By Bill Adams

The first equipment compartment on a fire truck located behind the cab on the driver’s side is often designated “L1” on manufacturers’ blueprints and in purchasing specifications - L1 obviously meaning left side, first compartment.

This article addresses L1 full-height compartments on traditional-style pumpers and rescue-pumpers equipped with conventional midship pump houses. What the compartment is designated or numbered and how it’s fabricated are irrelevant. How and why it is described in a set of purchasing specifications (specs) are important.

1 This traditional-style pumper body by HME-Ahrens Fox has a decent size L1 compartment. Note the yellow wheel chocks and uncluttered pump panel. (Photo courtesy of HME-Ahrens Fox.)

Technical purchasing specifications including compartment dimensional requirements are generated by three entities. The first is by the authority having jurisdiction (AHJ) or the fire department on its behalf. Writing effective purchasing specifications in-house is challenging at the least and intimidating at most. Fire departments commonly use outside sources for advice and technical expertise. The second is when the document is provided by a preferred apparatus manufacturer (OEM), which, as expected, ensures the verbiage totally favors the apparatus it builds. It is commonplace and understandable. When a manufacturer’s “standard” specification is published by the purchaser, it is readily obvious to other OEMs what the purchaser wants. It can influence their decision on whether or not to bid. The last are specs generated by a third party such as a local dealer or a consultant. Dealers’ specifications understandably reflect the product they sell. Although a dealer may tell a prospective purchaser a nonproprietary specification is being provided, experienced dealers can subtly skew verbiage and narrative to be self-serving. That’s business. It’s their job - get over it. Anticipate it. Some are better at doing it than others. Experienced dealers can look at a spec and immediately identify the dealer that wrote it. That can also influence whether or not to bid.

2 Two vertical dividers mounted on a slide tray on the floor of compartment L1 with an adjustable shelf above it. Note the vertical up and down handles on the pump panel’s discharges and inlet.

Most consultants and professional spec writers claim to write nonproprietary documents. However, some - and I emphasize some and not all - have preferences for specific manufacturers and will slant their verbiage accordingly. That is human nature, especially for those previously employed in the fire service or industry. Purchasers should read between the lines. Principles and ethics aside, there is nothing illegal when dealers and consultants write a proprietary purchasing specification. Sometimes end users will request a spec writer to do so. The AHJ promulgates the document; hence, the spec writer is not accountable or culpable - the A

By Bill Adams

The first equipment compartment on a fire truck located behind the cab on the driver’s side is often designated “L1” on manufacturers’ blueprints and in purchasing specifications - L1 obviously meaning left side, first compartment.

This article addresses L1 full-height compartments on traditional-style pumpers and rescue-pumpers equipped with conventional midship pump houses. What the compartment is designated or numbered and how it’s fabricated are irrelevant. How and why it is described in a set of purchasing specifications (specs) are important.

1 This traditional-style pumper body by HME-Ahrens Fox has a decent size L1 compartment. Note the yellow wheel chocks and uncluttered pump panel. (Photo courtesy of HME-Ahrens Fox.)

Technical purchasing specifications including compartment dimensional requirements are generated by three entities. The first is by the authority having jurisdiction (AHJ) or the fire department on its behalf. Writing effective purchasing specifications in-house is challenging at the least and intimidating at most. Fire departments commonly use outside sources for advice and technical expertise. The second is when the document is provided by a preferred apparatus manufacturer (OEM), which, as expected, ensures the verbiage totally favors the apparatus it builds. It is commonplace and understandable. When a manufacturer’s “standard” specification is published by the purchaser, it is readily obvious to other OEMs what the purchaser wants. It can influence their decision on whether or not to bid. The last are specs generated by a third party such as a local dealer or a consultant. Dealers’ specifications understandably reflect the product they sell. Although a dealer may tell a prospective purchaser a nonproprietary specification is being provided, experienced dealers can subtly skew verbiage and narrative to be self-serving. That’s business. It’s their job - get over it. Anticipate it. Some are better at doing it than others. Experienced dealers can look at a spec and immediately identify the dealer that wrote it. That can also influence whether or not to bid.

2 Two vertical dividers mounted on a slide tray on the floor of compartment L1 with an adjustable shelf above it. Note the vertical up and down handles on the pump panel’s discharges and inlet.

