Projekt Konstruktiv Fahrzeugtechnik.
Mr. Mario Hirz
Projekt Konstruktiv
Fahrzeugtechnik
Written report.
Williams Mérida Parard.
Daniel González Gil.
09
Projekt Konstruktiv Fahrzeugtechnik
INDEX.
Index.
1
1. Introduction.
2
“Spar bike and shop competition”.
2
Two different ideas.
2
2. Convertible shopping car.
5
Description
5
Operation
6
Characteristics
7
Parts
8
Structural analysis
13
Innovations
15
Advantages
17
3. Post-design study
21
Improvements
21
4. Poster
24
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Projekt Konstruktiv Fahrzeugtechnik
1. INTRODUCTION.
“Spar bike and shop competition”.
This project was made to participate in this competition. The
target of the competition was to design a system able to transport all
the stuff we buy in the supermarket by bike.
The project had to be shown just with a poster, without written
report or spoken presentation. The poster we presented for the
challenge is going to be shown later in this statement. In this poster
we also had to tell something about the main characteristics of the
product (materials, price, dimensions…).
There were no restrictions for the system, but the final price
and the real possibility of the product realization were valuated as
well as the design itself. Participants in the competition were free to
use any material and to choose any size for the final gadget.
Two different ideas.
We started working with a first design but after working on it,
we decided to develop a different one.
Support for shopping car.
The first idea was to build just the support for a usual shopping
car, so the owner of the article would be able to use his old shopping
car.
This product would be really cheap and simple, and would offer
the chance of buying it with an additional shopping car (specially
designed for this support), use our old car or even use the support to
transport other different stuff (like luggage or boxes).
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Projekt Konstruktiv Fahrzeugtechnik
After working for few weeks, we noticed two main problems:
-If the shopping car is loaded, the whole set bike-support-car is
quite unstable. When the shopping car is on its support, the car load
is pretty high, that’s what makes the conjunct unbalanced.
-When a shopping car is loaded, it´s difficult to handle and
would be quite complicated to fix it with the support. Anyway we
were working to solve this trouble, and we designed a simple
mechanism to fix the car without uploading it.
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Projekt Konstruktiv Fahrzeugtechnik
Convertible shopping car.
This is the design we finally presented for the competition. After
studying it, we decided that it’s better than the other one for 3
principal reasons:
-It has a better kinematic behavior when it’s joined to the bike.
The conjunct is very stable even at high speeds.
-It can be used as we use the metal shopping cars inside the
supermarket, and that’s a big advantage for these establishments
(they would need lees of these metal cars) and for the customers
(it´s more comfortable to use inside the supermarket the same car
you’re bringing from outside).
-It’s a more “commercial” product; it’s easier to sell this
product because of the idea (it’s an all-in-one) and because of the
more striking design.
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Projekt Konstruktiv Fahrzeugtechnik
2. CONVERTIBLE SHOPPING CAR.
Description.
The basic idea of the product is to have 3 different cars (to use
inside the supermarket during the shopping, to carry when we’re
walking and to carry when we’re cycling) in 1. It´s a light shopping
car mainly made of steel with a textile basket which can easily be put
in two different positions.
We decided to build a real item, fleeing from post-modernist
and unrealizable designs. The main characteristics of this design are
the use of simple mechanisms and materials accessible for all
budgets.
We also were careful with all the mechanisms, because we were
trying to get a friendly-handling product valid for people of all ages.
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Projekt Konstruktiv Fahrzeugtechnik
This is a picture of the whole set bike-car designed with Catia V5.
Operation.
As we said before, the shopping car has 2 different positions. To
move it from a position to the other one we just have to pick up or
extend the rods and block them using the block system (we´ll see the
procedure of the mechanism in the point “Innovations”).
When we have the car in the extended position, we can use it
inside the supermarket as we use the classic metal shopping cars,
and it´s as easy to handle as they are (even more, because it´s
lighter). In this position we have the basket totally opened and we
can easily put all the shopping stuff in.
In the closed position, the car can be used both to go walking
and riding a bike. To connect the car and the bike we use a clutch we
can see in the “Project Work in Automotive Design”.
The one on the left is the closed one; on the right we can see the extended one.
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Projekt Konstruktiv Fahrzeugtechnik
Characteristics.
We are going to see the main characteristics of the Convertible
Shopping Car divided into four groups:
Materials.
We use standard steel in all the metallic parts but in the main
rod, made of spring steel to get a suspension effect while cycling. We
chose this material because it’s the cheapest one and its weight is not
a big problem because the rods are quite thin.
