Wednesday, April 23, 2014

Bicycle bodywork (3 of 4) Body shapes

Up to about jogging speed, (6 to 8 mph), power loss on a bike is for practical purposes about equal from mechanical, tire, and air drag.  Above that speed air drag rapidly becomes dominant, and since I wish to travel quickly over a longer distance between towns, it becomes a main consideration for the design of the third solar cargo bike.  Having a slippery shape (low Coefficient of drag), and a small frontal area (pushing less air around), are the most practical ways to reduce energy use, increase speed, and extend battery range in the forward direction, and increase stability and safety in crosswinds.  I'm working through the compromises between a very efficient shape, and ease of use.

The most important concept for air drag is the swirling air left after the bicycle passes by:
Swirling vortices pattern in stone garden path, Photo credit: Awesome stone path design

If something is pushed along through the air and the air flows around it smoothly and leaves still air behind it, (imagine a canoe coasting through water), it uses much less energy than if the air flow is broken up and swirling air is left behind (imagine a barge with eddies behind it in the water).

Still water in wake of a canoe, in laminar flow the water doesn't mix around.
Diagram credit: 

It takes energy to make the air swirl, and you can think of the swirling eddies as energy left behind and wasted:
Swirling eddies means wasted energy, Diagram credit: Wings of the World,

I'm going to ignore the Reynolds number concept here, because most bicycle aerodynamics are so lumpy, (like the turbulent example), that you are guaranteed to get eddies.  We don't need to predict them, just to reduce them.  I'm also going to assume this is for solo biking and ignore drafting.

Drag Coefficients for various generic shapes.
Air is flowing at them from the left.  A smaller number is less drag.
Notice the half sphere has less drag than the whole sphere.
Diagram credit:  TheOtherJesse,

A vehicle's frontal area at the leading edge of any bodywork would start at nothing, increase to a maximum to make room for me inside, and then decrease back to zero.  Because the air in the front is under pressure, it is possible to use a variety of smooth rounded shapes and the air flow will stay laminar.  A round sphere works well in front on airplanes and submarines, but on the road you don't want to push air underneath the vehicle (it causes weird handling and extra drag), so the shape ends up looking more like a person's chin (similar to the Streamlined Half-body on the chart above).  The problem location is when the body shape has reached it's maximum area and starts decreasing, causing the air pressure to drop:
Sphere in wind tunnel, air flowing from left.  Laminar air flow on left in air under pressure,
Turbulent on right in reduced pressure. Photo credit: unknown, from

Surrounding air pressure has to press the air flow back against the decreasing body shape for it to stay laminar.  If it doesn't, a vacuum forms, and turbulent air swirls in to fill it.  One way around this is with a long gradual taper- the classic teardrop aerodynamic shape:
Prius with aerodynamic vertically tapered tail added, Photo credit: unknown
This approach has problems with weight, crosswinds, and street maneuverability. 

Back in 1969 Porsche built a Grand Prix race car for the 24 hours of Le Mans that had a smooth horizontally tapered tail to reduce drag:
Porsche 917 long tail, 1969,  Photo credit: Porsche 917 owner's manual

Porsche had historically run small engines (their 356 series was related to the Volkswagen Beetle), and they needed aerodynamics and handling to make up for other manufacturer's larger engines. However this particular shape is very much like an airplane wing, and at speed it has a large amount of lift (i.e. starts to fly).  While this is good for tire wear, the drivers did not like not being able to steer, and in fact one driver died in a crash.  This flying problem is present in any vehicle that has a rounded upper body and a flat bottom, making it into the basic shape of a wing.  This lift happens not just with forward movement, but also with crosswinds. Production cars can have a ridge or a reverse camber in the hood, or square cornered fenders to break up the airflow and reduce this effect (but square corners on the front will cause a lot of drag).  Average cars have enough weight per surface area to lessen being pushed around, but a strong gust or crosswind may take a motorcycle or bike with rounded bodywork and unload the front tire (besides the sideways push), resulting in constant steering corrections.  The 917 was immediately modified with rear wings that pushed downwards:
Porsche 917K (Kurzheck, or short tail), 1970

