Monday, November 3, 2008
D: the bike must be
D: this reminds me of the old mechanic joke. You can have 2 out of 3 of the following. Cheap, fast, good. You can have good and cheap but not fast. And so on....
1) easy. I assume this means easy to operate for the end-user. No fancy controls. No complex technical aspects
2) comfy. Ergonomics. Feels good.
3) efficient. This one is trickier. This sounds like 'light' to me, with good gearing.
4) fun. I imagine 123 would make it fun. Not dealing with technical stuff is also fun.
Well, the above bike is just a 26" wheel DIY version of the Greenmachine I want to build.
The Gm is great - and about 5000 bux, with no support in North America.
I thought about dual suspension and whatnot. But that makes it heavier, more expensive, less efficient and complicated.
I wanted to make the frame very light.
Well just by isolating the rider, who weighs say 150 or so pounds from a bike that weights 20-30? pounds, on makes it both light (efficient) and fun (particularly with the seat).
I thought two parallel parallelogram thudbuster setups with a few inches of wiggle room by the frame on each side would suffice. Elastomer is adequate for non-winter cycling.
This does mean the seat must be free-floating. I.e. it is not leaning on the rear wheel assembly.
The square tube frame just makes my life easier. No concern that the seat can fall sideways!
A few holes or indents and the seat mounted on a sliding mount and the thing can adjust for rider height.
Of course (see the Optima Condor) below 5' 10" or so, 26" wheels become problematic.
There are 24 and 20" wheels about.
The chain is completely enclosed. No grease on yer work clothes. Pretty quiet.
The NuVinci drive is cheaper though heavier than an I-motion 9.
I suppose efficient favours the IM9, but I disliked the technical support.
The NVd is also easier in that it is a variable drive lacking discrete gears.
The SWB recumbent layout is amenable to a partial fairing and a motor assist if desired.
A backpack mount is a must! I'd like a Y-shaped shoulder mount on the back of the seat.
I don't like the idea of strapping a backpack to the luggage rack area. I always worry about those straps getting caught in the tires.
I could ride a 'bent the first weekend I tried it, so there is not much learning curve.
(Unlike a front-boom style - I still don't trust myself in traffic! ).
Well that is what I think a commuter bike should look like.
Other than the seat-suspension, the whole thing should be pretty simple to make.
Friday, September 19, 2008
Tuesday, September 16, 2008
- the 2 -wheels forward design, the delta (v.s. tadpole) is more stable.
- a full width trike generally does not play well with traffic
- a narrower leaning trike addresses this.
D: I bike to work on Waterloo Westmount-Northfield.
For c. 500 feet past University, it is as narrow as 1' before becoming a bike lane.
By placing a white line on the road edge, despite a clear curb and whatnot, it implies to traffic that
- that is where bikes go
- maybe it is wide enough for bikes
- just staying on the other side of the white lines will avoid me.
Nope. This road would be much better off with NO white line until it reaches a full bike lane width.
Why such a wide bike lane?
No surprise at all.
With a car, the mirrors stick out. Allowing another 6" of wander on both sides, that amounts to an additional 2' lane width v.s. the actual car width.
Bikes are much the same.
If I ride the curb,
- I risk the tire catching on the curb lip.
- I risk the pedal hitting the curb.
I ride a decadent (sarcasm) 1' away from the curb itself.
Deal with it.
Monday, September 15, 2008
Between classical front-wheel steering, and strictly rear-wheel steering, is a class of bikes with a pivot point somewhere between these two extremes and referred to as 'center-steering'. These design allow for simple front-wheel drive and appear to be quite stable, even ridable no-hands, as many photographs attest.
These designs usually have very lax head angles (40° to 65°) and positive or even negative trail. The builder of a bike with negative trail states that steering the bike from straight ahead forces the seat (and thus the rider) to rise slightly and this offsets the destabilizing effect of the negative trail.
D: compare to the disastrous handling of the original Flevobike.
No one who was present that day would consent to demonstrating the machine, but several people volunteered that they had seen a rider earlier in the day who displayed extended no-hands riding! I couldn’t believe it. I didn’t think it was possible to ride a recumbent without hands. At least my experience to that point hadn’t convinced me that it was possible.
