Friday, May 23, 2008

clever dynamo circuit, light power assist

"My assist philosophy has been based on the concept of truly low power giving just enough assistance.

This allows for a lighter weight system such that when the assist is not in use it doesn’t detract from the overall efficiency of the vehicle/rider combination. This means the low assist weight requires very little additional energy from the rider when climbing or accelerating (a lightweight vehicle also helps).

My design goal was around 100 input watts to the motor and less than 10 pounds total system weight. It came in at 4.2 pounds, 1.9kg ! -- That’s every thing – motor/gearbox/freewheel/mounting bracket assembly, battery, electronic controls."

D: I priced the components at c. 1/2 of a full-power electric assist.
(D: their own website index was a dead end. Huh. Helluva way to run a business...)
D: prices vary from $1100-1800 for 250-500Watts.
Weight is 17-16lbs. That sounds funny, but the high-end system uses lithium-ion batteries.

D: a combustion motor is 'in the works' but is not yet on the market- the Revopower.
Powered by: 25cc two-stroke engine; 1 HP or 0.8 KW power maximum output at 7500rpm;
Power Train: The Wheel is driven by a series of sprockets & chains which drive the engine (and the wheel) around a fixed axle
Top Speed: 20 mph (32 kph) over flat terrain; normal bicycle brakes are sufficient to stop it
Fuel Used: Standard two-stroke fuel (a mixture of normal gasoline and oil)
Fuel Consumption: Over 100 miles per gallon
Weight: Less than 15 pounds (5 kg); 12 pounds net of additional weight once the original wheel is removed
Noise Levels: Less than 65 dB at a distance of 7.5 m; very quiet operation
Emissions: Extremely low; using the latest technology, it meets EPA and CARB regulations; The Wheel stops when you stop, eliminating idling and emissions caused by idling
Clutch Operation: Automatically engages when engine is running
Starting & Stopping: Single user interface of throttle and starter; User must pedal to start the motor; no idling possible

D: I contacted Revopower for additional technical information. They sent the usual generic canned info packet. I wonder if these companies realize how many sales they lose, doing that.
I-motion did the same, refusing to divulge the gear combos by gear for the I-motion 9.
I reciprocate their contempt for me.
For example, I'll be going with a NuVinci instead of a SRAM due to that.

Anyway, back to Mr. Tetz's idea.
D: I did a thought experiment for a solar-power assist. The Watts provided are marginal.
Solaris 26 Features
  • 12V output for charging laptops or running cameras and DVD players
  • Overall dimensions open: 21.5”x37.5”
  • Overall dimensions folded: 11"x8.5”x1”
  • Weight: 28 oz
  • Max output: 26 watts
D: Not cheap - a coupla would run c. 1000 bux!
I figured a Wisil Missile top fairing, with a 2x3' section fore and aft, with a gap being the 'windshield'.
This works better with my secure-clamshell idea (another day).

The idea of a12V setup is of benefit. This will never move you much without pedalling, but it can be recharged by a car battery, and from the solar appliance product listed above.

A 12volt motor could double as a serious generator, able to power motorbike LED lights.
Or, during the day, power a consumer appliance like a cellphone.

The solar setup could allow:
1) a capacitor/battery pack for brief high-power assist and ? an hour of partial assist.
2) park and secure it at work, with the solar power recharging.
3) come out after work to find the battery pack recharged.
Your bike solar could power camping electronics in the field.
I found the Powernet pseudo (high voltage) setup using D-cell sized ultracapacitors.

I'd like to stow the batteries in an oversized mountain bike tubing frame, but I hear overheating would need to be addressed.
D: reasonably cheap, though I hear they might have power leakage issues.
D: this author was also willing to correspond with me.
We both lamented that nobody seems willing to use just electronics v.s. computers for an auto gear shift changer. More on that tomorrow!

Friday, May 2, 2008

pedal-thru-front wheel mid-wheelbase. air power.

D: the top pic is the subject of discussion- a new "Penny and Farthing" bike.
"The ordinary, high wheel or penny-farthing was the first true bicycle with which actual speed and distance could be achieved in a practical manner. Given the absence of a stabilising steering system, larger and larger wheels were built with the intention of increasing stability at speed. The classically oversized penny-farthing wheel, which measured 1.5m (60") in diameter resulted in such large gyroscopic force that it was stable without a caster steering system. The name refers to the British penny and farthing coins of the time; the former being much larger than the latter so that the side view of the bicycle resembled two such coins placed next to one another."

