KHITCHDEE industrial design
We design and produce land-vehicle prototypes and a related CAD tool. We also produce a general-purpose developer tool.
Bicycle suspension redesign (2018-2019)
The Origional Design
A stock roadster bike in India looks like the preceding picture. Several manufacturers produce this design with very minor variations.
The design features:
- a metal-tube frame connected via custom-made lugs.
- 28" wheels.
- a jointed metal-tube based braking system (as opposed to a brake-wire based system).
- the handle design is associated with the braking system. The handles are aligned longitudinally with the bicycle -- i.e. perpendicular to the handlebar. This creates a constraint for the rider -- the have to keep their knees on the insides of the handles.
- There is no suspension except for heavywieght tires -- typically 1.5" wide. The seat has a dual heavyweight coil-springs to absorb bumps at the sitting location.
Our modifications
We created a carrier design below the head-tube, by creating a triangular frame extending from the down-tube to the head-tube. The frame was wide at the front handlebar area (30cm) and narrow just below the seat (10cm). It was useful for groceries.
We removed the seat tube,
attached 3 staggered iron strips above the top-tube in a leafspring like formation, to be somewhat flexible at the back.
We added dual lighweight coil-spring containing cylinders (in a piston-like structure) to both side of the rear-wheel-spindle.
We attached the top of these 2 springy cyclinders to the back of the leaf-spring system and added a seat on top.
This design moved the rining position slightly backward, creating a small forward angle in the vertical pedalling thrust. But it gave good shock-absorption on very bumpy roads and incerased riding speed substantially. Also, with the seat having been moved back, the rider contsraint associated with the handle-design was removed.
SUV: Roof redesign (2018-2022)
Origional Design
Produced till 2003 by Toyota for India.
2.5 L 4-cylinder diesel engine, with 5 speed manual transmission.
3 row seating.
SUV: Roof redesign
We cut out the roof and added a hollow galvanised iron tube based framing system to strengthen the frame with cross-bracing at the roof level (similar to a rollbar). We also built a sloped receptacle framing system on top of the strengthening frame for adding roof panels for both weather protection and to channel wind through the car.
Design considerations (for 3-wheeled transportation)
Methodology
Based on an observation of bare-bones, cost-optimised operational designs.
Definition:
A single front-wheel, and a 2 wheel rear-axle.
Drive trains:
DC-motor, ICE, or pedal-powered.
Primary design considerations:
1) Ratio of wheelbase (distance from front wheel spindle to center of rear-wheel-axle) to rear-axle-width (WB/RAW ratio).
2) Diameter of front wheel, rear wheels
3) Width of tires.
1 effects vehicle stability and aerodynamics. A large ratio is less stable and more difficult to turn, but has better aerodynamics.
2 & 3 effect engine-load, shock-absorption and road-drag.
Larger wheels travel longer per turn, hence lower engine r.p.m is required to achieve a given speed, but also greater low-end torque.
Wider tires introduce greater road-drag but improve shock-absorption.
ICE based designs use very small wheels (10-12") and wide tires (10-12cm), and a WB/RAW ratio close to 1.25.
This provides good stability at high speeds (50 kmph).
The inefficiency of using smaller wheels and the extra drag created by wider tires is compensated for by the higher r.p.m available in an internal combustion engine.
DC-motor based designs have higher low-end torque and operate at lower rpm.
They use slightly bigger wheels (14"), for greater efficiency and slightly narrower tires (6-8 cm wide) to reduce drag.
They use a WB/RAW ratio close to 2.25.
These designs operate at intermediate speeds (30 kmph) and turn slowly to maintain stability.
Non-motorized designs use 28" bicycle wheels, narrow bicycle tires, about 3 cm wide and a rear-axle width of about 1m (designed to accommodate 2 passengers) and a WB/RAW ratio of about 1.25 for passenger-carrying designs or 1.5 - 2.0 for load-carrying designs. These designs move at under 10 kmph and are very stable at these speeds.
A key design consideration in 3-wheeled transportation is reducing the effect of road-bumps on the rear wheels.
These bumps are usually uneven (hitting only a single rear wheel at a time), and due to the presence of only a single front wheel, they tend to twist the vehicle (like lifting a triangular plate from one corner).
The effect of rear axle bumps can be reduced by using
1) a lower WB/RAW ratio, 2) smaller wheels, 3) wider tires and 4) lower bump traversal speeds.
The worst effected are DC-motor based designs, since they have a very large WB/RAW ratio
(or a narrow isosceles triangle), and negotiate bumps at intermediate motorised speeds. A small displacement of one rear wheel is felt along the length of the vehicle.
Shock-absorbers:
Motorised designs,
since they are designed quite heavy for motor-driven speeds, typically use small pneumatic shock-absorbers coupled with coil-springs.
Low-speed, non-motorized designs, designed lighter, use some form of leafspring.
Flow-through sub-compact car (planned)
Introduction
This is a planned design that flows air through the car.
2 air-inlets are incorporated into the front-cabin and rear-cabin roof.
Some air-inlets are also added at the front for floor level airflow.
An air-outlet is incorporated into the trunk flap.
A mild air-conditioning system processes the air flowing in at all air-inlets.
The prototype will be a 4-door sub-compact hatchback with about the same wheelbase as a Honda Brio.
It will feature body-on frame construction for simpler maintenance and repair.
It also featurs a center-cabin driving position.
Review of existing air-conditioning systems
3D object-visualisation on a PC display (technology review)
Methodology
A solid object is visualized on a display-screen by creating a 3D model using an app
and rendering the 3D model to the 2D screen.