The 917K had more drag and a slower top speed than the longtail, but it illustrates a bodywork trend that was being applied to everyday cars starting about that time- the Kammback.  If you can't have a long tapered tail, the next best thing is an abrupt cutoff.  This is the rear trunk spoiler on modern cars (even minivans)- it doesn't actually push down for traction as much as it separates the air flow for reduced drag.  Air flowing around a body will try to press in towards the surface of the decreasing second half, but if it can't fill the space completely then a vacuum forms.  The vacuum is filled by turbulent air, giving a large increase in drag.  A sharp lip also ruins any hope of maintaining laminar flow, but it reduces further loss by shedding the air flow and reducing the area the suction is working on.  This is why the half sphere in the chart above has less drag than a whole sphere, and is also the same principle at work with the dimples that promote turbulence and detach the air flow on a golf ball, instead of letting it cling for another quarter of an inch.
Left- newer Porsche 904 Kammback tail, right- older 550 Spyder classic teardrop tail.
Photo credit: Simon Gaspirc, Slovenia, Maisto model car collection

If you took the Half-Sphere in the above chart and turned it around with the flat face forward, the shape would be similar to a parachute, and the drag would be probably be closest to the Short Cylinder further down.  (A parachute has a vent which makes the airflow slightly different and increases drag even more.)   The Coefficient of drag for each generic shape relevant here is:
-Short cylinder               1.15
-Sphere                         0.47
-Half-Sphere                  0.42
-Stream lined half body  0.09
Unfortunately an upright bicycle riding position with arms, legs and head forward is probably closest to the parachute shape, and it is only acceptable because the area is small and the speed is slow.  Using the short cylinder as the worst case, then adding a spherical shape in the front would give about a 0.70 reduction in Cd, and adding a stream lined tail to that reduces Cd another 0.35.  In practice the leading edge is also more important because it is in undisturbed air (unless you are riding in traffic), whereas anything in behind is more likely to be in a turbulent airflow where streamlining is not as effective.   (The front tire aerodynamic rim matters more than the rear.)

A front bike fairing reduces drag by spreading the air flow apart in a laminar fashion over an area large enough to fit the rider in behind, but it can also reduce air drag further by cleanly shedding it's own air flow.  Often times lips are added to the top of a windscreen to aim the air flow above the rider for increased comfort, but adding something to the sides can be just as important for cleanly shedding the airflow.  This can be a small curve or lip, an extra thick section, or even molding glued on.  It is also possible to have secondary vents that feed controlled air to behind the fairing to reduce the strength of the vacuum, (air bleed ports have been tested on the trailing section of airplane wings for reducing drag and found to work, but the air supply system was too complex to be practical).

Kraig Schultz's Dustbin style front fairing, 2009, Photo credit: Kraig Schultz

Kraig Schultz's Delta-11 fairing with more comfortable riding position, 2011
Notice the very unaerodynamic tail with the battery box stuck out on a frame.
Photo credit: Kraig Schultz

Speed vs power for the two fairings shown above on Kraig's electric motorcycle.
Red line is 2009 Dustbin fairing, Blue is 2011 upright riding position fairing.
Despite the 2011 tail having much more drag, the power use is similar.
Tails in turbulent air matter much less than front fairings.  
Graph credit: Kraig Schultz,

One other consideration with fairings is the location of the Center of Pressure from the side.  The crosswind force on a fairing can be summed up and represented as a push on the side of the bike in one spot.  In a similar manner the weight of the bike can be summed to find a Center of Gravity (or Mass), and the tire traction and wheelbase also affect turning dynamics around a central point.  If the Center of Pressure is near the Center of Gravity or the central turning point, it won't affect handling much when a stiff crosswind hits.  However if the Center of Pressure is a distance in front of the other Centers, it will steer the bike in the wrong direction (with the wind), and if the Center of Pressure is behind the others, it will be self correcting and steer the bike into the wind.  This can be interpreted as either making the front fairing small to reduce it's effects, or including a rear fairing in the plans.  Note- this is a separate issue from mounting the fairing on the handlebars (instead of the frame), which is even worse than a forward Center of Pressure, because a crosswind will then directly steer the handlebars.