So I spent half the day trying to learn to ride it, and it certainly exhibited some strange behaviors. To begin with, it just wouldn’t stay upright. The front half wants to fall over, and fall over fast. It isn’t the kind of bike that you can push along gracefully while holding the back of the seat. In fact, holding the back of the seat is a sure way to let the front half fall over and of course, that happens rather quickly. And to make matters worse, just like more conventional underseat-steering recumbents, the handlebars are a little low to be comfortably used to direct the bike when standing to the side. But in the case of the Chinkara, the handlebars don’t even provide enough leverage to counteract the front half of the bike, which seems to have a mind of its own. Such behavior made it hard to handle the bike. It wouldn’t stand up on its own. It seemed impossible to control, and this was before even trying to get on...
I thought something like the Triton Trike for steering would be desirable.
I'd be curious about a steering system with some gears to amplify the effect near the far range of motion. By that I mean:
- handles normally for minor movements
- when turned, say 45 degrees, amplifies the turn on front wheel by 1.5x
- at much more, by 2x.
I hear under-seat-steering has problems turning the wheel severely.
In a bike very sensitive to steering, maybe even reducing the wheel-turning below 1:1 in the middle would be desirable.
Steering which is speed-sensitive would be nice, but the mechanical details would be a nightmare.
D: latest Cruzbike thought.
I think an even more severe oval that exists commercially *might* be desirable.
I do wish the company website had warned against the combo of short wheelbase AND high seat height.
Like I said, I wouldn't trust the stability of mine at faster than 30kph.
I suppose that is fine for a commuter.
I finally figured out the aluminum sleeve included is to serve as a gap-filler on a stem adapter.
The spare parts for use in other kits were confusing.
Aside: I found a 135 degree angle for seat/pedal combo. It looks ideal for future models, with the pedals below seat height and a modest seat back angle.
I am also intrigued by laying in all electric lo/hi power wiring and shifter/brake cables internally on the internal-chain version.
Wednesday, September 10, 2008
D: I hope this will address an issue with my Cruzbike.
Biopace is a patented non-round chainwheel design made and licensed by Shimano. To a casual glance they resemble elliptical chainwheels, but on closer examination they turn out to be the exact opposite of the classical elliptical design. The product of extensive research and computer-aided design, Biopace chainwheels have the small radius engaged when the cranks are horizontal, the large when they are vertical. This is because the Biopace design is based on a dynamic analysis of the motion and momentum of moving cranks and legs, unlike the static, geometric analysis that produced classical ellipticals.
The theory is that during the power stroke, when the cranks are more or less horizontal, you are using the power of your legs to accelerate your feet, which get going quite fast in the lower gear provided for that part of the stroke. The momentum of your feet then carries the pedals through the "dead spot" when the cranks are near vertical. Since the rider doesn't push as hard during the power phase of the stroke, and motion is slower when the leg is changing direction, the Biopace design is gentler on the knees than even round chainwheels."
I am only used to normal bikes. I once rode a SWB recumbent.
I am totally unfamiliar with anything that feels like a mid-steering bike.
So I push too hard on the pedals, and this pulls around the steering.
With practice, I can keep my pedals smoother, or countertug on the handlebars.
But there must be an easier way!
I think there is.
An asymmetrical chain-ring should manage to smooth out this 'power crank' I do, thereby minimizing the steering demands on me.
I am not yet precisely sure what sort I should be looking for, though.
Aside: see KneeSavers for a nifty add-on to
1) prevent knee pain on a normal bike
2) minimize 'heel clip' on a SWB 'bent.
Wednesday, September 3, 2008
I measured my wheelbase. It's 43"'
That is less than Bacchetta's 47 but more than the Cruzbike Sylvio.
I think that is why the latter has only 8 gears.
If it had more, it would destabilize at high speed.
I used a kid's (?) 15"? v.s. suggested 17" frame as the basis.
I am unsure if I should try to expand my gear range.
I think it might destabilize at high speeds anyway.
In time, I'm sure I will think of the bike as 'nimble'.
