Some of you have arrived here by looking on Google for "Wally Dolly." That's a different kind of Wally Dolly than the one I'm talking about. I'll save you some time and tell you now that while this is a site about professional Dolly Gripping, there's nothing about the actual product Wally Dolly on this site.
That's what a cameraman I worked for a few years ago called the dolly when it was on skates. The whole phenomenon of skateboard wheels is kind of strange when you think about it. You take a precision piece of machinery made to roll on track, and put it on another set of wheels to roll on the same track. But they do help. Sometimes a lot. I think it all has to do with the quality of track available nowadays. I may be wrong about this, but it started when DGs wanted to use a Fisher (which uses square track, a really bad idea) on round track. The easiest solution was to put the thing on skateboard wheels, specially modified to fit the track. Then, someone noticed that the more wheels you add, the smoother the ride. Thus, a new industry is born.
Skateboard wheels do traditionally have a flaw, though. They flatten. The longer they sit in one place with the dolly on them, they develop flat spots and you have to roll them out just before shooting. This can be a problem with long takes with dialogue. We've all heard the claims of this company or that saying that they've developed the perfect formula for wheels that don't flatten, yet are soft enough to be effective. Guess what? They flatten. The good folks at Porta-Jib found a way around this. They put wheels of slightly different diameters on their skates and Bam! No flat spots. Last night, I had a Fisher 23 jib sit in my Porta-Glide wheels over lunchtime, something I would never do unless there was no way around it. It was a good 45 minutes for upwards of 2500lbs to be sitting there. I walked in after lunch and went right to work rehearsing and they rolled as smoothly as if I had just put them on. At $1400.00 a set you can't beat them. Visit them http://portajib.com/ and check them out. Look for the Porta-Glide section.