Concept for a low-cost-velomobile for short daily trips in rural areas

Transcription

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http://www.buschbacher.at/reginnomobilen.html
Innovative Regional Mobility solutions: perspectives of technically and financially feasible, socially and ecologically
sustainable systems
Concept for a low-cost-velomobile for short daily
trips in rural areas
1.1. Preamble
This is a first draft, elaborated accordingly to research results concerning traffic safety and
considerations upon the needs of various target groups.
Hints and comments are welcome: harald.buschbacher@reflex.at
2.
Main version of a velomobile for short daily trips in
rural areas
This main version represents a compromise between the aim of a prefereably complete
satisfaction of the mobility needs of different groups concerning short trips in rural areas,
and the necessity to achieve a single vehicle type with a sufficient realistic lot size for the
mass-production.
2.1. Propulsion energy
The main version is a purely human powered velomobile, because auxilliary electric
propulsion systems are in spite of their mass production still relatively expensive. They
cause additional weight and time to be spent for charging and care about the battery
whilst their use is quite limited on short trips in plain areas. (A separate chapter about
optional motor assistance will be prepared).
2.2. Basic geometry and steering
In order to avoid falling and make loading and entering possible without acrobatic skills,
the vehicle is planned basically double-tracked, but it should be three-wheeld in order to
reduce weight and avoid complicated mechanisms. For increased stability concerning
toppling laterally or over the front wheel when breaking, but also in order to reduce
aerodynamic drag, the velomobile is a recumbent cycle. This means, that children or load
have to be placed beyond the driver, otherwise they would obstruct his/her view. Thus,
the best basic geometry regarding to stability and utilisation of space is a tricycle with two
backwheels and one front wheel.
For the decision, which wheels should be steered and which should be powered, there had
been considered the following facts:
•
•
•
•
•
•
•
•
Steered drive wheels means a more complicated construction, than steering nondriven wheels.
One single drive wheel is less complicated, than two drive wheels where the
different length of run in curves has to be compensated.
A single wheel is less complicated to be steered than two wheels because of the
necessity to turn the inner wheel more than the outer one.
Front steering is for the most drivers more familiar, than rear steering and is
more suitable for coupling.
The closer the centre of gravity to two-wheeld axle, the more stable is the
vehicle concerning toppling.
The closer driver and load to the wheels, the less the mechanical stress of the
frame
A short chain saves weight and costs, but with a longer one, the potenzial of a
derailleur gear can be fully utilised without stressing the chain with too diagonal
chain run.
The vehicle’s width can be reduced, if the wheels are not placed at the maximum
necessary inside width.
Dr. Harald Buschbacher
harald.buschbacher@reflex.at
Financed by the Austrian ministry for Transport, Innovation and Technology within the programme „ways2go“
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Finally, the combination of rear drive and front steering had been chosen as the best
solution. The width of the vehicle could be a bit reduced in the way, that the maximum
with of the frame (requiered for carrying two children, a folded, bigger children’s pushcar
or two drinks crates) is reached just 35 cm beyond the rear axle. The set of problems
concerning kinematics in curves is solved by powering both wheels symmetrically, but with
a free-wheel on each one. This means, that in curves there is always driven only the inner
wheel while the outer wheel turns a little faster, than the sprocket. The disadvantage of
an one-side drive, that less than the half vehicles weight lasts on driven wheels, is
effective only in curves and even there, a slightly slipping inner wheel would support the
gripping outer one. For the rare case, that one of the powered wheels is standing resp.
rolling on a surface of much lower grip than the other, this solution is even better than a
real differential gear, which will not be applied due to his weight and costs.
A similar solution with two free-wheels is also used by one of the “Berkut” recumbent
tricycles1. The frontwheel is steered by two steering armes, which are connected with the
fork by cable pulls and tensioned back by springs.
2.3. Size adjustment
In order to ensure preferably optimal visibility conditions, it is important, that drivers of
different body height have their eyes nearly on the same level. Because of this, the
adjustment for different sitting body heights is performed by lifting the seat whereas the
adjustment for different leg lengths is done by shifting the bottom bracket.
In case of problems with different lengths of the forearms, the length of the steering
cables can be adjusted as well.
