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Velomobiles: The most efficient form of individual transport

Unread postPosted: Tue 30 Jul 2019, 02:13:46
by The_Toecutter
I've built one off of a KMX frame with added front suspension. It currently has no motor and is entirely pedal-powered. Here's videos of me doing 30-40 mph down a street in the local hood:

It would be much faster if I got the aerodynamics right, but on this first build, I did get the ergonomics correct for my needs the first try. It's very comfortable to ride and easy to use, with plenty of storage space. It can also be brought through a doorway into an apartment.

From downhill testing, I was able to derive a CdA figure of 0.25 m^2, but commercial models exist that have less than 1/5th that amount of aerodynamic drag. With the first body I made for it shown in the above videos, it required approximately 500W of power to hold 30 mph on flat ground. I've reached more than 50 mph downhill in it and it has proven stable while making a lane change at that speed over imperfect roads, and the mechanical braking system has proven adequate.

I’ve put more than 500 miles a month on it since building it. I no longer use a car for transportation(I might again one day when I can finally get the electric Triumph GT6 finished).

Specs as shown in the above videos were as follows:

-KMX framekit with added coroplast body; unladen weight of about 65 lbs with a CdA of 0.25 m^2
-Exa gas shocks set up for 60 psi for front suspension
-Ackerman steering
-Velocity USA 20" double-walled rims up front with 13ga spokes with 26" rear wheel with 12ga spokes
-Schwalbe Marathon Greenguard 20x1.5" e-bike tires up front rated for 50 km/h continuous use with a Schwalbe Marathon Plus Tour 26x1.5" tire in the rear
-Shimano Tourney 165mm crankset with 28/38/48T gearing and a DNP Epoch 32-11T 7-speed freewheel
-KMC "gold" 7/8-speed chain

Of course, I plan to put an electric motor to it when financing permits.

I took the body off last year to make repairs to the drivetrain and have the next body shell designed, and am waiting on a friend to get his truck legal so I can pick up the plastic sheet I need to finish the 2nd design iteration of the shell. The goal is a CdA of 0.12 m^2, which would allow me to do 30 mph on only 250W of power, and possibly reach close to 50 mph on flat ground when pedaling hard for short periods.

Adding a motor to it, with enough power, could make it capable of performing like a car.

The long term goal is to build a vehicle with the following traits:

-Less than 100 lbs total unladen vehicle weight. This figure includes having installed the motor, battery, and rest of electric drive system with the vehicle ready to ride. Just add rider, tools, luggage, ect. to get laden weight.

-CdA of under 0.12 m^2, but the lower the better(current guesstimate for the new shell I'm building may be around 0.10 m^2, but really don't know. It will have wheel farings to cover the outboard front wheels and streamlined boots over the suspension arms).

-Conventional bicycle parts for the human power drivetrain; derailleurs, chain, sprockets, ect.(Currently planning a 26/39/52T chainring set up front with 152mm crankarms, an 11-34T 8 speed cassette in the rear, and will be adding a Schlumpf high speed drive sometime after the financing permits me to convert it to electric). The bicycle drivetrain will be sealed from outside the velomobile. This will allow it to last tens of thousands of miles, and the gearing would be appropriate for anything from slogging up a 20% gradient with the motor disabled at 3.5 mph with 60 cadence, to careening down the highway at 55 mph with 140 cadence with the motor on or downhill at that speed with the motor off, and cruising along on flat ground at 30 mph with a leisurely 90 cadence without even needing to be in top gear. With a Schlumpf high speed drive added in combination with an electric motor, it becomes theoretically capable of cruising along at freeway speeds, like a car, and exceeding any U.S. speed limit, with human power adding useful motive force at any operating point.

-Torque sensing PAS to multiply pedal output. The assist doesn't add power unless the user is pedaling. For emergencies, in case of failure of the bicycle drivetrain, a throttle could be added with the Cycle Analyst computer limiting throttle-only mode to 20 mph to keep it legal in areas where this is necessary

-Electric drive system capable of no less than 6 kW peak and 1 kW continuous(Currently planning to use a Leafbike hub motor which can handle 4 kW peak and 1500W continuous out the box and can be modified for 6 kW peak with ease)

-1.5+ kWh pack of Tesla Model 3 batteries with aftermarket BMS

-Light duty DOT-compliant moped rims laced on all hubs, with Schwalbe Energizer solar race car tires all around. Must be safe at highway speeds, have a low enough rolling resistance to be pedaled like a normal velomobile with the drive system disabled, and as light as possible to minimize the acceleration penalty over normal bicycle wheels/tires from inertia

-Hydraulic disc brakes on all wheels set up with a single pull lever

-Full suspension, keeping the gas shocks at the front and adding a gas shock to the rear

-The rider must be enclosed for all weather riding. NACA ducts aimed at neck and armpits for cooling, with more air drawn in from footholes.

