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Thomas Saf-T-Liner C2

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Not to be confused with Thomas Saf-T-Liner.

Thomas Saf-T-Liner C2
Front 3⁄4 view
Overview
ManufacturerThomas Built Buses (Freightliner)
Production2004–present
AssemblyGaffney, South Carolina
DesignerJohn M. Mellberg
Body and chassis
ChassisFreightliner C2
RelatedFreightliner M2 106
Powertrain
Engine
  • Diesel
    • Cummins ISB 200–260 hp (2007–2016; CNG option since 2016)
    • Caterpillar C7 (2007)
    • Detroit Diesel DD5 5.1 L I4 (2018–present)
    • Mercedes-Benz MBE 900 (2004–2009)
  • Propane
    • Powertrain Integration PIthon 8.0 L V8 (2014–2022)
Drive Force/PSI 8.8L V8 2019-2022
Capacity14–81
Transmission2-speed automatic (Jouley)[1]
Battery226 kWh (Jouley)[2]
Plug-in chargingVehicle-to-grid (V2G)
Dimensions
Width96 in (2,438 mm)
Curb weight18,000–35,000 lb (8,165–15,876 kg) (GVWR)
Chronology
Predecessor
Saf-T-Liner C2
Interior view, looking back

The Thomas Saf-T-Liner C2 (often shortened to Thomas C2) is a bus manufactured by Thomas Built Buses since 2004. The first cowled-chassis bus designed by Thomas following its acquisition by Freightliner, the C2 debuted the first all-new body design for the company in over three decades. Produced primarily as a yellow school bus, the model line is also produced for commercial use and other specialty configurations.

Distinguished by its tall, single-piece windshield, the C2 uses a chassis derived from the first-generation Freightliner Business Class M2 medium-duty truck. In contrast to previous conventional-style buses, the C2 adopts the dashboard of the medium-duty truck in its entirety. Replacing the previous Saf-T-Liner Conventional/Saf-T-Liner FS-65 (the latter, produced alongside the C2 until December 2006[3]), the C2 inherits several design elements of the 1990s Thomas Vista to improve loading-zone visibility.

Alongside its distinctive exterior, the C2 is also available in up to 81-passenger capacity, the largest of any conventional-type school bus in North America.[4] In addition to traditional diesel-fuel engines, the C2 has been offered with multiple fuel options, along with both hybrid and fully electric powertrains.

Thomas manufactures the C2 in a dedicated facility in High Point, North Carolina while the chassis is built in Gaffney, South Carolina.[5]

Background

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Thomas Saf-T-Liner FS-65, predecessor of the Saf-T-Liner C2

Coinciding with the development of the Freightliner Business Class M2 medium-duty truck, Freightliner began work on an all-new bus chassis to replace the FS-65 bus chassis. As the parent company of Thomas Built Buses, Freightliner sought to pair the new chassis with a new body design for its Saf-T-Liner Conventional (which had not undergone a complete redesign since 1962). The Saf-T-Liner FS-65 remained in production through the end of 2006, outliving the rest of the medium-duty FL-Series by nearly three years.

To assemble the new model line, Thomas constructed a second production facility in its hometown of High Point, North Carolina, adding 275,000 square feet of production capability.[5]

In October 2012, Thomas delivered its 50,000th Saf-T-Liner C2 to Dean Transportation of Lansing, Michigan.

In June 2018, the 100,000th Thomas Saf-T-Liner C2 was delivered to Montgomery County Public Schools in Virginia.[6]

In 2016, Thomas Built Buses released the 100th Anniversary model of the C2.

Overview

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2013 Thomas Saf-T-Liner C2 in Virginia

Design and manufacture

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As the Thomas Saf-T-Liner C2 marked the first completely new bus body for the company since 1962, Thomas redesigned a number of its manufacturing techniques coinciding with its introduction.

To minimize the number of rivets and welds (a weak point of structural integrity on a bus body), adhesive bonding was used to complete a number of body joints. In the cases where fasteners are needed, self-piercing rivets are used. These engineered fasteners join layers of metal together without punching completely through the bottom layer, thus reducing the likelihood that rivets will become the source of leaks in the future.

Chassis

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Cummins ISB6.7 in a Saf-T-Liner C2

As with all conventional-style school buses, the C2 is derived from a cowled-chassis conventional; the C2 uses the Freightliner C2 variant of the M2. As with 2000s and 2010s industry practice in school bus manufacturing, chassis and body manufacturers are paired, with Freightliner and Thomas developing the C2 as an integrated vehicle (the Freightliner grille badges are replaced with Thomas badges).