The adjustment range of the most important body dimensions are from the 5th percentile
of adult women to the 95th percentile of adult men, thus the following measurements are
applied2,3:
Body height (standing)
Body height (sitting)
Eye height (sitting)
Eye height (standing)
Shoulder height (standing)
Length of backside and legs
Height of elbows above seat
Width of hips
Width including elbows
Height of seat level
95th
5th percentile Average of
of the smaller the medians percentile of
sex (mostly of men and the taller sex
women)
women
(mostly men)
153,5
168,75
185,5
81
88,5
96,5
70,5
77,5
85,5
143
157,25
173,5
126
139,75
155
92,5
101,75
114
18,5
23,5
28,5
35
38,25
46
39,5
48,25
55,5
37,5
43,25
49
Table 1: Considered ranges of body dimensions of adults.
Concerning the length of feet, there had been assumed european shoe sizes between 31,5
and 49,5, corresponding to a inner shoe length of 21,5 to 33,5 cm4.
For taller or smaller people, the velomobile is not generally inusable, but it is less
comfortable, e.g. because of to near pedals, or there are individual measures like an
additional seat cussion necessary.
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Figure 1: Adjustment of seat and pedals for different body heights, displayed with pedals in
horizontal and vertical position.
2.4. Luggage space and children’s seats
The luggage space of the velomobile is 90 cm long, the inner width is 61-65 cm. In the
luggage space, there can be placed two children’s seats, offered as an optional feature
(see 3.1).
In order to utilise the remaining space with one or two children as best as possible, each of
the children’s seats can be removed individually and they can be shifted longitudinally as
well. In comparision to a length of 46cm for legs and backside of a child in an usual bicycle
trailer, a luggage space of 44 cm length remains beyond or in front of the children’s seat
as well as the space below the seats. The maximum inside height of the vehicle is 105 cm
for carrying folded strollers upright between the rear axle and the children’s seats.5 This
height, which is a bit more than necessary for the driver including a helmet, is favourable
from the point of view of traffic safety, because the overall 135 cm high vehicle will rather
not be looked over and the rollover protection (see 2.5) ends significantly above the head
of the driver.
There can be carried the following combinations of children and other load:
•
•
•
Without children: goods in an extent, which seems rather critical concerning the
weight, e.g. four drink’s crates.
One child can be transported optionally on the buildt-in child’s seat, eventually
with a special baby seat as offered for child trailers. One child can also be carried
with an automobile type baby seat, maybe even in a set up pushcar: Despite it is a
question of sufficient anchorage of the pushcar in the velomobile and the child in
the pushcar, it would have the advantage that a sleeping child as well as luggage in
the pushcar can be moved easily between the velomobile and a means of public
transportation. Regarding to the space within the velomobile as well as to traffic
safety, most suitable would be strollers with a low seat level. Due to the possibility
to mount the children’s seats individually, there will be enough space left around a
child: without a pushcar there can be still carried two to three drink’s crates, with
a compacty folded stroller one to two crates and with a larger pushcar it should be
at least enough for weekly shopping without drink’s crates if well packed.
Two children can be carried on the buildt-in children’s seat, for babies can be used
special baby seats as offered for children’s trailers.6 Two automobile type child
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seats could be placed only shifted and thus taking much space, if at all, because
their width exceeds the inner width of the velomobile significantly. Without a
pushcar there can still be transported one or two drink’s crates, with a compactly
folded twin stroller still one or the result of some intermediate shopping efficiently
packed. A twin stroller, which could fit into the velomobile even set up, is
theoretically imaginable, but there had not been found any model, which would not
exceed the inside width by far.
Hand trolleys including their content can be directly put into the luggage space between
rear axle and children’s seats too.
The position of the rear axle between the driver’s seat and the luggage space causes good
stability and best traction particulary with load, but a heavily loaded vehicle without
driver could topple over to the rear side. Because of this, there is a supporting stand on
the rear of the vehicle, which can be retracted or moved out from the driver’s position.
For many users without children, a shorter luggage space might be sufficient, but it is
doubtful, whether the achievable weight reduction would not be compensated by worse
aerodynamics of the steeper rear end.
2.5. Frame and cover
In opposite to the most existing velomobiles, the velomobile developed within this project
has no usual, recumbent tricycle type frame in the middle of the vehicle, but a loadbearing base tub, which is as well part of the fairing. The first advantage of such a
construction is, that nearly every part of the base plate can be put under mechanical load,
and it is not necessary to enter the vehicle very carefully without holding up onto a wrong
part of the fragile fairing. Another advantage is better protection of the centrally belted
driver in case of a crash.
