Drew's car-drag calculations got me thinking about vehicles with
somewhat higher efficiency.  Specifically, HPV's (and assisted HPV's).

There's an Australian outfit (whose URL I have mislaid) which has done
a lot of stuff with recumbent bikes and trikes.  One of the things they
tried was a fully-faired trike.  If I recall the numbers correctly, they
measured the drag at 10 newtons at 60 kilometers per hour (about 37 MPH).
Rolling resistance of high-pressure bike tires is usually negligible
compared to air drag, so it's likely that the net power requirement for
that vehicle (carrying 1 person) would be under 200 watts to cruise at
that speed.  Cruising at 30 MPH would need maybe 110 watts.

Last summer I did some riding up hills.  After a little time to whip
myself into shape, I was able to climb a 575 foot hill in a bit over
24 minutes.  This amounts to almost 150 watts of power exerted against
gravity alone; drag from air and the knobby tires went well beyond
that.  I know I could manage a 30 MPH cruise in such a highly faired
vehicle easily.

Then there's assists.  I just went to Meijer's and looked at batteries.
One of their offerings is a deep-cycle/starting unit rated at 23 amps
for 140 minutes.  This is about 54 amp-hours, or about 640 watt-hours.
It weighs perhaps 15 pounds.  If you powered the vehicle entirely from
the battery, you could cruise for about 3 hours at 37 MPH (111 miles)
or 6 hours at 30 MPH (180 miles).  The battery would let you store energy
when stopping or going down hills, and use it to start up again or climb
the next hill.  (That particular battery is rated at 650 cranking amps -
over 9 horsepower.  This is a lot more than I'd expect the motor to use.)

The fairing had quite a bit of area.  If you covered some of the upper
portions with solar cells, you should be able to get at least 50 watts
out of it.  This would let you cruise at perhaps 20 MPH indefinitely
in full sun, or get ~30 minutes of cruising at 30 MPH for every hour
parked in full sun.

Then there's combined power.  Pedalling would let you go somewhat faster,
or cruise for a lot longer.  Pedalling lightly for 100 watts and using
100 watts from the battery would give a speed of 37 MPH for over 6 hours
(220+ miles range).  With 50 watts from the solar panels, you'd be able
to cruise for 12 hours before exhausting the battery (450+ miles range).
With a dead battery, 50 watts of solar assist plus 100 watts pedalling
would get you almost 34 MPH.  50 watts of solar and pedalling hard for
200 watts would achieve about 40 MPH.

A vehicle with these capabilities is more than just a toy.  It starts
being a serious contender for commuting, light shopping and even
vacation travel.  A properly designed enclosed fairing offers protection
from rain, so a traveler in one would be able to contend with most
weather conditions aside from snow.

It would also do a lot for the driver.  Many people (myself included)
don't have enough opportunities for exercise.  If I could cruise at
nearly automobile speeds and didn't have to worry about getting soaked
if it rained, I'd be very likely to use one instead of a car.

Then there are the benefits to the environment.  Aside from a little
bit of tire noise, chain buzz and motor whine, such a vehicle would
be silent.  Besides sweat and CO2, there would be zero emissions.  It
might be charged from the grid at night, but 600 watt-hours costs less
than a dime.  Enlightened employers might put solar panels on carports
and let their employees charge from those.  A 1-meter by 50-cm panel
puts out around 50 watts peak; charging from 4 of those would have the
battery filled in 3 hours or so under full sun.

We should be able to build vehicles like this now.  Even the solar
panels aren't that expensive; at $3/watt, a solar-charging carport
would only need about $600 of panels.

So why aren't we?

26 responses total.

Insufficient market?

It certainly sounds interesting.  My only nit is that the deep cycle
batteries I've seen weigh more than 15 pounds; 30 is probably a better
estimate.  I'd probably take one of these if I could overcome my fears of
being crushed by a truck.  That's my main problem with recumbant bikes;
they're too low.  Drivers who can't be bothered to look for motorcycles
certainly won't see a recumbant that's lower than their hood.  And you'll be
at exactly the right height to suck in everyone else's exhaust.

Re #1:  Yeah, but *why*?  Something like this would be a natural
anyplace where pollution is bad, parking is at a premium or people
prize peace and quiet.  Many parts of California seem like they'd
qualify.