Right now, it just feels unstable.
A coupla thoughts:
1) one part requires matching allen key sizes. Having 2 different ones might mean less tools are needed.
2) a modified handlebar holder can also mount the front boom. Easier, cheaper?
3) I would like to find an aftermarket seat that can be adjusted more.
We tapped out and threaded extra anchor points for the seat.
I wouldn't feel comfortable with just a coupla straps.
A tap kit would be a welome addition, or suggested supplement.
I'm having a hard time finding place on the frame to mount all my accessories.
D: I had the worst time figuring out how to put the battery in!
Push the tabs on both sides simultaneously. It's tricky.
Once the battery was in, I could not find any way to test it.
A spare cable, in case the first is cut, or a spare shorter one would be welcome.
Where I want to mount it, the extra-wide rear spring housing wants to hit it.
THIS concept, I'd like to incorporate inside a bike frame.
I'd like the bike to be structurally compromised if the alarm is bashed.
Honestly, the plastic U on the mount doesn't look so tough.
A bike has all these widgets that require power of some variety.
A horn. A light(s). Power assist. Signal? A cellphone would be nice. A siren alarm.
Point is, wiring the whole bike for power of various levels, with internal cables too, would make for a neater looking bike. A central power supply for all these would be nice.
The off-the-shelf 12V battery pack for Tetz's power assist would do nicely.
Aside: once my 'closing clamshell' fairing is a reality, then throwing a solar thinfilm recharger inside could be practical.
D: terrific primer.
D: to get yer ergonomics, just use cardboard to replicate your hip/knee/ankle joints. Pin it all together. Make sure your bike suits your ergonomics.
Seat back (ergo hip tilt) will also affect performance.
A look at nice finished bikes.
D: I wish to create a variant Greenmachine.
My bud Fern in London is an accomplished welder.
I plan to use the Python's choice of material - 16gg square tubing. Stainless for me.
The cuts for square tubing are simpler, with only a slight weight penalty.
By the time paint coats and gloss finish are considered, the weight savings of a carbon steel frame are partly gone. Plus I can just satin the stainless - no paint chips.
D: it won't be monotube though.
I want to parallel pipes. I plan to run the whole rear-wheel-drive chain through them.
With gear hubs, this will mean the chain is totally sealed away from the outside world.
I don't imagine that is really true- I'd need hermetic seals v.s. moisture.
Still, it should keep rain off, and dirt out.
I'm intrigued by placing all valuable hub drives in the bike frame.
The wheels, if stolen, are cheap and easy to replace.
Alternatively, they can house fancy stuff like a hub motor or a SON dynamo hub.
What would be very nice for a rear-drive is if those kevlar belt products were made in a more useful length.
Monday, September 1, 2008
D: I dislike fairing design as it exists.
Keep in mind that a fairing is a design compromise.
It is not only to minimize drag.
It is also to keep the rain off sometimes.
This means it often has a larger front cross-section than is needed.
I imagine production methods (the blown bubble) has something to do with that.
D: there are 2 concepts to be understood.
1) laminar flow (or else turbulence) and
2) air pressure
D: the first step and what 'bents do is to minimize front cross-sectional area.
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: practical, my ass. Recumbents get enough cross-wind, are top-heavy and are plain heavy enough already.
The typical 'bent partial fairing is a nose cone and tail box.
Sadly, one is better off with
1) maintain laminar flow over >1/2 the length
2) suddenly truncate to induce turbulence once body taper has reduced the rear to < 1/2 the surface area.
To avoid pressure spikes on the front and delaminated flow (turbulence) on the rear half, the surface angles should all be gradual. The surface texture needs to be fairly smooth.
Road vibrations will also disrupt it.
1) Pantour hub elastomer on a stiff frame
2) ? special padded fairing mounts or
3) full suspension
After all, a poorly designed fairing is just so much dead-weight.
I prefer a total-body-length cover for the TOP and bottom.
With open sides.
Ergo, no crosswind.
There is risk of being top-heavy, though.
Aggressive design to place all mass as low as possible is wise.
The chopper handle hands-out is the lowest drag.