Figure 2: Load bearing metal frame of the velomobile
The load bearing frame of the velomobile is a truss construction out of bars of the
following dimensions:
• Most of the horizontal bars are rectangle shaped tubes of 15/25 mm side length
• Most of the vertical bars are square shaped tubes of 25 mm side length in order to
fix on both sides other bars
• Diagonal bars in the side walls are angle profiles of 15 mm side length
In order to reduce the effort for production and distribution, it is intended to distribute
the velomobile as an assembly set like self-installation-furniture. For setting up the
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velomobile, there should not be necessary any bicycle-specific skills (e.g. setting up a
wheel out of hub, spokes and rim), but the frame should be set up out of the bars by the
customer him/herself, evtl. by the bicycle dealer. Because of this, the frame is not
welded, but screwed. In order to avoid self releasing because of vibrations, there can be
used self-locking screw nuts or special, form-locking screw locking devices, which are
clipped around the nut and the bar (dark red in Figure 3).
Figure 3: Details of the bolted assembly of the metal frame and the plastic fairing
The thickness of the used screws is M4 for less stressed connections, eg. those of the
diagonal bars, M6 for the most connections and M8 for the most stressed connections, e.g.
fixing the front fork or at the bend of the side walls beyond the rear axle.
In order to achieve a closed bottom tub and a certain bearing strength between the bars
too, the metal frame is covered by a plastic cover (light red in Figure 3). This cover
consists out of panels. The maximum dimensions of those panels are the half inner width of
the vehicle (32,5 cm) and the maximum distance between two cross-bars (67 cm). The
inner panels are thicker and cross-ribbed, so they are mechanically more resistant and
fitted onto the metal skeleton. The outer panels are thinner and serve rather for
aesthetics, aerodynamics and protection against dirt and corrosion.
Between the metal bars and the plastic panels, there is placed foamed material for more
crash safety and damping of noise and vibrations. (white-violet pattern in Figure 3). The
base and the walls of the bottom tub are 5 cm thick, only in the area below the pedals the
thickness is between two cross-bars reduced to 1-2 cm in order to achieve more space for
the feet and reduce the necessary height of the cover at this position.
Above the rear axle, between the driver’s seat and the space for load and children’s seats,
there is an overroll protection device, arranged laterally to the vehicle and constructed
similarly out of a metall skeleton and plastic cover. The purpose of this overroll protection
device is to protect the driver in case of a rollover or to avoid it at all, but also to absorbe
the belt’s force in case of a frontal crash, hold back eventually carried children and load.
In case of a rear-end collision, the overroll protection and a head rest should avoid a
whiplash injury. At eye-level, the overroll protection device is narrowed to ensure a better
view backwards, if there are no other obstructions, e.g. an upright packed, folded stroller.
Concerning the used materials and thicknesses see 2.11 about the vehicle’s weight.
2.6. Cover
The upper part of the cover, above the bottom tub, is made out of tent textiles, beared by
elastic poles. Viewing windows are made out of transparent foil or acrylic glass, if the
optical quality of foils is too poor. At each side of the vehicle, a tent pole is stretched
from the front to the rear corner. Whilst this tent pole goes up to the shoulder height of
the driver, a second, shorter one covers the rest until the full vehicle’s height. The lower
part of the tent is out of intransparent textile only whereas in the area between the two
tent poles there is a transparent stripe in order to ensure 360°visibility for the driver, but
also rear view for children.
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In case of the use of transparent foil, view-obstructing cuttlings should not arise neither on
the side windows, which are within one plane, nor on the front and rear windows, which
are curved cylindrically, but not spherically.
Figure 4: Velomobile with bearing metal frame (grey), plastic parts of the bottom tub (red) and
cover (transparent parts light blue, rest violet)
The shape of the two tent poles one above the other is necessary, because only in this
way, the front window is near enough to the driver to keep a visibility field of sufficient
width free of obstructing tent poles.
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Figure 5: vertically and horizontally unobstructed visibility field of the velomobile driver
It is doubtful, whether a full-fledged windscreen wiper is feasible with regard to the
screens curving, the necessary eletricity supply and the bearing capacity of the tentpoles.
Possible alternatives could be elastic bands to be pulled over the screen or magnetic wipes
as used for cleaning aquaria7. With regard to the possibility of persistant visibility
obstructions (e.g. fogging), the front window can be anyway opened. At the same time, a
kind of skirt can be applied between the window and the shoulders of the driver in order
to protect him/her from rain or snow.
