The document discusses the possibility of creating a spring-powered car. It notes that while spring-powered toys were common, using springs to power a vehicle faces challenges around energy density. However, springs could potentially work on the moon or Mars where gravity is lower. The document proposes designing a car powered almost exclusively by springs, using modern watchmaking materials and technologies, as a truly green alternative to gasoline or electric cars.

1. THAT'S ENOUGH! I WANT A SPRING CAR...
by Matteo Bortolotto
After the resounding flop of Tesla
Battery Day (at least as far as the stock
market is concerned), it is clear that
the world of electric cars is still very
hazy and far from being that
technological paradise that should
free us once and for all from the
"dinosaurs" bursting engines, just as
the likes of Elon Musk have tried to sell
us to this day.
The fact is that, many automakers, have prepared medium or long-term electrification plans, with
the intention of making Full-Electric vehicles and/or hybrid versions; but despite efforts to do so,
and the capital invested, no solid-state battery, or lithium-air, or lithium-sulfur, or zinc-air or
aluminum-air has still reached a degree of refinement that allows for large-scale production.
So, the dear old liter of gasoline, with its 34.6 Mega Joules of fully available chemical energy, still
dominates it (at least until we can handle hydrogen in the same way).
34.6 Mega Joule, however, remains a very high energy value, corresponding to 9.6 kWh (34.560.000
Nm.). Try to imagine what kind of cell would come out of it if we wanted to put that amount of
energy into a battery intended to power an electric car...
Unfortunately, the best petrol engines arrive at a maximum thermal yield of 40% (50% those of F1),
while electric motors are much more efficient at converting energy into motion, due to their
simplicity of construction. Therefore, a car travelling 16 km with a liter of petrol will consume
approximately 600 Wh per kilometer, compared to 140–160 Wh per km in the same conditions as
an electric car.
This means that with the equivalent of a liter of gasoline, an electric car will travel from 60 to 70 km
only thanks to the higher performance of its engine. However, this will have a "tank", much heavier
than the petrol car, so much of its energy will be absorbed by its mass.
Then we drop a pitiful veil on hybrid cars, which add up components of both technology for an even
higher overall weight. These vehicles, as well as the Full-Electric vehicles, also use a regenerative
braking system to recover some of the energy that is normally wasted in the form of heat in
conventional braking systems.
However, the data indicate that most hybrid-electric regenerative braking systems operate with less
than 50% efficiency when kinetic energy is converted into electricity, and then re-entered into the
vehicle's propulsion.
Not to mention the price of batteries, which last an average of between eight and ten years and are
extremely expensive to replace. The devices are assembled in specialized companies because for
safety reasons, the devices must be virtually perfect, so as to reduce as much as possible the risks
of fire or explosion related to the presence of a liquid component inside the battery pack.
To implement the highest possible degree of safety, the battery pack is then treated with a special
retardant, in order to limit overheating problems. The entire module, closed by an automatically

2. sealed plate, must then be airtight, i.e. water-proof and dust-proof, as required by the IP67
certification.
For the same reason, the production facilities of the devices have a high degree of automation, as
they use numerous automated devices dedicated to the assembly and storage of batteries... Put
simply, too many complications!
In addition to all this, to establish exactly the true environmental impact of an endothermic or
electric vehicle, you then have to calculate how you get the energy, both to produce the fuel and to
charge the batteries, since refineries and fossil fuel plants make a green or hybrid medium, on the
whole, much worse for our health than you want to give to.
So, what about a spring car?
The idea is certainly not new, since as usual "HE" had already theorized it five centuries ago in the
812r sheet of its Atlantic Code, as can be seen here:
Now the question arises, that is, if "HE" succeeded in 1478 why can't we try it too, given the technical
evolution that in the meantime materials and technological processes have undergone over the
centuries?

