[python] Re: Pedal Induced Steering
- From: DB <midget1488@xxxxxxxxx>
- To: python@xxxxxxxxxxxxx
- Date: Tue, 25 Apr 2006 18:57:08 -0700 (PDT)
Dirk, 25hz and all,
Thanks very much for sharing your insights and links
to your bikes. More information on the Cruzbike can be
had at http://sports.groups.yahoo.com/group/Cruzbike/
if you're interested in some other mechanical
interpretations of the design and applications of the
kit.
25hz, I take a lot of encouragement in what you say,
because although I've been working on the bikes for
about a year, I haven't had the opportunity for much
seat time, and the bike does respond well to circular
pedalling and forced relaxation (is that an oxymoron?)
of the shoulders. Come to think of it, I also
experience some pedal steer on my Vision R40 SWB. And
as you observe, it gets more pronounced as my legs
become tired.
I guess one of my background concerns is that on a
moving bottom bracket FWD, pedal steer can work the
upper body and shoulders, and things that are a minor
annoyance on short rides can become endurance issues
on long rides (I intend to ride this bike on a 150
mile, two-day charity ride in early June.) So if there
is a mechanical route to lessen the effect, I'm
interested.
Perhaps practice and discipline are the first order of
the day however...
Dirk, thanks for describing in detail the effect of
increasing the trail dimension on your Camel Bike. You
have saved me another path of experimentation, as I
was about to increase the trail dimension as a test.
25hz, I would like to post your observations about
riding style on the Cruzbike Yahoo group. Is this
acceptable to you?
Again, thanks for your observations.
Doug
--- 25hz <25hz@xxxxxxxxxx> wrote:
> On other lists/pages/forums that refer to
> recumbents, it's also called PIS
> or pedal induced steering. This may be all over the
> map a bit, but
> hopefully I get the information across that I want
> to, wihtou being too
> epic.
>
> I think there's a lot more going on than just frame
> geometry of a bent with
> regards to the phenomena. In my experience from
> building 17 or 18 bents of
> different designs and modifying 5 or 6 other bents,
> the majority of the
> issue is the rider and how smooth they ride and how
> much effort they want to
> improve their riding skill/style. Even on normal
> uprights I have seen
> people go down the street as if they were a swimming
> fish, and again, this
> has nothing to do with the bike and everything to do
> with the rider. Even
> with the same rider on the same bike, if they ride
> with no hands, the PIS
> goes away.
>
> Now, that's not to say that some designs are not
> easier to ride smoothly
> than others, but I have yet to ride a recumbent
> (I've ridden close to 30
> different styles and shapes of recumbents in the
> last 3 years) that COULDN'T
> be ridden smoothly. On conventionally steered bents
> like SWBs, or on SWB
> tadpole trikes, if they have close to 50% of the
> weight on or near the front
> wheel(s), they have a tendency to produce pedal
> steer fairly easy because of
> the weight over the front wheels (and the front
> wheel(s) contact patch ends
> up being more like the pivot for a teeter-totter)
> and also because the
> weight is constantly shifting forward and back,
> which adds to the "pulsing".
> Unless the bent is SO front heavy that it wants to
> tip forward even while
> sitting still on flat ground, even those can be
> ridden WITHOUT pedal steer
> IF the rider expends the effort to concentrate on
> spinning smoothly and
> evenly. I've ridden SWB tadpole trikes that were so
> front heavy that on
> even a moderate down-hill with very light braking,
> they would start to lift
> the rear wheel off the ground, but again, with
> effort, PIS could be
> eliminated.
>
> My brother is a grinder and uses a TON of body
> language when riding. DF,
> high racer, trike - doesn't matter. Riding behind
> or beside him, you can
> see his arms moving around, his shoulders moving up
> and down and his hips
> twisting left to right. On an upright, this "dirty'
> pedalling doesn't seem
> to produce as pronounced of an effect because subtle
> weight shifts along the
> entire height of the body can take it out of the
> equation. On a recumbent,
> especially ones with laid back seats, all of this
> extra body movement turns
> into steering input because you can't use body
> language to compensate. When
> my brother rides my one trike, he gets a ton of PIS.