D: good thing it's stable. Just imagine hitting your head on the road from that height!
Without a gear hub, I imagine this was hard to start, then hard to accelerate beyond a certain point. To this day, a few bikes don't have gears. Which is fine, I guess. If you only every wanna go about 10kph or whatnot.
The size of the tire v.s. a person's leg is the ultimate speed limit for bike like this.

Well, what is old is new again. I am exploring reintroducing the pedal-thru-front-wheel concept. However, in my case, with a mid-steering full or semi recumbent.

Regarding my pic:
1) top: this sort of bike going uphill, with power assist on rear tire.
2) right: front profile of a variant partial fairing based on the 'Wisil Missile'.
3) bottom: a concept bike that can be both pedal behind or in front of front tire.
4) left: toying with the Tron Lightcycle theme, a look at today's bike inside a Tron style fairing.
With a few tweaks, the overall body shell shape is not bad for drag!

(Aside: I am exploring a motorcycle with similar motif. The motor is inside the centre of the ridiculously oversized front tire.)

This bike concept bears a resemblance to the mid-wheelbase recumbent design.
In this, the pedal and crank are over the small front wheel.
It also bears some resemblance to the Cruzbike. With that bike, the rider pivots his legs to keep them aligned with the front wheel during turns. This makes the chain line simple.
I did find one SWB (short wheelbase) 'bent with that concept.

The idea of front wheel drive (FWD) is appealing. No long chain to the rear tire.
No heel clip issues with mine.

I could use various mid-steering approaches. Flevobike has historically been synonymous with mid-steering. In the DIY category, the Python.
"Learning to ride a Flevobike takes some time, in contrast to almost all other recumbent bicycles. It took me in total about 5 evenings of practice on a regular Flevobike. After that, riding the Racer was not difficult anymore.

I am very enthusiastic about the centre-pivot steering of these bikes. It makes for a very relaxed ride, as you do not need your hands to steer. However, there are disadvantages, too. Going up a steep hill you will notice the lack of surface grip under the front feel, due to the fact that the weight is transferred to the rear wheel because of the inclination. And with heavy loads (holiday luggage), the bike can become somewhat unstable and you will need both hands on the steer. "

D: the Python was listed yesterday.

I figured I would need to use a Rohloff speedhub with internal gears in the front tire axle.
I'll be honest - I have no idea how I plan to attach this thing!!!
For a commuting bike, a more modest hub would work. The Rohloff is over a 1000 bux - yikes!
Still, think about it. No chain, no dirt in it, no grease on your pantleg. No noise from the chain.
No chain to break or fall off.
This is even more elegant than the 'chainless challenge' variants!

The mid-price drives that come to mind are I-motion 9 and the NuVinci.
Both are 300-400ish bux. Both have a c. 350% gear range.
Contrast that with the Rohloff with more like 525, 575 on their next-generation prototype.
I tried repeatedly to contact the I-motion company for details about their drive. First, I got interrogated as if I was some industrial spy. Then he simply sent the canned PDF of info. I was specifically asking how many gears were internally being used in gears 1-9. He was a useless P.O.S..

I needed to know that! For example, the Rohloff uses only one internal gear in gear 9. However, 3 in gears 8 and 10. But 2 in 7 and 11. Ergo, one should try to stay in 9, but switch from 8 to 7 when slowing down and switch from 10 to 11 when speeding up.
I had some ideas about using the Browning product below with programming tweaks to sweet-spot the cadence with this in mind. Pretty sophisticated stuff.

He also made me mad enough that I started researching the NuVinci.
It is superior in every respect except for weight- about twice as much.
D: I've seen it online for as little as 350 bux.
It doesn't have gears per se.
It is the first practical bicycle CVT (continuously variable transmission).

I'd like to find some parts from the defunct Browning Automatic Transmission to try to link to it.

D: I need to deal with the lack of traction uphill on poor surfaces. The best I could think of was power assist on the rear wheel with the ballast for it in front of the front tire. It could be electric or air or whatever.
I will be looking into getting some firefighter air tanks. They're 4500psi. A bud of mine works at a scuba shop, so I have access to safely underpressured 3000psi refills.
The composite tanks are pretty light!
They are, however, rather bulky.
For that reason, a series of propane air tanks might be desirable.
I'd like to suggest one variation in the design suggested. Don't use paint inside.
Take a model kit for models. The scrap plastic, dissolve it in acetone.
As the acetone evaporates, the plastic is laid back down in a thin layer on substrate.
The result is an excellent plastic layer v.s. water corrosion.
Alternatively, a 300psi BBQ propane tank would be HUGE but could be easily refilled with a tire air pump at any garage.

