[python] Re: Geared Steering
- From: Patrick van Gompel <patrick_van_gompel@xxxxxxxxxxx>
- To: "python@xxxxxxxxxxxxx" <python@xxxxxxxxxxxxx>
- Date: Mon, 3 Jun 2013 17:57:29 +0200
I am still reading about those steering concepts, but I have the idea that
quite a few people are talking about ideas but never cycled with a Python.
There's nothing bad about that (don't get me wrong), but I think it would be a
shame if somebody builds a wicked bike with some of those ideas to find out it
doesn't work and gets disappointed. Of course, it's always nice to try out new
ideas, but for your first build a 'normal' Python might be hard enough.
So my advise is: build a normal Python first, learn to cycle and see how you
like it. Then you might want to change things.
I have a cycled for hundreds of kilometers with a handle bar so I have quite
some experience with that. I think my main point is: you don't steer a Python
with you arms. You can think about very smart designs, but in my eyes your arms
are not strong enough for this. It is not like you are steering an upright
bike. For example: if you want to steer to the right and your legs are
basically just pedalling, you just can't steer enough and you will get very
tired if trying.
My conclusion after a few years is that you use a handle bar for sharp corning
(to aid you hip/leg steering) and to stabilize your steering in general. I do
like the handle bar too to put my arms at rest (and not always having to put
them on my lap).
"I think you could probably even go downhill with ordinary peddles, if
you could simply push on them so they are roughly equidistant, pushback
into your seat and hold onto stern, then tilt at your hips to move them
one way or another."
Yes, it does help I think. I use it quite often when going to a bump on the
road or whatever and it does prevent the sterring from sudden changes. For
downhill (not extremely fast, but still), I use the same leg position.
Date: Sun, 2 Jun 2013 00:21:17 -0400
Subject: [python] Re: Geared Steering
From: weyounet@xxxxxxxxx
To: python@xxxxxxxxxxxxx
the Torben ref http://en.openbike.org/wiki/Torben started with a steering
damper,
however he later took it off, as said it interfered with making corrections
when "about to lose control". I guess sometimes fast corrections are
necessary, when tipping to a side and such.
maybe after hitting a pothole also.
Kevin interesting, I think I get your idea now,
the levers would have a horizontal motion along a plane,
rather than turning around an axis.
The advantage over simply attaching a handlebar to the front of the bike, at
least for the geared steering, was that would be able to hold a certain angle
between stern and fore.
I read somewhere that it's important to maintain good contact with the seat,
and someone else that preferred handlebars at the back.
having handlebars on the front really does seem quite pointless, as then both
your arms and legs are at the front, and only your bum and maybe back are
maintaining angle with the stern boom.
Rather since it's really that to steer you bend at the hips, and turn fore
wheel with your legs,
so it's more important to hold onto the seat, or stern boom to maintain angle.
I think you could probably even go downhill with ordinary peddles, if you could
simply push on them so they are roughly equidistant, pushback into your seat
and hold onto stern, then tilt at your hips to move them one way or another.
Kevin the main thing is actually doing it, when you're just reading about it
may seem daunting, but when you get to it, typically it all works out, can
always fine-tune make adjustments and redo.
When I was building my first boat I made a few models first, that could help.
I've started on an openSCAD model of the python I'm planning on making,
inspired by Futon Express, he models just about everything before building.
I've been contacting Futon Express, and hopefully we can make an open source
package of the openSCAD drawings to make it easier for python and bike
designers in general.
On Sat, Jun 1, 2013 at 10:35 PM, Kevin <sunnymidnight@xxxxxxxxx> wrote:
I attached a sketch of what I envision the bell-crank solution being. I'll try
to describe it also...
A tab extends rearward from the pivot. Crank arms are mounted outboard on
either side, and oriented such that one leg extends rearward, and the other
extends out (left or right) from the pivot. Moving the outboard end of the
crank arm from front to rear will turn the front wheel from left to right. A
rowing oar setup is used to create this motion. Another analogy is the ball
& socket orientation of a shifter in a manual transmission car. It pivots at
hip height and the levers extend up to your hands.
But what advantage does this have over just attaching bars to the front half of
the bike? Is the goal to gain greater mechanical advantage, so that a larger
hand motion results in a smaller wheel movement?
It looks like the Resatec pivots are constructed with two pieces of square
tubing. One is small enough so it can freely rotate in the other. The inside
piece is oriented at 45 degrees to the outside, and the space between them is
filled with rubber. That way it can go through small rotations, but still hold
it's position reasonably well. That's my take on what it is anyway. The picture
here helped me... http://www.resatec.com/index1.html
p.s. I'm a long time lurker, and have been wanting to build a python for the
last 10 years or so. Hopefully my life is coming to a point where I can
make it a reality!
