Apparatus Purchasing: Bolted Bodies

Bill Adams

The majority of metallic fire apparatus bodies feature welded construction; however, a handful of manufacturers bolt their bodies together. Some use bolted construction exclusively, while others offer it as an alternative to the welding process. Some use a combination of both. This article does not endorse, prefer, or recommend any method of construction, body material, or manufacturer, nor will it compare one to another. The intent is to inform the reader of the procedure and process of bolting apparatus bodies together and why some manufacturers market that method. Whether one is better than the other is a matter left to manufacturers’ marketing people and individual purchasers.

Manufacturers offering bolted construction were contacted for input. Some replied and are quoted herein. Some did not reply. Several expressed hesitation in participating for fear of getting into a “heated debate” over why one is better than the other. One manufacturer said it would be hard to objectively opine on one method of construction without it resulting in a “tit for tat” comparison with other methods. I will try not to. Another inferred it would become “proprietary.” My interpretation of proprietary is something that is exclusive, copyrighted, trademarked, or brand named. Bolting and welding are methods of construction available to all manufacturers.


In 1912, the E.G. Budd Company in Philadelphia spot welded the first automobile body. Around 1914, the Heil Company began acetylene and electric welding of bodies, claiming to have built the first “electrically welded compartment tank” for motor trucks. The first all-welded automotive body was fabricated in 1923. A historical record cannot be found for the evolution of fire apparatus bodies, although Mack Fire Apparatus’s 1925 catalog notes, “The bodies used on all but the Hook-and-Ladder and Squad Car types of apparatus are constructed of only five sheets of gauge steel plate, 3⁄16 inches thick, electric welded to form the sides and front ….”

Lieutenant (Ret.) Mahlon Irish, of the Ithaca (NY) Fire Department and an antique American LaFrance (ALF) aficionado, owns more than a dozen antique rigs. He states ALF’s 1920s-era bodies were riveted together with accoutrements such as fenders and steps bolted to the body. In the 1930s and 1940s, ALF’s sheet metal was bolted to a welded framework. In the mid 1930s, Ward LaFrance riveted formed sheet metal around wood planks into a “sandwiched” type body. A 1932 Buffalo engine, in Mendon, New York, has a wooden hose body skinned with formed steel attached with wood screws and metal fenders riveted together. A 1938 Mack Type 75 pumper, in East Greenwich, Rhode Island, has sheet metal doors and a sheet metal cab screwed to a wood framework. The late 1940s ALF 700 Series introduced all-welded bodies. The late 1950s 800 Series featured bolted-on compartment modules. Most builders during that era used untreated steel compartments. They didn’t last long, and the bolted-on compartment modules were easy to replace. In 1971, ALF’s Century body featured all- welded bodies and compartments. The Century 2000 body went back to bolting compartments to a welded body. No date can be found for the introduction of all-bolted construction.

This bicycle, laser cut from a sheet of 14 gauge 304 stainless steel, is used by one manufacturer to demonstrate the exactness achievable with precision tooling
(1-2) Bolted construction typically requires the process of computer numerical control (CNC) high-precision manufacturing to achieve high levels of accuracy and exactness. This bicycle, laser cut from a sheet of 14 gauge 304 stainless steel, is used by one manufacturer to demonstrate the exactness achievable with precision tooling. (Photos courtesy of CustomFIRE.)

Modular or Bolted

The definition of “modular” and “bolted” construction has become synonymous. Some manufacturers call modular construction bolted construction. That is confusing and can be misleading because premanufactured parts, such as compartment modules, can be fabricated by being formed, welded, or bolted together and in turn bolted to the apparatus body. For the sake of clarity, bolting major prefabricated parts together is defined as modular construction in this article. All-bolted construction means all the parts and pieces of a body’s sheet metal are attached to each other using mechanical fasteners-in particular, nuts and bolts.

Paul Christiansen, Ferrara’s marketing director and aerial sales manager, notes that there is a segment of the market that requests modular body components including hosebed side sheets, compartments, wheel wells, and the front and rear body panels. From Ferrara’s published specifications, “The fire apparatus body shall be fabricated using modular design consisting of independent body parts bolted to an independent heavy-duty superstructure framework.” Christiansen also observes that modular construction, when called for, is predominant in Ferrara’s tanker and pumper market, although the company will do an aerial body if requested.

Mike Watts, national sales manager for Toyne, says Toyne’s modular body is built in halves on a fixture, then bolted together. Watts says bolted (stainless) bodies comprise a large share of the company’s business.