Re #2:  Maybe I don't know my own strength, but the battery didn't
feel like 30 pounds to me.  I wasn't about to carry it over to the
part of the store where they sold scales and check it. ;-)

I'm with you about the hazards from conventional vehicles.  I suppose
that one way to address that is to design "rails to trails" roadways,
other bikeways, and perhaps overhead bikeways (like pedestrian bridges,
only for HPV traffic and parallel to roadways) to provide limited-access
routes for HPV's and keep the automobiles safely away from them for
most of the time.

I would like to crunch the numbers to see what can be done with an ordinary
bicycle. But I don't have good data.

From what I can remember, on a good day I could with some effort maintain 15
MPH. If I was only putting 200 watts into the pedals, and if most of the
resistance was from air drag, then maintaining 60 MPH with the same overall
vehicle shape ought to require 4^3 == 64 times as much power, which is 12800
watts. This is enough power to push a _Grand Am_ at around 67 MPH! (See item
63.) Conversely (again assuming air drag being the dominant force) it ought
to be possible to *pedal* a _Grand Am_ at 15 MPH. Not a bad idea for an
emergency drive; it would get the car to the nearest gas station or at least
off the road and someplace relatively safe. But I don't quite buy it.

(OTOH, 200 watts converts to over 4000 food "Calories" per day, which I seem
 to remember as being considered a hearty diet.)

Clearly I need better data.

Further thoughts re #2:  Since you'd need tail lights anyway, put them
on a "wing" on a pylon, above head level.  Flashing red LEDs are highly
visible.  The exhaust-sucking problem isn't tractable.

Re #4:  You probably used quite a bit less than 200 watts on the bike.
Just how much less I'd have to guess, but if you were pedalling 80 RPM
with 50 pounds force and a 12-inch stroke, that's 67 ft-lb/sec or about
90 watts.  Pushing half your weight would make it 135 watts.

I don't know the drag coefficient of a human being on an upright bicycle
(not a racer), but it wouldn't surprise me if it was greater than one.
That power calculation might not be all that far off; cars are a lot
more slippery than they used to be.

Which doesn't mean that you could pedal the Grand Am at any significant
speed.  If I recall correctly, automobile tires have a rolling resistance
coefficient typically around 0.005-0.01.  Assuming the lower figure, a
vehicle weighing in at 3400 pounds would have 17 pounds of drag from the
tires alone.  200 watts is 147 ft-lb/sec; pushing against 17 pounds of
drag, you'd be able to manage barely 6 MPH.  For the higher drag, about
3 MPH.  And for a 1% uphill grade, you can cut that in half again.
Bike tires are a lot less draggy than car tires because of the lighter
sidewalls and higher pressures.

Typical resting metabolism is 75 watts or so, I think.  Actually doing
200 watts of work requires converting energy from food to ATP (which
ISTR is about 50% efficient) then to mechanical energy.  It wouldn't
surprise me if the net efficiency was 33% or so.  Pedalling at 200
watts for 2 hours would burn about 350 calories.  This is about a pound
of pure fat (not fat tissue, pure fat) in ten sessions.  If nothing
else, it would keep you really fit and strong in the legs.  There has
GOT to be demand for that, especially if you can combine it with your
daily commute!

I just biked halfway up the hill on my 23 pound bike with 18 pounds of library
books, then walked the rest of the way. I can bike all the way without a load.
I cannot imagine having to bike around with a 15 pound battery.  (I weigh 112
pounds).  Much less doing any shopping with it unless the battery did all the
work to get me home.  Also I would be scared stiff to bike 30 mph even without
cars around.  A fairing is not much protection if your bike even falls over
sideways, much less hits an object at that speed.  What weight battery would
produce 10 mph?  Five pounds, I would consider.  

Food is converted to ATP with 50% efficiency, and ATP converts to half work
and half heat, giving 25% overall efficiency, says my nutrition book.  
Energy consumed is proportional to body weight.  Sleeping consumes 0.9
kcal/kg/hr.  Vacuuming floor 4.2.  Presumably biking consumes more.
For a 50 kg person, vacuuming for a hour uses up 210 kcal.  Including
metabolic energy, says the book.  Other energy-consuming activies are writing,
driving car, doing laundry by machine.   

