Re: Fairings for upright bikes?

[RonSonic]

On Fri, 16 Jun 2006 12:43:16 -0600, [email protected] wrote:

>Then there's something to do with polar moments and lower centers of
>gravity. Weirdly, the tall-boy circus-style bicycles are more stable
>at low speeds.

Balance a stick on the end of your finger, a longer stick will be easier.

Ron

>After kind folk here at RBT explained the physics to me, I realized
>that I'd been watching recumbents wobbling slowly (and happily) along
>my bike path for years, but I'd never connected their unsteady
>progress with their handling characteristics.
>
>I assume that the recumbents that I see would stop wobbling at higher
>speeds, but any cop would stop them and ask the riders if they'd been
>drinking.
>
>Cheers,
>
>Carl Fogel

 

[Michael Press]

In article
<[email protected]>,
Simon Brooke <[email protected]> wrote:

> > That's balanced by lower stability on
> > rough surfaces,
>
> Really?

Yes. Actually less stabile on all surfaces. The interval
between noticing the bike tipping to one side and the
rider reacting to the change of balance is the same for
upright bicycles and recumbent bicycles. The lower
recumbent tips further in the time interval, measuring
`further' both as angle and as gravitational potential.

--
Michael Press

 

[[email protected]]

Michael Press wrote:
> In article
> <[email protected]>,
> Simon Brooke <[email protected]> wrote:
>
> > > That's balanced by lower stability on
> > > rough surfaces,
> >
> > Really?
>
> Yes. Actually less stabile on all surfaces.

Incomplete info, eh?

Any experience in the field?

Doubtful.

Height isn't everything, now is it.

Them highwheels were oh so stable, huh?

Other factors at play, too...

--JP

 

[Michael Press]

In article
<[email protected]>,
[email protected] wrote:

> Michael Press wrote:
> > In article
> > <[email protected]>,
> > Simon Brooke <[email protected]> wrote:
> >
> > > > That's balanced by lower stability on
> > > > rough surfaces,
> > >
> > > Really?
> >
> > Yes. Actually less stabile on all surfaces.
>
> Incomplete info, eh?
>
> Any experience in the field?
>
> Doubtful.
>
> Height isn't everything, now is it.
>
> Them highwheels were oh so stable, huh?
>
> Other factors at play, too...

I stated my case complete with relevant physics. Tell us
more.

--
Michael Press

 

[[email protected]]

Michael Press wrote:
> In article
> <[email protected]>,
> [email protected] wrote:
>
> > Michael Press wrote:
> > > In article
> > > <[email protected]>,
> > > Simon Brooke <[email protected]> wrote:
> > >
> > > > > That's balanced by lower stability on
> > > > > rough surfaces,
> > > >
> > > > Really?
> > >
> > > Yes. Actually less stabile on all surfaces.
> >
> > Incomplete info, eh?
> >
> > Any experience in the field?
> >
> > Doubtful.
> >
> > Height isn't everything, now is it.
> >
> > Them highwheels were oh so stable, huh?
> >
> > Other factors at play, too...
>
> I stated my case complete with relevant physics. Tell us
> more.

Is height the only measure of stability? No.

Recumbents can readily be much longer than uprights, as I mentioned
before. Which is more stable: a crit bike, a touring bike or a tandem?

Recumbents separate the steering plane from the support and
transmission planes. They're all tied together with an upright.
Separation brings more stability. If body weight is bounced around on
an upright that gets transmitted to the handlebars because the hands
are weighted. A recumbent can be jostled around but because the hands
are unweighted their reactions are independent of the jostles.

I also mentioned braking stability: if you hit the brakes hard on an
upright what is happening to your stability? If you ride into a dip or
if your front wheel hits a sizeable hole or depression of any kind,
where's your stability then? The tipping moment is an important aspect
of stability, is it not? With an upright you can easily find your
saddle unweighted due to a wide variety of common road conditions and
go head over heels and acquire the most common of uprighting injuries:
the separated shoulder or broken collarbone from your "stable" free
flight landing. Doesn't happen with hardly any recumbents (can't happen
with many of them).