At its launch, Mercedes-Benz MBE diesel engines were the standard engines, with optional Caterpillar C7 and Cummins ISB diesels. In 2008, the Cummins ISB6.7 replaced the MBE900 as the standard engine, with the C7 discontinued. From 2010 to 2018, the sole diesel engine in the Thomas C2 was the Cummins ISB6.7; for 2018 production, the Detroit Diesel DD5 becomes an option.[7]

The C2 comes standard with an Allison 2500 automatic transmission with an Allison 3000 automatic transmission as an option. The Saf-T-Liner C2 is the only school bus in North America offered with a manual transmission; a rarely ordered option is a Fuller 6-speed transmission.

Engine Production Configuration Fuel Notes Transmission
Caterpillar C7 2004–2008 7.2 L (441 cu in) turbo I6 diesel optional engine Allison 2500 automatic

Allison 3000 automatic

Fuller 6-speed manual

Cummins ISB6.7 2004–2014 6.7 L (409 cu in) turbo I6 diesel

CNG available 2009–present; produced with diesel-electric powertrain from 2009 to 2013

Cummins B6.7 2015–present
Detroit Diesel DD5 2018–present 5.1 L (313 cu in) turbo I4 diesel optional engine
Mercedes-Benz MBE900 (OM904LA) 2004–2009 4.2 L (259 cu in) turbo I4 (MBE904) diesel standard engine at launch
4.8 L (293 cu in) turbo I4 (MBE924)
6.4 L (388 cu in) turbo I6 (MBE906)
7.2 L (438 cu in) turbo I6 (MBE926)
Powertrain Integration PIthon 2014–2022 8.0 L (487 cu in) OHV V8 propane/LPG Gasoline
Power Solutions International DriveForce 2019–2022 8.8 L (535 cu in) OHV V8
Proterra ProDrive 2019–present Permanent magnet motor battery electric Thomas C2 Jouley Proterra 2-speed automatic
Mount Olive Township School District #77, a 2020 Saf-T-Liner C2, viewed from the side. This picture was taken from MOTSD #70.

Body

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Rear view, Thomas Saf-T-Liner C2 (2007)

In a break from traditional bus body design, as body manufacturers acted as second stage manufacturers adapting the body to the chassis, in the design of the C2, Freightliner-owned Thomas Built Buses designed the body and chassis of Saf-T-Liner C2 as fully integrated components. A separate body from the Saf-T-Liner EFX/HDX and Minotour, the C2 body shares no parts with its Saf-T-Liner Conventional/FS-65 predecessor.

While Freightliner has also produced cutaway-cab buses derived from the M2 for commercial/transit use, Thomas Built Buses is the only manufacturer to produce a cowled-chassis bus body derived from the M2. Coinciding with the shift to the Freightliner M2 cowl, several changes were made to improve the functionality over its predecessor. Most visibly, to improve aerodynamics, the traditional multipane vertical windshield was replaced by a sloped single-piece curved piece of glass (allowing the use of the stock windshield wipers).[4] Above the windshield, the front bodywork matches the windshield slope; to further improve aerodynamics, the warning lamp lenses are faired into the body (where allowed by regulations).

On the rear of the C2, the body also used flush-mounted glass and warning-lamp lenses. While not substantially physically taller than its predecessor, Thomas visually extended the height of the C2 with larger passenger windows than previous school buses, along with larger exit doors.

On the exterior, the C2 has largely remained the same throughout its production run. In late 2007, the passenger windows saw a minor change, with a shift to equal-size window sashes (previously, the top half was larger). In the rear, the taillights were redesigned and enlarged, later becoming a standard design for all Thomas buses. To improve driver sightlines, the mirror bracket for the passenger-side rear-view mirrors was extended forward.

In the interior of the C2, Thomas made many advancements in an effort to maximize parts compatibility between the bus body and donor chassis. In previous conventional-style school buses, from the firewall rearward, only the steering column and instrument cluster were used. With the interior of the Thomas C2, the dashboard of Freightliner M2 is used in its entirety, adopting only minor changes (the ignition switch was required to move to the center of the dashboard, due to a driver control panel replacing the driver-side door).

Along with the optimization of aerodynamics, the body of the Thomas C2 also optimized driver visibility. Following the redesign of the windshield, the entry door was repositioned, creating a large window between the entry door and windshield to view sightlines in the loading zone (a feature adopted from the Thomas Vista and nearly all small school buses); a smaller quarter window was located forward of the driver's sliding window. In comparison to other Thomas buses, the C2 has enlarged passenger windows and larger emergency exits.[8]

While initially equipped with an air-operated entry door, in 2012, an electric-operated entry door became offered as an option. Since 2016, a manually operated passenger entry door was added as an option.[citation needed]

At the end of 2023, Thomas debuted the Saf-T-Liner C2 Evolved for 2025 production, marking the first major update to the C2 in over 15 years.[9] While the underlying body structure saw few changes, the C2 Evolved followed suit with the updates of the Freightliner M2 Plus. Along with a digital dashboard and a stalk-operated transmission shifter, the update saw a modernization of the electrical system (allowing for better integration of future technology).[9] Externally, the C2 Evolved adopted the slatted grille style of the M2 Plus (in line with the larger Freightliner Cascadia).