-Roll cage. It only needs to be strong enough to match the weight of the laden vehicle in a wreck to protect the rider.

-Ability to carry tools, camping gear, a few changes of clothes, hygiene items, 2 gallons of water, and a 2-3 days worth of food, all at once, with room to spare OR carry tools, 1 gallon of water, and 2 weeks worth of groceries

-Small 12V auxiliary battery fed from traction pack via DC-DC converter running headlights, running lights, brake lights, turn signals, and gauges(speedometer, cadence meter, heart rate monitor, power meter for rider, power meter for motor, battery pack state of charge, motor temperature, Cycle Analyst)

Theoretically, if all of the above were done, with the motor activated, it should be good for 0-30 mph acceleration in around 3 seconds and 0-60 mph acceleration in under 10 seconds pedaling as hard as I can with the hubmotor doing the rest, a top speed of more than 100 mph with the Schlumpf drive engaged while human power still accounts for 10% or more of the motive force needed to hold 100 mph(even if not for long), maximum "safe" cruising speed around 45 mph(it is a short wheelbase tadpole after all, but full suspension will make a big difference for stability. With just the front suspension I have now, it is stable downhill at 50 mph for short durations and I'd trust it all day long at 35 mph over bad roads) where human power still accounts for roughly 30% of what is needed to maintain speed, perhaps 200 miles range at 35 mph with rider input of 150W and 120 miles range at 45 mph with a rider input of 200W, and with the motor deactivated, it would still be able to move like a velomobile, perhaps with the rider able to do flat ground speeds of 20 mph on 100W, 30 mph on 250W, 35 mph with 350W, and brief sprints of up to 45 mph with 650W.

Perhaps if I can fit it within the allotted weight budget, solar panels could even be added to greatly extend the range. A 100W solar panel system would go a very long way to extending its usable range, especially when combined with the pedal input.

It would be legally an "electric bicycle" in a few U.S. states and "undefined"/"unregulated" in many others, while also highly illegal in many jurisdictions as well. For the states where it would be illegal, turn the motor off and ride it like a normal velomobile. For states where it's legal, have fun on state highways and side roads, just stay off the interstates.

The energy efficiency equivalent when operating the motor would be in the thousands of miles per gallon range. If it only needs 250W to do 30 mph and 1,600W to do 60 mph, with 33 kWh in a gallon of gasoline, this is the equivalent to 4,000 miles per gallon at 30 mph and more than 1,200 MPGe at 60 mph. Far better is possible, if I had wind tunnel access and knew enough about aerodynamics to get there. By comparison, a Milan SL velomobile needs 130W to do 30 mph and 750W to do 60 mph, which could yield close to 7,500 MPGe at 30 mph and more than 2,500 MPGe at 60 mph with a high efficiency drive system.

It would be a great off-grid bug-out vehicle. If I end up homeless, I may end up living out of it. I'd be able to cover quite a bit of distance in it as well, almost as quickly as a car, but without any of the expense.

In the long run, as better motor technology enters the market, I could make this thing much faster. There exist prototype PMDC motors that weigh in at only 7 lbs that can make 30 kW peak. Such a monster would allow this vehicle 0-60 mph in under 4 seconds, IF it can get enough traction to achieve that...

Re: Velomobiles: The most efficient form of individual trans

Unread postPosted: Tue 30 Jul 2019, 07:38:38
by Newfie
Yup, you need a job. Turn that creative energy into cash!

There a bunch of folks who are hot on building electric powered sailboats. IF you ever get bored with land transport.

Neat stuff you are building.

Re: Velomobiles: The most efficient form of individual trans

Unread postPosted: Tue 30 Jul 2019, 13:12:55
by The_Toecutter
Newfie wrote:Turn that creative energy into cash!

That's something I've been wanting to do since I was in high school.

There a bunch of folks who are hot on building electric powered sailboats. IF you ever get bored with land transport.

I'd do that job. There's a lot of overlap in design principles between the two.

Neat stuff you are building.

I'll be able to finish it when I get the money. There are solutions to the coming energy crisis all around us that entail minimal or no reduction in living standard. But they would also mean rich assholes no longer get access to our money.

We could have had mass market electric cars going mainstream in the 1990s with 150+ miles range at an affordable cost, but powerful interests held it back. It wasn't until Tesla got a foothold in the market 20 years later that things started to change. History is riddled with technological advances that have been deliberately kept out of the mainstream consciousness as being viable or that were already implemented and deliberately destroyed(such as the U.S. widespread mass transit system of the early 20th century) because they threatened some powerful interests' revenue stream and control, all under the guise of convenience or "market forces".

Future generations are going to curse us for having allowed the world's plenty to be squandered for the purpose of profiting an elite few.