Most consultants and professional spec writers claim to write nonproprietary documents. However, some - and I emphasize some and not all - have preferences for specific manufacturers and will slant their verbiage accordingly. That is human nature, especially for those previously employed in the fire service or industry. Purchasers should read between the lines. Principles and ethics aside, there is nothing illegal when dealers and consultants write a proprietary purchasing specification. Sometimes end users will request a spec writer to do so.

By Bob Albano

Air-ride suspensions have steadily increased in popularity in nearly all segments of the trucking industry. Approximately 75 percent of the trailers manufactured today and almost all highway tractors use air-ride suspensions.

Air has even proliferated into the specialty segments of the trucking industry. It is not uncommon to find air-ride suspensions on heavy-duty vehicles that operate in extremely rugged environments - dump trucks, refuse, logging vehicles, and even concrete mixers. Following this logical progression, the migration from leaf spring suspensions to air ride is gaining momentum on fire and rescue vehicles. Specifying the right suspension should be a high priority for decision makers in this industry. Suspension systems affect the performance and life of the vehicle, frequency of maintenance, and comfort and safety of the operator. Upgrading to an air-ride suspension typically results in less than a one percent increase in the total cost of an apparatus, a great value for benefits gained.

What Factors Control Ride Quality?

Suspensions with a lower natural frequency reduce the force transmitted to the vehicle, which improves ride and vehicle protection when properly engineered. Natural frequency includes the spring rate of the suspension and the amount of weight supported by the suspension. The spring rate of the air springs is a measure of the vertical stiffness of the air springs or how much the suspension deflects for a given load being carried. The natural frequency of a suspension will increase if the suspension spring rate is increased or decreased. Because of a softer spring rate, air suspensions provide greater equipment protection over traditional mechanical suspensions. This is because of the air springs’ ability to cushion the equipment and passenger load. Outstanding ride produces superior driver and passenger comfort while helping to protect critical, lifesaving equipment and costly electronic components from excessive vibration and road inputs.

Understanding Roll Stability

Roll stability is a measure of how well the suspension and chassis resist rolling or swaying, especially when encountering a turn. A vehicle’s roll stability can be measured in two ways: (1) determining the maximum cornering speed before reaching the rollover threshold (when tires lift off the ground), and (2) measuring the amount of roll that occurs for a given turn at a given speed (the roll angle). Many elements of a vehicle’s design play a factor in determining its roll stability. Roll stability for a fire and rescue vehicle is influenced by the height of the center of mass of the truck body and the axle track width. These factors can have the greatest impact on the roll stability of the vehicle.

While suspension roll stiffness contributes to roll stability, it represents only one component of the equation. The chassis’s flexibility and tire stiffness, for example, must also be considered when determining the truck’s overall roll stability. Air-ride suspensions have come a long way over the past few decades, and we’re now at the point where properly engineered air-ride suspensions can deliver roll stability near that of a steel leaf spring suspension. For fire and rescue vehicles, higher rollover thresholds allow improved vehicle performance during the challenging, evasive maneuvers that are experienced when rushing to the scene of an emergency.

So, how can the vehicle’s suspension affect roll stability? The level of roll stiffness provided by a suspension is the best way to directl

By Bob Albano

Air-ride suspensions have steadily increased in popularity in nearly all segments of the trucking industry. Approximately 75 percent of the trailers manufactured today and almost all highway tractors use air-ride suspensions.

Air has even proliferated into the specialty segments of the trucking industry. It is not uncommon to find air-ride suspensions on heavy-duty vehicles that operate in extremely rugged environments - dump trucks, refuse, logging vehicles, and even concrete mixers. Following this logical progression, the migration from leaf spring suspensions to air ride is gaining momentum on fire and rescue vehicles. Specifying the right suspension should be a high priority for decision makers in this industry. Suspension systems affect the performance and life of the vehicle, frequency of maintenance, and comfort and safety of the operator. Upgrading to an air-ride suspension typically results in less than a one percent increase in the total cost of an apparatus, a great value for benefits gained.

What Factors Control Ride Quality?

Suspensions with a lower natural frequency reduce the force transmitted to the vehicle, which improves ride and vehicle protection when properly engineered. Natural frequency includes the spring rate of the suspension and the amount of weight supported by the suspension. The spring rate of the air springs is a measure of the vertical stiffness of the air springs or how much the suspension deflects for a given load being carried. The natural frequency of a suspension will increase if the suspension spring rate is increased or decreased. Because of a softer spring rate, air suspensions provide greater equipment protection over traditional mechanical suspensions. This is because of the air springs’ ability to cushion the equipment and passenger load. Outstanding ride produces superior driver and passenger comfort while helping to protect critical, lifesaving equipment and costly electronic components from excessive vibration and road inputs.

