[python] Re: AW: Re: Questions about Python-Trike geometry (project similar to Howard Stevens foldable Python trike)
- From: Rhisiart Gwilym <Rhisiart@xxxxxxxxxxxxxx>
- To: python@xxxxxxxxxxxxx
- Date: Fri, 29 Jul 2011 14:33:38 +0100
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.
http://www.wannee.nl/hpv/oefentri/index.htm
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 well.
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