[python] Re: Python Plans

  • From: Henry Thomas <whpthomas@xxxxxxxxx>
  • To: python@xxxxxxxxxxxxx
  • Date: Fri, 16 Feb 2007 08:27:10 +1000

Hi Mark,


The new front was based on the Speculoos, but if you have a link for a
Flevo - mini - Racer, I would be keen to see one...

a small picture is attached...

Thanks, it looks pretty cool. The steering pivot seems to be about 45°, mine is approx 57.5°, and the BB looks about 200mm above the seat, mine is only 50mm.



BTW: how high was your bottom bracket from the ground. Having your BB to
high would also cause wheel flop.

the BB-Seat Diff. is 25cm.

This and the low pivot angle could have been the problem.


After re-reading Jürgen´s "Frame Geometry"-Page, I think, the Wheel
Flop is also established in this:

"The optimal pivot angle is exactly the one where the weight of the
whole front part (including the riders legs) is in equilibrium with
the rest of the bike (including the rest of the rider). This is
different with every bike and rider. To be more exact: It is the angle
where the wheel flop effect is nullified by the seat rising effect."

I think the Pivot Angle at my trike is too low.

I thought Jukka's comment relating trail and seat hight, was also
interesting.

Trail -27 cm and seat hight 30 cm.


On my first tilting prototype, may BB-Seat Diff was 25cm too, and it noticeably contributed to wheel flop. Its not to say that you couldn't design a FWD FWS recumbent with a value like this, but you would have to be sure that the pivot angle and tail were such, that the weight of your feet and the seat lifting were in equilibrium. The thing I was worried about was what if any influence the rear tilting mechanism would have on this steering equilibrium.

This would have been a issue for the Rev B design.

I actually made that change to the original Jetrike (now Rev C - Photo
Attached) because I found it saved weight. The Rev C is 2 Kg lighter
than Rev B, just from squeezing the frame in.

Ok, that´s a fact...

How would you couple the rocker arm with the swing arms?


I went to a local chandler and purchased some M8 stainless turn buckles, removed the eye and hook bolts and screwed in the rod ends. The turn buckles also came with L & R threaded lock nuts which is handy. The coupler is now 170mm center to center, which has brought the lateral movement of the rod ends under 14°, which is their limit.

Which Program do you use to create your drawings?

Solidworks -- it took a while to learn, but now I seem to have the hang
of it. The best things about it are:

- it is parameter based, so you can change your mind, alter a dimension
or angle, and it will update your drawing,
- it supports weldments, so you can have all your structural member
profiles, draw your frame with lines, and then select the profiles you
want to apply to those lines,
- it does the whole cut list thing, so you can find out how much metal
you will actually need.

That sounds like the Office Premium version? - Wow!

Yes! I have access to a workstation that has it on, so I am making the most of it while I can.

-h

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