

Transparent plug-in hybrid retrofit for any car - rocky1138
http://mtsunews.com/wheel-hub-retrofit-update/

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rejuvenile
I wonder what the efficiency numbers are. The retrofit will add weight to the
car, but won't remove any in the form of a lighter engine. There is also no
regenerative breaking, and presumably no way to disengage the engine to run
purely on electric power. I also wonder, speculatively, if the power assist
will interact degenerately with the existing automatic transmission--perhaps
running the car in a less than optimally efficient gear.

~~~
tocomment
Actually I don't see why they can't put regenerative braking in. The motors
double as generators and they already have a connection running to the
battery. And the motors are right next to the brakes so they could easily
detect when the brakes come on.

Anyone know?

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pdonis
To do regenerative braking the motors have to know when you're braking. That
means hooking into the car's controls to detect when the brake pedal is
pressed. It also means preventing the normal mechanical brakes from engaging
while regenerative braking is being done. _And_ it means being able to engage
the mechanical brakes if the batteries can't accept incoming energy fast
enough. All this is a highly non-trivial controls problem, which requires
close integration with the car's control computers. I don't see how that can
be done with a retrofit.

~~~
rcvassallo
You're making the problem harder than it needs to be.

Knowing when the car is braking is trivial - the vast majority have a
dedicated brake switch wire.

Why do you want to prevent the normal brakes from engaging when regen braking
is happening? Since the electric motors are on the rear wheels, braking
traction will be severely limited. The majority of braking needs to happen up
front due to dynamic weight transfer.

Instead, use a simple brake balance controllers to reduce the mechanic braking
effort at the rear and make up for it with the regenerative braking. Brake
balance controllers are readily available in the aftermarket, so this is a
solved problem.

~~~
jack-r-abbit
The way the video describes the controller in the trunk, I believe it is not
interfaced directly to the car. I kind of assumed it uses an accelerometer to
notice the car is moving forward and engages the DC motors. If this is true, I
would imagine that the same accelerometer could notice that the car is
braking.

~~~
rcvassallo
Not sure why the trunk mount is relevant for interfacing with the car. The
brake switch signal activates your brake lights, those are typically at the
rear of the car :)

Admittedly, for a universal application you want to interface with as little
of the car as possible.

That said, in the US all cars made after 1995 comply with certain On-Board
Diagnostics protocols (OBD-II) so you can interface with several standard
systems.

One such sensor available in OBDII is the VSS or the Vehicle Speed Sensor.
Check out a device like the Scan-Gauge[1] to get an idea of other sensor that
can be interfaced with universally. It would be trivial to run some wire under
the carpet and plug into the OBDII port to give the hybrid system access to
all kinds of engine & sensor info.

[1] <http://www.scangauge.com/products/scangaugeii/>

~~~
jack-r-abbit
> _Not sure why the trunk mount is relevant for interfacing with the car._

I wasn't saying that. Let me rephrase: The way the video describes the
controller (the one in the trunk)...

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eslachance
This is awesome, except for one thing. As with all hybrid kits, you lose trunk
space. Unfortunately, if I can't fit my groceries as well as the stroller for
my daughter, it's out of the question. Obviously not _everyone_ requires this,
but how many commuters do you think never need the trunk space?

These batteries and controllers need to find another place. On the roof of the
car, perhaps, unless you're an outdoor sports person and need racks for bikes
or a kayak?

~~~
FelixP
They don't show any photos, but I wouldn't be surprised if the batteries don't
occupy the _entire_ trunk, especially on the production model. Obviously this
would also be dependent on the size of the original vehicle as well.

~~~
liberatus
FWIW 4:22 of the video shows the trunk. It ain't small.

~~~
illumin8
He mentioned the prototype is larger than it needs to be. They needed to have
easy access to data ports to pull diagnostics info from the batteries and
controllers.

The size of the final version should be about the size of a carry-on bag.

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jhaglund
I am not an engineer, but seems a retrofit like this adds un-sprung weight
which increases wear and changes handling.