According to Simon Kidd, a contributing writer to Cycling, some of the generally accepted savings for aerodynamic modifications are:
-tires            20-22 watts saved
-brakes               5
-water bottles  4-7
-helmet             12
-jacket               8
-shoes             3-4
For a car with 160 hp (120,000 watts), this amount of energy doesn't matter, but for bike with 200 watts it does.   It is possible to gain a total of 60-70 watts from being careful with airflow while still keeping a more upright riding position.  

What is aero worth? A shopping list by Rainer Pivit of the improvement
in drag from various modifications. (Cost is in German Deutsch marks.)
Multiply the % advantage by 250 watts to get an average racing watt savings value,
or multiply by 100-200 watts for a slower commuter.
click on image to enlarge

With a generic Cd reduction of 0.7 for a front sphere, and 0.35 for a rear tail, is it worth trying to come up with a practical bike tail shape?  With a more enclosing bodywork, most of the items in the above chart don't matter, (I can wear street clothes), and the performance takes a large step up.  The human speed record enclosed bikes are traveling at 80 mph, and I've read several reports from velomobile riders of commuting in the 30 to 40 mph range (using human power only).  Weather wouldn't matter very much either.  But it would be difficult to ride through mud, or to do frequent stops and starts.  It would not be as well suited for Vermont roads and I couldn't put my feet down, I would probably have to get out and push it along occasionally.  Would a practical body shape maintain laminar flow all the way to the tail?
To give you an idea of the frontal area of the speed record bikes-
most of the three wheel velomobiles are about twice this size.
Photo credit: Trisled, Australia

Velomobiles do work quite well in a more paved situation.  I love this video because it gives a good idea of riding in a velomobile and it is also a bit of a travel show, with excellent tourist video of the area around Giessen, Germany.  They are traveling 4 mph up hills, averaging about 18 mph, and hitting 50 mph downhill (without electric motor):
Velomobile meeting Giessen 2010, Video credit: Wilfred Ketelaar

I still seem to be working towards an Ultra Light Vehicle in a way, and it still seems like two wheels is the best compromise for my use in Vermont.  The body compromise might be that the body work only has to be done well in the front, and can have smoothly discontinuous sections in behind, so that I can still put my feet out.  Compare the bulbous shape of the 2014 Le Mans race car below with the 1970 version above.  There are several rounded shapes over the main components that flow into each other, with all sorts of slots and vents in the bodywork to make this work.  It is not very smooth, but undoubtedly has spent a lot of time in the wind tunnel.  The emphasis has been placed on minimizing frontal area, and less on streamlining:
2014 Porsche 919 hybrid electric race cars at the Silverstone race track, UK
Photo credit: Porsche

This seems like the most productive way to go for a street errands bike.  Maybe aerodynamic panniers that divert the cold winter air? In many respects this plan is very similar to town energy committee goals for buildings- first reduce the energy needed (i.e. conservation- by a smaller house or less vehicle frontal area), second make the energy you do use more efficient (a better heating system or vehicle aerodynamics), and then third add renewable energy.

 The next post in this aero series will look at taxifiets, the ELF, velomobiles, bubbles, some German project bikes, and other things on the road.

Monday, April 14, 2014

Waiting for the battery

I've been waiting for the battery before building the battery box, but it has not gone smoothly.  The promised delivery time of 7 to 8 weeks has become 11 weeks, the tracking number was entered incorrectly, and supposedly the battery is "now in customs".  I need to get started, the snow has finally melted down to just the banks and shady spots here, so I'll guess what the actual dimensions of the battery are, (they bulge out a little), and then hope the battery fits.  Maybe it will show up sometime in the next month or two, undamaged.  If I do much more of this, I'll probably start assembling the pouch cells into batteries myself.

The roads here have been good this spring, and I've been taking rides into the center through the winter, but not longer ones up to White River Junction.  I just don't want to get the bakfiets dirty...  
This isn't my road this year (thank you town road crew!),
the photo is from Fat Toad farm a couple of towns away in Brookfield.

Even riding in mid winter was rewarding, (and the mud is frozen).
Graph Credit: Knowledge Institute Mobility study, 2007

And of course it made me feel superhuman:
Cartoon credit: Stephan Pastis, Pearls Before Swine
Click on image to enlarge.