Bill Bruns, vice president of sales and marketing for UPF, spent 26 years with the former Grumman fire apparatus division. He states Grumman’s Firecat pumper line, although advertised as modular, was all-bolted construction. Bruns points out that Grumman also offered a line of welded bodies. Many manufacturers still offer both, including Ferrara, Smeal, and Toyne. Sutphen Corporation’s Web site shows bolted (stainless) bodies only offered on its custom pumper, aerial platform, and aerial ladder lines. CustomFIRE’s sole method of body fabrication has been all-bolted construction (aluminum and stainless) since its inception in the 1970s.

Use caution when defining and specifying methods of body construction. Compare “apples to apples” when evaluating the same. Specification writers and vendors should be on the same page regarding definitions. Use plain language-it will make life easier.

Lasers and CNC

Naysayers denigrating the bolting process question the accuracy and exactness of component parts. Fifty years ago, that question may have had merit. Manually measuring, cutting, and drilling parts and pieces are contingent on the expertise of the fabricator. Today, most manufacturers have invested in tools and technology such as laser cutters and the CNC machines.

Laser machining and laser cutting use very powerful beams of electromagnetic radiation to cut. CNC is not a proprietary process and is not restricted to builders who bolt bodies together. CNC is not a method of construction; it is an abbreviation for a process called computer numerical control. McGraw-Hill’s Dictionary of Scientific and Technical Terms defines it as, “A control system in which numerical values corresponding to desired tool or control positions are generated by a computer. Also known as computational numerical control; soft-wired numerical control; stored-program numerical control.”

In very simple terms (without offending the degreed mechanical engineers), the fire truck and its component parts are engineered and built on a computer with every part assigned a numerical control number. Combining laser technology and CNC technology is common throughout the manufacturing world. The degree of accuracy and exactness desired dictates the investment a manufacturer must make in laser and CNC technology. Jim Kirvida, president of CustomFIRE, notes that the CNC method of laser machining and fabricating was a million-dollar investment in infrastructure, training, and the computer-controlled machines themselves. CustomFIRE has used the Pro-E 3D Modeling Program and a Bystronic laser since the mid 1990s. Kirvida points out, “Everything we do everyone else could do.”

Regardless of how they build bodies, most apparatus manufacturers use some form of CNC and laser technology. Smaller manufacturers who can’t afford or will not invest in tools and technology must rely on the continuity of the craftsmanship of their workers. This is not a denigration of the skill and workmanship of those workers.

Lasers, CNC, and Bolting

The amalgamation of laser and CNC technology dramatically changed the dynamics of fabricating bodies and, in particular, all-bolted bodies. Prior to their use, a dozen skilled sheet metal craftsmen could take about four days to manually measure, cut, shear, saw, notch, hand drill, and fabricate a body. Precision engineering and CNC laser machining allows four assembly workers to build the same body in less than half that time. Although this time comparison is for all-bolted body construction, lasers and CNC technology can facilitate productivity and efficiency in any manufacturing process.

Also note any distinction between craftsmen and assembly workers is in the eye of the beholder. Ferrara Fire Apparatus offers both bolted and nonbolted bodies. Ferrara’s Christiansen notes, “In order to maintain expertise in each manufacturing process, separate fabrication crews are assigned to the modular body production line.” Wayde Kirvida, factory sales for CustomFIRE, comments, “We have always employed highly skilled welders in our production. They just never assembled our bodies. They were employed to weld steel booster tanks as well as substructures, tank cradles, tailboards, bumper extensions, steps, running boards, hosebed covers, ladder racks, and so on. Except the tanks, those parts are still being welded.”

Mechanical Fasteners

Rivets are rare in today’s apparatus industry. They are occasionally used to attach trim plates and pump panel tags, which now are mostly taped or glued on. Nuts and bolts are the mainstay. Some cynics claim that nuts used in body construction will loosen up and fall off or the seams will leak. Dispel rumors; ask for documentation to substantiate accusations. Almost all manufacturers use self-locking nuts with plastic inserts referred to as “Nylock® nuts” or “ESNA®-type” nuts-technology from the aerospace industry. While Nylock and ESNA are registered trade names, it is unknown if apparatus manufacturers’ specifications use the names generically. Ask them. Jim Kirvida claims, “Mechanically fastening seams can provide watertight fits without caulking or painting, providing mating surfaces are smooth and fastener holes are precise”. He adds, “Aircraft skins are not caulked before riveting.” And, they are seldom painted afterward.

Bolts can be pan-head, truss-head, or button-socket-head-cap, which has a lower profile. Some manufacturers use ¼-inch-diameter bolts when mating structural members and 3⁄16-inch-diameter bolts in nonstructural areas such as treadplate appliques. The spacing, location, and size of the bolts are unique, but not proprietary, to each manufacturer. This article shows no favoritism. Ask your favorite vendor what it uses where-and why.