From: Logan Streondj <weyounet@xxxxxxxxx>
To: python@xxxxxxxxxxxxx
Sent: Saturday, June 1, 2013 8:30 PM
Subject: [python] Re: Geared Steering
George, I'm not sure how the bell crank and link rods
would work,
since they change the direction of a straight line of motion,
whereas here we need to change direction of a turning motion,
so bevel gears seems more appropriate.
If you do know how it'll work, perhaps you could make a picture of the concept.
The rubber pivot idea is curious, though I don't know how to implement it,
if there was some kind of tutorial or at least pictures/videos of it in action
would make more sense.
Gerald, yes so the legs can help with steering,
by changing angle between stern boom and forward wheel,
So I'm wondering if perhaps can use clipless pedals on forward wheel,
and handle-bars on stern boom, to allow steering while going downhill,
or when using electrical assist without pedalling.
An alternative to clipless pedals, maybe a spot where can hold the front wheel
with feet, perhaps by squeezing it between feet.
That would certainly be an easier solution, than having gears,
and may achieve similar results.
On Sat, Jun 1, 2013 at 3:56 AM, Gerald <bepb@xxxxxx> wrote:
Hi Logan,
there is certainly Jürgens orginal construction
page:http://www.python-lowracer.de/construction.html
Also, there is some info on the Python WIKI:
http://en.openbike.org/wiki/Main_Page.
Concerning the lever system, I think you will face the same issue as
with the handlebars. If you want to steer with the levers, you have
to counteract the forces extended by your legs.
I like to point out, that with some practice, the legs only steering
becomes very comfortable.
BR
Gerald
On 30.5.13 17:28 , Logan Streondj wrote:
hmmm, I don't think a damper would really do the
trick.
So guess the gears and levers is worth attempting, would
probably cost 15-30 for the gears, and some more for the
levers, though can probably just use some bike frame
parts.
only thing gotta figure out now is some kind of pivot for
the side gears, though guess it could just be some kinda
short pipe that flares out or has a cotter pin at the end,
that may interfere with the lever placement, though guess
the "green" housing can simply be around that part so it
should work.
I'm hoping to get a chance to build a python this summer, can
probably use my parents backyard, since my apartment doesn't
have anywhere to do welding.
Is there a listing of python building tutorials somewhere? I
like to read up on as much information as I can usually before
doing something.
On Wed, May 29, 2013 at 2:28 AM,
Steffen Risse <big.skangster@xxxxxxxxx>
wrote:
Pay attention that you don't understand
me wrong please. if you lock the pivot on a bike it's sure
that you'll fall over. On a trike it's less a problem. The
thing is just to dampen fast big movements especially at
high speeds. A possible solution comes from the motorbikes:
steering damper @ ebay (Lenkungsdämpfer)
Make sure you're not using the spring ones for the ladies
bycicles, because there's no damping included.
2013/5/29 Logan Streondj <weyounet@xxxxxxxxx>
Steffen, that sounds like a pretty
good idea, a steering brake.
maybe even a cheap calliper break, with
rounded pads would do the trick.
assuming can make steering adjustments
with legs,
the steering brake would then hold the
adjustment.
likely can have the steering brake at the
left side,
so can use the rear/main brakes on the
right side, simultaneously.
considering that using a brake is a simpler
solution, it's probably the better one also, fewer
moving parts and components, next I guess it would
be good if someone could try it out, though I'm
not sure how it would be mounted, or even how to
keep a certain part of the pivot exposed to allow
for applying the brake pads, I'm sure there must
be a way.
On Wed, May 29, 2013
at 12:54 AM, Steffen Risse <big.skangster@xxxxxxxxx>
wrote:
Just a thought from a python triker:
Maybe the steering bar is the wrong
point to work on for high speeds. When I
built my trike I used my old first try
on a python frame and combined it with a
wheelchair. While completing it with
parts I didn't greased the bearings for
the steering pivot. Half a year later I
greased them. After that I noticed a big
difference while coasting down one of
the bridges here in Berlin. The bike was
more nervous. It also hadn't a
slip-stick like behaviour anymore. Maybe
a steering damper whould therefore help
more than a steering bar on the
frontpart. The problem is, that the
damper might has to be connected to the
speed. Some variable friction in the
steering system could might help - like
a brake on the steering.
Cheers,
Steffen
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