Stability isn't a single-factor scenario, now is it. Stick balancing
height is a lame way to evaluate a bike. And, of course, no bikes are
judged that way---otherwise the highest bikes would be popular. Of
course, too, you're being specious and using nothing from the real
world of cycling to show your point. Moreover, as I said before, it's
doubtful that you've ridden many 'bents.

But how 'bout them upright fairings? You're already making bikes in
freeform shape out of carbon, why not add aero features which double as
cargo/fender/lighting? Think of it: a carbon unit on the front and one
on the back to add FIVE aspects of functionality (I forget what the
fifth was, but it's in there). Any other innovations do that? Uh, no.
I'm not saying these would be perfect, I'm just saying they'd add more
functionality than any other accessory and would fit in with current
fabrication. Hello?

> --
> Michael Press

 

[Call me Bob]

On Sat, 17 Jun 2006 01:12:43 GMT, Michael Press <[email protected]> wrote:

>> > That's balanced by lower stability on
>> > rough surfaces,
>>
>> Really?
>
>Yes. Actually less stabile on all surfaces.

But this is a bit of a red herring. The lower stability isn't a
problem because recumbents still fall well within the manageable
stability range of most riders.

Bicycles are "less stable" than three or four wheeled vehicles, but
that doesn't mean they are difficult or impractical to ride.

"Bob"
--

Email address is spam trapped, to reply directly remove the beverage.

 

[[email protected]]

PS: I believe there are at least two major forces involved in keeping
moving bikes upright. One relates to the "long pencil balancing"
science---the other relates to gyroscopic force. So that 'bents are
sometimes wobbly on start-up (until one gets used to them) but once
under way I suspect they are basically on par with any bike in terms of
stability. I'm sure these forces could be measured and compared versus
the reactive forces people can use. For instance, some people think
they can control sliding rear and/or front wheels but in general once
they break loose all bikes GO DOWN promptly. I believe this is an axiom
from one of the top tire designers and wheel scientists, Ye Olde Jobst
Brandt. So that in some ways stability differences b/w 'bents and
uprights may be MOOT.

NEXT! (We have a nice long list of stability factors, don't we. All
real. Long pencil, schmencil.)

The head-first position of a sport upright bike is perhaps neither here
nor there in terms of stability but it is indeed far more dangerous. So
there's that. People are observant enough to notice that the
belly-recumbent (or "prone") seems wacky---riding on one's belly,
head-first. But some folks like it. It's done well in hillclimbs quite
recently. Seems like a thrill. I'd try it. But one might first make
sure the course is safe, clear, closed. Yet a regular sport upright is
basically just as "head first." Yet people think nothing of it. ---Yet
when there's a road disturbance or impact we very often get the classic
head-first swan dive or, worse, head injury or head impact. (Of course
bents have their own injuries---with the dread "foot suck.")

--JP

 

[[email protected]]

at number 9 From: Thomas David Kehoe -

I heat up immediately going down wind in the late fall wearing into the
wing windbreaker - and so the zipper on hi end jersey

but the coast down numbers given by Kehoe are in still air?
caws if there's a wind from the side cathcing the fairing from anywhere
less than straight on well then your hi tech fairing wind breaker
becomes a low tech drogue chute
i cannot see myself riding over an intercoastal bridge with an incoming
squall wearing a zipp fairing caws i'd zipp be out on the next tide
fersure

 

[[email protected]]

PPS: I'm not sure we should even give uphills and climibing entirely
over to upright bikes. Bike R&D is too new for such a gimme.

For one thing, I'm quite sure there are some fit enthusiast riders who
are faster on their 'bents up steep hills than they are on uprights.
For another, downhills are worth considering. Plunging headfirst down a
steep hill on a sport upright bike is something that some folks get
used to but many in such geography simply don't ride a bike. As the
poster said, Appalachia is intimidating with the hills! Even walking
can be hard around some of those towns, given the hills. Feet first
might be a MUCH BETTER and MORE STABLE way to descend such downhills.
If the bike was light it might even go up them OK, too.