Replacement Parts

Christiansen says Ferrara uses the CNC process, which guarantees accuracy of replacement parts. HME-Ahrens Fox’s Web site states, “Easy to repair-the modular bolt design of the HME-Ahrens Fox bodies allow fast and economical replacement of damaged panels.” Watts comments, “The CNC process allows more consistent parts to be manufactured and allows for replacement parts to be manufactured exactly as the original when repair is required. And, CNC is only as good as the person who develops the program and the person who runs the machine.” He adds, “Bolted bodies also offer significantly easier repairs when they are bent due to an accident.”

Jim Kirvida elaborates, “The CNC method of fabrication and mechanical fastening, or bolting, provides for inherently fast and efficient repairability. Replacement parts for an engineered all-bolted body have mating fastener holes which are guaranteed to fit within 5⁄1000 of an inch. That is equal to the width of two human hairs.” He also says most repairs can be done in-house, as painted parts can be ordered finish painted and shipped from the factory.

From Smeal’s Web site, “Our stainless steel pumpers are designed with laser-cut and bolt-together construction. This design provides maximum durability and allows for ease of repair in the unfortunate event of a crash.” From Ferrara’s published specifications, “The reason for specifying a modular designed body is for strength and ease of replacement in the event of incidental damage.”

Bruns says that Grumman’s “impetus [for bolting] was for ease of assembly and simple maintenance if a body had to be repaired or replaced due to an accident.” Bruns also notes that bolting allowed Grumman to inventory component parts for standard production models, which was a major portion of Grumman’s business. He says that the ease-of-repairability claim is not new. Grumman introduced its bolted body design in the late 1970s.


All-bolted bodies allow flexibility in using different gauges of metal and even intermixing metals. Most manufacturers who promote stainless steel advertise 12-gauge as the standard. Little known and seldom advertised is that nonstructural parts can be 14-gauge to save cost and weight. Watts states that Toyne does not mix and match different materials-i.e., stainless and aluminum-together. However, he says, “We use 14-gauge for nonstructural pieces like the back walls of compartments. If it is in any way a structural item, the stainless will be 12-gauge for rigidity and strength.” Jim Kirvida notes that aluminum apparatus can be constructed with, as an option, stainless components in areas requiring extra reinforcement or those subject to severe corrosion such as wheel wells. Regarding possible electrolysis, Kirvida says, “CustomFIRE uses dielectric tape, the exact same material used to separate layered windings in electric motors.”

There are unseen factors and savings-applicable to all methods of construction-a purchasing committee could consider. One is total cost of ownership-a topic to be addressed in detail in a future article. Briefly put, in one example, proponents of bolted bodies claim lower out-of-service times in the event of body repairs or modifications. Can a monetary cost be placed on the downtime because of body damage? Is there a value on the ability to reproduce parts and replace them in days vs. weeks? Jim Kirvida, says, “A long-term consideration is the ease in transforming a pumper that has exceeded its useful service life into a squad or rescue type apparatus.” Bruns notes that the hidden savings at Grumman were in engineering costs and having standard parts available off the shelf. Jim Kirvida concurs, noting there is a single engineering cost regardless of the number of parts produced.

Various Bolting Methods

Just as there are different techniques in welding a body, such as strip, stitch, spot, plug, and continuous welding, there are different ways of bolting bodies together. These include using overlapping, single, or double breaks on mating pieces; having exposed or hidden fasteners; and the types of fasteners themselves. Whether compartment interiors and seams are caulked, painted, or exposed is up to the purchaser unless, of course, it’s a prerequisite of the manufacturer. Ask. One industry insider comments that he knew of no warranty differences relevant to construction methods as they relate to materials. He’s wrong-there are differences. Again, ask your vendors. Because the verbiage, terminology, terms and conditions, and actual value of published warranties vary from manufacturer to manufacturer, they will not be addressed herein. Warranties and guarantees are volatile topics that will also be addressed-in depth-another day.

Whether a particular gauge, metal type, or method of construction is better than another is a decision that rests solely with the purchaser. This article shows no preference. It did not address cost because only the purchaser can place a value received for monies spent. The objective is to show that there is more than one way to build a fire truck. Let the salespeople make their pitches. Listen carefully. Choose wisely.

BILL ADAMS is a former fire apparatus salesman, a past chief, and an active member of the East Rochester (NY) Fire Department. He has more than 45 years of experience in the volunteer fire service.

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