Understanding Roll Stability

Roll stability is a measure of how well the suspension and chassis resist rolling or swaying, especially when encountering a turn. A vehicle’s roll stability can be measured in two ways: (1) determining the maximum cornering speed before reaching the rollover threshold (when tires lift off the ground), and (2) measuring the amount of roll that occurs for a given turn at a given speed (the roll angle). Many elements of a vehicle’s design play a factor in determining its roll stability. Roll stability for a fire and rescue vehicle is influenced by the height of the center of mass of the truck body and the axle track width. These factors can have the greatest impact on the roll stability of the vehicle.

While suspension roll stiffness contributes to roll stability, it represents only one component of the equation. The chassis’s flexibility and tire stiffness, for example, must also be considered when determining the truck’s overall roll stability. Air-ride suspensions have come a long way over the past few decades, and we’re now at the point where properly engineered air-ride suspensions can deliver roll stability near that of a steel leaf spring suspension. For fire and rescue vehicles, higher rollover thresholds allow improved vehicle performance during the challenging, evasive maneuvers that are experienced when rushing to the scene of an emergency.

So, how can the vehicle’s suspension affect roll stability? The level of roll stiffness provided by a suspension is the best way to directl

By Bob Albano

Air-ride suspensions have steadily increased in popularity in nearly all segments of the trucking industry. Approximately 75 percent of the trailers manufactured today and almost all highway tractors use air-ride suspensions.

Air has even proliferated into the specialty segments of the trucking industry. It is not uncommon to find air-ride suspensions on heavy-duty vehicles that operate in extremely rugged environments - dump trucks, refuse, logging vehicles, and even concrete mixers. Following this logical progression, the migration from leaf spring suspensions to air ride is gaining momentum on fire and rescue vehicles. Specifying the right suspension should be a high priority for decision makers in this industry. Suspension systems affect the performance and life of the vehicle, frequency of maintenance, and comfort and safety of the operator. Upgrading to an air-ride suspension typically results in less than a one percent increase in the total cost of an apparatus, a great value for benefits gained.

What Factors Control Ride Quality?

Suspensions with a lower natural frequency reduce the force transmitted to the vehicle, which improves ride and vehicle protection when properly engineered. Natural frequency includes the spring rate of the suspension and the amount of weight supported by the suspension. The spring rate of the air springs is a measure of the vertical stiffness of the air springs or how much the suspension deflects for a given load being carried. The natural frequency of a suspension will increase if the suspension spring rate is increased or decreased. Because of a softer spring rate, air suspensions provide greater equipment protection over traditional mechanical suspensions. This is because of the air springs’ ability to cushion the equipment and passenger load. Outstanding ride produces superior driver and passenger comfort while helping to protect critical, lifesaving equipment and costly electronic components from excessive vibration and road inputs.

Understanding Roll Stability

Roll stability is a measure of how well the suspension and chassis resist rolling or swaying, especially when encountering a turn. A vehicle’s roll stability can be measured in two ways: (1) determining the maximum cornering speed before reaching the rollover threshold (when tires lift off the ground), and (2) measuring the amount of roll that occurs for a given turn at a given speed (the roll angle). Many elements of a vehicle’s design play a factor in determining its roll stability. Roll stability for a fire and rescue vehicle is influenced by the height of the center of mass of the truck body and the axle track width. These factors can have the greatest impact on the roll stability of the vehicle.

While suspension roll stiffness contributes to roll stability, it represents only one component of the equation. The chassis’s flexibility and tire stiffness, for example, must also be considered when determining the truck’s overall roll stability. Air-ride suspensions have come a long way over the past few decades, and we’re now at the point where properly engineered air-ride suspensions can deliver roll stability near that of a steel leaf spring suspension. For fire and rescue vehicles, higher rollover thresholds allow improved vehicle performance during the challenging, evasive maneuvers that are experienced when rushing to the scene of an emergency.

So, how can the vehicle’s suspension affect roll stability? The level of roll stiffness provided by a suspension is the best way to directl