Fear of Flying

"Curtis L. Russell" wrote in message
...
On 25 Jan 2007 14:20:26 -0800, "chalo colina"
wrote:

So because
'bent bikes are (generally speaking) worse than upright bikes with
regard to stability at speed, 'bent trikes are /more stable/ than
upright trikes, and this makes two- and three-wheeled 'bents comparable
to each other in their sure-footedness at high speed.

Actually, 2- and 3-wheel recumbents are not in any way comparable. All you
ever have to do is to ride them for several years and you will discover that
they are totally different creatures.

I've raced diamond frames and ridden for some time a SWB Vision. I
find taking the Vision down a curving downhill more stable than the
diamond frames - and I've held my own in a decending pace line under
race conditions. So I simply do not agree with your assumption. Yes,
Armstrong or Merkx could out descend me - but the same would be true
with me on a diamond frame.

Old Russell should not be riding his recumbent in a pace line with uprights.
They just hate that sort of thing.

FWIW, a person that knows how to race an upright trike can make it do
wonders in a turn - something I have observed but been unable to
duplicate (and had the scars for a while to prove my lack of success -
it wasn't as easy as it looked, and it didn't look easy in the first
place). Not sure if they would try the same leaning process on a fast
downhill though.

You do not ever want to lean a recumbent much in a turn. If you do so, you
will end up in the emergency room of a hospital.

Regards,

Ed Dolan the Great - Minnesota
aka
Saint Edward the Great - Order of the Perpetual Sorrows - Minnesota

wrote in message
ups.com...
On one downhill run I got my Linear LWB up to 82 kph (50 mph). It felt
solid as a rock, and it was only my nerves that gave out. I started
having brief thoughts like "hope the front wheel's QR skewer is done up
tight enough", and then "what would happen if a tire blew out?". Well,
potential road rash at that speed didn't sound like any fun, and I was
already over the posted 60kph (40 mph) speed lilmit, so I was happy to
stop pedaling and just coast until the road levelled out more.

The next time I went down that hill I was happy to stay at only 70 kph.


It is possible to go much faster safely on a 2-wheeler than on a 3-wheeler.
But I do not feel comfortable on any bike at a speed much above 35 mph. Like
you, I start to think about all the things that could go wrong. Nope, it is
just not worth it! Speed kills; it always has and it always will. I can even
get into trouble if I walk too fast.

Regards,

Ed Dolan the Great - Minnesota
aka
Saint Edward the Great - Order of the Perpetual Sorrows - Minnesota

Hey guys -

Curtis wrote:

I rather doubt [Wayne's] premise about a diamond
frame rider making constant adjustments... At speed
a DF is rather forgiving...

As I said, most bikes have good short-term stability -
in both roll and yaw axes. However, they will not
maintain an upright posture for seconds without the
rider making minor, and most likely almost subconscious
corrections. It would be very easy to PROVE me wrong.
Just strap about 100 to 150 pounds of sandbags on a
(riderless) bike, secure the handlebar rotation however
you'd like, hook up a tow rope from another cycle, and
start off down a straight road with it. Have a friend
run alongside balancing it up to 5 or 10 MPH, then let
it go. Make a video if you're able to get one to stay up
for a mile or two, and I'll retract my unfounded opinion
after I've seen it. Towing a tadpole with a dead weight
is not a problem, even around the block...

Jeff said:

I forgot to stick up for the Tricruiser... Sid was a
pleasure to deal with and the Tricruiser was fun to
ride.

SHAMELESS PLUG - Link to the TriCruiser website:

http://www.americruiser.com/

I hope most folks understand that I wasn't 'attacking'
either the trike, its maker or snubbing it because of
its price. I was highlighting the clear distinction
between that tadpole - comfort oriented, with a very
high seat, fairly flexible frame and a lot of both brake
and bump steering effect - to a lower, stiffer, more
performance oriented design with more yaw stability at
high speed and much better roll stability at any speed,
and with virtually no brake or bump steer.