How about put the motors in a new differential? It'd take a larger casing, but
you could apply the electric torque to each wheel too.

~~~
lloeki
You're just concerned about unsprung weight? What about the now positive
torque applied to those wheels? That's the whole basis of how ESP works:
applying a counter-force to a wheel in order to balance the car thanks to the
torque generated around the yaw axis, so how does each motor knows what force
to apply so as not to actually throw the vehicle off balance?

Think RWD cars. Floor it on a curve and you can go into a tailspin. But RWD
cars are designed as having power on the rear while FWD cars have not, so the
effect could be much more dramatic with much less force.

It's not _that_ complex to solve... as long as you have access to the various
sensors (Hall, inertia... if any) and actual decisions of the ECU, and design
data (i.e everything the manufacturer has), but piggybacking on it is quite an
endeavor. And it has to be done for _each car model_ since they all differ
dynamically and in hardware.

~~~
rocky1138
One assumes that drivers will need to drive with ESP off after the retrofit.

~~~
lloeki
I'm not even considering collaboration/conflict between ESP and the retrofit.
A car whose chassis is designed to have force applied on the front wheels only
(hence with rear wheels freewheeling) may not react properly at all to rear
wheels having power. From suspension to weight distribution to force
transmission through the chassis rigidity.

For example (oversimplification), FWD cars have their suspension balanced to
be stiffer on the rear because it gives the front more grip (and the reverse
is true for RWD cars). This stiffness would not usually result in a loss of
grip under load (e.g in a corner), but adding a force to the wheel may
overcome the remaining grip and throw the car into a tailspin.

Applying a rotating force on the wheels creates a pinching effect, momentarily
changing the parallelism. This effect is sufficiently noticeable that some
cars are designed with wheels _not_ parallel at rest, so that when you drive
on the highway (and thus apply some power to the wheels) the wheels are
parallel.

There are countless scenarios where things can go wrong because you're simply
doing something that the car was not designed to handle.

(For the curious, the Forza Motorsports series has a nice sandbox mode
allowing to experiment with various settings by changing them on the fly, and
the inline help explains succinctly the impact of each knob on your car's
behavior)

~~~
rocky1138
That's all well and good, but does it make a difference under 50km/h in town?

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waivej
It seems like an excellent project to work on.

Hybrids do well on gasoline because they have efficient undersized engines
combined with light weight and excellent aerodynamics. This retrofit wouldn't
change any of those things so I doubt it would have the claimed mpg benefit on
a long drive. With a big battery pack, I could see it boosting MPG in city
driving but it doesn't have gearing to use the motors at high speeds like
highway driving. The big battery pack hurts city driving because you need to
accelerate and decelerate that added mass.

It reminds me of similar retrofits that might be comparable and easier:

1) Replace the alternator (or AC) with a small 6-10hp motor. This is like a
DIY version of the Honda IMA. I think GM was promoting something like this.
You're limited by the power a belt can transmit, but it does go through the
transmission and allows easy stop/start of the engine (ex: at a traffic
light).

2) Remove the rear drive-shaft from a 4WD like a truck and attach a motor to
the differential. This is also somewhat easy and a truck is better equipped
for carrying batteries. There was a Jeep design that did this. Stay in "4wd"
without applying power to the motor and it's like a front wheel drive. The
downside is that the motor isn't geared so it's only good for one speed range
(perhaps low end torque).

Unfortunately, both designs are just mild hybrids. To really go far enough
with the motor you need lots of batteries. For example, the 80lb NiMH pack in
my Insight can barely go a few miles. Regen makes sense but you lose a
surprising amount of energy charging/discharging. I get the best gas mileage
trying not to use the hybrid systems (even in city driving).

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pilom
Should be "any front-wheel drive car." It looks to me that they replace the
rear axle with 2 electric motors (one on each side). I don't think they could
install this on a car with powered rear wheels.

~~~
fein
I'm actually more concerned with how they've changed the design for rear drum
brakes vs. rear disc brakes.

If I recall, that model Accord wagon had rear drum brakes.

edit: yep, it does have rear drums. I'm VERY curious to see how they intend to
make this work for disc brakes, especially when the calipers have to wrap
around that huge assembly.

The idea of rolling down the road and having a few magnets come flying off
also scares the daylights out of me.

~~~
yello_downunder
I don't see how the design could be adapted to disc brakes. The majority of
vehicles sold have drum brakes on the rear, probably close to the 90% figure
the person in the video mentions. Furthermore, cars with disc brakes on the
back often have a cheaper trim version equipped with drum brakes, so reverting
these back to drum brakes would not be overly difficult - swap out the
mechanical bits and adjust the brake bias.

~~~
pilom
I would be very surprised if 90% of vehicles use drum brakes on the rear
wheels (at least in the US). Every car that myself, my parents, my wife, her
parents, have ever owned (except for one) has had disk brakes on the rear
wheels. While I know I'm using proof by anecdote, I'm just saying I would be
very surprised if it were even the majority.