And riding along was much different than being in a car:
Abra CARdabra, take me home, Credit: Ryan North,
Click on image to enlarge.

Photo credit:  Catalin Olteanu

Thursday, April 3, 2014

Bicycle bodywork (2 of 4) Power numbers

OK, now that I've got your attention, I'll say the usual "It's easy!"
to make sure that all of you who don't like math are properly scared.
Equation credit: Peter Cox, Energy and the Bicycle – Human powered vehicles in perspective

If you look at the equation above, you'll notice there are five plus signs in it.  That's because there are several things that drain your energy while riding a bike, and they are all being added together.  From biggest to smallest when riding on an average road at 15 mph without any wind, they are:
-air resistance (by far the biggest load)
-rolling resistance (tires and bearings)
-gravity (hills)
-acceleration (stopping and starting)
There are other things that drain energy (riding next to a mountain of magnetic ore, air turbulence from cars, eating too much at the church supper before riding), but they aren't usually entered into the equation.

The reason why the equation looks so complicated is because everything but the kitchen sink has been put into it and common terms have been canceled out, so it doesn't make sense anymore.  If you pull the things back out, you can get a much better idea of where the energy goes.  It's also possible to leave out the gravity or acceleration parts if you don't need them and get a much simpler equation.

Air resistance depends on how fast you go, how big you are, how slippery of a shape you have, and whether you are pedaling in thick air at sea level or thin air in the mountains.  The equation is like this:
Air resistance = Velocity cubed x Frontal Area x Coefficient of drag x Air density
Notice that everything is simply multiplied together, so that if you are twice as slippery (drag is half as big), you can be twice the size and still use the same power.  The part that should stick out like a red flag is Velocity, because it gets cubed.  (The physical drag increases proportional to the square of velocity, but because there is less time for doing a task at a faster speed, the power (watts) that must be used increases by the cube.)  Riding along at 6 mph would be a cube of 216, but riding at 20 mph is a cube of 8000, meaning 37 times as much energy is needed.  You'd have to be 37 times smaller, or 37 times slipperier, to stay at the same power level.

Added April 19, 2014:
Thinking back over the last several years of town energy committee work, I've realized the above energy explanation needs to be better.  Many people I've talked with haven't known the difference between kWh (kilo Watt hours, or the quantity of energy), and kW (kilo Watts, or power - the rate the energy is flowing) on their household electric bill.  Using the common analogy to plumbing,  kWh is a quantity similar to a gallon, and kW is similar to the rate the gallons are flowing through the pipe, (gallons per hour).  Since we can't collect a bucketful of electrons, we define their equivalent to a gallon as the quantity of electricity that has flowed at a specified rate (kW) for one hour.  Changing over to electric bikes, we get rid of the kilo (1000) prefix because a bike uses less electricity than a house, and say that the electricity is flowing to the motor at for example 200 Watts.  Then if the trip lasts an hour, the energy used was 200 Watt hours.

As a practical example for bicycle Air Resistance vs battery range, let's compare bike riding at 10 mph (running speed), and 20 mph.  The slower speed might use 30 Watts (depending on aerodynamics), and riding for one hour would use 30 Watt hours of energy.  But air drag increases as the square of speed, and because the time for traveling the same distance is half as long, the actual power needed increases as the cube.  Two thirds way down this Wikipedia page:  is this equation:

P = gmVg(K1+s) + K2Va(squared)Vg

We can toss out the first part, gmVg(K1+s), because it is about friction and hills, and simplify the second Air Resistance part to Power = K2Va(cubed).   Since K2 is a constant, power needed from the motor is simply proportional to the cube of speed Va.

Doubling the speed to 20 mph would need 8 times the power (2 cubed), or 240 Watts.  (You can also calculate the numbers using K2 = 0.03 for mph and watts units.  Note that K2 would be larger for more air resistance, and smaller for less.)  However the trip would take only half an hour, not a whole hour, so the total energy used would be half of 240, or 120 Watt hours.   Thus to go twice as fast, the motor would need to be 8 times as powerful (240 Watts/30 Watts), and the battery would need to have 4 times as much energy capacity (120 Wh/30 Wh).