3. The engineers will surely tell you that the energy density possessed by the springs currently on the
market, is still too low compared to the chemical contained in traditional fossil fuels or in the last
generations of lithium-ion batteries for self-traction...
I myself tried to ask that question on Quora without success...
However, a hypothetical automatic spring car, it would end in itself point and that's it!
It would not need refueling or processing plants, let alone distribution. Its bill of materials would
also be much simpler compared to that of a conventional or hybrid car, with substantial economic
savings.
A spring car theoretically would not need any thruster, which would already be a nice step forward
in terms of weight, but it still needs an even larger "tank" given the lower energy density it is able
to accumulate.
Its large limit is largely due to the law of the square cube.
It, in a very simple explanation states that, the surface area of any element increases by the square,
while its volume (i.e. weight and mass) increase in the cube.
So, the ability to store energy in a spring will decrease as it grows, because the mass of the springs
increases faster than their energy density, which depends in part on their surface area.
The larger they are, the less efficient they become, and exceeding their mass will eventually absorb
almost all of the stored energy.
(For more information, read: Here )
Okay, all true for goodness' sake, but what if we were on the Moon or Mars where gravity is
significantly lower?
Zero petrol pumps or electric charging columns... limited oxygen to the use of cylinders to be able
to breathe (which translates means limited journeys to a few kilometers for humans).
In such a context, the spring car could certainly make sense, as it would weigh significantly less than
the energy it could develop.
That's why, the thought of being able to make a spring car according to the most current criteria of
modern watchmaking, looks damn green here on Earth, as useful for future space missions.
Personally, I find it really strange that the refined mechanisms and materials developed for the latest
generation watches, by the Swiss Haute Horlogerie, and the constant research carried out by this at
such high levels, have not yet been poured into the automotive world.
Such engineering "laziness" is truly disconcerting, since it could be solved at least in part of today's
serious ecological and energy problems instead of simply keeping it on your wrist.
The mere fact that after five centuries we have been able to replicate Leonardo da Vinci's spring car
project gives me a lot to think about...
Someone tried to carry on as reported in this old patent of 1892:
Link
someone else in later eras by trying their hand at different paths:
Read article 00
Read article 01 Read article 02
Read article 03 Read article 04

4. In short, there are a lot of discussions out there on this issue, but very few notable projects... carried
on most of the time, by some mechanical enthusiast or makers, in the garage of the house in lost
time.
Now as I imagine you will have already understood from the title, in these pages I will try to illustrate
my concept of a truly green car, powered almost exclusively by spring, thanks to the materials and
technologies currently available. And if I can't, I would at least like to lay the groundwork for a
constructive discussion about a future generation of really clean and affordable vehicles.
So, raise your hand if you've never had to deal with any toy or spring-loaded device as a child?
Well, these toys were driven by a particular twisting spring that was rewinded from time to time
when it discharged, and which acted as an energy storage device (Elastic Potential Energy), given its
inherent tendency to return to its original state after being twisted.
The energy accumulated by the spring was then released through a series of gears, aimed at
preventing it from happening too quickly, ensuring a more gradual flow and constant speed of the
device until it was completely discharged, as seen in the sample footage.

5. The spring was usually of this type:
and was enclosed in a plastic or serrated metal "barrel" in
order to preserve its operating characteristics, while
ensuring an adequate degree of protection for its user.
The Elastic Potential Energy stored by the spring was
therefore the result of the deformation that we went to
imprint them by acting on the stick or rather, on the charge
device.
So, twisting it, we did a job on it, transferring energy to it.
Here, however, we encounter the first problem, that is, it
takes more energy to wrap the spring than can be obtained when it is discharged completely,
precisely because of the energy transfer... However, once released, the spring transformed that
potential energy into kinetic energy, allowing it to operate the object in which it was inserted or
connected.
Now the elastic potential energy formula, is given by:
𝐸 𝑝𝑒 =
1
2
∙ 𝑘∆𝑥2
where k indicates the elastic constant of the spring while ∆x represents the strain (stretching or
compression) exerted from the outside on it.
Here are the inverse formulas:
𝑘 =
2𝐸 𝑝𝑒
∆𝑥2
∆𝑥 = √
2𝐸 𝑝𝑒
𝑘
When the spring is in its resting position, that is, the deformation x is nothing, even the elastic
potential energy is nothing, but every time it is stretched or compressed the elastic force intervenes,
which, by opposing its deformation, causes it to regain its initial length (i.e. the length at rest).
For some applications, springs can have different advantages over other ways of storing energy.

