Thomas Saf-T-Liner C2

Thomas Saf-T-Liner C2
Front 3/4 view
Interior view, looking back
Overview
Manufacturer	Thomas Built Buses
Production	2004-present
Assembly	High Point, North Carolina
Body and chassis
Chassis	Freightliner C2
Related	Freightliner M2 Business Class
Powertrain
Engine	Diesel Cummins ISB 200-260hp (2008-present) (also as a CNG Option) Caterpillar C7 (2004-2007) Mercedes-Benz MBE 900 (2004-2007) Propane GM 8.0 L V8 (2012-present)
Capacity	14-81
Dimensions
Width	96 in (2,438 mm)
Curb weight	18,000–35,000 lb (8,165–15,876 kg) (GVWR)
Chronology
Predecessor	Thomas Conventional/Thomas Saf-T-Liner FS-65 Thomas Vista

The Thomas Saf-T-Liner C2 (often shortened to C2) is a Type C (conventional-style) school bus produced by Thomas Built Buses. In production since 2004, the C2 is based on a Freightliner C2 chassis, itself derived from the Freightliner M2 Business Class medium-duty conventional. It was introduced as the replacement for the Thomas Conventional and Thomas Saf-T-Liner FS-65; the latter was produced alongside the C2 until December 2006.^[1] Due to elements of its design, the C2 can also be considered the successor to the Vista line of Type C buses from the 1990s. The C2 is unique in that it is available in capacities up to 81 passengers, the largest of any type C conventional school bus in current production.^[2]

The Saf-T-Liner C2 is built at a $40 million manufacturing facility in High Point, North Carolina.^[3]

Background

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

Following the introduction of the Freightliner Business Class M2 medium-duty truck in 2002 as the replacement for the FL-Series, Freightliner began work on an all-new bus chassis based on the M2 to replace the FS-65 bus chassis. As the parent company of Thomas Built Buses, Freightliner sought to pair the new bus chassis together with a new Thomas body, allowing the bus company to update its Saf-T-Liner Conventional bus body for the first time since 1962.

In 2004, the Saf-T-Liner C2 entered production. The Saf-T-Liner FS-65 that it replaced remained in production until the end of 2006, outliving the Freightliner FL-Series it was derived from.

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

Overview

2013 Thomas Saf-T-Liner C2 in Virginia

Design and manufacture

As the first new Thomas full-size bus body since 1962, manufacturing techniques for the C2 were redesigned. To minimize the number of rivets and welds on the bus body, adhesive bonding was used for many body joints. In the cases where fasteners are needed, self-piercing rivets are used; ideally these do not punch completely through the bottom layer of the metals being joined together, thus reducing the likelihood that rivets will become the source of leaks in the future.

To simplify vehicle maintenance, Thomas introduced multiplexed wiring, replacing individually wired circuits. In the system used in the C2, it also has the advantage that switches on the control panel next to the driver can be rearranged to suit the driver and continue to function without any rewiring or reprogramming.

Chassis

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

Although the Freightliner M2 was also developed for use in cutaway applications at its launch in 2002, the use of the M2 chassis for school bus applications paired lead Freightliner subsidiary Thomas Built Buses and Freightliner to develop the Saf-T-Liner C2 as an entire vehicle. Unlike its FS-65 predecessor, the C2 chassis has been paired exclusively with Thomas-manufactured bodies; the Freightliner grille badges are replaced with Thomas badges.

At its launch, the Mercedes-Benz MBE904 and MBE906 diesel engines were the standard engines, with optional Caterpillar C7 and Cummins ISB diesels. In 2008, the Cummins ISB6.7 replaced the MBE900 and C7 diesels.

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

Exterior

Rear view, Thomas Saf-T-Liner C2 (2004-2007)

Along with the Freightliner M2-derived chassis, for the Saf-T-Liner C2, Thomas Built Buses uses a body design unique for the vehicle. Sharing no parts with any previous Thomas school bus, the C2 was designed with several key factors in mind, many of them to tie into the advanced design of its donor chassis.

To improve aerodynamics of the bus body, the windshield was sloped rearward rather than vertically; instead of multiple flat panes, a curved, bonded piece of glass was used, in order to resist chips by more effectively deflecting objects.^[4] Where state regulations allow, the lenses for the red and yellow warning lights are faired into the body as well.