In the basket we have waterproof textile material and a simple
plastic sealing system.
Price.
We have calculated that the price of the final product could be
around 80 €.
This would be the price of the shopping car taking into account
the materials price, a hypothetic mass production and a quite little
profit. Even if the car producer raised the price to get a greater
benefit, the end-product would still be cheap.
Dimensions.
We have to specify the dimensions in the two different
positions:
Extended position: 128 x 67 x 921 cm
(Basket length x basket width x height floor- top of the basket).
Closed position: 128 x 67 x 310 cm
(Basket length x basket width x height floor- top of the basket
(when the car is lying on the ground)).
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Projekt Konstruktiv Fahrzeugtechnik
Weight-maximum load.
The total weight of the empty shopping car is around 11 kgs.
The maximum load that can lead is 50 kgs (we´ll see the
behavior of the car with this load in the point “Structural Analysis”).
The maximum volume that can be in the basket is around 77
liters.
Parts.
We’re going to see the seven different parts of the car with a
picture and a short description of each one.
Backbone.
This is the part that holds the basket and where the rows are
fixed. The handle of the car is also integrated on it.
It’s made of thin steel bars, not too heavy but very resistant.
Backbone
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Projekt Konstruktiv Fahrzeugtechnik
Main rod.
This part is constituted by the two legs that go from the front of
the backbone to the ground.
It´s made of spring steel. With this material we get a
suspension in the shopping car very useful when we are riding the
bike; the cycling is going to be more comfortable and safer.
Main rod
Secondary rod
Secondary rod.
This is the part which goes from the rear part of the backbone
to the ground and which crosses the primary rod.
It´s made of normal steel because this part is not in contact
with the ground when the car is fixed to the bike and so we don’t
need suspension on it.
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Projekt Konstruktiv Fahrzeugtechnik
Crank lock.
This part is used to block the car legs either in the extended or
in the closed situation.
It consists of two flat discs that rotate over themselves
following the route of the legs when opening or closing, and two
horseshoe-shaped pieces that block these discs with their legs in the
final standings.
The lock is also made of steel.
Crank lock
Coupling joint.
It’s the connection part between the car and the bike. It´s fixed
to the bike and it doesn’t have to be removed from it when we’re not
carrying the shopping car because it’s well integrated. It also has a
very simple security system to fix it with the car.
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Projekt Konstruktiv Fahrzeugtechnik
The material used to build it is normal steel.
Coupling joint
Wheel.
It’s a standard wheel with steel rims and rubber cover.
For each car we use 4 wheels:
-Two big ones in the rear part with a diameter of 15 cms.
-Two small ones in the front part with a diameter of 10 cms.
They’re not in contact with the ground when the car is going fast
(when it’s fixed to the bike), and they are smaller to save costs.
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Projekt Konstruktiv Fahrzeugtechnik
Wheel
Basket.
It’s the part we have on the backbone and where we put all the
shopping stuff.
It´s total volume is around 77 liters, it´s made of textile
material and it has a plastic sealing system.
It can be opened from the front (in the closed position) or from
the top (when we have the car in the extended position).
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Projekt Konstruktiv Fahrzeugtechnik
Basket
Structural analysis.
After designing the car, we made its structural analysis with a
distributed load of 500 N (≈50 kgs) on the basket surface.
This analysis has been made with the finite elements method
available in Catia V5. There are three different studies: deformation,
Von Misses stress and Translational displacement.
Analysis results were satisfactory.
The vertical arrows on the backbone represent the 500 N loads,
and the crosses in the wheels places mean grounded points.
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Projekt Konstruktiv Fahrzeugtechnik
Deformation
Translational displacement
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Projekt Konstruktiv Fahrzeugtechnik
Von Misses stress
*Factor 10 representation (real results are 10 times lower)
Innovations.
In our shopping car we tried to include some technical
innovations to make the product more attractive and friendlyhandling. However we tried to find cheap construction ideas to get a
no more expensive end-item.
We have two different technical innovations in the final design:
Opening & closing system.
Before we change from a position to the other one, we have to
take off the horseshoe-shaped pieces (in red in the picture).
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Projekt Konstruktiv Fahrzeugtechnik
Then both rods will go closer to the backbone or away from it,
and the movement of the secondary rod will turn the flat discs (in
yellow) because they are fixed to it (through the yellow Z-shaped
row).
Once the rods have finished the movement, the flat discs holes
will match the main rod holes again and we´ll be able to place the
block (horseshoe-shaped pieces) again.