Figure 6: Left side: front window closed, right side: front window open, inner rain protection
skirt applied
For entering the velomobile, the cover is opened on the side along the overroll protection
device. The lower tent pole is opened up too and the textile side wall is folded up along
the line from the highest point of the vehicle to the front corner. For loading or seating
children, the cover is opened from the rear similarly to the roof of child trailers. For
ventilation and avoiding of heat, there can be opened the front window and the rear
cover, maybe also additional openings in the side walls. Basically, it is also possible to
remove the whole textile cover, but this may not be practical, if it must be set up again
for parking. In order to avoid heat, the transparent areas are kept small and the roof is
intransparent as well. Light colours would also be useful.
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2.7.
Gear and chain guide
Figure 7: Seats, pedalling and steering devices of the velomobile
Instead of a conventional bottom bracket, the pedals of the velomobile are assembled onto
the frame’s side walls, just the derailleur has to be assembled close to the front sprockets.
The chain is guided from the front sprockets downwards to the bottom, there it is turned
horizontally by guide rollers on a slide, passing between the bottem and the driver’s seat
and finally turned up again to the rear sprockets on a dummy shaft between the driver’s
seat and the overroll protection device. Both slides with the guide rollers are horizontally
moveable, which enables a wide gear range using all combinations of front and rear
sprockets without too diagonal chain run. The slide in the front is moveable longitudinally
too in order to adjust the chain’s length according to the leg length’s adjustment. Because
of insufficient space in the area of the rear derailleur, the chain tensioner should also be
arranged near the guide rollers in the front.
The dummy shaft leads through the side walls to sprockets on the outer side of the frame,
which are connected via additional chains to the free-wheel sprockets of the driven
wheels.
A possibility of driving backwards would be preferable e.g. for leaving a parking position,
but it is clearly unfeasible with the choosen construction with free-wheels on both rear
wheels, but probably with conventional derailleur gears (opening up the chain tensioner)
as well as with backpedal brake hubs too. As an alternative, the rear wheels can be turned
directly similarly to a wheelchair, but this causes dirty hands of the driver. It seems to be
the most realistic solution to move the vehicle into a suitable position already before
entering.
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2.8. Suspension
On the one hand, suspension is for a velomobile particulary important for preserving the
frame, the driver, children and load. On the other hand, usual suspension constructions for
bicycles are expensive and often inapplicable in case of a tricycle with a truss frame. In
order to achieve a certain suspension effect anyway, the following devices are applicable:
•
•
•
•
Balloon tyres are sometimes mentioned as an alternative to conventional
suspension, e.g. in case of the low-cost recumbent bike “AZUB Eco”8. Despite the
better suspension effect, balloon-tyres are mentioned not to have a higher rolling
restistance than conventional bicycle tyres9,10,11,12.
The rear axle is some centimetres above the bottom of the frame, because the
relatively high ground clearance would not be useful, if e.g. the edge of a sidewalk
is hit by the tyre nearly at right angles. As far as the frame is anyway “hanging”
down from the rear axle, the axle can be hanged up on pull-springs and glide
between two vertikal bars. For damping, a foam-plastic filling between these bars
can be applied.
If necessary, a conventional suspension fork can be used for the front wheel.
Driver’s and children’s seats can be manufactured out of elastic plastics.
If the rear axle is spring-loaded, there will be necessary a tensioner for the dummy shaft
too in order to keep steady tension on the connector chains between the wheels and the
dummy shaft.
2.9. Parking brakes and locking devices
In order to enable quick parking, the closure of the cover’s side walls is located near the
steering arms, so within one single locking procedure, the cover can be locked, one of the
brakes and also the steering can be fixed. Therefore, suitable rings should be mounted
onto the frame and the steering arm, so it is possible to lock either the velomobile alone
with a padlock, or to connect it with a bicycle lock to some immobile device like a traffic
sign.
Accepting some effort for closing the cover, significantly higher safety can be achieved by
threading a wire through eyes on the cover and the frame around the whole vehicle. In
order to prevent disassembling and theft of parts, as much parts as possible should be
mounted from inside, particularly the mounting screws for the plastic panels should be
driven in from the inner side. A significant weak point is anyway the cutable tent cover,
though a certain protection can be achieved with a commercially available alarm device
for backpacks or bicycles containing a motion sensor (see also 3.7).
2.10. Illumination
Headlight, rear light and blinkers are allocated compactly at the highest point of the
vehicle, on the overroll protector. A power supply by a dynamo only would be unfunctional
because the blinkers are necessary during daylight too. On the other hand, usual battery
lights often tempten cyclists to ride without illumination if batteries are empty.