> He tells me it's
> "twitchy". Even though he constantly squirms all
> over the place, when I
> tell him the 'twichiness" is because he's not
> sitting still, he adamantly
> claims he's as steady as a rock. While pedalling,
> if I tell him to let go
> of the handle bars of the trike, it immediately
> stops swerving and tracks as
> straight as a train on rails. This is because by
> letting go of the
> handlebars, he has lost the leverage points that he
> uses to push and pull
> himself around in the seat while pedalling. When I
> ride this trike, it
> tracks perfectly and in fact, when I raced it on the
> velodrome last time, I
> let go of the handlebars around the banked corners
> and let the trike pick
> it's own line based on the speed I was doing. It
> worked fine. Also, on
> most of the trikes I build, by riding with no hands,
> you can steer the trike
> by leaning left or right. This wasn't intentional,
> it just seems to work,
> and again, there is no pedal steer while doing it.
> Even on bents that I can
> ride smoothly with no pedal steer, if I exceed a
> certain pedal RPM, my
> pedalling technique starts to get sloppy and pedal
> steer (not to mention a
> "pulsing" sound coming from the tires) is generally
> the result.
>
> The nice thing about non-center steered bents is
> that the "power system" and
> the "steering system" are separate and they can
> remain that way unless
> sloppy riding habits combine them. On the python,
> it's obviously a little
> more complicated because those two systems overlap.
> You can also steer with
> your hips, your shoulders and even slight
> down-pressure on the "handlebars",
> but it seems, at least to Marcel and I, that most of
> our steering is done
> with our legs. While accelerating hard, we still
> tend to steer with our
> legs/feet (even though we don't want to) but we can
> counter that steering
> input by using our hips and shoulders and try to
> keep the python going
> straighter and take the power lost from going left
> and right, and try to
> redirect it back forward. Marcel spent a lot of
> time on racing road bikes
> with clipless pedals and learned how to pedal very
> smoothly a long time ago.
> as a result, he is extremely smooth on the python,
> which enabled him to not
> only learn to ride it in a matter of minutes, but
> also enabled him to race
> it on ice as well as race it quickly SLALOMING on
> ice :) When our legs get
> tired though, we both get pedal steer. When my legs
> start getting tired I
> actually INDUCE pedal steer. Why? Well, when I'm
> tired and trying to ride
> perfectly straight, it takes a fair bit of
> concentration to keep it going
> perfectly straight and react to small steering
> corrections. If I use pedal
> steer on purpose (and I'm talking just a small
> amount to make a small
> swerving motion) I'm always either in a slight left
> turn or slight right
> turn. The act of turning helps stabilize the python
> for me and it's easier
> to ride because I don't need to try to stay in a
> "neutral" upright position.
> So with always being in a slight, gentle turn, it
> makes it much more
> relaxing to ride. Obviously, I don't do this when
> I'm in tight traffic or
> when I see cars coming up behind me :)
>
> At any rate, in the end, pedal steer, I believe, is
> a fact of life on a
> recumbent because of their design. Regardless of
> the design of the bent, I
> have yet to ride one that can't be ridden smoothly
> if you really want to.
> Conversely, I have yet to see a bent get ridden by a
> new rider that DOESN'T
> have pedal steer, regardless of how smooth or easy
> it is to ride. :) It's
> a natural biomechanical function for our entire
> bodies to move in rhythm
> with the motion of our legs. Only through conscious
> effort and practice can
> we reduce and eliminate it. While some bents might
> be "easier" (relative
> term . . ) to ride than others, to get ride of pedal
> steer, you just need to
> find the rhythm of the bent and adapt yourself to
> it, and the pedal steer
> will subside. People who ride on rollers a lot are
> extremely smooth riders
> because in most cases the rollers are only 12 to 15"
> wide. Sloppy riders
> who swerve a lot either learn to control extraneous
> body movement or they go
> off the rollers a lot. On the high racer I just
> finished, I used a recycled
> road bike frame
>
(http://www.fleettrikes.com/high%20racer%20stage%206.jpg).
> If I don't pedal smooth and allow my shoulders to
> roll and arms to move in
> sync with my legs, I can get heavy pedal steer. If
> I pedal circles and
> relax my arms, it tracks straight as an arrow.
>
> Try this experiment. Find a chair that spins fairly
> easily. Lean back in
> it and pick your feet up free of the chair base and
> the ground. Hold your
>
=== message truncated ===
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