Get on your Soapbox — Derby, that is

Speed-demons are on their marks for the Open Source Gallery’s third annual Soapbox Derby.

Last year, the judging criteria came down entirely to speed; this time around, not only is the style of each car going to be a factor, but also its structural integrity — a tall order, since all entrants are required to build their cars out of found materials such as cardboard, discarded lumber, or (as in one case last year) a bathtub.

Still, the race, which runs down 17th Street from Seventh to Sixth avenues on Aug. 13, should have some of the fastest, flashiest cars around, as at least 40 kids — and adults, too! — are expected to compete for soapbox derby glory.

Soapbox Derby outside Open Source Gallery [17th Street between Fifth and Sixth avenues in the South Slope, (646) 279-3969], Aug. 13, with the kids race at 11:30 am, adults at 1 pm. For info, visit www.open-source-gallery.org.