Furthermore, pure battery illumination is illegal e.g. in Germany13. The following
compromises between usability and reliability are conceivable:
•
•
A combination of photovoltaic cells and rechargeable battery, if the vehicle is not
parked indoor most of the time, eventually with the optional use of normal
batteries, if the rechargeable battery is empty.
A combination of a dynamo and rechargeable batteries. In this case, thanks to the
battery it would not matter so much, if a cheap sidewall dynamo fails sometimes in
case of snow or rain. In any case, a reliable double-pole wiring should be applied,
protected from tearing and using a strain relief on both ends.
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If the vehicle is not equipped with a dynamo, the illumination device should at least warn
the driver acoustically before the battery gets empty. A possible solution could consist out
of two rechargeable batteries, one of which is always used as a reserve and the user is
reminded acoustically, if one of the two batteries is empty and must be recharged.
2.11. Weight and dimensions of the vehicle
The metal frame of the bottom tub is manufactured out of aluminium shaped tubes and
profiles of 2 mm thickness. This means a weight of about 11 kg, whereas profiles out of
steel would weight even in case of just 1,5 mm thickness more than the double weight14. In
theory, due to the three times higher elastic modulus of steel15, a much more light-weight
steel frame could offer the same solidity, but there are not offered steel profiles of less
thickness and less side lengths would reduce the bending stiffness due to the profile’s
geometry. Because the big difference in the weight significantly reduces the higher
energetical effort for the production of aluminium compared to the same mass of steel,
and the lower weight is of crucial importance for the attractiveness of the vehicle,
aluminium is the recommended material. (see also excursus 2.11.1 concerning embodied
energy).
The next important share of the whole weight after the metal frame represent the plastic
panels around the frames with about 8 kg corresponding to the following assumptions:
•
•
•
Material: HDPE, 0,95 g/cm³
Outer panels and panels of the overroll protector: 1mm thickness, no ribs
Inner panels: 2mm thickness, rib area representing 50% of the flat area
Screws and Nuts have a weight of about
Weight of the components of the velomobile
4-5
kg,
representing
significant
Metal frame
incertainity, because thicker screws are
1,5 1,5
disproportionately heavier. The weight
2,0
Plastic panels
of the foam plastic parts is of low
0,2
11,4
Screws
importance (about 0,25 kg). The weight
Other conventional bike
of the residual parts has been assumed
parts
as following:
Foam plastics
11,0
• General parts of a bicycle, not
Driver's seat
specific for a velomobile, like
a
wheels , chain, gear, brakes
Children's seats
8,0
etc: 11 kg (15 kg minus 4 kg for
4,5
Cover
the frame)
• Seat incl. Belt: 2 kg
Figure 8: Weight of the individual components of
• Children’s seats: 1,5 kg
the velomobile in kg.
• Cover incl. tent poles: 1,5 kg
Ready to ride, the velomobile weights about 40kg, this is on the upper end of the weight
scale of existing velomobiles16.
With a height of the lights of about 135 cm above ground, the velomobile is just about 1020 cm lower than smaller cars. The width of the vehicle over the wheels is 90 cm, with
regard to the straighter trajectory of the tricycle this might represent the same necessary
road’s width than a conventional bicycle. The whole vehicle’s length about 290 cm, this is
about 30 cm more than the velomobile “Alleweder” or a two-seated Smart, about the
same length as some electric cars or “Micro-Cars” and about one to one and a half meter
shorter than usual cars from the compact to the medium class.
The rectangle around the vehicle has an area of 2,6 m², this is about a third to the half of
common cars. If several velomobiles are parked diagonally on a 2,2m wide parking lane for
a
It has been assumed, that the additional weight for the third wheel is compensated by the smaller
diameter, and unnecessairy parts of conventional bikes like baggage rack, mudguard, saddle etc.
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cars, each needs a 1,6 m length of the parking lane, this is about 30-40% of the length,
needed for a conventional car.
The velomobile has 24” rear wheels and a 16” front wheel, the ground clearance is 19-20 if
relatively thick baloon tyres are applied.
Due to the widely swiveable front wheel, a turning circel of less than 5 m is imaginable,
although the drive one the inner wheel causes a lower gear ratio.
2.11.1. Excursus: Embodied energy in the aluminium frame compared to a steel
frame
Assuming a recycling rate of 33%, the manufacturing of an 11-kg-aluminium frame requires
about 1690 MJ primary energy, whereas a 24 kg heavy steel version means about 1430 MJ.
