[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.


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.

Other related posts: