Technical Support Report for Regulatory Action
12 Hoar Cyclic Operating/Non-operating Procedure
for Distance. Accumulation
Motorcycle
January 1976
Notice
Technical support reports for regulatory action do not necessarily
represent the final EPA decision on regulatory issues. They are in-
tended to present a technical analysis of an issue anc! recommendations
resulting from the assumptions and constraints of that analysis. Agency
policy considerations or data received subsequent to the date of release
of this report may alter the recommendations reached. Readers are
cautioned to seek the la.test analysis from EPA before using the in-
formation contained herein.
Standards Development and Support Branch
Emission Control Technology Division
Office of Mobile Source Air Pollution Control
Office of Air and Waste. Management
U.S. Environmental Protection Agency
-------
Abstract
The rationale for proposing the 12 hour soak requirement fol-
lowing each 12 hour increment of motorcycle distance accumulation
is presented. This procedure for motorcycles deviates from the
light duty vehicle procedure which allows continuous operation.
It is considered that the motorcycle procedure provides a more
realistic simulation of the motorcycle deterioration process
without additional cost or time over the LDV procedure due to the
substantially shorter distance accumulation required of motorcycles.
\\ f
ulliidkl^^i-
Prepared by
Project
Motorcycles
Manager
Approved - Branch Chief'', SDSB
'proved -- Division
-------
The purpose of the distance accumulation and associated durability
vehicle is to assess the aging or deterioration characteristics of the
mechanical systems which influence the vehicle emissions. There are
numerous factors which are expected to influence deterioration characte-
ristics of a particular design. The total operational period is certainly
a major factor. As well, cyclic'operation and environmental exposure;
such as temperature extremes, thermal shock, vibrational stresses,
impact loadings, precipitation, corrosive atmospheres, time, etc. are
also important factors influencing deterioration of mechanical systems.
Clearly, subjecting each prototype motorcycle to a representative
exposure of all factors impacting deterioration would be economically
prohibitive and infeasible in a reasonable period of time.
Therefore, with consideration of time, economics and potential
effect on deterioration, those factors which are impractical to simulate
should be eliminated. With motorcycle lifetimes of 5 to 7 years, the
element of time is not a reasonable stress to fully impose. Repre-
sentative requirements for temperature, precipitation, thermal shock,
vibration, impact loading and corrosive atmospheres stresses would be
difficult to specify, expensive to simulate and of uncertain impact on
deterioration. Thus, the deterioration program should be reduced to
require the vehicles to be operated over a specified distance under
reasonably normal environmental and operational conditions. It is
recognized that the environmental exposure will vary considerably depend-
ing on the location of dis.ta.nce accumulation and time of year. However,
modification of this exposure should be minimized. Operational conditions
should be based on a driving schedule representative of overall operation.
This driving schedule should provide for cyclic driving operations and
total distance. To provide simulation of overnight cool down and some
reasonable number of cold starts, the distance accumulation should
include cold soak periods. Soak periods of 12 hours are recommended as
being reasonable and are consistent with the soak period required for
cold start emission testing. Further, such soak periods should be
required sequencially with operational periods of not greater than 12
hours. This appears to be a reasonable compromise of simulating repre-
sentative use to allow rapid assessment of deterioration.
This procedure of requiring 12 hour soak periods during distance
accumulation is a departure from the distance accumulation procedure for
light duty vehicles (LDVs). This further compromise in the case of LDVs
is accepted to allow the implementation of the certification process
within a reasonable length of time. To accumulate the 50,000 miles
necessary for LDV durability vehicles in the certification process, the
vehicles are frequently driven continuously except for maintenance and
test periods.
However, in the case of motorcycles, this compromise need riot be
made. The maximum durability distance for large motorcycles is 30,000
km or 18,641 miles which is approximately one third of the LDV
-------
distance. Since maintenance and other down time needs may be performed
during the soak period, the rate of motorcycle distance accumulation
(e.g. miles per week) is estimated to be slightly more than one half the
LDV rate. Accounting for this rate and the one third total distance-
requirement, -the time period for total motorcycle distance accumulation
remains below the period required'for LDV's.
The benefit of this 12 hour on/off procedure is an. improved simu-
lation of the deterioration process. Therefore, it is recommended the
Motorcycle Emission Regulations state the following:
"Distance accumulation for emission data and
durability data vehicles shall be conducted in
increments of time, the sum of which shall not
exceed a total of 12 hours of operation. A non-
operating soak period of not less than 12 hours
is required following each 12 hour total operating
sequence. Engine shut downs are allowed while
accumulating the 12 hour total operating sequence.
Shut downs occurring before the accumulation of
a 12 hour total operating sequence which exceeds
12 hours may be considered as non-operating soak
periods, and the next operating sequence may
continue for 12 hours. During the non-operating
soak period, the vehicle shall be exposed to normal
outside ambient temperature and humidity conditions
unless vehicle maintenance or servicing is being
performed."
------- |