It has been calculated the average between more energy saving, low-alloyed steel and
high-alloyed steel with a higher energy consumption.
The difference corresponds to a 650 km ride of a vehicle with a energy consumption of
1,25 l gasoline-equivalent, representing an “acceptible” specific fuel consumption within
this project. By nature, this amount of embodied energy is some dimensions lower, than in
case of a 40 times heavier conventional, or even 10 times heavier lightweight car.
3.
Extras und special versions
Several functionalities would be very useful for relevant target groups, but they would also
represent significant additional manufactory effort and thus cause an inappropriate price if
included in the main version. Some of the extras are already fully developed and
commercially available, so it would be sufficient to distribute them as extras. For some
other features, new development would be necessary and could be started in case of
satisfying sales numbers of the main version. Furthermore, there should be considered,
that all additional features do not only represent additional costs for purchase, but the
increased value also raises the seduction to steal the whole vehicle or particular valuable
parts of it.
3.1. Children’s seats
Although it was a main criterion for development and dimensioning of the velomobile to be
able to carry children, children’s seats should be offered as an extra in order to keep the
price lower for the majority of users, which do not live together with (small) children.
For most efficient utilisation of the baggage space, there is not one wide seat for two
children planned, but two single seats, which can be removed individually. On one side,
they are to be fixed onto the side wall of the bottom frame, on the other side they stand
on the bottom plate or a crossbar.
3.2. Auxiliary drive
For elderly people and other physically less capable users as well as such, which regularly
carry heavy loads or have to overcome significant altitude differences, an electric power
assistance can significantly increase range resp. save riding time. (A separate chapter
about the cost-benefit-ratio of electric power assistance for different applications is being
elaborated).
The easiest and in terms of minimally necessary lot sizes lowest-risky solution is the
utilisation of a commercially available retrofit package. Unfortunately, packages with hub
motors are rather unsuitable, because an asymmetric drive is unwanted as well as a driven
front wheel, which would often slip because of to few weight lasting on it. Two driven rear
wheels would be expensive and maybe exceed the legal power limit of 250W for licencefree power assisted bicycles (Pedelecs)17.
A chain drive system18 could be allocated above the bottem in front of the driver’s seat, if
the device is small enough (no obstruction for pedalling) and there are no problems with
the derailleur gear and the diagonal chain run. More suitable seems to be a type of chain
drive, which turns the front sprockets via an additional chain and may be assembled
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between the pedals and the front wheel19. Therefore, an additional front sprocket can be
used, or the smallest sprocket ist used for the driving chain, loosing the lowest gear
speeds, which might get anyway unnecessary due to the motor assistance.
If leg-length adjustment should be possible after mounting the auxiliary engine too, it
should be possible either to shift the motor longitudinally or there must be used an
additional tensioner for the driving chain.
An option for regenerative braking would be favourable, because the share of regenerable
energy consumption for steeps and acceleration is relatively high in case of heavily loaded,
but relatively aerodynamic velomobiles. Thus, regenerative braking could save energy and
reduce the necessary battery capacity. Unfortunately, such an option of regenerative
braking seems to be inconsistent with the concept of retrofitting the cheap, mass
produced main version with a fully developed, commercial available auxiliary drive kit,
because regenerative braking is common in hub motor systems20, but with a chain drive it
would require special design and is in any case impossible with a derailleur gear.
3.3. Coupling
Particularly, if there should be coupled more than two vehicles, but also on narrow paths,
there would be preferable a coupling construction, ensuring that all coupled vehicles
follow the trail of the first one as exactly as possible. This can be realised by a coupling
triangle, which is fixed to the first vehicle if the length distance between the rear axle and
the linking point is the same as between front wheel and rear axle. The linking point is
exactly above the front wheel, but the wheel is not fixed to a drawbar, but freely turning.
Figure 9: two coupled velomobiles in a curve
If there should not be carried just one empty vehicle (e.g. within a rental system), but
composed a train of two or more, eventual even occupied vehicles, an overrun brake is
essential in order to ensure sufficient deceleration. Such a brake can be realised in that
way, that the braking cables of the normal brakes run over guider rollers, which are
shifted in case of a pressure onto the link. The overrun brake should be activated only, if
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there is a force limit exceeded, because if there are coupled two or more occupied
vehicles, in case of same driver’s power in both vehicles, the rear one always slightly pushs
the first one because of less air drag. Such a force limit can be realised using a knop with a
spring.