You can see that a little bit of work on aerodynamics goes a long way...

I should mention that no one has a clue what the Coefficient of drag (Cd) of a design is, until it is built and tested in a wind tunnel.  I've included a couple of generic charts below to help you make a guess for your project, and compare it with other projects.

Rolling resistance is the tire deforming as it hits the ground (bigger), and the friction in the bearings and chain (smaller- as long as you oil your chain).  The Coefficient of rolling resistance (Crr) is the force needed to move the bike forward divided by the force downward (weight) and is effectively independent of speed, but again velocity must be included to calculate the power needed because of the effect of a shorter amount of time:
Power used for rolling = Velocity x Crr x weight + Velocity x bearing drag
Crr is often given values like this:
     0 is no drag at all
     0.001  for a wooden indoor bike track with slick tires
     (i.e. it takes 0.001 pound of pushing to move 1 pound of weight forward)
     0.004  for a typical 100 psi road tire
     0.0044 for 27"x 1.25" road racing clincher tires at 95 psi on a smooth road
     0.007  average bike- good
     0.008  bad asphalt
     0.010  average bike- not so good
     0.013  27" x 2.25" 45 psi BMX knobby tires
Clunker average tires can have twice the rolling resistance that racing road tires have.  Weight is included because the heavier you press down the more the tire deforms, and the larger rubber flexing absorbs more energy.  High tire pressure reduces deforming, but when the tires are so hard that they cannot flex, the bike and rider are pushed upwards over every little bump.  This is lost energy because it isn't converted to forward motion by coasting back down the other side of the bump (you just fly through the air for an instant), so a very tiny amount of tire flex will actually give the lowest energy use.  I should mention here that narrow tires aren't faster because they flex less, it's because they have a smaller frontal area with less air resistance, (actually fat tires have less energy loss due to flexing, and if you ride only at slow speeds then fat tires are a better choice).  Aerodynamic rims are used to further save energy.
Air turbulence (i.e. lost energy) around a tire traveling towards the left.
Photo credit: Schwalbe Ironman Triathlon tire simulation
On racing motorcycles that are in an open bodywork class (front and rear axles
and driver must be visible from the side) there is often a very tightly fitting
aerodynamic front fender to try to smooth out this turbulence.  This type of fender
is not practical on the street, where there must be a larger gap so that mud buildup
doesn't rip the fender off.  
Bearing drag is so small that it can be ignored for many general calculations.  As long as your chain isn't a rusted solid piece of metal, then doubling a very small number is still a very small number, with not much chance of using it to improve the design of a cargo bike.  (Just don't put a dozen bearings, chains, and gears in your project.)

Gravity can be thought of as you lifting yourself and your bike up or down a hill.  The faster you lift per unit of time, the more power that is needed, so Velocity is included again:
Power needed for hills = Velocity x (Mass x Gravity constant) x % Grade
As I briefly mentioned in the Regeneration post, you do not get all the energy back going down the other side of the hill that you put in when climbing.  Some is lost to braking, and some to air resistance, so the useful energy in the downhill momentum is less.  The best thing you can do here is to make the bike (and yourself) lighter.

Acceleration is the same equation as gravity, just in a horizontal direction, so you remove the % grade number, and the fixed gravity constant is changed to your desired acceleration:
Power needed for acceleration = Velocity x Mass x Rate of acceleration
Sometimes the rotational mass of the wheels is included in more complete equations, but if you are not accelerating it doesn't matter for other considerations.
Like gravity there isn't much to work with here other than keeping things light.

Drag forces on a bike relative to speed.  (Wind is air resistance,
Roll is the tires, Drivetrain is bearing drag)
This is rolling down the road numbers, gravity and acceleration have been left out.
Credit: Drag Forces in Formulas, Article for Radfahren magazine, Rainer Pivit

As you can see by looking at the parts of the power equation and the above graph, most of the energy lost is due to air resistance, and aside from keeping your tires inflated, oiling the chain and bearings, and traveling slower, the best power efficiency improvements are found in reducing air resistance..  (Tightening up loose clothing is an easy fix.)