Once more bents are made out of carbon and ti to get their weight down
we might see more riders doing much better up hills with them.
Basically, a common 30-lb 'bent might just climb mostly like a 30-lb
upright. We're seeing more 20-lb bents these days, so we might start
seeing climbing ability like upright riders of 20-lb bikes have.

For our local rolling hills, the fastest clubby rides a bent. I don't
think he's superfit either. His bent helps him on the uphills, too. At
any rate it doesn't hold him back. I ride bents on and off---I found it
took me a couple years to adapt fully and get good at uphills. But I've
never done supersteep hills. And my bike is more like 32 lbs anyway.

--JP

 

[[email protected]]

Jeff who? surmises:

> PS: I believe there are at least two major forces involved in
> keeping moving bikes upright. One relates to the "long pencil
> balancing" science---the other relates to gyroscopic force.

Don't attribute things that you don't know or understand to others:

http://www.sheldonbrown.com/brandt/gyro.html

> So that 'bents are sometimes wobbly on start-up (until one gets used
> to them) but once under way I suspect they are basically on par with
> any bike in terms of stability.

You may mean polar moment of inertia which depends on the distance of
the center of mass to the axis of rotation (the road). You don't need
a recumbent to test that. You can try riding on a thin stripe on the
road sitting or standing on your bicycle and recognize the higher you
are the easier it becomes.

> I'm sure these forces could be measured and compared versus the
> reactive forces people can use. For instance, some people think
> they can control sliding rear and/or front wheels but in general
> once they break loose all bikes GO DOWN promptly.

Stability while skidding the rear wheel is something every youngster
discovers when riding a coaster brake bicycle. I take it you ride
cautiously and don't approach the limits of what is possible on a
bicycle or you wouldn't be so sure of things that aren't certain.

> I believe this is an axiom from one of the top tire designers and
> wheel scientists, Ye Olde Jobst Brandt. So that in some ways
> stability differences b/w 'bents and uprights may be MOOT.

I don't know how you arrive at this conclusion but it is off the mark.

> NEXT! (We have a nice long list of stability factors, don't we. All
> real. Long pencil, schmencil.)

Who's "we"?

Jobst Brandt

 

[Bill Bushnell]

In article <[email protected]>,
[email protected] wrote:
> But another rough-surface problem for many 'bents is the very lightly
> loaded front wheel. I tried a long wheelbase 'bent in a campground
> with gravel drives. Although I could ride my upright on that surface
> with no problem, I found the 'bent quite difficult due to front
> washout.

You don't say what model recumbent you tried or if it was the right size
for you. Some models (often called CLWB, compact long-wheelbase) place
the rider almost directly over the rear wheel. This gives a poor weight
distribution that can cause front wheel washout under the conditions you
describe.

The other problem is user error, using the wrong brake. On a LWB
recumbent one should use the front brake lightly or not at all unless
the road surface has little or no tilt relative to the direction of
travel. The rear brake has good grab even when the front starts to skid
on a straight stop on clean pavement. One of the most common LWB newbie
mistakes is to use the front brake as one would on an upright bike or a
short wheelbase (SWB) recumbent.

--
Bill Bushnell
http://pobox.com/~bushnell/

 

[Alistair Gunn]

In uk.rec.cycling [email protected] twisted the electrons to say:
> PS: Here are a couple links to images of carbon aero addons:

Correct me if I'm wrong, but aren't those all carbon aero parts for
recumbents?
--
These opinions might not even be mine ...
Let alone connected with my employer ...

 

[[email protected]]

[email protected] wrote:
> Jeff who? surmises:
[ ]
> > I'm sure these forces could be measured and compared versus the
> > reactive forces people can use. For instance, some people think
> > they can control sliding rear and/or front wheels but in general
> > once they break loose all bikes GO DOWN promptly.
>
> Stability while skidding the rear wheel is something every youngster
> discovers when riding a coaster brake bicycle. I take it you ride
> cautiously and don't approach the limits of what is possible on a
> bicycle or you wouldn't be so sure of things that aren't certain.
>
> > I believe this is an axiom from one of the top tire designers and
> > wheel scientists, Ye Olde Jobst Brandt. So that in some ways
> > stability differences b/w 'bents and uprights may be MOOT.
>
> I don't know how you arrive at this conclusion but it is off the mark.