To maximize parts compatibility, the stock Freightliner M2 cowl is used; while the windshield is taller, the Thomas C2 uses the same windshield wipers seen on the M2.

In late 2007, a minor update to the Saf-T-Liner C2 was made. To improve driver sightlines, the mirror bracket for the passenger-side rear-view mirrors was extended. The passenger windows were redesigned, with equal-sized 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.

Interior

In the development of the Saf-T-Liner C2, many advancements were made in the development of the interior of the school bus. In previous conventional-style school buses, from the firewall rearward, few parts from the chassis manufacturer were retained aside from the steering column and instrument cluster. For the design of the C2, Thomas and Freightliner designed the vehicle to retain the dashboard of the Freightliner M2 106 in its entirety. Only a few changes were made, with the ignition moved to the center of the dashboard, as a driver switch panel was located to the left of the driver (full-size school buses do not have a traditional driver-side entry door).

Along with its role in aerodynamics, the larger windshield played a role in safety by minimizing blind spots. Due to the slope of the windshield, Thomas moved the entry door further back, adding a large window ahead of the main entry door to improve visibility around the loading zone (similar to the Thomas Vista and nearly all small school buses). Along with a taller body, the passenger windows were enlarged compared to other Thomas buses. Additionally, the C2 has larger emergency exits compared to the FS-65 and the Thomas Saf-T-Liner Type D buses.^[5]

Along with an air-operated entrance door, in 2012, Thomas added an electrically-operated entrance door as an option. in 2015, Thomas added an manually-operated entrance door as an option.

Variants

Other uses

Alongside the yellow school bus version, Thomas Built Buses offers MFSAB versions (activity/childcare versions) of the Saf-T-Liner C2, along with the commercial-use Transit Liner C2, and specialty versions of the C2 converted by aftermarket manufacturers for various uses.^[6]

C2e Hybrid (2007-2013)

In 2007, Thomas introduced a hybrid-electric version of the Saf-T-Liner, named the C2e. Designed as a parallel hybrid, the C2e retains the Cummins ISB engine, adding a lithium-ion battery pack with an electric motor/generator. In the summer of 2013 Thomas removed the C2e product literature from their website; it is uncertain if the C2e remains an offered product.

Propane c2

In late 2012, Thomas introduced a propane-fueled variant of the Saf-T-Liner C2, utilizing an 8.0L V8 LPG engine from General Motors. This engine is completely different than the previous 8.1 liter GM truck engine. The two engines share no parts, as the new 8L engine was designed with water jackets between the cylinders, unlike the old 8.1. Propane has 18 times the hydrogen content of CNG, so the engine must run cool when operating on propane. The 8L engine was purpose-designed to operate in the high-temperature environment that burning propane creates. The new 8.0 liter engine is square, with both a 4.25 inch bore and stroke. GM has no plans to offer the new 8.0 liter industrial engine in its own trucks at this time. Original dyno development tests on the first GM 8.0 engine operating on gasoline, showed 518 Lb feet of max torque at 1,800 RPM with a slightly higher compression ratio than the old 8.1 which had a 9.1:1 CR. GM showed a 2 percent power increase on the old 8.1 liter on propane compared to gasoline on its Industrial version of the 8.1 engine at 511 Lb feet at 1,800 RPM. On CNG, natural gas, exactly the same engine on the same dyno reached only 460 Lb feet of torque at the same 1,800 RPM. Propane burns very hot and has 104.5 octane ( R+M ) so knocking and pinging are not a problem with higher than normal compression ratios. The higher the CR, the better the fuel mileage and power at all RPM levels. Propane is very widely distributed in North America and the standard automotive grade is HD5. The HD5 grade of propane is the most pure and consistent in the world as used for automotive fuel. It is limited to only 4 to 6 percent butane, unlike the LPG sold in Europe which has butane levels of about 30 percent.

Comparable products

• Blue Bird Vision
• IC Bus CE-Series

External links

• Yellow Bus, Thomas Saf-T-Liner C2 - Thomas Built Buses - manufacturer website

Wikimedia Commons has media related to Thomas Saf-T-Liner C2.

See Also

Freightliner C2

References