Figure 10: Schematic sketch of an overrun brake: above: brake released as pushing force below
the limit, below: brake in function as pushing force exceeded the limit
3.4. Child version
Despite the size adjustment feature, children with a body height between about 125 and
155 cm, this means an age of about 7 to 12 years21, are still to small and probably also too
weak for driving an adult version of the velomobile, but at the same time they are too tall
to be carried in a velomobile, particulary if there should be carried goods or a brother oder
sister at the same time. Because of this, in any case a child version, which would be
adjustable in the mentioned size range, would be preferable. Such a child version should
differ from a simply downscaled adult version in the following properties:
• Regard to different detailed body dimensions (e.g. body-leg-ratio)
• Significant smaller baggage space, maximum width closer to the middle and more
narrow rear
• Smaller dimensions of the aluminium profiles and the screws in order to reduce
weight
• A pennant or something similar for better visibility despite less vehicle’s height
Particulary the child version should be able to be coupled, also with the adult version.
3.5. Seat height adjustment with a gas pressure spring
For less agile persons, particulary elderly or overweight people, the necessity to sit down
into a low seat in the bottom tub can represent a relevant barrier. This problem could
solved in that way, that the seat can bei lifted and lowered by one ore several gas pressure
springs as used in office chairs. In such a case, the seat height for entering would be about
50 cm above ground. For lowering the seat, it would be sufficient to press a button, for
lifting, the driver must hold up a little on the frame. In order to achieve a preferably low
force necessary for holding up, the gas pressure spring should be adjustable or there
should be a choice between different springs.
RegInnoMobil
sustainable systems
3.6. Shorter or swinging pedals
Another obstruction for people which are restricted in terms of agility and physical
capability could be the necessity of pedalling. Although the necessary physical power can
be with the use of electrical power assistance (see 3.2) lowered down to symbolic figures,
a pedalling motion is still necessary, because controlling the motor by tuning a gas pedal,
a throttle or a joystick would be countradictory to the definition of a licence-free,
electrically assisted bicycle (pedelec)22. On the other hand, a vehicle, requiring driving
licence, insurance and licence plate would also exclude many users particularly in the
target group of elderly people. A possible problem of usual pedalling might be even at low
power input the angles at knee- and hip joints. Basically, there are conceivable two
solutions:
• Shorter pedal arms and lower allocation of the pedals
• Replacing the conventional chain drive by hanging, swinging pedals with electrical
power transmission together with the electrical auxiliary drive.
3.7. Alarm device
In order to compensate the disadvantage of the cutable textile cover at least partly, there
can be distributed as an extra an alarm device, sensitive to motion or cutting a cable
around the vehicle. Such battery-powered systems are commercially available for
backpackers as well as for bicycles23. Another conceivable solution, though technologically
more sophisticated, would be a motion-detecting system that sends an alarm to the owner
via mobile communication, eventually including positioning of the vehicle.
3.8. Locker for small valuables
A small locker would be functional for leaving valuables in the vehicles, but also for safety
equipment like a first aid kit, a visibility jacket or a breakdown triangle.
1
Liegeradforum: Erfahrung mit Differential im Kettwiesel?:
http://www.liegeradforum.net/topic,279,-erfahrung-mit-differential-im-kettwiesel.html; 12.3.2010
2
Büro-Forum: Körpermaße sitzender Personen: http://www.bueroforum.de/de/ergonomie/datensammlung/koerpermasse-sitzend/; 12.3.2010
3
Büro-Forum: Körpermaße stehender Personen: http://www.bueroforum.de/de/ergonomie/datensammlung/koerpermasse-stehend/; 12.3.2010
4
Wikipedia: Schuhgröße: http://de.wikipedia.org/wiki/Schuhgr%C3%B6%C3%9Fe; 12.3.2010
5
Examples for the length of folded strollers (also such, which are suitable for newborn babies):
Inglesina ZIPPY FREE – passeggino (100,5 cm):
http://www.inglesina.com/sites/default/files/Zippy%20Free_0.pdf; 12.3.2010, Bugaboo Bee (88
cm): http://www.bugaboo.com/learn/bugaboo-bee?id=6010; 12.3.2010, Peg Perego Pliko P3 (103,5
cm):
http://www.pegperego.com/page.php?sid=13c09d27d54c3f326e465271e52b8835&pageid=IJVNL001&
idf=04&idp=0000000252&cl=N; 12.3.2005, own measurements in the pushcar-shop “be-mom.com”.