6. Unlike batteries, for example, springs can provide energy stored effectively quickly and intensely, or
more slowly and steadily over a longer period, as exemplified by the difference between the spring
in a mousetrap and that of a mechanically charged clock.
In addition, unlike batteries, the energy stored in the springs does not normally disperse slowly over
time.
A mousetrap can stay ready to shoot for years without dissipating its energy.
So, after scouring the web for weeks, I was finally able to find spring devices powerful enough to
move a car when combined with each other:
See here
The company that produces them has several models, but only in the top-of-the-range ones (of the
SZH series) Are used Archimedes spiral springs that allow to develop up to 3765 Joules of energy,
for a limited number of rotations of the shaft (17-19 max).
It goes without saying that in order to be able to power a car properly, you would have to have that
energy for a long enough period to allow you to travel at least a few kilometers... already but how
to do it?
Someone seems to have partially solved this problem too, serially connecting the "barrels" and
making them work interconnectedly as if they were a single spring, so as to obtain a higher energy
density and force output for a longer period of time, as can be observed in the following document:
Read article
But to give you a clearer idea of the result I strongly recommend to take a look at the really
interesting prototype made by Mr. David Outteridge:
Go to site
The following video shows the stunning results he obtained after several attempts at optimizing
and disposition of springs and transmission for his locomotive model:

7. Of course, a similar but much more refined
mechanism can also be found in the Hublot "MP-05
LaFerrari" watch.
I admit, however, that Mr. David Outteridge had
come very close before the well-known Swiss
maison to this unique solution, especially with
regard to the drill charging system, which seems to
have been taken up of healthy plant by the latter!
Unfortunately, Mr. Outteridge certainly did not
have the economic resources of the famous Swiss
brand, so he had to deal with what he had at his
fingertips.
However, if the same materials and technical
measures adopted for example on Cartier's ID TWO
concept were applied to the "barrels" and
mechanics of his locomotive, I am sure that he would have achieved and greatly exceeded the goal
he had set himself... that is, to cross the mile of travel!
Link CARTIER ID TWO
However, I believe that Mr. Outteridge could have already achieved this by adopting a different
range of springs, for example those with constant force (Tensator type), even if this would have
involved the entire redesign of the locomotive and its transmission.
Such springs, are described well in this post
by Mr. John Hubby:
Read
Hubby himself, in a later post, then proposed
his solution to power a car with the Tensators
by providing some indicative data here:
Read
Inspired by what emerged in these posts, and
given the results obtained by David
Outteridge despite the use of less efficient springs, I realized that the time and technology for the
realization of an advanced prototype of spring cars with an automatic charging system similar to
that found in many watches, are now mature, just want it and put a little effort to look for all the
elements necessary to assemble it, in addition to raising funds for the project through a
crowdfunding campaign on the web, thanks to dedicated platforms such as Kickstarter, Indiegogo
etc. just to mention the most famous.
But let's go with order...
Step 01) - Before getting hurt it is good to validate the idea. To understand whether the market is
interested or ready to accept a means of transport powered by these devices... and most
importantly, totally independent of current energy sources.
Economically it would be advantageous and clean, but far from performance (forget so
numbers at Fast and Furiors at least for the moment), at least until we are able to store