Opening and closing system
Suspension.
To get the suspension effect we just need to have spring steel
instead of standard steel in the rods.
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Projekt Konstruktiv Fahrzeugtechnik
When the car is in the extended position, both rods are on the
ground, but we carry it walking so the speed is not very high and it’s
enough if we have suspension just on one of them.
When we’re carrying the car fixed to the bike is when the speed
is high and when we need the suspension. In this case, only the main
rod (in yellow) is in contact with the ground and so we use the spring
steel just on it. Using normal steel in the secondary rod we save costs
in the production materials.
With this independent suspension for the car, cycling is more
comfortable and safer because we won´t feel the shocks and
vibrations coming from the car.
Spring steel main rod to get a suspension effect
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Projekt Konstruktiv Fahrzeugtechnik
Advantages.
The convertible shopping car presents several advantages over
other similar designs. Basically, its greatest advantages are its
versatility, simplicity, weight-carrying capacity and price.
We are going to see these characteristics more closely:
Versatility.
The main distinguishing of this product is that it can be used in
three
different
circumstances
during
the
shopping:
inside
the
supermarket (extended position), walking on the street or arriving
home (closed position) and riding a bike (closed position).
Let’s see it with three different pictures:
Position 1: extended position
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Projekt Konstruktiv Fahrzeugtechnik
Position 2: closed position, walking
Position 3: closed position, fixed to the bike
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Projekt Konstruktiv Fahrzeugtechnik
Besides these 3 possible uses, we can take off the easilyremovable basket from the backbone and use the car to carry any
other stuff (like luggage or big boxes).
Weight-carrying capacity ratio.
This is another big advantage of the Convertible Car. When it’s
unloaded, its low weight (≈11 kg) makes it a friendly handling
device.
Although it’s a very light car, it’s shown that it can resist a 50
kgs load without any problem. When it´s loaded, its lightness is also
important because you don’t add much extra weight by the car itself
and the set load-shopping car is a little bit easier to use.
Simple mechanisms.
There are just few mechanisms in the device, and all of them
are really simple. This has several advantages:
-Everybody can use it; it´s not a sophisticated device at all, so
you don’t have to understand how it works to be able to handle it.
-You don’t have to produce complicated mechanisms; so the
production process, the production chain and therefore the final car
are going to be cheaper.
-These simple mechanisms will hardly be damaged.
Price.
Compared with similar designs it´s, with a big difference, the
cheapest one. You can get the convertible car for a price of around 80
€.
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Projekt Konstruktiv Fahrzeugtechnik
3. POST-DESIGN STUDY.
Improvements.
Studying the final project we noticed some improvements that
would make the car be a better product. To implement these
improvements wouldn’t be necessary to change the production chain,
so the producers could start making the original car and add later the
improvements if they are interested.
The
improvements
can
also
be
added
to
the
already
manufactured cars with a simple adaptation.
These are the ideas:
Bigger rear wheels.
For a better behavior of the convertible car while it´s fixed to a
bike moving would be necessary to have bigger wheels in the rear
part.
If the wheels are small and we’re cycling fast, main rod wheels
will have to turn very fast to follow the speed of our bike; this high
rotation speed can be counterproductive to the comfort ability while
carrying the car and can cause long term problems (like the wheel
breakdown).
An appropriate diameter for the new rear wheels could be 30
cms.
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Projekt Konstruktiv Fahrzeugtechnik
Shopping car with bigger wheels.
Separation shelves in the basket.
If we leave the basket without any divisions, the burden sharing
would be proper while the basket is horizontally; but if we have the
basket loaded with shopping products in the extended position and
we change to the closed position, all the stuff could go downwards,
overloading the bottom of the basket and making the car difficulthandling.
The best solution to solve this problem is to introduce 2
separation shelves made of the basket textile material inside the
basket cavity.
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Projekt Konstruktiv Fahrzeugtechnik
Shopping car with separation shelves.
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Projekt Konstruktiv Fahrzeugtechnik
4. POSTER.
For the competition we just could present a poster, we had no
chance to add any written explanations of the product. So the poster
had to be, while colorful (to sell the product idea), explanatory.
We introduced in it some photomontage that we thought that
could be quite explanatory about how the convertible shopping car
works.
We also emphasized the technical innovations, which we
thought that were pretty good to sell the product.
In the characteristics part, we introduced data like the
dimensions, carrying capacity, price…
Finally, we introduced a part of engineering study with the finite
elements method structural analysis results.
In the last page of this report you can see the competition
poster.
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