Our concept chooses to focus on uniquely combining concepts that have been tested and proven rather
than pushing the envelope of vehicle design. It combines lightweight technology used by the building
industry with a unique and powerful drivetrain inspired by modern locomotives. We call our concept
“Tomorrow’s car, using today’s technology” or T-CUTT.
You’re probably saying to yourself “That’s just a stock photo of a sedan!” and - you’re not wrong.
Visually, the T-CUTT will be designed to fit in at any supermarket parking lot. While this may limit the
number of breakthrough mechanical and aerodynamic innovations, we feel that looks are very
important to automobile culture. Furthermore, sticking with a familiar design allows us to adhere to
current automobile safety standards. The T-CUTT doesn’t skimp on safety, and will be engineered to
provide the highest levels of occupant protection using proven industry safety features.
Unibody Construction
The T-CUTT uses a unibody chassis design similar to most vehicles on the market today. As mentioned
before, this provides us with a predictable model for occupant safety. The standard sedan look will also
reduce gas station questioning and pedestrian whiplash.
What makes the T-CUTT chassis different is that it will use a layer of thin honeycomb perforated steel
sheeting embedded in Aramid fiber reinforced epoxy composite (AFRP) for interior frame composition
and structural components. Further weight reduction could be obtained by using carbon fiber in place
of aramid fiber, however we feel that the weight reduced by using CFRP over AFRP is not enough to
justify the difference in cost. CFRP and AFRP are both variants of the even more affordable GFRP (glass
fiber reinforced polyester), commonly known as fiberglass.
GFRP is an amazing structural material who’s benefits are well known. One of the most famous
examples of the strength of GFRP was Disney’s “House of the Future”. From Wikipedia “The building was so sturdy that when demolition crews failed to demolish the house using wrecking
balls, torches, chainsaws and jackhammers, the building was ultimately demolished by using choker
chains to crush it into smaller parts. The reinforced polyester structure was so strong that the half-inch
steel bolts used to mount it to its foundation broke before the structure itself did.”
Further advancements in both resin technology and reinforcement fibers have given us GFRP, AFRP, and
CFRP. These composites are commonly referred to by their reinforcement fibers as fiberglass, Kevlar,
and carbon fiber. While the fiber selected is important, the resin composition is of even more
importance. The three types of resin used are polyester, vinylester, and epoxy. Epoxy resin is three times
as strong as vinylester resin, and vinylester is twice as strong as polyester. Polyester is the resin most
people associate with fiberglass, and was the resin used in the House of the Future. Aside from it’s
strength, Epoxy also has superior adhesive and saturation properties. It is the most expensive of the
resins, but well worth the cost. Using epoxy resin would make an excellent structural material using
even fiberglass fiber, but we’ve chosen to go with the more “bulletproof” fiber, Kevlar.
The T-CUTT goes one step further with our composite, embedding thin honeycomb steel sheeting in the
areas surrounding the passenger cabin. The steel adds weight to the composite, but provides an added
layer of elasticity in the event of an impact, increasing occupant safety exponentially. We would also add
a layer of lightweight Nomex honeycomb embedded within the composite that makes up the vehicle
firewall and fuel storage areas, increasing fire resistance properties where it's needed most. We
estimate a gross frame weight reduction of 30 to 50% using this composite over current automobile
manufacturing methods.
Honeycomb steel sheeting
The Body Panels
Example of removable body panels
The T-CUTT gets it’s good looks and aerodynamics using a non-structural removable body panel system.
Panels that cover areas such as fenders, doors, trunk, and roof are made using honeycomb reinforced
plastics that are individually removable from the vehicle. As an added bonus, manufacture of the panels
is independent of the vehicle, and can also be outsourced or 3D printed. The combined weight of all of
the T-CUTT’s body panels would be able to weigh less than that of a hood and trunk of a typical steel
sedan.
Interior
While making considerations for the interior of the T-CUTT, we kept arriving at the same dilemma. We
feel that any amount of weight saved by significant changes in the vehicle interior was done so at the
expense of the driver’s experience. Therefore, the T-CUTT only has minimal changes to the interior,
including memory foam seating that eliminates steel springs, frameless motors for power seats and
windows, and aluminum framed seats. As technology progresses, speakers with large heavy magnets
will be replaced with ultra-light graphene speakers.
Drivetrain
We found that modifying a standard gasoline drivetrain was the most effective way to reduce the
weight of modern automobiles.
Converting the inertia of a gasoline engine to vehicle momentum has some serious compromises. The
largest of these compromises is in the clutch and transmission. The most basic explanation of these
components is they are a mechanical way to convert engine rotation to wheel rotation. There are very
few examples of this method of power delivery outside of the automotive world. We’ve chosen to base
our modified drivetrain on what we consider to be one of the most rugged and proven examples of
power delivery in the world – the modern locomotive.
The weight of a locomotive doesn’t allow for direct mechanical power delivery. The engines in modern
locomotives don’t directly drive the wheels of the train, they drive large generators. The generators
convert the mechanical power into electrical energy that feeds large motors that turn the wheels. Most
trains in the United States use large DC generators that drive DC motors that are controlled by massive
motor controllers. And while DC motors still rule the rails of the US, in other countries as well as in
industrial applications, DC motors and controllers have been almost completely replaced by AC motors
using Variable frequency drives, or VFDs.
Variable frequency drives offer huge advantages to automobiles. The first is that they have massive
amounts of torque. From a dead stop a single 5hp 3 phase motor could easily get a sedan up and
moving. Another advantage is that a VFD driven motor inherently has traction control. Tires slipping in
poor conditions and burnouts by the kids down the street would be a thing of the past. Add to that the
fact that VFDs give motors braking capability similar to ABS, and you’re probably already wondering why
auto manufacturers aren’t using them yet. (We don’t know either)
The basic setup for an automobile using this configuration is that a small engine would turn a 3 phase
alternator. This combination would power the VFD used in this application, and the VFD would be
engineered using technology that is currently used in Industrial motor VFDs and engine management
technology that is currently used in portable Inverter Generators. Using inverter generator technology in
the VFD would be able to reduce engine power when it wasn’t needed, saving fuel. The VFDs would then
drive a motor connected to the differential that drives the front wheels of the car, similar to a modern
front wheel drive sedan. Although braking could be accomplished using only the VFDs and motors, the
T-CUTT would retain traditional disk brakes for additional safety. Since the breaking load factor is
reduced, the rotor and caliper size could also be reduced by 25-60% based on testing.
This drivetrain system has huge potential in vehicle lightweighting. If the generator was driven using a
small lightweight turbine engine, or even using an air cooled 1000cc Wankel rotary engine, the
combination of engine, generator, VFD, and drive motor could weigh less than 150lbs, significantly less
than the 350+ lbs of the combined weight of a modern engine and transmission. In fact, this design also
saves weight over electric car designs by eliminating heavy and expensive battery packs, although at the
expense of not being able to be powered using electricity obtained from alternative energy sources.
We’ve enjoyed putting this concept together for the Litecar challenge, and look forward in participating
in future challenges. Thank you for taking the time to read our T-CUTT concept and letting us know what
you think of it in the comment section.
Shiny Things Lab, Inc 2015