Variants

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2018 "Jouley" prototype, electric-powered Thomas Saf-T-Liner C2 school bus

Alternative fuel powertrains

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In May 2014, Thomas Built Buses began production of a propane-fueled version of the Saf-T-Liner C2.[10] Powered by a 339 hp 8.0L V8, the C2 Propane is paired with the Allison 2300PTS automatic transmission.[11] The engine is designed by Powertrain Integration (an OEM supplier to General Motors) with the 8.0L V8 named the PIthon.[12][13] In 2019, the propane engine was enlarged to a DriveForce-branded 8.8 L,[14] supplied by Power Solutions International,[15] which had acquired Powertrain Integration in 2015.[16]

In 2016, a compressed natural gas (CNG) variant of the Saf-T-Liner C2 was released. The first Type C (conventional-style) school bus produced with a CNG fuel system, the Saf-T-Liner C2 CNG is powered by a version of the Cummins ISB 6.7 engine.[17]

C2e (hybrid-electric bus)

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In 2007, Thomas introduced a hybrid-electric version of the Saf-T-Liner, named the C2e (stylized as C2e). The parallel hybrid drivetrain was designed by Eaton Corporation; the C2e retains the Cummins ISB engine and adds a 1.9 kW-hr lithium-ion battery pack with a 44 kW electric motor/generator.[18][19][20] Annual fuel savings were estimated to range from 300 to 450 US gal (1,100 to 1,700 L) assuming 10,000 miles (16,000 km) per year.[21][22] This is a 20% increase in fuel economy, and the buses can drive under battery propulsion for up to 15 miles (24 km).[23] At least 24 C2e buses were built and delivered to operators in Kentucky and Michigan.[23][24] In the summer of 2013, Thomas removed the C2e product literature from their website, marking its discontinuation.

C2 Jouley (electric bus)

[edit]

In November 2018, Thomas unveiled a battery-powered prototype of the Thomas Saf-T-Liner C2 designated eC2 or "Jouley" (after the unit of energy).[25] The prototype previews an all-electric C2 intended for production during 2019;[26] it was developed in partnership with Proterra, Inc., who offer a line of transit buses using the same battery-electric drivetrain.[27] The C2 Jouley uses a single traction motor with an output of 295 / 170 hp (220 / 127 kW) (peak/continuous) and a two-speed gearbox; this configuration is branded ProDrive by Proterra. The traction battery has a total capacity of 220 kW-hr, providing a range of up to 135 miles (217 km), assuming an efficiency of 1.4 kW-hr/mile (24.6 mpg‑US (9.6 L/100 km) equivalent). The bus is charged using the SAE J1772 CCS Combo 1 connector; a full charge takes approximately 3 hours using a 60 kW DC charger.[28]

The first large order for 50 Jouley buses was placed by Dominion Energy in December 2019 as the first phase of their school bus replacement program, to be delivered by the end of 2020.[29] In February 2021, the Montgomery County Public Schools (Maryland), largest school district in the state, announced they had ordered 326 Jouley buses.[30] On October 17, 2022, Thomas delivered the 200th Saf-T-Liner C2 Jouley to Indiana-based Monroe County Public Schools.[31]

Other uses

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Alongside its yellow school bus configuration, Thomas Built Buses produces multiple configurations of the Saf-T-Liner C2, including MFSAB versions (activity/childcare versions), along with the Transit Liner C2 commercial-use bus. Through aftermarket manufacturers, the C2 also serves as a donor vehicle for multiple types of specialty vehicles derived from bus bodies.[32]

