2wd road bike

[Gregory Sutter]

Well here's one I've never seen before. I could understand this
for a mountain bike, or even CX, but still haven't come up with any
decent justification for a 2wd road bike.

http://sfbay.craigslist.org/sfc/bik/5782282216.html

(linked from the CL post:)
http://www.bikerumor.com/2012/09/17/found-tretta-2wd-bicycles-all-wheel-drive-road-mountain-cruiser-bikes/

Also note how the R-to-F drive chain goes up the left side of the
frame, then crosses over to the right side of the fork on the
steering axis. Bizarre!

--
Gregory S. Sutter Mostly Harmless
mailto:gsu...@zer0.org
http://zer0.org/~gsutter/

[Sir Ridesalot]

How do raise or lower (change) the front gear on that road bike? If the front gear you're in is different from the rear gear you're in you're going to have problems with the wheels turning at two different rates.

Cheers

[John B.]

The front drive chain is driven by a sprocket attached to the "other
side" of the rear hub so it turns at whatever speed the wheel is
turning. So, assuming 1:1 sprocket sizes the front wheel will turn at
the same speed as the rear wheel.

Based on the price quoted in the Cragslist post they are extremely
valuable and undoubtedly in great demand :-)
--
cheers,

John B.

[John B.]

On Wed, 14 Sep 2016 23:29:32 -0500, Gregory Sutter <gsu...@zer0.org>
wrote:

>Well here's one I've never seen before. I could understand this
>for a mountain bike, or even CX, but still haven't come up with any
>decent justification for a 2wd road bike.
>
>http://sfbay.craigslist.org/sfc/bik/5782282216.html
>
>(linked from the CL post:)
>http://www.bikerumor.com/2012/09/17/found-tretta-2wd-bicycles-all-wheel-drive-road-mountain-cruiser-bikes/
>
>Also note how the R-to-F drive chain goes up the left side of the
>frame, then crosses over to the right side of the fork on the
>steering axis. Bizarre!

The cross over at the front fork allows the use of some sort of
flexible joint between the chain from the rear sprocket and the chain
to the front wheel sprocket.
--
cheers,

John B.

[AMuzi]

On 9/14/2016 11:29 PM, Gregory Sutter wrote:
> Well here's one I've never seen before. I could understand this
> for a mountain bike, or even CX, but still haven't come up with any
> decent justification for a 2wd road bike.
>
> http://sfbay.craigslist.org/sfc/bik/5782282216.html
>
> (linked from the CL post:)
> http://www.bikerumor.com/2012/09/17/found-tretta-2wd-bicycles-all-wheel-drive-road-mountain-cruiser-bikes/
>
> Also note how the R-to-F drive chain goes up the left side of the
> frame, then crosses over to the right side of the fork on the
> steering axis. Bizarre!
>

I met an earnest guy from St Louis at a bike show around
1980 who showed a flex cable drive with bevel gears from
left side rear to the front hub. He was convinced the world
was waiting for his two wheel drive. He wasn't there the
next year.

--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971

[DATAKOLL MARINE RESEARCH]

amlost not visulally clumsy


goo.gl/9lfs64

ROKON was first used in oil exploration in the Everglades/Big Cypress...salty oil owned by Colliers

too heavy. always too heavy.

attempts were made at 4WD F1 cars ....what with 800HP on 1300 pounds plus midget...


tooo heavy. Unless the F1 is going thru a swamp.

[Joerg]

On 2016-09-14 21:29, Gregory Sutter wrote:
> Well here's one I've never seen before. I could understand this
> for a mountain bike, or even CX, but still haven't come up with any
> decent justification for a 2wd road bike.
>

Even for MTB it doesn't make much sense. By the time my rear starts to
spin the front usually carries so little remaining weight that it would
not contribute much, on account of being on a steep hill.

> http://sfbay.craigslist.org/sfc/bik/5782282216.html
>
> (linked from the CL post:)
> http://www.bikerumor.com/2012/09/17/found-tretta-2wd-bicycles-all-wheel-drive-road-mountain-cruiser-bikes/
>
> Also note how the R-to-F drive chain goes up the left side of the
> frame, then crosses over to the right side of the fork on the
> steering axis. Bizarre!
>

The riders will probably complain about notorious oil stains inside on
their left legs. Imagine riding this bike as a commuter with decent
office clothes. Oil is hard to wash out.