Fortunately if you don't wish to sum up equations, there are plenty of Fitness Freaks who ride bikes and only want to know how many watts they are putting out and calories they've burned, without doing the math either.  In the sidebar on the right you'll see five web based calculators in the Tech list to help you pick out one you like:
-Oldest bike calculator
-Kreuzotter bike calculator
-Lamancusa bike calculator
-Geocities bike calculator
-Analytic Cycling bike calculator

Now that we have some basics, we start getting into the fun stuff of how they interact.  Here are a few charts and graphs for roughing out some boundaries for working on this:

How long a rider can last at different power levels.  Do not use these numbers
for design unless you want to arrive exhausted.  Smaller power levels,
such as 50 to 200 watts are probably OK for an average rider on an average trip,
and 300 watts for a short time up a hill.  (746 watts is one horsepower.)
Source: "NASA, 1964", part of motorcycle aerodynamics essay from Kraig Schultz, , original document unknown

Drag and power numbers for different bicycle riding positions.
In the first column of numbers, the upper number is air resistance,
the lower is rolling resistance, both are in pounds of force at a speed of 20 mph.
The second column is the Cd number for that configuration, note that a commuter bike
(Dutch Oma bike) has a Cd of 1.1, and the speed record bike's shape is closer to 0.1.
One person's power, (or one battery's worth), can go 10 times further in the streamlined body.
The sixth column is how much energy that riding position uses relative to a touring bike.
Source: The Aerodynamics of Human Powered Land Vehicles, 
Albert Gross, Chester Kyle, Douglas Malewicki, Human Powered Vehicle Association
The cleanest copy I can find of this chart for downloading is from Kraig Schultz at:

A common shorthand is CdA, which is the Coefficient of drag x the frontal Area.  With it you can compare different body configurations without having to calculate out the rest of the power equation for many different velocities, it's the fourth column in both the chart above and this chart, (note that the wattage columns are for 22 mph only):
Energy use of various bike types.
The fifth column is watts needed due to air drag at 22 mph.
The last column is watts needed due to rolling resistance at 22 mph.
Credit: IHPVA Human Power Issue Number 54

Commuter bike (Dutch Oma bike), Photo credit: Berlin Cycle Chic
The top line, "Upright commuting bike", lists 345 watts to push against air resistance at 22 mph, and 53 watts for rolling resistance.  Since we know an average commuter is good for 150-200 watts, we know that 22 mph isn't going to happen for more than a few seconds.  This is a problem when doing long errands to the next town.  Adding an electric motor would make it possible to travel faster, but at the cost of using 400 watts of energy.  Trying to design something with longer battery range will require paying attention to air resistance.

Looking at the fourth line down "Road bike + Zzipper fairing", the air resistance becomes 157 watts and the rolling resistance is 38 watts, a 200 w improvement from a front mounted bubble, lower riding position, and more efficient tires:
Eric Brill on 1984 Kestrel with Zzipper zz-os fairing, Photo credit:
This bike is using about half the energy of an upright commuter bike.
It doesn't offer much rain protection or place to mount solar panels though,
and I don't want to ride 30 miles bent forward.

Frontal area can be greatly reduced by riding position.
Commuter, touring, road racing, flat track, and touring and
racing recumbent frontal areas.  Photo credit:

Less frontal area and a fairing- a long wheelbase recumbent with Zzipper fairing.
Lowering the riding position with a pedal forward design reduces the frontal area,
and the fairing reduces drag.  My estimate for this bike's frontal area loss
based on the Kestrel above is a little over 100 watts for air resistance,
and about 45 watts of rolling resistance.  This should have well over twice the battery range
of an upright commuter bike.  A problem with this example is the fairing is fork mounted,
and will be steered by crosswinds.  Photo credit:

In the next post I'll look at Cd, air flow, and play with some basic shapes used in airflow design.

Wednesday, April 2, 2014

Less Car More Go film being made

Liz Canning has been trying to make a film about Cargo bikes for the last 3 years, and just began a Kickstarter campaign for it that will be running for the next 38 days:

If you would like to see what she is working on, there are links to the first two film sections in the Working Bike Sites sidebar list, under "Liz Canning's movie phase 1 / phase 2".  She's been collecting video from around the country, and I hope she gets enough support to finish the movie.

