360° vs. 270° vs. 180°: The Difference of Balancing a 2 Cylinder Inline Engine: Design, Simulation, Comparative Measurements 2012-32-0106
Beside the automotive industry, where 2-cylinder inline engines
are catching attention again, twin-cylinder configurations are
quite usual in the small engine world. From stationary engines and
range-extender use to small motorcycles up to big cruisers and
K-Cars this engine architecture is used in many types of
applications. Because of very good overall packaging, performance
characteristics and not least the possibility of parts-commonality
with 4-cylinder engines nearly every motorcycle manufacturer
provides an inline twin in its model range.
Especially for motorcycle applications where generally the
engine is a rigid member of the frame and vibrations can be
transferred directly to the rider an appropriate balancing system
is required. A 360° parallel twin engine does generate both: free
1st order mass forces and free 2nd order mass forces. 1st order
mass forces can be compensated by a balancer shaft which is the
most common, the implementation of a reciprocating balancer weight
would eliminate both but has certain drawbacks like complexity,
friction and additional excitations.
A 180° crank-pin offset does produce 1st order mass-moments and
free 2nd order mass forces. In addition to that an uneven firing
order gives drawbacks in orifice noise and excitations in other
orders.
The option of a 90° crank-pin offset in an inline 2-cylinder
engine features a design, without free 2nd order mass forces on the
one hand but small mass moments and an uneven firing distribution
on the other hand.
This paper investigates the difference on the NVH behavior
between 360°, 270° and 180° inline 2-cylinder engines by the means
of design and engine mount simulations and shows the comparative
results of structural vibrations, airborne noise and orifice noise
of these 2 versions having the same basic design and engine
specifications measured on an acoustic chassis dynamometer.
Citation: Hubmann, C., Schoeffmann, W., Friedl, H., and Graf, B., "360° vs. 270° vs. 180°: The Difference of Balancing a 2 Cylinder Inline Engine: Design, Simulation, Comparative Measurements," SAE Technical Paper 2012-32-0106, 2012, https://doi.org/10.4271/2012-32-0106. Download Citation
Author(s):
Christian Hubmann, Wolfgang Schoeffmann, Hubert Friedl, Bernhard Graf
Affiliated:
AVL LIST GmbH
Pages: 11
Event:
2012 Small Engine Technology Conference & Exhibition
ISSN:
0148-7191
e-ISSN:
2688-3627
Related Topics:
Engine mounts
Two or three wheeled vehicles
Noise
Acoustics
Simulation and modeling
Suppliers
Noise, vibration, and harshness standards and regulations
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