The book also says my ideal weight is 135.

I've gone 30 mph on a bike and it isn't that scary, though it does make you
want to wear a helmet. You also start to notice that unlike car wheels,
bike wheels aren't even remotely balanced.  I'd actually feel more
comfortable with that speed on a recumbant, because it'd be closer to the
ground and as a result probably more stable.  On a three wheeler, with 3/2
the contact patch and no worries about losing balace due to a skid, I'd have
no problem at all with speeds considerably higher.  It takes a *long* ways
to stop a bike from 30 mph, mostly because your contact patch is about the
size of two postage stamps.

As long as you're on something stable like a three-wheeled vehicle, you could
have a foot of some sort that is lowered to the ground for extra braking
power.  Rather like dragging your heels to keep your tricycle from speeding
downhill.  (Or at least it felt like speeding when I was five....)

Are their any good human powered four-wheel vehicles with battery assist?

I rode DELMAC with a couple of friends who each had full-faired recumbents
(Well, almost...)  They averaged around 25 MPH as I recall, not something I
was able to keep up with.  I tried a couple of hand dynometers at the Henry
Ford Museum this spring.  I was able to crank both of them to 760 watts.  My
two kids, 10 and 11, were able to manage about 200 watts.  It surprised
the dickens out of me that I was able to generate 1 HP with my arms!
There are several electric assisted bicycles on the market.  They all seem
to use 400 watt motors and are able to go about 30 miles at 15 MPH.  I
think a recumbent makes a lot more sense.  The visability issue is usually
addressed with a simple bicycle flag.  You have to be in pretty good shape
to ride for two hours at 15 MPH on a standard road bike.  200 watts is the
right order of magnitude but I'd guess twice that to maintain 15 MPH on a
good road bike. (400 watts)

Re #6:  The battery may weigh 30 pounds.  It will also give you in excess
of 250 watts of power for more than two hours.  Going 10 MPH, and assuming
20% losses, that would be an extra ten pounds of thrust; that would be
enough to push 100 pounds up a 10% grade.  That's the battery, 10 pounds
of motor and running gear, your 23-pound bike, 18 pounds of books, and 15
pounds of you.  Cut it to a 5% grade and the motor lifts all the weight
while you overcome air drag and tire friction.  I'm sure you're up to that.
Maybe you like fighting hills some days, but on other days maybe you'd
enjoy having a battery-powered motor to flatten them out for you.  A
smaller battery would carry less energy, so wouldn't push for as long
and probably wouldn't be as efficient at the same power level.

Thanks for the figures.  25% is less than I expected for efficiency.
It's no wonder I work up a sweat climbing a hill, I'm trying to
dissipate 600 watts or more!

Re #7:  It's not hard to balance a bike wheel, just wrap solder around the
spokes on the side that wants to be up until the wheel stops having a strong
preference.  Static balancing is about all you need for such a narrow wheel.

Stopping a bike is limited more by balance than contact patch.  On a standard
bicycle you sit very high and fairly close to the front wheel; if you brake
too hard, you go over the handlebars.  Recumbent bicycles have a much
shallower angle between the center of gravity and the front wheel contact
patches (on long-wheelbase models the angle is maybe 30 degrees) and you can
use a lot more braking power without going unstable.

Re #8:  Stick to braking the wheels.  Static friction is greater than sliding
friction, and if you "put down a foot" you're taking weight off the wheels
and reducing your steering ability.  In an emergency braking situation, this
is not desirable.

r.e. #7  I've never had to worry about wheel balance on either of the two
motorcycles I've owned.  Why should it be a problem on a bicycle?  I too
have ridden at 35+ MPH on bicycles and some are better than others.  I think
it was more to do with the frame geometry and stiffness than wheel balance.
I have an Italian bike that shakes back and forth violently around the
headset almost any time I take my hands off the bars at any speed.  At 30
plus MPH you can even feel it with both hands firmly planted on the bars.
I have the feeling that an old cruiser with a long wheel base, generous
angles and lots of fork rake would be more stable at high speeds than a
tightly angled racing bike with very little fork rake.

Was this on flat-level ground in calm air?

