[python] Re: python Digest V8 #63

  • From: Rhisiart Gwilym <Rhisiart@xxxxxxxxxxxxxx>
  • To: python@xxxxxxxxxxxxx
  • Date: Wed, 18 Aug 2010 01:58:43 +0100

But Howard, what about Dennis Renner's apparently workable FWDRWS bikes? If that's really what they are, then perhaps they're an all time world first. If you look at Dennis's videos of him riding his Mark 2, you see a very easy, stable ride, and some very interesting movements in the hip area as he turns.

I do tend to the suspicion though that instead of calling it a true RWS bike, its really a PX5 layout, with the steering pivot even further towards the back end of the middle section of the bike frame. Dennis just seems to have hit a sweet geometry by chance on his Mark 2. Apparently he was helped also by not knowing too much about the established opinion that RWS bikes are impossible. He just went ahead and did it anyway, regardless. Great!

Cheers, Rh

Hi again Dirk,
I very much appreciate all your comments and experience in riding pythons and flevos.....it is very useful to me because I am working alone here and haven't met or contacted anyone in the locality. I have made a couple of prototypes... the first had a pivot angle of about 70 degrees and the current one is at the 62 degrees that Jurgen recommends. The 70 degree one was rather twitchy but easy to turn, while the current one is more stable with less PSI and a bit more difficult to turn. So I would expect that by reducing the angle closer to 45 degrees that it would be as you say and have less PSI still, go like a train, have more difficulty turning and maybe considerable wheel flop. Did you notice wheel flop being a problem on the Flevo? As my vehicle is a trike do you think that could be less of a problem at low speeds? WHat exactly do you mean by having trouble fumbling at takeoff and low speed? Perhaps a compromise of say 55 degrees may be the optimum for a trike, as I read somewhere that that was the theoretically best angle for seat rising effect without too much wheel flop?? What do you think? I went to a motorbike shop today and checked out their steering dampers and I think you are right...they would be of no use for a trike, because they are basically to smoothe out high frequency shudders and so would not be effective for a low frequency PSI oscillation, unless they were adjusted to be so strong that you really couldn't turn the thing!! So why were they so strongly recommended for the Hipparon trike? Was it because the pivot angle was so high that steering became very unstable without it? It probably was not for PSI in that case. And yes, I can't see that the rubber cylinder damper would be useful for anything but parking.

I feel a bit guilty tampering with such a successful design as the python and can imagine that you don't have any noticeable PSI. I have used 20 inch wheels and the reason I am having some problems is because I haven't got the pivot in the right place, it is about 150mm in front of the line of the hips!! But I am limited by my desire to make the thing fold up into a box!! The problems I am having are not great, as putting the handlebars on, as you suggested has been a great improvement. I just want to be sure to get it as good as possible within these restrictions. I think I won't be so radical as to put it behind the seat especially as it didn't help the situation in the PX5. Maybe some other time!

Thanks again for your input, cheers  Howard


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