?

Jobst Brandt: "For smooth tires on pavement, slipout occurs at slightly
less than 45 degrees from the road surface and is both precipitous and
unrecoverable."

from: http://www.sheldonbrown.com/brandt/descending.html

--Jeff Potter
allbikemag.com

 

[[email protected]]

Alistair Gunn wrote:
> In uk.rec.cycling [email protected] twisted the electrons to say:
> > PS: Here are a couple links to images of carbon aero addons:
>
> Correct me if I'm wrong, but aren't those all carbon aero parts for
> recumbents?

They are. But carbon is moldable. These items represent what can be
done. Alter slightly to add 5 types of functionality to any upright.
--JP

 

[Rob Morley]

In article <[email protected]>
<[email protected]> wrote:
> [email protected] wrote:
> > Jeff who? surmises:
> [ ]
> > > I'm sure these forces could be measured and compared versus the
> > > reactive forces people can use. For instance, some people think
> > > they can control sliding rear and/or front wheels but in general
> > > once they break loose all bikes GO DOWN promptly.
> >
> > Stability while skidding the rear wheel is something every youngster
> > discovers when riding a coaster brake bicycle. I take it you ride
> > cautiously and don't approach the limits of what is possible on a
> > bicycle or you wouldn't be so sure of things that aren't certain.
> >
> > > I believe this is an axiom from one of the top tire designers and
> > > wheel scientists, Ye Olde Jobst Brandt. So that in some ways
> > > stability differences b/w 'bents and uprights may be MOOT.
> >
> > I don't know how you arrive at this conclusion but it is off the mark.
>
> ?
>
> Jobst Brandt: "For smooth tires on pavement, slipout occurs at slightly
> less than 45 degrees from the road surface and is both precipitous and
> unrecoverable."
>
> from: http://www.sheldonbrown.com/brandt/descending.html
>
Which is about cornering forces, not braking forces ...

 

[[email protected]]

Bill Bushnell wrote:
> In article <[email protected]>,
> [email protected] wrote:
> > But another rough-surface problem for many 'bents is the very lightly
> > loaded front wheel. I tried a long wheelbase 'bent in a campground
> > with gravel drives. Although I could ride my upright on that surface
> > with no problem, I found the 'bent quite difficult due to front
> > washout.
>
> You don't say what model recumbent you tried or if it was the right size
> for you. Some models (often called CLWB, compact long-wheelbase) place
> the rider almost directly over the rear wheel. This gives a poor weight
> distribution that can cause front wheel washout under the conditions you
> describe.

This was some years ago, and I don't remember the brand name, but it
was a "normal" LWB/USS very much like the Infinity. When I showed
interest, the owner offered to let me test ride it. The size was
reasonably close.

I don't doubt that it would have been fine on road, or even on a smooth
limestone bike trail. The issues in the campground were the uneven,
sort of rutted & washed out drives with dirt/gravel surfaces. They
were the kind surface on which you'd pick your path carefully with an
upright, sort of zig-zagging to get to the smoothest patches.

>
> The other problem is user error, using the wrong brake.

Not in this case.

- Frank Krygowski

 

[[email protected]]

Rob Morley wrote:
> In article <[email protected]>
> <[email protected]> wrote:
> > [email protected] wrote:
> > > Jeff who? surmises:
> > [ ]
> > > > I'm sure these forces could be measured and compared versus the
> > > > reactive forces people can use. For instance, some people think
> > > > they can control sliding rear and/or front wheels but in general
> > > > once they break loose all bikes GO DOWN promptly.
> > >
> > > Stability while skidding the rear wheel is something every youngster
> > > discovers when riding a coaster brake bicycle. I take it you ride
> > > cautiously and don't approach the limits of what is possible on a
> > > bicycle or you wouldn't be so sure of things that aren't certain.
> > >
> > > > I believe this is an axiom from one of the top tire designers and
> > > > wheel scientists, Ye Olde Jobst Brandt. So that in some ways
> > > > stability differences b/w 'bents and uprights may be MOOT.
> > >
> > > I don't know how you arrive at this conclusion but it is off the mark.
> >
> > ?
> >
> > Jobst Brandt: "For smooth tires on pavement, slipout occurs at slightly
> > less than 45 degrees from the road surface and is both precipitous and
> > unrecoverable."
> >
> > from: http://www.sheldonbrown.com/brandt/descending.html
> >
> Which is about cornering forces, not braking forces ...