I did the calcs for solar power assist/electric last night, but we'll save that for another day.
D; here is my initial foray into air power assist.
Recumbents stand to benefit from brief high-torque assistance. They are soooooo hard to start on an incline.

Thursday, May 1, 2008

my experience with 'bent bikes

D: and what is this a pic of? It is a recumbent bicycle profile from the front.
And therein lies the key appeal, performance-wise, for a 'bent bike.

The faster you go, the more air resistance matters relative to other factors.
Air drag increases as the square of speed.
This has 2 implications:
1) at lazy commute speeds, a 'bent doesn't matter
2) anyone performance-oriented at speeds around 30kph or so should care.
D: a primer on 'bents.


Recumbents hold all human powered speed records. Period! The world’s cycling organizations, or even national cycling organizations such as the USCF recognize none of these records. These organizations have decided that the diamond frame bike (traditional road bike) is the only device they will admit to the record books"
This translates into measurably faster speeds. Many cyclists who ride both types of bike (diamond frame as well as recumbents) report 3 to 8 mph faster average speeds on the recumbent bikes."

(Recumbents hold the world speed record for a bicycle and were banned from international racing in 1934.)
D: a more scientific analysis.
For the standard bike in the upright position, we have this:
"At 250 Watts, the upright bike goes 29 Km/Hr or 8.0556 m/s. To go 40 Km/Hr or 11.111 m/s, the upright bike needs 622 Watts.

For the recumbent bike with the full foam fairing, we have this:
At 250 Watts, the bike goes 51 Km/Hr or 14.167 m/s. To go 40 Km/Hr or 11.111 m/s, the bike needs 135 Watts.

For the recumbent bike with the full hard shell fairing, we have this:
At 250 Watts, the bike goes 69 Km/Hr or 19.167 m/s. To go 40 Km/Hr or 11.111 m/s, the bike needs 75 Watts."

D: with such a potential for speed, many dabble with even lower CD (drag) with fairings - shells.

(Insert bitter ranting about cruddy blog interface here.)
Ahem. See the start of the page. I have a pic of a Rotator Tiger short wheelbase recumbent with 20" wheels, and no suspension.
I rented it from
D: they were oddly difficult to contact.
If you instead wish to purchase 'bents in town, there is Rebel Cycles.
I sent them a query and never heard back from them either. Nice business model...

Anyway, my impressions of a Rotator:
1) felt like I was being karate chopped on the backside on sidewalks and bumps.
Those high pressure small 20" tires with no suspension are no fun.
2) it was very hard to start from a stop. On an incline, forget it!
3) you don't steer by leaning, only by turning the handlebars. You learn to not oversteer in a hurry.
4) you feel very invisible in traffic. You cannot see past cars. You are grill height on a sedan, bumper height on a SUV.
5) you are at doggy-bite level. Leaning back you also feel vulnerable.

As fun (and scary) as it was, I remain convinced that recumbents are simply not practical in typical commuting situations.
There are a few improvements on this basic model.
For example, here is the full suspension award-winning alternative.,nl/

And here is a highracer with dual 26" wheels.

Here is a mountain bike tire and dual suspension, available in kit form.
D: THIS is the only 'bent I consider practical for commuting.
It can handle potholes and bumps. The rider is quite high.
It might be able to mount on the front of bus for transport during rain.

Since I will be exploring variations later, I'll mention the mid-steering DIY, the Python.
D: you'll notice it is a more fully mid-steering arrangement than the Cruzbike, which still technically remains a front steering arrangement, although your legs remain aligned with the front wheel.
I assume that prevents sharp turns though.
Without a midsteering arrangement, a front steering short wheelbase bike has 'heel clip' issues.
That is the term for when your foot on the pedal hits the front wheel when you turn too sharply.
This concern limits the size of the front tire unless you switch to a highracer layout.

Specialized racetrack designs just don't worry about turning much.
This is a treasure-trove for how-to.

In future posts, I will instead discuss my various design ideas.
The themes will be
1) adjustable seat height
2) able to change between short and long wheelbase in process
3) a midsteer/front steer dual arrangement, able to change over in a few minutes
4) partial fairings that attach to the front and rear frame on a mid-steering bike
5) an attempt to create a new practical partial fairing for commuters
6) a mid-steering approach that mounts the pedals through the front wheel axle area. Essentially, a hub gear powered modern version of the ancient "Penny and Farthing".
7) various power assist concepts including electric, solar and compressed air. This serves 2 purposes:
i) a front wheel drive has problems getting purchase uphill on gravel.
ii) an assist to accelerate from a stop, particularly on an incline addresses a major 'bent issue
8) optimizing the benefits of a fairing without too many weight/crosswind issues.