8. and manage mechanical energy at the molecular level through carbon nanotubes (read
Fullerene), which however are still very complicated to obtain in homogeneous
structures...
Clarifying the real needs that should cover our vehicle is a priority for the project.
It doesn't have to be a car, initially it could be a motorcycle or a trike or something else...
The important thing is to evaluate whether or not people appreciate the basic idea, so
that we get as much feedback as possible that will allow us to move on to the next steps.
Once you have identified the problem and the reason why any competitors have not
solved it yet, we move on to phase two, so for now no prototypes, no business plans etc.
To advertise only the basic idea and expose it to those concerned without being jealous
of it, because "no one earns money in the automotive industry apart from the taxman.
The biggest gain on any car is always the government."
Step 02) - Once all our data is collected, we will carefully analyze it, adjusting our initial idea based
on the issues that have arisen. So once the correct solution has been found, it must be
validated in turn, that is, it must be identified who really needs such a means of transport
immediately, and is willing to fork out any amount in order to solve its problem quickly,
even though the project is still in the embryonic stage.
Summing up who our ideal user is and how we can sell them such creation... that is, how
we can get out on the market as soon as possible with what is technically called an MVP
(Minimum Viable Product) or minimum working product.
Step 03) - From this point on we move on to the actual realization of the first prototype, which will
have to be as cheap and simple as possible, since it will serve to estimate whether we
have correctly interpreted the problems of potential customers and what corrections we
will have to make exposing us as little as possible to unnecessary risks.
The MVP will be optimized over time based on the criticisms and additional information
we will collect to make it as functional as possible from time to time.
In short, you have to start light as will be our initial product to comply with the law of the
square cube.
Given this dutiful premise, let's try to establish in theory the powertrain necessary to ensure its
movement.
Spring choice – As previously seen the main spring (mainspring) should be of a constant force type,
for the reasons expressed very well by Mr. John Hubby in his posts in response to Mr.
Rodericke. These springs are very efficient and have two or more drums depending on
how much energy you want to get.
At the following link you can get a clearer idea of their use in double or multiple version
and some configurations:
Read here
Driven by curiosity I then tried to look for the most suitable version for the project
proposed by this manufacturer (Spiroflex), current division of the Kern-Liebers group.
The first problem I immediately came across based on the data proposed by Mr. Hubby
was the one relating to the size of the drums.
In fact, such springs are characterized by a very uniform force-shift curve.

9. This curve can be adjusted within defined limits for specific applications, thanks to special
machinery made within the manufacturer. But the idea of wrapping the tape directly on
a 100 mm tree. doesn't seem viable at the moment.
In the catalogue the spring that is closest to our needs is the SR120.
This includes 198 mm drums, respectively. (main) and 119 mm. (secondary).
Then there is the problem of the thickness of the tape, which for this product rises to 0.64
mm. 51 mm. compared to a nominal thickness of 0.50 mm. 300 mm. width always
suggested by Mr. Hubby. The SR120 is guaranteed for 20,000 work cycles and manages
to develop 81.5 kg/cm2 (8 N/m). I assume that this type of tape is the same as used in
Kineteko starters seen previously. Driven by curiosity I then tried to look for the most
suitable version for the project proposed by this manufacturer (Spiroflex), current division
of the Kern-Liebers group.
The first problem I immediately came across based on the data proposed by Mr. Hubby
was the one relating to the size of the drums.
In fact, such springs are characterized by a very uniform force-shift curve.
This curve can be adjusted within defined limits for specific applications, thanks to special
machinery made within the manufacturer. But the idea of wrapping the tape directly on
a 100 mm tree. doesn't seem viable at the moment.
In the catalogue the spring that is closest to our needs is the SR120.
This includes 198 mm drums, respectively. (main) and 119 mm. (secondary).
Then there is the problem of the thickness of the tape, which for this product rises to 0.64
mm. 51 mm. compared to a nominal thickness of 0.50 mm. 300 mm. width always
suggested by Mr. Hubby. The SR120 is guaranteed for 20,000 work cycles and manages
to develop 81.5 kg/cm2 (8 N/m). I assume that this type of tape is the same as used in
Kineteko starters seen previously.