--
Regards, Joerg

http://www.analogconsultants.com/

[Andre Jute]

FYI, generally speaking, the wheels of a modern, sophisticated car don't turn at the same rate because of irregularities in the road, and when there is four wheel drive, even the front and rear wheels on the same side of the car don't turn at the same rate. In fact, there are electronics which will in consideration of each succeeding piece of road under each wheel keep each wheel turning at the correct speed for the desired forward progress.

As the electronics are developed, it would probably not cost a huge amount to adapt them to bicycle use, perhaps to release and reapply freewheeling clutches, so, in theory at least, efficiently working all wheel drive on a bicycle seems distinctly possible.

Note the "in theory at least". I think that the necessary mechanical linkages will screw up the efficiency to a far greater cost than any possible gain.

A more likely possibility is a motor in each hub, or bottom bracket centre and front motors, either mechanically scaled at a fixed relation (more drive at the front than the rear to avoid dangerous push-oversteer, or electronically self-adjusting current (=power) division front/rear according to slip angles of the tyres. Not necessarily expensive because all the electronics already exist, some of it already bike-specific, and the pedals plus a single electronic mode-switch can be both the controls and the gears. For instance, my bottom bracket motor has nine assistance settings that are as good as a sequential electronic gearbox, and torque and rotational speed sensing already sit on the bike too, together with umpteen other sophisticated electronic settings I haven't even bothered to read about in the manuals. Such controls needn't be fitted to an electronic motor: as long as they are on the bike: the motor can be the cyclist's legs, attached to the electronics via the pedals.

Andre Jute
A little, a very little thought will suffice -- Maynard Keynes

[Andre Jute]

I think it rather likely that a test fine enough to discriminate changes the rather low powers involved, will discover that on a road bike any kind of a flexible link (even the short flexijoint Slow Johnny posits) will lose enough power to cancel any gain all wheel drive offers, and then some. Also, the weight weenies won't be pleased by what a flexible coupling weighs, even if it has to transmit only 250W.

On the whole, the entire AWD bike, and this flexible coupling, is a solution in search of a problem,

***

More evidence, albeit only a thought experiment rather than empirical experience:
At first sight, it may seem as if a balloon-tyred bike could use all-wheel drive. But, in fact, my 60mm Big Apple shod bike has so much grip at speed on really twisty (as distinct from sweeping) turns on downhills that the problem is too much grip at both ends, causing safe understeer, rather than too little grip, causing fast oversteer which is dangerous but exhilarating for cyclists who can control it and aren't frightened of taking a spill. More power in the front wheel (in which there is presently none) will just aggravate the problem; what you want is less grip at the front so you can induce smooth push-oversteer from the rear wheel.

I was hoping that a bike which already corners exceptionally fast would be elevated to another class altogether when I switched from front hub-drive to centre motor/rear drive, but it turned out my fat tyres screwed me; it seems quite possible that to corner faster by means of all-wheel drive I'd have to go down to tyres so narrow that they would be dangerously unstable all the time, and godawfully uncomfortable besides, so there would be no gain in extreme conditions, and in normal conditions I'd lose efficiency, speed and handling (handling is what you do when you exceed the roadholding of your bike and it all starts to go wrong).

Interesting bike, Ridealot, in a Ripley's sort of way, but not very practical.

Andre Jute
Amused but not impressed

[Gregory Sutter]

On 2016-09-15, Joerg <ne...@analogconsultants.com> wrote:
> On 2016-09-14 21:29, Gregory Sutter wrote:
>> Well here's one I've never seen before. I could understand this
>> for a mountain bike, or even CX, but still haven't come up with any
>> decent justification for a 2wd road bike.
>
> Even for MTB it doesn't make much sense. By the time my rear starts to
> spin the front usually carries so little remaining weight that it would
> not contribute much, on account of being on a steep hill.

It would help in some nice slick mud. Especially for CX.

I'm still not buying, though! Imagine shouldering an extra 7lb
for every run-up...