The modeling is done at a very low level to make the rendering process efficient.
A classic 3D modeling and rendering pipeline, has a modeling component and a rendering component.
1. Modeling:
Any 3D object is described as a connected set of 3D surfaces,.
A 3D surface is represented as a set of 3D triangle (location and orientation) units.
Camera viewing parameters are specified.
The oriented 3D triangle is associated with a corresponding 2D triangle on a 2D image called a texture.
Lighting conditions are specified with one or more light sources.
3D model-editing tools are available to create an oriented 3D triangle-mesh representation of any 3D object.
Examples are Maya and 3D Studio Max.
2. Rendering
All rendering is done by a dedicated GPU that is included in an SOC (in addition to a CPU)
or by an externally connected GPU.
Rendering is done, broadly speaking in one of two ways:
a) Texture-mapping
The oriented 3D triangle is mapped to a planar 2D triangle based on camera parameters.
A corresponding triangle in its associated texture is mapped onto this planar 2D triangle.
Lighting-conditions control the final display of each planar 2D triangle.
The display of these planar 2D triangles is ordered, either using a (hardware) Z-plane buffer
that orders the planar 2D triangles on a pixel py pixel basis based on their correspding Z-coordinates,
or by ordering the triangles first and then sequencing the rending operation.
b) Ray-tracing
Ray-tracing, starts with the same model, including a 2D texture
associated with an oriented 3D triangle.
Instead, of texture mapping and illumination control,
it traces the path of each light-ray from each-lighting source from the source to the camera
after multiple reflections from oriented 3D triangles in the scene and their associated surface textures.
This is more realistic model of a physical objcet, but far more computationally expensive.
GPU advancements mainly target better ray-tracing efficiency.
Widely used existing tools for 3D solid object modeling and visualisation
Solidworks-Desktop by Dassault Systems and Autodesk-Inventor by Autodesk
are 2 commonly used apps for design specification.
Both apps are designed for Windows.
A design is specified as a collection of 3D objects connected together.
Libraries of existing specifications for commonly used design-objects are included in these tools.
The design is initially described as a wireframe model.
Surface materials and finishes are specified for the design elements in the model.
The app translates the design to a format for a 3D rendering API, such as DirectX, OpenGL and Metal.
The app rpvoides the user with visualisartion controls and renders the design using a GPU.
These tools also provide convenient connections to Computer Aided Manufacturing ( CAM ) tools.
Both tools have been in use for over 20 years.
Solidworks-Desktop was the first solid-object design tool,
released ( as SolidWorks 95 ) in 1995 ( 29 years ago ).
Autodesk-Alias was released 4 years later ( in 1999 ).
Solidworks-Desktop
- Trusted, industry-standard SOLIDWORKS 3D CAD, deployed and managed through a named user license
- Production-ready documentation and drawing solutions
- Built-in, real-time collaboration tools for sharing and marking up designs
$2820 USD / Year
Autodesk Alias
Autodesk Alias is used to design innovative products and communicate ideas in a visual medium from 2D sketch to 3D form, and from conceptual models to production-level data.
$2510 USD / Year
Design and Design-specification
Our focus within industrial-design
We focus on structural design and the design of metal-based structures.
What is design specification?
Land-vehicle design specification
How do you describe the design of a wheel-barrow? a bicycle? a motorcycle? a car?
A wheel-barrow design example
A wheelbarrow is easy to describe. Its construction is simple.
2 wheels, a container. 2 handles to push the wheelbarrow.
Then if you want someone to build you that roughly described design,
you have to get into details and that is a process of specification.
The wheels have to roll around an axle.
The axle has to be attached to the container.
The handles have to be attached to the container.
(This is structural specification).
Then you have to choose the width and diameter of the axle.
The material to be used (solid steel, heavy gauge iron pipe etc).
Then you have to specify the wheel geometry and Its hub characteristics.
(This is still all structural specification).
Then there is construction-process specification.
How the axle will fit through the hub.
How the wheel will be prevented from moving across the axle.
How friction at the wheel-hub axle interface will be handled.
How the container frame will be attached to the chassis
(which is likely made of flat or angled iron strips)
to the circular cross-section axle.
Similarly, how the handles will be attached to the container,
their choice of material (e.g. wooden holding sections attached to iron angled strips).
This could still be called structural specification
but relates more to the construction-processes involved
(and less to the resulting structural form).
Surface Materials
Then you might specify surface materials
and how they are to be affixed to the (metal) frame.
Such as rubber coatings for the wooden handles.
The material to be used for the bed of the container and the one for the side walls.
Tolerances
Then you might specify tolerances.
If there are threads cut onto the outer surface of the axle,
how closely should they be spaced
(which effects the ease of tightening or loosening the nuts),
e.g. (1mm, 1.5mm 2mm) per turn.
How well do you ensure the axle is perpendicular to both handles.
How wide apart are the handles, what is their length?
Both factors effect how easy the wheelbarrow will be to turn.
Summary
Approximately, the process of specifying a design involves
describing the final structure and how it will be built.
Structural specification and Construction-process specification.
Observation
Design and construction/production are related to each other
in the following way:
The ability of the designer to predict the produce-ability of a design
improves over time.
Once this ability is good enough, design iterations are efficient.
So the process of design becomes more efficient over time.
The hexagonal-grid -- CAD tool development aid.
A Hexagonal grid is like an extended virtual protractor
(the instrument used to measure angles).
The use of a hexagonal-grid helps choose or specify angles in a design process.
It is easy to make small rotations in 3D on a hex-grid.
In a Cartesian grid based system this is done through numerical (degree) input.
