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

  • From: Patrick van Gompel <patrick_van_gompel@xxxxxxxxxxx>
  • To: <python@xxxxxxxxxxxxx>
  • Date: Fri, 29 Jul 2011 19:53:50 +0200

Are you saying that you abandoned a beautifull trike design because of rear 
wheel skiding when braking? I want to build a python trike myself, so I wonder 
why you would worry about it. I mean, if just the front wheel is enough for 
braking, then why bother about the rear? My two wheel Python doesn't even have 
a rear brake. Or is it a safety concern? Though, you could always fit multiple 
brakes on just the front.
Please let me know you thoughts,

Date: Fri, 29 Jul 2011 14:33:38 +0100
To: python@xxxxxxxxxxxxx
From: Rhisiart@xxxxxxxxxxxxxx
Subject: [python] Re: AW: Re: Questions about Python-Trike geometry (project 
similar to Howard Stevens foldable Python trike)

[python] Re: AW: Re: Questions about Python-Trike
Hi Frank,

When running my 20" Python as a delta trike, I've found that
I can ride up 33% (1 in 3) gravel slopes without wheel
slippage. That's because I have the frame geometry arranged so that
about 60% of the total weight is carried on the front wheel. The only
problem from that is that with the two rear wheels each carrying only
about 20% of the weight, they both lock up and skid at once, at
anything more than the gentlest pressure on the rear brakes.

For this reason I abandoned my trike rig, even though it works --
beautifully -- on the same tilting principle that Erik Wannee invented
for his Flevo training back end rig. This means that the rider and the
front and middle parts of the Python all bank over into curves, just
like a bike. But at the same time you have these two handlebars
attached to the very stable, non-banking rear part, so that you can
keep yourself balanced with downward hand pressure on them, even
before you've learned the knack of balancing the Python in the
original Mages-pioneered way. And oddly, even though these hand-holds
don't steer in the usual sense they do assist strongly, because you
can brace against them laterally, as you steer the front end with legs
and hips. Really helps!

Apart from the calamity with the braking, this rig feels so easy
to control with confidence -- even downhill at 40-45 KPH -- that I
rode 20 kilometres on it in traffic on my very first time out.
This was after weeks of trying to learn the knack of balancing the
bike rig (admittedly on short grass) and failing all the time.

I've now almost finished a new idea to add on to my standard
Python 20" bike, to replace the tilting trike, which will let me
have the same lean control as the trike by downward hand pressure
against solid handlebars, and let me dawdle uphill without worrying
about staying balanced upright. I'll post vids of both the trike and
the new bike+aids as soon as this one is running assuredly.

Forgive my snail slowness at posting pictures, Pythonauts. I make
Dirk look like lightning by comparison, and Vi seems to build
inventive HPVs and youtube his adventures with them at warpspeed. 
In contrast I'm an old guy who always seems to have too much to do.
(71, supposedly retired, yet still making bespoke furniture because
friends see pieces that I've made for other friends, and keep
pestering me to make something for them too; just can't seem to say
no; but then, the end results are just too alluring to give it up:
recycled and found old timber, irregular, 'sculptured' forms, and so
on; about one in three gives me the satisfaction of a piece that
really seems to work beautifully; can't give it up)

Here's a link to Erik Wannee's training trike back-end. Text only
in Nederlandse, but the picture tells it all. My tilting trike works
on exactly the same principle. Interesting thing is that as well as
the fixed handlebars on the back end, Erik has the standard bars
further forward, for when you've learned to ride the Flevo
confidently. But don't be fooled: it's those rear bars that make all
the difference when learning the knack of steering and balancing Flevo
or Python.


Hwyl fawr,  Rh

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

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