Re: Extensive article on Rivendell and Grant Petersen

Catrike Ryder <Soloman@old.bikers.org> wrote:

On Wed, 25 Sep 2024 14:46:35 GMT, Roger Merriman <roger@sarlet.com>
wrote:
 

Catrike Ryder <Soloman@old.bikers.org> wrote:

On Wed, 25 Sep 2024 10:57:52 GMT, Roger Merriman <roger@sarlet.com>
wrote:
 

Catrike Ryder <Soloman@old.bikers.org> wrote:

On Wed, 25 Sep 2024 09:05:25 GMT, Roger Merriman <roger@sarlet.com>
wrote:
 

Frank Krygowski <frkrygow@sbcglobal.net> wrote:

On 9/24/2024 3:17 PM, Catrike Ryder wrote:

On Tue, 24 Sep 2024 14:14:41 -0400, Frank Krygowski
<frkrygow@sbcglobal.net> wrote:
 

You might do well to read some of the archives of this group. There have
always been people posting opinions that were factually wrong, and there
have always been people pointing out those mistakes. As I've noted
earlier, having mistakes pointed out is a necessary part of the process
of education.

 
That's fine of the person being corrected understands that the
corrector is qualified to do so and is truly interested in making
things better. In my opinion, you fall far short of both those
standards.

 
Your opinion on that matter is worthless. You don't have anywhere near
the background needed to judge technical proficiency. Professional
Engineering licensing boards of two different states have disagreed with
you, not to mention those conferring my engineering degrees and those
institutions for whom I've worked.
 

There are many examples of ideas that were posted frequently, and noted
as wrong. Most of them seldom pop up any more - and not only, I think,
just because there are fewer posts. I think people actually learned things.
 
Examples of mistaken claims? Chains wear by stretching the metal. Old
frames get "soft." Increasing spoke tension makes a wheel more rigid.
Tying and soldering spokes makes a wheel stronger. Headsets fail by true
brinelling due to impact loads. Hanging a bike by the front wheel makes
the spokes stretch... and many more.
 
BTW, what was that stopping distance from 20 mph again?  ;-)

 
20 MPH would be maybe 9/10 feet if I didn't concern myself with
slamming the chain rings into the ground or doing a face plant on the
ground in front of the bike. 30 MPH would be a little further. Two
front brakes work better than one, especially when the rider's weight
is already more over the front wheels before he applies the brakes.

 
Right, good one. There is no way you can stop your tricycle in 10 feet
from 20 miles per hour. That would require a deceleration of 43 ft/s^2
or 1.34 times the acceleration of gravity. IOW you'd need tires with a
static coefficient of friction at least 1.34, plus absolutely perfect
application of both brakes so that both wheels were at the absolute
limit of traction but not skidding. And you'd have to be in a "nose
wheelie" all the while, with your rear tire up in the air so every bit
of your weight was on the front wheels. It's essentially impossible.
 
For 9 feet, your acceleration would have to be nearly 48 ft/s^2, and
besides absolutely perfect braking reflexes, you'd need tires with a
static coefficient of friction at least 1.48.
 
And 30 mph would be _much_ farther, not "a little." The velocity term
gets squared in the relevant calculation, much as it does when
calculating kinetic energy.
 
I'm sure you don't know what a lot of that means. But what you're
claiming is practically impossible. Feel free to prove me wrong by doing
what you claim and posting video evidence.
 
 

Even if he means without thinking time

 
Yes, I know I'm going to stop and my fingers are already on the brake
levers.
 

20mph is 6 meters or 20ft for a car,
which almost certainly can out brake the trike.

 
I doubt that.
 

If a planned braking action on the MTB probably could reduce that a touch
as it has huge amounts of grip and braking force, and frame allows one to
get behind the rear wheel.
 
Other bikes at best would equal, the old commute bike as it has weight to
the rear is surprisingly effective at emergency stops or just using the
rear brake hard, but even that will during a emergency start to lock the
rear.
 
Neither of the road/gravel bikes would do well at emergency stops as your
in the wrong position ie far too forward.
 
Roger Merriman
 

 
A few weeks ago, after posting about braking, I tested the Catrike's
brakes at 15 MPH. I stopped at about 6 feet, keeping the chain rings
off the ground.

 
That?s really hard to see how, you?ve mentioned that the trike pitches
which suggests that its weight is quite forward.

 
Indeed it does pitch forward. It's easy to lift the rear tire off the
road, however, the center of gravity of me on the Catrike compared to
someone on a two wheeler is much lower. LIfting the rear wheel of the
ground still requires a lot of braking force.

 
Lifting the rear wheel on the MTB in position ie off the rear wheel Is not
easy at all, if it?s more of emergency brake the rear wheel might lock if
I?m not in position in position your not lifting the rear wheel on flat
ground.
 
Even my gravel bike tipping forward isn?t particularly an issue if I can
get in position and if not it?s more likely to lock the rear than lift it.
 
My old commute bike with a lot of rear weight even on an emergency stop
your not going to lift it at worse it will lock.
 
The weight being low isn?t the issue it?s the weight forward/rear and that
your weight is static.

 

Note that cable disks are by some margin less powerful than hydraulic
systems, ie even a fairly modest cheap twin pot is going to be many times
more powerful, let alone 4 pots and so on.

 
I really don't understand the issue of more powerful brakes. I changed
my Avid bb7s from long pull to short pull and I still have to back the
calipers off so as to not lock up the brakes at high speeds. The
brakes are perfectly capable of slamming the chain rings into the
ground and pitching 205 lb me out on my face. I've heard of people who
have had that experience. One on a Catrike 700 with an even lower
center of gravity than my Expedition.

 
That?s all to do with the CatTrike Geometry ie it?s weight forward so it?s
limited by its pitching, that doesn?t make the cable disks powerful just
that the geometry limits the trikes braking, I have had bikes with cable
disks a few different models in fact, powerful they are not, about the same
as rim brake bike.

 

I run Magic Mary?s at 2.40 they are soft and gummy tires and on tarmac they
are effectively glued to it! Even with that 6ft at 15MPH seems ambitious!

 
I use road tires, of course. 40MM at 70/80 psi. I suspect my tires are
glued to the road better than your knobby MTB tires.

 
Not a chance, Marathons are designed for touring and commuting get many
thousands of miles out of those, compounded with higher pressures, my
Gravel bike with similar sized tires but half the pressure and more volume
and softer rubber and so on. Is likely to be a better at this.
 
Let alone the MTB with soft sticky rubber much more volume 700*64 is a lot
of air a frame that allows one to get off the back its geometry etc, ie I
can if break to the limits of the tires for that reason.
 
Your limited clearly by the trikes geometry, where as upright bikes
particularly slacker geometry MTB are able to utilise not just more
powerful brakes but brakes with absolutely enormous amounts of power, see
my posts few months back with the DH brakes.

 

--
C'est bon
Soloman
 

Roger Merriman
 

 
--
C'est bon
Soloman
 

Roger Merriman
 

 
Do you really believe that a lower center of gravity does not make a
bike more stable?
 
--
C'est bon
Soloman
 

>
Look at your trike and how much the chainrings and thus your legs overhang
the front wheels, it’s clearly going to be prone to pitching forward with
the weight so forward, that the weight is low isn’t really going to change
that significantly.
>
Roger Merriman