Friday, February 27, 2009

transforming bikes

D: a trike with built-in baby carriage. The baby is up front to cushion any impacts you have with cars, LOL.

D: I saw a vid last year of an upright bike that could transform into a semi-'bent.

I wonder if that inspired me to consider a variable seat height. The height of the seat means it must be on its own boom.

Also, I am pondering a dual-mode front and mid-steerer.
This would require re-arranging some pins in the frame.
It would reuse the steering grips for either under or over seat steering.

Regarding the variable height seat on a recumbent - this was my way of
1) having a low drag fast bike but
2) a good visibility option for commuting in traffic.
I will never use a lowrider in traffic!
Even the short wheelbase recumbent 'highrider' seemed very low.
That is part of why I settled on a Cruzbike.

The highracers would be brutal on the pot-holes around here.
Our winter freeze-thaw cycle wreaks havoc on roads.

Aside- regarding my Mark I bike design contest offering, with the suspension built into the seat...
For intense cycling, one wants the suspension between wheel and frame.
Otherwise, the bike loses contact with the ground and doesn't hug the riding surface.
However, given the frame simplicity that results, I am willing to accept the trade-off.
Plus also recall that light wheels make for a light feeling bike frame.
It is less punitive for acceleration - imparting all that centrifugal force.
It gets wasted in braking as heat anyway.

Sunday, February 15, 2009

mechanical and electronic gear shifters, hydraulic drive, bottom bracket dynamo

The good and the bad and the prohibitively expensive.

Two earlier attempts at electronic gear changing by a French company, Mavic, often malfunctioned in rain. Another company, Campagnolo, has delayed bringing its version to market because of the economic downturn.

D: only 4000 bux (!!!) and reliant on a battery...

There was a nifty earlier attempt by Browning. The gear changing method is something else. (pic)

The critical feature that differentiates the Browning from standard derailleur systems is the continuous gear/chain engagement during shifting, there is no skipping or grinding even under the heaviest loads. The transmission will shift under any combination of speed, cadence and pedaling force. Shifts are smooth, fast and nearly silent. The chain stays fully in contact with the gear teeth during either up or down shifts. In contrast, even with the best standard derailleurs, on upshifts, the chain loses contact with the smaller sprocket before it is fully engaged on the large sprocket which often leads to grinding or skipping under heavy loads.

Another unique feature of the Browning transmission is that it is ideally suited for complete electric operation including computer controlled automatic shifting. This eliminates derailleur cables and cable adjustment.

D: I had pondered the idea of computer control after studying the efficiency analysis of the Rohloff gear hub.
Love these guys!
As you can see, the Rohloff's efficiency varies by 4%, depending on the gear.
That is because the number of internal gears engaged varies.
I think between 1 and 4 at a time.
Obviously direct drive is always preferable.

D: yet another lament by me. I asked about the I-motion 9 internal gears.
Not like I couldn't crack one open to find out.
I got the third degree and then no answer to my question anyway.

OK - back to the Rohloff. A computer would be able to accommodate the gear efficiency versus optimal cadence equation. For example, let us a say that a certain cyclist spins at 80rpm best. In a good gear - one with fewer internal gears engaged - maybe we want him/her/it/them (sigh) to expand the cadence range by say 5 or 10 rpm prior to gear shifting.
Conversely, in an inefficient gear, we might wish to reduce the spread of cadence in that gear by a like amount. This is just the sort of equation a computer could do easily and well.

Frankly, the simpler solution is to use a NuVinci hub with a continuous variable gear. Then it's a simple matter of up and down.

A quick aside on drive efficiency.
1) a non gear-hub is likely ideally a bit more efficient. Dust, grit, rust et al makes me think is only true in theory.
2) a severe chain wrap around a small sprocket is inefficient
3) a taught chain is a must
4) oddly, lube seemed to serve no purpose here.

Another aside- a hydraulic drive was designed but never seemed to reach the market.
It would have the potential to allow dual-drive on a bike.
Pretty terrific for snow and up hills/gravel on a front wheel drive 'bent.
Their site doesn't even seem to up any more.

Yet another unrelated aside. Shimano has the patent on a bottom bracket internal dynamo generator. I think this is to suppress it, so they can promote their wheel hub dynamos.

D: I like the idea of all the expensive components embedded within the frame itself.
This way, the wheels are 'naked'. They can be stolen but won't be worth much.
Or they can be used for other options.

Since my partial fairing closing-clamshell design (and the later pure-design 'lobster') covers the frame when closed and locked shut, the frame ought to be pretty safe.
Embedding some police anti-theft devices like RFIDs could also help.
With carbon composites hiding some RFIDs during construction is a snap.
There would be no way to remove them without causing catastrophic failure in the frame.