6
27 cm wide baby seat for children’s trailers, see for example: ebay Österreich, WEBER Babyschale
für Croozer Chariot usw.: http://cgi.ebay.at/WEBER-Babyschale-fuer-Kinderanhaenger-CroozerChariotNEU_W0QQitemZ350310623541QQcmdZViewItemQQptZSport_Radsport_Fahrrad_Anh%C3%A4nger?has
h=item519023e935; 15.3.2010
7
see for example: aquaristic.net: Mag Float L: http://www.aquaristic.net/mag-float-l.html;
15.3.2010
8
Azub Bike: AZUB ECO – Liegerad: http://www.azub.eu/DE/liegerad-azub-eco/; 15.3.2010
9
Fahrrad-Trends.de: Neuerungen im Fahrradbau: http://www.fahrrad-trends.de/neuerungen.html;
15.3.2010
10
Liegedreirad Weblog: Der Big Apple von Schwalbe bei Outdoor Experts:
http://liegedreirad.wordpress.com/2008/01/22/der-big-apple-von-schwalbe-bei-outdoor-experts;
15.3.2010
11
www.brix.de: das komplizierteste aller Räder: Das Alltagsrad:
http://www.brix.de/verkehr/fahrrad/alltags-fahrrad.html; 15.3.2010
RegInnoMobil
sustainable systems
12
Pickup: Das sichere und wartungsarme Alltagsvelo: http://www.pickupbike.ch/wartungsarm.html; 15.3.2010
13
Wikipedia: Fahrradbeleuchtung: http://de.wikipedia.org/wiki/Fahrradbeleuchtung; 17.3.2010
14
Weights and dimensions of different aluminum and steel profiles and shaped tubes out of the
assortment of the company “Ferona”: Ferona, sortimentní katalog:
http://www.ferona.cz/cze/katalog/search.php?kat=1; 15.3.2010
15
www.smolik-velotech.de - Online-Glossar: Aluminium: http://www.smolikvelotech.de/glossar/a_ALUMINIUM.htm; 15.3.2010
16
Velomobil-, Trike- und Liegeradforum: Modellübersicht:
http://www.velomobilforum.de/wiki/doku.php?id=velomobil:allgemein:modelle; 15.3.2010
17
RICHTLINIE 2002/24/EG DES EUROPÄISCHEN PARLAMENTS UND DES RATES vom 18. März 2002
über die Typgenehmigung für zweirädrige oder dreirädrige Kraftfahrzeuge: http://eurlex.europa.eu/LexUriServ/LexUriServ.do?uri=CONSLEG:2002L0024:20070101:DE:PDF; 26.2.2010,
pursuant to informations from DG TREN, there had not been undertaken no particular study was
carried out to define some optimal speed limit for pedelecs.
18
See for example: akkurad.com: Elektroantriebe für Fahrräder, Spezialräder und Fahrzeuge:
http://www.akkurad.com/html/kettenantrieb.html; 16.3.2010
19
See for example: akkurad.com: Tretkurbelantrieb für Fahrräder, Spezialräder und Fahrzeuge:
http://www.akkurad.com/html/tretkurbelantrieb.html; 16.3.2010
20
See for example: BionX: Technologie – BionX: http://www.bionx.ca/de/products/technology/;
26.3.2010
21
Forum Gesundheit: Körpergröße von Mädchen und Buben:
http://www.forumgesundheit.at/mediaDB/531585_K%C3%B6rpergr%C3%B6%C3%9Fe_Kleinwuchs_graf
ik.jpg; 16.3.2010
22
RICHTLINIE 2002/24/EG DES EUROPÄISCHEN PARLAMENTS UND DES RATES vom 18. März 2002
über die Typgenehmigung für zweirädrige oder dreirädrige Kraftfahrzeuge: http://eurlex.europa.eu/LexUriServ/LexUriServ.do?uri=CONSLEG:2002L0024:20070101:DE:PDF; 26.2.2010,
pursuant to informations from DG TREN, there had not been undertaken no particular study was
carried out to define some optimal speed limit for pedelecs.
23
See for example: Visor Tech Fahrrad Diebstahlsschutz mit Alarmschloss: http://www.pearl.de/aPE4481-5451.shtml; 16.3.2010

Concept for a low-cost-velomobile for short daily trips in rural areas

Transcription

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