The Bachetta bikes are a good example.
Under-seat-steering increases front cross-section.
Of course, a fairing that is one blown bubble will occupy far more front area than is needed.
For this reason, some fairly complex shapes are justified.
The additional perk of over-the-top fairings (and window) is sun/rain use.
A simple non-moving version would be the transparent middle fairing on the mid-down pic.
Then chop out the sides on a diagonal, narrow at the bottom.
A body sock lends itself to use with a top/bottom fairing. It has plenty of anchor points.
Thursday, August 21, 2008
D: the only one on the market today is the Schlumph (pic)
It has very high and low gear options. They're called the mountaindrive and the hyperspeed drive.
For somebody stuck with one chainring, or looking for more gear range, this is it.
It runs 500bux though.
D: the Dana 3 speed crank is made by an automotive company.
I cannot find anything on gear ratios or range at all. Ideas?
I saw one on sale at E-bay for 30ish bux.
I read of a Shimano 5-speed crank tranmission, but cannot locate it.
Sure, the new Rohloff will have a 580% range. And will cost 1500 bux.
The Flevobike Greenmachine embedded a gear hub in the bike frame. This allowed a bike frame that covered the chain easily. But it costs many 1000s.
By stacking a, say, I-motion9 or a NuVinci with a Schlumph, I figured I could cheap out.
If I manage to poach that Dana on E-bay, well, I just saved myself 500 bux.
The bike frame idea involves stainless steel square tubing.
I have a Schlumph at the chainring, and a NuVinci CVT drive embedded in the bike frame.
The frame tubing has 2 parts that run parallel, with occasional triangular cross struts.
Other than the hub drives, such a bike is pretty cheap to build.
Let's hope my c0sts just dropped by 500....
Eventually, for the crank-thru-front-wheel mid-steer concept, of course, I will need a Rohloff. But I hope the new 2008 model pushes down the price of the standard model.
Monday, August 18, 2008
A limited-speed motorcycle is:
- a motorcycle that:
- can attain a rate of speed of more than 32 km/hr on level ground within a distance of 1.6 kilometres from a standing start;
- has a maximum attainable speed of 70 km/h or less;
- has steering handlebars that are completely constrained from rotating in relation to the axle of only one wheel in contact with the ground;
- has a minimum seat height, when the vehicle is unladen, of 650 millimetres;
- has a minimum wheel rim diameter of 250 millimetres and a minimum wheelbase of 1016 millimetres;
- has a maximum engine displacement of 50 cubic centimetres or less; or,
A motor-assisted bicycle is a bicycle that:
- is fitted with pedals that are operable at all times to propel the bicycle;
- weighs not more than 55 kilograms;
- has no hand or foot operated clutch or gearbox driven by the motor and transferring power to the driven wheel;
- has a piston displacement of not more that 50 cubic centimetres; and,
- does not attain a speed greater than 50 km/h on level ground within a distance of 2 km from a standing start.
It is half the price of competing electrics.
There is whole lotta legalese here. Read the rest over if you want.
Most power assists seem to think I'm decrepit. They're substitutes, not 'assists'.
Guess what? On a half-dead steel frame mountain bike junker, for an HOUR, I can already sustain 32kph on pavement.
At first, I wondered what math was wrong.
I mean, I KNOW I am not generating anything near a full horsepower.
Yet the Revopower needs to, to go 30kph.
So what gives?
Heat loss inefficiencies.
A typical combustion motor only manages to deliver a few 10s of percents of initial power to the wheel.
Ergo, all is well in math-land.
I am just dang efficient that I might as well be a full horsepower.
Likely more like half a horse though. <: <: Tee hee.
I ordered the special handlebars.
After all, they were only 85 bux.
Nope. With shipping, they're an extra HUNDRED.
This didn't come to mind when I ordered. OMG.
1) fold-down 2-part handlebar kit or
2) bolt-on for a more conventional and local handlebar
would be VERY welcome...
D: My bud Mike ordered no-contact induction-powered LED lights for me from UK's
I plan to turn the 2 sets into sideways amber running lights.