Tuesday, April 1, 2014

Vermont Walk / Bike Summit 2014 report

Chittenden County Regional Planning Commission did a nice job of hosting this year's Vermont Walk / Bike Summit.  It had only a slight bias towards the more urban areas (as Chapin Spencer noted "Yes, Vermont does have cities with over 5,000 people"), but I did learn a lot about more rural initiatives.
The first thing I did after unloading the bike was a short ride up the hill to look out over Lake Champlain, which is still frozen over.  Fortunately it stayed dry the whole day so that activities could go on outside the conference too.
After riding around a bit, (I love this bike and the electric drive!), I went back to the Hilton and registered, and then brought everything inside and cruised the other displays.  There were several Complete Streets orientated engineering firms waiting to design downtowns, (many municipal people were attending), but one manual I picked up (actually begged for the next to last copy) was from the Vermont Department of Health, here is the online version:
This is a good summary of Complete Streets principles, and highly readable.  The morning presentation I attended was about intersection and street design, it was good but more for Burlington, I attended mainly because one of the presenters is working on the Hartland 3 Corners (square) redesign in the center of my town.

There were also displays from the UVM Transportation Research Center, a few cycling companies,, Local Motion, and Vermont Bike and Ped coalition.  It took a while to absorb the info.
This Invacare TopEnd Excelerator XLT Gold handcycle is so hot!  The young woman who owned it said that she had knobby tires on it at first for riding on roads around her town, but ended up racing it and putting on racing tires.  For those of you who have read my posts about Front Fork Geometry, look at the head tube angle on this!  It's shallower than many choppers, but the trail still looks reasonable.

Mayor Miro Weinberger stopped in during lunch to give a summary of Burlington's efforts at making the city a more bike and ped friendly place, and then Caroline Samponaro of Transportation Alternatives in NYC gave the keynote address.  Even though her experience was urban, it was great to learn more about serious relations with traffic.

After lunch I attended fellow cargo bike enthusiast Dave Cohen's presentation about the sensory deprivation caused by cars.  He is an ecopsychologist from Brattleboro, and covered the takeover of American streets by automobiles during the early 1900's, and where it has lead our transportation planning today. He summarized the resulting impacts on our lifestyle, and explored using cargo bikes as a car alternative.  There were about 200 people attending the conference, and about 60 to 70 of them attended his presentation.  When leaving the lecture many stopped to look at my cargo bike display outside the door.
I always have a great time talking with people about building the bike.  Most of the questions are about the electric drive, and less about the cargo bike aspect. The most common questions are about the basics, many people don't notice the motor in the rear hub, so they wonder what the solar panels are for, and then we usually talk about driving the bike, and the battery and range,
Albert Echt and Deb Sachs stopped to look at the bike.
This conference was extra rewarding because there were people there who work on bikes and professionals working on transportation issues, so we also talked about details and practical technical aspects of the solar electric cargo bike.

However the real fun came after the conference ended at 5 and we took the bike outside for test rides.
Dave Cohen using the electric drive.
Ron Manganiello of Bike Recycle Designs covering some ground.  Getting from my town to the next is one of the design goals for this bike, something that most cargo trikes and the ELF won't do as well.
Thomas Cohen of Local Motion pulling in after a short ride.  On the first ride most people start out slow, but after a minute of getting used to the bike, it handles pretty good.
I have to end with this picture, because it is Stuart Lindsay from the Burlington Walk/Bike Council (northwest VT), Dave Cohen from Brattleboro (southeast VT), and me from the center part of the state, all talking utility bicycling. 

Footnote: There were 6 test rides, and when I recharged the battery the energy usage was 68.8 watt hours for 3.671 miles, which is 18.7 watt hours per mile.  This is equivalent to 1765 miles per gallon.  I would characterize these test rides as using more energy than an average ride.  The Kill A Watt meter measured 0.08 kWh (80 watt hours) to recharge the battery, which at $0.15 residential electricity rate is 1.2 cents worth of electricity.  The difference between the Cycle Analyst's tally of 68.8 watt hours and the Kill A Watt's 80 is the efficiency of the charger, which works out to 86%.