The concept design challenge:
In the concept design stage of the gearbox design process, translating the numerous concept ideas into virtual models in order to visualise the ideas and assess feasibility can be time consuming. This can results in fewer concepts being evaluated which in turn can decrease the possibility of selecting the best concept design.
In the normal product development cycle, even when a concept model has been chosen, it can take significant time and effort to create a detailed
model for further analysis and optimisation.
The longer the design phase, the higher the cost.
The concept design solution by Romax:
Romax has developed an effective and versatile concept design tool within RomaxDesigner (the concept modeller module)
which helps users achieve process improvement by allowing quick visualisation and initial assessment of concept ideas through its easy-to-use modelling methods. The stick-diagram input generates 2-D and 3-D representations which can be easily visually analysed by selecting cut planes through the design.
These concept models can be exported to CAD for packaging analysis and taken directly into RomaxDesigner for detailed design and analysis without the need for any remodelling.
A wide range of gearbox layouts can be modelled, including complex ravigneaux and plus-planet planetary arrangements and the newest dual-clutch arrangements.
The benefits:
- Easily and quickly build concept models to assess various layouts at the initial stage of the design process
- Allows initial gear sizing calculation without needing gear design capability
- Allows clutch sizing calculation
- Supports for centre distance selection
- Visualize the concept and export to CAD for packaging analysis
- Easy to upgrade the model in RomaxDesigner for further detailed analysis
Application example
In this example, 2 different concept layouts of a 6 speed DCT transmission have been created and
assessed. On the basis of the concept analysis, one of the models was taken forward for initial sizing.
Concept model
Concept ideas can be easily formed into concrete models and manipulated according to user's needs, allowing multiple variations which can improve the speed of concept design by more than 20 times.
Option B of the 6 speed DCT concept
Option A of the 6 speed DCT concept
Assessment
From the two options above, Option B was selected for assessment and initial sizing. The following table lists the axial
dimensions of the basic components and overall length of the gearbox required:
| Gearbox span |
Maximum 510 mm |
| Synchronizer width |
40 mm |
| Main support bearing width |
20 mm |
Gear Sizing Calculation
A gear sizing methodology is implemented within RomaxDesigner which allows the user to develop the concept idea into a candidate model that meets the design requirements.
An assessment method considering centre distance, facewidth and gear ratio has been used in order to adjust the dimension of the gears and thus obtain an acceptable overall length.
Based on the gear report from the initial concept model, gear facewidth, gear position and centre distance were iteratively adjusted to develop a concept model that is within the boundaries of the design requirement.
| Gearbox span |
Initial concept model |
Developed concept model |
| Overall length |
533 mm |
507 mm |
| Gear Safety Factor |
1.20 ~ 2.17 |
1.21 ~ 1.51 |
Clutch capacity calculation
Clutch capacity can also be checked within the concept modeller by inputting the corresponding properties, such as
friction coefficient, clamp force, number of clutch plates, etc. The static torque safety factors for both clutches were
above 1.2.
Export to CAD and integration in RomaxDesigner
The concept model generated can be exported to CAD and also, automatically becomes a RomaxDesigner model, therefore it is part of a larger design process where the model can be further developed for detailed design and analysis without the need of remodelling.
Left: the CAD model, Right: the Romax model