10. However, there is a fairly similar version in size but a little more efficient the SR99, able
to develop up to 103 kg/cm2 (10 N/m) guaranteed for only 5000 work cycles.
However, this spring can count on a slightly longer tape length that allows it to perform
27 complete rotations of work, compared to only 20 of the sister.
Either way, we're a long way from the 540 meters of tape proposed by Mr. Hubby. vehicle
to have a range close to the optimal one.
I have no idea whether or not this company is able to provide custom products with such
features, but if anyone has more information about it or knows other companies that can
make springs of this type close to the dimensions seen above, I would appreciate it if you
reported them to me.
Normally these springs are made of high-yield 301 stainless steel, but to contain as much
weights and sizes as possible, gaining a 20% more torque, I would recommend using the
Elgiloy alloy although notoriously more expensive:
Read
In reality, to effectively counteract the law of the square cube, the ideal springs should be
made of fiberglass and reinforced plastic (FRP) like those produced by SOGEFI for AUDI
models.
Lighter than 40-70% than steel sisters, they are unassailable from corrosion, last longer
and are even quiet.
Unfortunately, I do not yet know the production process of this product well, but it is said
to be more convenient and sustainable than the traditional one, since it requires fewer
stages of processing and surface treatments, for the benefit of the environment.
However, if it were possible to print them in 3D (See here) and/or make them for
pultrusion in tapes suitable for our purpose, keeping the physical/mechanical
characteristics unchanged, they would really be the top.
Transmission Choice – Returning to Mr. Hubby's directions, to get a transmission ratio of 900:1 to
the 30-inch diameter wheel of our vehicle, we would need a gear train that releases on
average about one meter of spring per mile with only 2/3 rpm of the main shaft,
compared to 600 rpm of wheel speed, equivalent to about 53 mph.
In watchmaking a transmission report like this would be translated as follows:
6:1 x 6:1 x 5:1 x 5:1
And it would give rise to a gear train very similar to the one shown in the following image:

11. However, such an "elegant" provision, referring to the "complications" of a "tourbillon",
must clearly be simplified for use in a spring vehicle, where frictions and masses must
necessarily be reduced to a minimum, in favor of overall efficiency, as well as energy
transfers.
To simplify the task, a harmonic gearbox could then be inserted inside the main drum of
the moving spring, which is still to be verified during the project.
The substantial characteristics and benefits of such devices are the high reduction ratio in
a single stage, the absolute absence of play, the high torsional stiffness on the torque
values, small size and reduced weight, as well as reversibility.
Only real mole remains the price... but it is the best that can be found on the market at
present.

12. If the main spring is too voluminous and we are forced to use more than one in series, as
in the example of Mr. Outteridge, but adopting the Tensators, it would be appropriate to
consider the insertion of a trigger/disengagement device similar to this:
... giving each spring a recharge while the others work, without affecting the vehicle's
pace.
Always following Mr. Hubby's instructions, a 900:1 transmission would require an initial
thrust provided by a flywheel or electric motor, otherwise the vehicle would be too slow
to start.
The company Flybird has developed a very interesting mechanical Kers that could do just
for us:

13. This device, already successfully tested by Volvo on some of its models, is very useful in
stop and go driving, and could limit the use of the main spring to the bare minimum.
However, it should be appropriately modified, in fact the CVT group in the foreground on
the left of the photo, is too
complicated and heavy for a
spring car with clearly limited
performance.
In addition, this type of gearbox
provides for a complex hydraulic
control system that is totally
inappropriate, which should be
replaced with something much
lighter and more efficient, given
the low powers at play, such as
the one next to it...
In its latest evolution this cvt has
been further simplified and no longer requires complicated external control systems.
Tightening pressures on the rollers are also lower than on other similar devices, offering
significantly higher returns.
The driving spring should still be able to recharge automatically on the go, a bit like in
automatic clocks with a kinetic mechanism, as well as through deceleration or when
traveling downhill.
Examining the various "Energy Harvesting" solutions on the network, I identified this very
interesting device that captures energy from movement on all six axes:
It is produced by Witt Energy in various sizes, and depending on the size can develop from
5 W to 1 KW.