Right-turning vehicles at intersection keep trying to sideswipe me - and this with TWO lights for and aft each! Plus a square foot of reflectors.
Total Cruzbike cost so far:
120: steel y-frame from Sportchek.
200: < class="blsp-spelling-error" id="SPELLING_ERROR_6">Cdn. Tire. For the Shimano components.
(their bike geometries were no good for the 'bent seat)
660: cruzbike conversion kit with handlebars plus S&H to Canada.
D: so that is nearly 1000 bux so far.
In other words, an entry-level 'bent bike cost.
However, it is filling the role of an Optima Orca or Condor, which costs c. 4-5000 bux!
D: we are a little confused about how the wide rear tire gets fitted to the narrow front forks of a bike, but are hoping the kit makes this clear.
I plan to videotape the making-of Cruzbike for YouTube.
Friday, August 8, 2008
D: we all know it. Those small, narrow hard bike seats can cause impotence problems.
Me, I have a wide padded/spring loaded 'granny seat' on my bike.
I don't like the sensation of bone bruising.
I don't think bikes in China are linked to penile impotence issues.
They don't have our silly seats.
Women, too, benefit. A little-discussed fact is that women with protruding inner labia find a standard bike seat painful. Terrible thing, to be unable to bicycle.
Of course, the recumbent 'lazy boy' seat addresses all these issues.
It also offloads some pressure from the butt to the back.
So forget about a tiny seat on most bikes, trimming maybe 1/2 pound off the bike's weight.
Monday, August 4, 2008
D: this is hilarious! The guy with bike-wheel-for-inline-skate is just nuts.
I thought the tandem bike with a standard rear and SWB front rider was pretty clever.
I suppose a kid's seat on a SWB with a little pedal to the rear tire could be cute.
You'd hafta extend the frame to place the pedals up/front of the rear tire though.
Aside: my sis is ordering me a Cruzbike kit from the USA. There were no dealers locally.
I am talking about renting my bike out when completed through Bicycle Forest.
I plan to make a simple camcorder tape of building a Cruzbike to post on youtube.
Has anyone ever tried under-seat steering for it?
(pic of a prone 'bent)
Tuesday, July 29, 2008
D: I wanted a mid-steer too.
D: see the chart on Flevobike. I read about somebody trying to learn to ride a Chikara on the top link. It was very very hard.
I found a vid of a Cruzbike rider both pedalling and turning in a tight radius.
Putting pedals through a wheel will lead to heel-road-clip just like a standard bike.
So you want very big tires. I was thinking 28".
The measurement system is pretty nuts.
D: I am not sure what raising the seat will do to handling on a mid-steer though.
Plus the weight distribution between tires will be totally different than with a SWB.
It will be all on the rear tire. But the drive is the front tire.
With a I-motion9 hub drive, the bike could be quite light.
With a 350% gear range, though, this means no great granny gear and no great fast one either.
This relegates the concept to a simple commuter.
With a Rohloff, particularly the new 2008 with almost 600% range, it could rock.
BUT that will cost likely c. 1500 bux! Ouch.
D: I was thinking to build the frame in front of the front tire to mount battery ballast.
I had considered doing so on the rear for a trailer hitch.
Aside: my bud used 2 forks to make a trailer. He attached it with hydraulic hose connectors and one additional pivot point. It works like a charm!
D: if I make a low bike like this, I will be paranoid about visibility.
I planned to order 2 sets of freelights.
I initially wanted Reelights. They are likely more robust but expensive.
Neither company exhibited any interest in sideways amber running lights- but I think that would be brilliant.
With 2 sets, I
1) take 2 white ones, assign sideways with amber covers.
2) use one red rear
3) place 2nd red one on top of a flag.
4) use a proper high power light at the front for visibility.
Keep in mind I have fore/aft flashing LEDs on my helmet.
D: making bikes in the factory with internal wiring and these setups would seem sensible.
The freelights would be good for entry-level bikes.
Friday, May 23, 2008
"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.http://www.greenspeed.us/bionx_motor_bike_kit.htm
(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
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
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
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.
"SpeedRecumbents 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 http://www.bikeforest.com/rentals.php
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.
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.