~~~
kevinpet
Unless your parents are very young, or exclusively drove sports cars their
entire life, that's almost certainly not true. Front disc / rear drum was a
standard design for a long time.

You're more likely to notice disc brakes -- they are more visible from outside
the car and require slightly more frequent maintenance -- so you may not be
able to think of many cars with rear drums.

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ck2
My electric bicycle wheel works the same way.

Electric motors are great at low speed torque which is why it helps the gas
milage so much with city driving. I bet it also can take a chunk out of the
0-60 time.

The next step is to add power regeneration during braking.

If this is practical, I am sure the big car manufacturers will just do an end-
run around any patent with their own tweaks and then it will just be a lawsuit
battle.

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tocomment
Is there anyway someone could offer natural gas conversions for around this
same price? That would also give you a huge savings (possibly comparable to
this).

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yello_downunder
It is unlikely that a natural gas conversion could be done for this price. The
tanks to hold natural gas are quite expensive and I doubt we will find a
significantly better way to build a high pressure tank than we already know
about.

Then you have the issue about a filling station.

Then considering taxes on fuel are nearing 50% of fuel cost, you're right
around where this conversion gets you. (I don't know if NG at the pump would
be taxed)

Electric solutions work around the issue of fuel cost and filling locations
nicely. Electricity is cheap and basically available in every garage. If you
have a garage. Having a hybrid electric works around the issues of limited
range and cold weather.

~~~
tocomment
I'm just thinking people would fill up at home. If nothing else use it for
commuting. Most Americans already have a natural gas line coming into their
house.

So charging stations wouldn't be necessary and taxes wouldn't be an issue
either.

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robomartin
Another fine example of an IMPLEMENTATION, not an INVENTION that should not
receive any patents whatsoever.

Good work, of course, but, if you tasked any capable team of engineers to
build a DC brushless motor as a retrofit into a car wheel this is what you
would get. In fact, there are thousands of teams all over the world that could
do this inside of six to twelve months with equal results.

~~~
lloeki
This is probably already patented in some way by Peugeot since that's (almost)
how their 'hybrid4' (diesel+electric) work. The engine is not in the wheels
but that's really not a stretch to place them there. I would be surprised it
they did not try it.

[0] [http://carscoop.blogspot.com/2010/08/new-
peugeot-3008-hybrid...](http://carscoop.blogspot.com/2010/08/new-
peugeot-3008-hybrid4-world-first.html)

~~~
Lagged2Death
Putting the motor in the wheels must produce a hefty increase in rotating mass
and in un-sprung mass, both undesirable. It's necessary in the case of a
retrofit, but in a from-scratch design I doubt an automotive engineer would
try this.

~~~
lloeki
They do:
[http://www.youtube.com/watch?v=gnUGvfCkvbk&feature=playe...](http://www.youtube.com/watch?v=gnUGvfCkvbk&feature=player_detailpage#t=29s)

Make the rims part of the engines (or the opposite).

~~~
Lagged2Death
That video is about a show car, and it says the technology will show up in he
2010 model year. But it didn't happen.

Electric cars face big challenges in terms of cost and weight; I expect that a
design like this, which increases both, is far, far away.

The Tesla cars, which cost a huge amount of money, don't do things this way.
The Toyota hybrid system, probably the most developed in the world at the
moment, doesn't do things this way. The people who designed those things were
smart people.

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stcredzero
When I lived in Houston, I would've loved to see a hybrid retrofit of the type
the original Honda Insight had -- a motor/flywheel. That could have turned my
old biodiesel Mercedes into an acceptable hurricane emergency diesel power
generator.

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3amOpsGuy
Is there potentially a major efficiency issue here, through adding rotational
mass in such quantity?

~~~
yello_downunder
The design _decreases_ the efficiency of the car in total, through increase in
weight, increase in mass and probably a few other things we haven't thought
of. It makes up for it by allowing you to replace gasoline with electricity,
which is much cheaper.

Less efficient, much cheaper, and hopefully less environmentally harmful.

I like what this solution offers - a chance for someone like me who will
probably never buy a new car to easily modify an older car to run at least
partially off electricity.