My bike starts to put a noticable shimmy into the handlebars at around 25 or
30 mph.  I assumed this was because of the wheel being unbalanced,
especially since the weight of the valve stem is enough to rotate it.  If I
had a spoke reflector I imagine it'd be even worse.

Re #9:  In the back of _Mother Earth News_, I often see an ad for
something called a "Bikecar".  It seems to be something like what
you're asking about.  Next time you see it in the magazine rack,
go through the classifieds and check it out.  (At least, I think
that's where I saw it.  Maybe it was _Home Power_.)

Re #14:  I think you'll find that the shimmy frequency is quite
a bit higher than the rate at which the wheel turns (higher
than 1/rev), and besides... how is an up-and-down oscillation
from an unbalanced wheel going to translate to a left-and-right
shaking of your frame?

I've noticed the same oscillation on bicycles of my own, and
I believe it's due to instabilities in the feedback between
the fork's caster and the frame itself.  If you can tighten or
stiffen the frame and fork far enough, the oscillation will go
away until a somewhat higher speed.

(This would be a really interesting exercise for a control theory
class, if you could come up with an equation for the phase delay
between the torque of the contact patch against the front fork
and the motion of the headset relative to the frame against the
frame's left/right flexibility.  Analyze when the oscillation
should start, and test it empirically.)

I had a bad shimmy on one of my first (second hand) motorcycles,
which turned out to be worn bearings in the fear-wheel fork: much
the same effect as russ mentioned. 

What is the grade on Spring St.?  I usually have no trouble biking up it and
assume it is more than 5%.  With a 30 pound battery, I would have to use the
battery to go up any hills so don't see the point, as it would also be more
work to pedal on level surfaces.  A very small solar-charged battery might
make some sense, for use 10 minutes out of an hour.  How long would they take
to recharge?  What is the minimum such a gadget could weigh?

I did a web search the other day and found the company which had
built the ultra-streamlined trike:  Greenspeed.

Leave it to the Ausies!  The Greeenspeed link is:
http://www.greenspeed.com.au/special.htm
Why is it that when I search on such topics that most of the intersting sites
are either in the down-under or the UK?

Back in the '70s various news and science/documentary TV shows would
occasionally show footage of what was supposed to be a wind-powered car. It
was a single seat vehicle that looked like a race car of some sort, with what
appeared to be an inverted-U shaped airfoil on the back.

I'd like to find out some technical info on it if possible. I've done a couple
of web searches using Jeeves and Alta-Vista, but have not managed to find
anything on this particular vehicle. Can anyone suggest a website or a search
string? What was the name of the inventor or the vehicle?

The URL for the Greenspeed machines is:
http://www.greenspeed.com.au/special.htm#Greenspeed Faired Trikes

Re #21:  That was actually created in Ann Arbor, IIRC.  It was
written up in the Ann Arbor Observer.  It was designed to be a
sail/electric hybrid, using motors to get up to a sufficient speed
where the wing-sail could un-stall (the sail, being fixed in
position, couldn't develop thrust from a standing start under most
conditions).  After that it could run on sail alone (given a
sufficient crosswind) and even run the motor regeneratively to
recharge the battery.

If the Ann Arbor Observer has an on-line index to past issues you
might be able to find the article.  I *think* it was the AAO...

I remember my mother telling me about this article, saying to myself
"that's impossible", reading the article and realizing immediately
that my first impression was dead wrong.

The vehicle didn't go anywhere commercially.  I recall that a variant
(without sails, with a small gas engine) was equipped with a warming
oven and marketed to Domino's for delivery work.  That died too.

The car was designed by James Amick.  I went to school with one of his sons
and we are good friends with another one of his sons.  The last time I saw
the car was about four years ago, in the garage of one of the sons.  Several
had been built to use as pizza delivery vehicles for Domino's Pizza, but
that fell through at the last minute.  It's a pretty cool concept but it
never took off.

Thanks a bunch, Klaus!

I still had not been able to find any technical details on this, though I did
find a website of someone selling the plans, along with an assortment of
everything from innovative to crackpottery.

I'm particularly interested in what the NACA profile of the wing is, and
whether the two halves are alligned inboard, outboard, or centered; and what
the lift/drag/moment/stall characteristics are.

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