14. Containment of car body weights – Once the problem of springs and transmission is solved, the focus
will be on the tank.
Personally, I have always appreciated the design and chassis of the Dome Daihatsu X-021
concept although unfortunately I have never been able to find the related blueprints or
scale drawings:
It is a 1991 project that never went into production (who knows why),
on whose boxed aluminum frame was fixed the fiberglass spider body with still decidedly
pleasant shapes.
The car weighed only 700 kg. It had independent sports-type suspension, two lightweight
Recaro shell seats and rear-wheel drive.
If until some time ago I had been asked how to further lighten a car like this to fit the
Wind-up car/Clockwork-car project, I would have replied: replacing the steel frame with
an equal one but made by INREKOR:

15. Unfortunately, this company was decommissioned in 2015, and it's a shame because it
had developed lightweight structural panels that could be used cheaply to build a chassis.
In practice, a 2D element that created 3D structures and involved a plastic foam core of
ARPRO expanded polypropylene glued between two thin sheets of aluminum or other
metal materials or even composite as needed.
By changing the density and thickness of the core to ARPRO, the designers could thus
derive different tensions in the panel, due to its flexibility and the ease with which it could
be modeled.
As for the bodywork, I would have replaced the fiberglass of the X-021 concept with
aluminum alloys, certainly more comfortable to work with features now known to
everyone.

16. Anyway, dead one Pope makes another one is said to be from my side, and technology
has continued to progress as well as the design tools.
Today, thanks to advances in computing and 3D printing, we can count on "generative
CAD design", which allows designers to explore multiple compromises between different
approaches.
This allows them to address and solve the various problems they encounter on a daily
basis at work, through a more accurate definition of goals and constraints.
Autodesk's Dreamcatcher project is a concrete example of this.
That's why, what until yesterday could be considered an innovative frame, very light and
cheap, developed thanks to INREKOR technology, today could instead look more like
something like this:
Of course, the weight would still decrease, while the resistance would increase further.

17. However, for those who feel like they're getting on a web rather than a vehicle with a
state-of-the-art chassis, or still have skepticism about 3D-printed products, there are
alternatives.
The iStream technology developed by Gordon Murray in collaboration with Toray
Industries, Innovate UK and ELG, allows you to combine formula1's lightweight
technology with high volume production flexibility and excellent safety standards to
create lighter vehicles with multiple advantages in terms of both low emissions and
production costs, reduced by up to 80%:
In short, the solutions and products to make a spring car nowadays certainly do not lack...
What I have illustrated in these pages is, from my point of view, the concept closest to
reality, but it is not said to be the definitive solution.
Every day we deal with spring devices of various kinds without even realizing them, so
why not exploit them also for urban mobility, rather than spending capital on copper and
lithium etc...
From this point of view, I find society really distracted or rather too addicted to oil and
electricity...
If the economic effort made every day in the search for new, more efficient batteries, had
instead focused on the search for metal alloys or polymers with higher energy density for

18. springs, today on the roads we would have far better and cleaner vehicles, even if
analog...
Also, in the worst case that mainspring was completely unloaded, you could start it with
a simple crank, just like the starters of Kineteco, which also does a bit vintage:
Other elements such as OEM parts, wheels and
interiors could be 3D printed in various ways, using a
combination of selective laser fusion (SLM), electron
beam fusion (EBM), stereolithography (SLA) and
other technologies...
I had already proposed some solutions in a previous
project for the Lite Car challenge promoted by Local
Motors a few years ago.
You can find the relevant tab on my Linkedin profile
if you want to delve into...
In conclusion, it is likely that I am neither the first nor
the last person to submit such a project, and there will certainly be some engineering
problems that should not be underestimated... but never give up!
Opinions as well as objections are always welcome, so feel free to comment!

19. (The search continues... in the meantime let's console ourselves with this!!!)