nicbordeaux wrote:In a previously published vid there were some pesky details which weren't worth bothering about. However, now that Fletcher stands to loose 10 euros to me, it's time to start looking at things again.
http://www.youtube.com/watch?v=S9igFhQnP38
For reasons of retaining a modicum of sanity, I have stated that the the tether attchment point is to right of wheel axle. In all truth, this is a pretty dubious statement which will need a rerun of the experiment.
First of all, Nick, let me take this opportunity to say welcome back.
I
kinda remember at one time (maybe in your old forum? - 'cause I can't find the 'quote') you had said that the tether attachment point was directly opposite the position where the ball 'sat' on the rim (through the valve stem hole?). If you pause the video at the point where the ball has passed the apex and has descended to the top of the curtain/blind in the window, you can see the tether line coiling up and it appears to confirm this? If that is the attachment point, these comments may make sense to someone.
(It's a little rough to interpolate some of this because it happens so quickly that the video frames are a little far apart, but I think it's within reason.)
The wheel stops rotating when the tether is near the lower 45 degree angle to the ground (7:30), very close to being at a tangent to the attachment point on the rim.
The wheel begins back-rotating when the tether is nearly horizontal to the ground (9:00).
The wheel stops back-rotating when the tether is near the upper 45 degree angle to the ground (10:30), just about where it gets to the 'apex', before the line goes slack. One could practically draw a line through the point where the ball was sitting on the rim behind the drive weight, the axle, the (presumed) attachment point and the ball at the apex.
I also
kinda remember reading somewhere (out there on the internet) something about centrifugal force and a reference to the tangent having some relevance. Not my specialty, maybe someone that knows more than me will chime in and add (or detract) from this?
Of course, it could be that the tether length is simply out of tune with the system and is just yanking the wheel back and forth. :-/
You're way more experienced with this than me, and I'm sure you already thought of it, but, maybe trying slightly different tether lengths could lead somewhere?