Coefficient of friction error???

[dawilliams]

We did a simple test of inline and transverse dynamic coefficients of friction. We made a platform from plywood and wood plates. Screwed the wheels to it. Using a fishing scale, we measure the force of friction sliding the platform inline and transverse to the wheels. The weight on the wheels in the video was approx 140 lb (kid plus weights). We attempted to pull the platform at constant speed once it started moving.

Results? We recorded 12-15 lbs friction force in BOTH inline and transverse modes of dragging the platform. The flooring we used was Lowes sku# 8566, FRP with pebble finish. This means our coefficient of friction was about 0.1.

According to Kit of Parts the inline dynamic coefficient is 0.05, and the transverse dynamic coefficient is 0.1. Thus we should get twice the friction force pulling transverse.

See sample video:

http://www.youtube.com/watch?v=YUwjRcBckn0

Anybody have good phyics explanation for this? Or has the KOP given us bad info? Anybody else try this test?