Zoom blur

I was playing around with zoom blur today after reading about it in Amateur Photograper magazine (Feb '09 issue).  Of course I've known about the technique for ages, and played around with it before, but I was looking for something interesting to try today.  I took inspiration from the first photo I'd seen demonstating the technique - from John Freeman's "Photography".  It was a shot of flowers, a subject that I had readily available.

Here are some of my earlier, not so good attempts:

 

This shot was my favourite.  Shutter speed was 1/5s and the focal length started out at 33mm and I zoomed in to 85mm, but I don't know at what point the shutter would've closed.  Aperture was f/16 (shot in Manual)