My impression of the TriCruiser is that it was designed
as a sort of 'neighborhood cruiser', especially for
folks who lack the flexibility or strength to cope with
a laidback trike seat less than a foot off the ground.
IMHO, it was simply (and I would hope very obviously)
not designed for the downhill speeds that most cyclists
reach on day trips - especially with a big dog flopping
around on its sky-high rear rack. ;-)

Regards,
Wayne

Dave Larrington wrote:
In article ePbuh.19361$pb7.13011@trndny09, lid
says...


On reading these posts about instability at speed in trikes or at least
a sense of instability, I began to wonder if there were any trikes that
incorporated wheel lean in their designs. I've noticed on the cutting
edge tech sites many designs for motorized vehicles with wheel lean. Why
not for human powered?


It /has/ been tried, but the additional weight and complexity were
usually deemed not to be worth it. The Tripendo, for example, was a
German all-carbon leaning trike weighing about half as much again as my
steel Trice.

And hanging out of the seat on a tight corner is part of the fun


Thanks for the link. That may be the trike that I saw though I can't be
sure. I only rode along side for about a minute with my concentration on
the front suspension. With a rider seated I couldn't see the futuristic
seat. The wheels were spoked. The monocoque was similar though white or
light gray with a distinctly apparent weave pattern - probably fiber
glass. Though I noticed the double wishbone suspension I didn't think of
it as a leaning trike. It was a flat straight away though so there was
no basis to see lean.

I was looking at some of the linked trikes from this page -
http://home.mindspring.com/~kb7mxu/trikes2.htm

... and saw some other leaning designs.

This one seems to have been dropped since there's only a picture at the
site.
http://home.mindspring.com/~kb7mxu/images/berg.jpg

This one is in development.
http://www.kerrelcycles.com/index.html

The Tripendo is also on the link page.
http://www.tripendo.com/EDEFAULT.htm

As for wheels that permanently lean in the style of sport wheel chairs,
I'd guess that steering and propulsion would have to be via the third
wheel or fairly complex.

MkTm Wrote:
Jeff Grippe wrote:
On reading these posts about instability at speed in trikes or at
least
a sense of instability, I began to wonder if there were any trikes
that
incorporated wheel lean in their designs. ... Even simpler, in the
manner of current autos, the suspension could be designed to force
wheel lean depending of the downward force on it. Don't understand your auto reference. Car suspension design strive to
achieve and maintain a neutral or slight negative camber through all
driving conditions. Suspension travel and body roll makes this quite
challenging. For a car wheel with its basically rectangular tyre
profile and laterally strong rims there is nothing to be gained from
increasing this angle.
MkTm Wrote:
Jeff Grippe wrote:
I've also seen rollerbladers with unusual skates. Rather than having
many small wheels vertically mounted the unusual skates had two large
wheels (about 8 to 10 inches in diameter) mounted such that they
leaned
from the outside of the foot to meet the ground just at the center of
the foot, though obviously some few inches below. Though this lean
seems
opposite to the direction needed for turn stability it seems to test
the
endurance of the bearing mechanisms involved in lean.
But they have their own reason for going that way. The sworn enemy of
recreational inline skating is poor road surfaces, and bigger wheels
helps reduce the amount of vibration generated by smaller wheels. Big
wheels w/o the angle forces you either to build very high skates, or to
stretch the wheelbase until the foot will fit between the wheels.
Besides the unwanted length the stretched 2-point wheelbase also messes
up cornering ability.
MkTm Wrote:
Jeff Grippe wrote:
Sport wheel chairs have used a leaning wheel design for some time. Why
isn't this used with trikes?

It's either done to increase track width, or to prevent wheels from
buckling when cornering, or both.
A DF or 2-wheeled 'bent lean in curves, so they can get by with using
wheels with limited lateral stability. A sport wheel chair can't lean,
so a pre-loaded configuration reduces wheel loads when cornering.

Smaller wheels, like those often found on a trike, can take higher
lateral loads, and the track width of the trike isn't limited to
operator's reach.
I also suspect that steering response would be decidedly odd it you
tried steering with a significantly leaning wheel.


--
dabac