Comparable products

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See also

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References

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  1. ^ "Brochure C2Jouley and Proterra summer 2020" (PDF).
  2. ^ "Saf-T-Liner® C2 Jouley® - Thomas Built Buses". June 25, 2022. Archived from the original on June 25, 2022. Retrieved June 25, 2022.
  3. ^ "Thomas retires the FS-65". Archived from the original on April 20, 2010. Retrieved February 20, 2010.
  4. ^ a b "Saf-T-Liner® C2 School Bus by Thomas Built Buses". www.thomasbus.com. Archived from the original on November 10, 2006.
  5. ^ a b "Company History | Thomas Built Buses". thomasbuiltbuses.com. Retrieved November 15, 2018.
  6. ^ "Thomas Built Delivers 100,000th Saf-T-Liner C2 School Bus - Management - School Bus Fleet". www.schoolbusfleet.com. Retrieved June 13, 2018.
  7. ^ "Thomas Built Buses Debuts First Saf-T-Liner C2 School Bus Equipped With Detroit DD5 Engine | Thomas Built Buses". thomasbuiltbuses.com. Retrieved January 14, 2018.
  8. ^ "Saf-T-Liner® C2 School Bus by Thomas Built Buses". www.thomasbus.com. Archived from the original on November 10, 2006.
  9. ^ a b October 31; Bookmark +, 2023 • News/Media Release •. "Thomas Built's Saf-T-Liner C2 Gets Some Upgrades". www.schoolbusfleet.com. Retrieved December 15, 2024.{{cite web}}: CS1 maint: numeric names: authors list (link)
  10. ^ "New Propane-fueled Saf-T-Liner C2 in Production at Thomas Built Buses - Bus Report: May 2014 - Thomas Built Buses". www.thomasbus.com. Retrieved July 8, 2016.
  11. ^ "The Saf-T-Liner® C2 Propane Bus". Thomas Built Buses. Archived from the original on June 30, 2014.
  12. ^ "8.0L PIthon engine to power Thomas Built propane bus - Alternative Fuels - School Bus Fleet". www.schoolbusfleet.com. Retrieved July 8, 2016.
  13. ^ "8.0 Liter Liquid Propane Gas (LPG) Engine Specification" (PDF). Powertrain Integration. August 2013. Retrieved March 13, 2020.
  14. ^ "Introducing the New DriveForce 8.8L Propane Autogas Engine" (PDF). Summer 2019. Retrieved February 26, 2021.
  15. ^ "8.8 Liter, Transportation". Power Solutions International. Retrieved February 26, 2021.
  16. ^ "Power Solutions International Announces Agreement to Purchase On-Highway Engine OEM Powertrain Integration" (Press release). Power Solutions International. May 6, 2015. Retrieved February 26, 2021.
  17. ^ "Saf-T-Liner C2 (Type C) Compressed Natural Gas (CNG) - Green Bus - Thomas Built Buses". www.thomasbus.com. Retrieved June 30, 2016.
  18. ^ "Saf-T-Liner® C2e Hybrid". Thomas Built Buses. Archived from the original on September 8, 2010.
  19. ^ "The future is now en route: C2e Hybrid" (PDF). Thomas Built Buses. July 2010. Archived from the original (PDF) on March 4, 2011.
  20. ^ Select Engineering Services (March 1, 2012). Heavy Duty Diesel Truck and Bus Hybrid Powertrain Study (PDF) (Report). U.S. Army Tank Automotive Research, Development and Engineering Center. p. 67. Archived (PDF) from the original on March 24, 2020. Retrieved March 13, 2020.
  21. ^ "Thomas tests hybrid technology on school buses" (PDF). Bus Report. Thomas Built Buses. Winter 2008. Archived from the original (PDF) on July 15, 2014.
  22. ^ "New Thomas Built hybrid shown at Arizona dealership". Schoolbus Fleet. October 1, 2009. Retrieved March 13, 2020.
  23. ^ a b MotorWeek (January 4, 2014). "Michigan Transports Students in Hybrid Electric School Buses (Text Version)". Alternative Fuels Data Center, US Department of Energy. Retrieved March 13, 2020.
  24. ^ "Thomas Built Buses Delivers Saf-T-Liner C2e Hybrid School Buses to Kentucky" (Press release). Thomas Built Buses. September 17, 2010. Retrieved March 13, 2020.
  25. ^ "Thomas Built Buses (Daimler) and Proterra, the first electric school bus together". Sustainable Bus. November 15, 2018. Retrieved March 13, 2020.
  26. ^ "Daimler and Proterra, a cooperation is born. North American school bus market in the spotlight". Sustainable Bus. September 19, 2018. Retrieved March 13, 2020.
  27. ^ "Thomas Built Buses Electric School Bus Powered by Proterra® Technology Receives Full CARB and HVIP Certifications" (Press release). Thomas Built Buses. June 24, 2019. Retrieved March 13, 2020.
  28. ^ "Jouley brochure" (PDF). Thomas Built Buses. Summer 2020. Retrieved February 26, 2021.
  29. ^ Weaver, John (December 17, 2019). "Dominion chooses 50 electric Thomas Built Buses powered by Proterra". PV Magazine. Retrieved March 13, 2020.
  30. ^ Gitlin, Jonathan M. (February 26, 2021). "Maryland school district places largest-ever order for electric buses". Ars Technica. Retrieved February 26, 2021.
  31. ^ "Thomas Built Buses has delivered 200 Proterra-Powered electric school buses". Green Car Congress. October 17, 2022. Retrieved October 11, 2023.
  32. ^ "All Thomas Buses - Thomas Built Buses". www.thomasbus.com. Retrieved October 17, 2015.
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