“The apparatus industry has endured mandatory cab redesigns since 2005 because of a combination of the NFPA 1901 changes and EPA engine emission regulations. These cab redesigns were costly, and while all custom cabs meet the minimum requirements, the educated fire department apparatus committee really needs to consider the seating arrangements and safety aspects for their personnel. If a department really wants to have all personnel seated and belted at all times in personal protective equipment, then it is incumbent to design the cab with safe seating arrangements with adequate spacing to allow this to happen. Don’t expect a 220-pound firefighter in personal protective clothing to sit comfortably in an integral ‘all-belts style’ self-contained breathing apparatus seat with seats on either side that are eight inches apart. It might meet the standard, but it’s probably not safe.”

BILL ADAMS is a member of the Fire Apparatus & Emergency Equipment editorial advisory board, a former fire apparatus salesman, and a past chief of the East Rochester (NY) Fire Department. He has 50 years of experience in the volunteer fire service.