[python] AW: Re: AW: Re: Questions about Python-Trike geometry (project similar to Howard Stevens foldable Python trike)

  • From: Gerald<bepb@xxxxxx>
  • To: python@xxxxxxxxxxxxx
  • Date: Thu, 28 Jul 2011 17:05:33 +0200

Hi Frank,
Obviously You can ride a trike uphill as slow as you like. But, at least in my 
expirience, going uphill with a front wheel drive trike - or bicicle at that - 
your limit might not be your power to pedal, but traction. 
If your front wheel slips excessivly, you will have a poor and exhausting ride 
going  uphill  with a trike, even more so with the bike.

The issue is that if you pedal uphill,  you dynamicaly deload the front wheel, 
and load the rear wheel. Good for rear wheel drive bike. 






 
 


 

-----Ursprüngliche Nachricht-----
Von: Frank Schmaus <frank.schmaus@xxxxxx>
An: python@xxxxxxxxxxxxx
Gesendet: Do., 28. Jul 2011, 13:53:34 GMT+00:00
Betreff: [python] Re: AW: Re: Questions about Python-Trike geometry (project 
similar to Howard Stevens foldable Python trike)

Thanks for the input. I anyhow have to place the backwheels far behind, to be 
able to roll the collapsed box around and still have enough room for my 
laguage. But somehow I thought the wheelbase should not be too wide as it will 
increase the danger of tilting to the side, the more lengthy the triangle of 
the wheel becomes.

Traction is an important issue for me, as I have one specific track in mind, 
that I will use quite often, that is a steep mountain road. That's also why I 
prefer a trike with 20 inch wheels instead of a small foldable bike with a 
trailer. The trike can be run as slow as you like, if the gear is choosen well.

Am 28.07.2011 15:07, schrieb Gerald:
> Hi,
> based on my own expirience with a Python trike, I suggest to aim for more > 
> weight on the front wheel, if possibe ~50% on the front wheel, ~25% on the > 
> rear wheel. Otherwise going uphill will give problems with traction. This can 
> > be archieved by place the rear axle/wheels far enough back, behind the seat 
> > about as far as for a two wheel python.
> For the pivot angel, I made good expirience with 50 degree.
>
>
> Gerald
>
>
>
>
>
>
> -----Ursprüngliche Nachricht-----
>
>     *Von: *"gdurbrid@xxxxxxxxxxxxxx" <gdurbrid@xxxxxxxxxxxxxx>*
>     An: *python@xxxxxxxxxxxxx*
>     Cc: *Frank Schmaus <frank.schmaus@xxxxxx>*
>     Gesendet: *Do., 28. Jul 2011, 11:19:25 GMT+00:00*
>     Betreff: *[python] Re: Questions about Python-Trike geometry (project
>     similar to Howard Stevens foldable Python trike)
>
>     Frank,
>
>     I assume you propose to build a delta trike (two rear wheels), as a Python
>     tadpole (two front wheels) is a challenging thought. There are several
>     trikes in Jurgen's hall of fame, but the best documented front-wheel drive
>     centre-steer delta trike I know of is the Hipparion (Google for it, but
>     avoid the horses). It isn't strictly a Python, because Esko Meriluoto
>     built it before Jurgen built the first Python. But it's very much the same
>     sort of design, and is now in its fourth iteration.
>
>     Most successful trikes have a wheelbase of about 1 metre, and a track of
>     60 - 80 cm. Tadpoles generally have about 1/3 of the weight on each wheel.
>     Rear-wheel drive deltas such as the Anura and Kettwiesel often have more
>     than 1/3 on each rear wheel. These are not golden rules, just experiences.
>     Your front wheel must provide traction, steering and braking, so don't
>     unload it too much.
>
>     On any trike, the wider the track, the less the trike will tend to tip
>     over sideways when cornering. On a Python trike, your weight must be close
>     behind the front wheel, so the wheelbase should be short. Draw a triangle
>     on the ground, connecting the points where your wheels touch the ground.
>     Mark a point under your centre of gravity: the longer the line from one
>     side of the triangle to the other through this point, the stabler the
>     trike will be. How wide a trike can be made usually depends on space in
>     the house, door widths and so on. If the seat is low enough, a track of 66
>     cm is satisfactory on tadpole trikes. I would not use less on a delta
>     trike, unless you mean to ride very slowly and carefully, because delta
>     trikes are very tippy: see the Hipparion site.
>
>     One golden rule is that the lower the centre of gravity, the better the
>     trike will corner and brake. This really means your own centre of gravity:
>     riders weigh a lot more than trikes. Trikes are completely different from
>     bikes as regards cornering (though not braking). You should have the seat
>     as close to the ground as you can arrange: 15 cm is high, and 10 cm is
>     better, unless you will be riding off road, or over gutters and rocks. The
>     low seat does make it harder to get off, but you can put a loop of webbing
>     around part of the front frame and use it to lift yourself up.
>
>     Python trikes seems generally to work best with lower pivot angles than
>     Python bikes. I don't know why, but it seems that 57 - 60 degrees has
>     generally been found preferable. Since bikes lean when they corner, but
>     (most) trikes do not, it does make sense that the inverse pendulum should
>     work differently for bikes and for trikes. Perhaps the lean of the bike
>     increases the effect, so that a steeper pivot angle is satisfactory, but a
>     trike depends entirely on the inverse pendulum, so needs more of that
>     effect i.e. a shallower angle. Dirk may have a view on this.
>
>     Best of luck,
>
>     George
>
>     ---- Frank Schmaus wrote:
>     > As I got quick reply and really good help last time, I try it again:
>     >
>     > I'm planning to build some foldable python trike like this one:
>     > 
> http://en.openbike.org/wiki/Python_Trikes#Howard_Stevens_Mk2.2C_Australia
>     > But with larger laguage capacity. On the python page
>     > (http://www.python-lowracer.de/geometry.html) there's a lot of good
>     input on
>     > geomtry questions concerning pythons. But how is all that with a python
>     trike? I
>     > gues the requirements and the conditions are quite different. Is there 
> any
>     > written summary about trail and angle for a trike? I would like to
>     follow well
>     > approved standards instead of having to build several trikes, just
>     because the
>     > first ones are ugly to stear.
>     >
>     > Any other parameters e.g. wheelbase, minimum ground clearance, track
>     width...
>     > are also still quite a myth to me, but those are more bound to other
>     > requirements of the vehicle, whereas angle and trail are free of choice 
> to
>     > assure the best performance possible.
>     >
>     > Hope to get a lot of good suggestions,
>     > Cheers from Germany,
>     > Frank
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