?

Jobst brought up the braking, not me. I was talking about stability
concerns and tires breaking loose when reaching limits of traction in
cornering. (When you reach the limit of cornering traction there's
little or nothing you can do to rescue yourself so that it's a moot
point whether you're riding an upright or recumbent.) Except that Jobst
seems to forget what he wrote. And he also thought I was talking about
brake-skidding. No braking mentioned, except elsewhere where I mention
that 'bents often have no tipover tendency in contrast to uprights.

Jobst also goes off about the already-mentioned idea about the high
bike (long pencil) being easier to balance. I never disagreed with
that. I say there are additional aspects to two-wheel stability
(length, tipover and gyro being three of them). For those who are
really into highbikes you can ride a highwheeler---or get most of an
upright's bigwheel stability by way of a highracer recumbent which uses
bigger wheels and has a higher CoG but still probably has safer tipover
moment than an upright.

--JP

--JP

 

[[email protected]]

Bill Bushnell wrote:
>
> You must have missed my recently posted photos. Clear Creek Rd. was
> unpaved for 14 miles and climbed and descended 2000 feet. We aren't
> supermen.
>
> I'm not familiar with the section of the C&O towpath you rode, but I
> doubt it would have been impossible on the kind of recumbent I ride if
> you managed it carrying camping gear on an upright bike.

Well, the C&O surface varies tremendously. Near Washington DC it was
quite smooth and pleasant, but generally speaking the further northwest
we got, the rougher it got. IIRC, it smooths out again near Cumberland
MD.

It's significant that the touring experts I consulted in the area were
split on whether we should even try the C&O. As it was, we rode it
joyfully for a while out of DC, then hit sticky mud and abandoned it
for Virginia's hills, got tired of the hills and got back on the C&O,
got tired of the bumps and abandoned it for Maryland's Appalachian
grades, got tired of the grades and returned to the C&O... you get the
picture.

For most of the length, the surface is not "improved." It started life
as a path for mules pulling boats, and it's never been graded. It's
often just a rough double track through the forest. Personally, I
really enjoyed it. But my wife and daughter were pretty displeased at
the surface.

BTW, when you talk about climbing 2000 feet with a recumbent - or any
bike - you should state something about the percent grade. As I said,
Appalachian grades are extreme. Western grades are usually much, much
gentler, IME. We climbed grades in Maryland and Pennsylvania that had
us standing and groaning to move uphill in our 20 inch low gears!
Those roads were paved. If they weren't, we'd have been off the bikes
and pushing.

Anyway - horses for courses, as someone said.

- Frank Krygowski

 

[Rob Morley]

In article <[email protected]>
<[email protected]> wrote:
<snip>
> Jobst brought up the braking, not me. I was talking about stability
> concerns and tires breaking loose when reaching limits of traction in
> cornering.

Perhaps you should have said that then, rather than expecting us to be
psychic.

 

[[email protected]]

Rob Morley wrote:
> In article <[email protected]>
> <[email protected]> wrote:
> <snip>
> > Jobst brought up the braking, not me. I was talking about stability
> > concerns and tires breaking loose when reaching limits of traction in
> > cornering.
>
> Perhaps you should have said that then, rather than expecting us to be
> psychic.

To further the discussion both you and Jobst could've said that I was
including two kinds of skidding under one description, one which fit
the other which didn't. Jobst was funny in disavowing an important part
of one of his own major essays to go after my overly broad remark.

My point is that the pencil-balancing concept is only one of several
important stability factors for bikes.

--JP