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.....TMC-The Maintenance Council-is a council of the American Trucking Associations.It was actually started by
a predecessor organization,the Regular Common Carrier truck lines were in transition to diesel power and equipment reliability
and durability were lacking.
The truck manufacturers at the time were not particularly receptive to solving fleet complaints.Waranties
were typically ninety days then the fleets were on their own.Common carriers,many family owned in those days,decided it would
be to their advantage to have their head equipment and maintenance men participate in what was known as the RCCC Maintenance Committee
to help solve their problems collectively.
Common engine issues in the late fifties were overheating,smoke, oil consumption
and short engine life.Fleets reaching 250,000 miles before
an in-frame overhaul were the exception.Horsepower for over
the road
tractors were typically in the 160-250 hp range and naturally aspirated
turbo-charging or supercharging options
increased power to 335 hp or more for fleets,primarily in the west,that operated over the Rockies.
By today's truck engine
standards,torque rise was quite low in the 20% range--and all big bore truck diesel engines were governed at 2100 RPM.
Peak
torque was in the 1600-1700 RPM range.All of this changed in the late sixties with Mack Maxidyne,the industies first high
torque rise engine-- 52% as I recall.More on this later.
With natarully aspirated power, truck drivers were taught from day one to
keep engines wound up.Thats where
the power was .For decades drivers
would go to 2100RPM in pratically every gear before shifting.This led to the Fuller
ROAD RANGER family of truck transmissions with ten speeds all on one mshift lever(five speeds in low range,flick the
range shift button and
use the same five gear positions for ratio's six through ten).Fuel economy was not an issue.Power
was and 4.5 to 5 miles per gallon was very acceptable.Diesel was cheap.
Mack Trucks' exec VP of Egineering Walter
May and chief Engine Engineer Winton Pelizonni set the truck engine business on its ear when
they developed what became
the Mack Maxidyne diesel.It needed only five-speed transmission,unheard of at that time.
Walter and Win took Macks 11 L naturally aspirated 170 hp engine,
turbocharged it and reworked the Bosch injection
system so that as
engine RPM decreased,fuel rate and turbo boost were increased.
Engine power was nearly constant
at 237 hp from 1700-2100 RPM
and peak torque was way down at 1200 RPM.Tiffs was unheard of.
People thought the engine
would blow up,lugging it down to 1200
RPM before shifting.I was one of them.I remember vividly my first drive
in an
experimental tractor with this revolutionary powertrain.The
engineer riding along with me saw me reach to shift at 1600
RPM
and whacked my knuckles to remind me to lug down to 1200.
The rest is history,of course.All truck diesel engine
manufacturers
have high torque rise options in their engine ratings.Their most popular in vocational applications such
as dumps,refuse,mixers,etc.The five speed transmission has grown to seven speeds and engine speeds have dropped
to 1700
to /800 RPM,primarily to gain fuel economy....
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