[python] Re: Wheel movement numbers for four-bar-linkage python (was Re: Sketches of...)

Hi Michael,

Michael Rienstra wrote: 
ground link = G = 30 cm = ~12"
side links = S = 15 cm = ~6"
coupler link = C = 21 cm = ~8"


Don't know what you mean with the 12/6/8?

When the front wheel is in the neutral position, the distance 'D' from the midpoint of the coupler link 'G' to the virtual pivot point 'V' is given by (attached image of formula may be at end of file depending upon your email program:

Is there not a more general formula that plots the position of the virtual pivot point in function of angle of a side link? (i.e x=vppx, y=vppy and points on the graph indicate the angle of one of the side links). (Gladly a formula for a symmetric 4bl, thank you ;-) )

A quick skim over the internet reaped only formulas for some fixed point in relation to the coupler link, but that is not very interesting in this application.

When the wheel is turned 40 degrees to the left, the right-hand 'S' side link will be parallel to the long axis of the bike, while the left-hand 'S' side link will be perpendicular to the long axis of the bike. Which means that the virtual pivot will be located at the right-side 'G' ground link pivot, meaning that during a sharp turn it would behave somewhat like a Python! Just like a Python the wheel axis would actually be far to the left of the centerline during a sharp turn.

I understand, and with big turning angles the position of the virtual pivot may not be so important, because we're slow riding anyway. Although it is difficult to imagine what it would mean if the VPP goes to the side of the bike (does it?).

So at least theoretically the turning angle may be ok still.

Dirk
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