Blade Inspect

Rocker and bend along the whole blade, from a phone video and a sheet of paper. The video never leaves this device.

Why Blade Inspect

A blade's rocker (the curve of its running edge along its length) and its bend decide how a skate turns and glides. They are measured with a 3-point gauge such as a Marchese or an SCP: one number for the sag over 101.6 or 80 mm, at a few places, by hand. Good gauges are precise, but they show a few points, not the whole blade, and not every skater or club has one.

Blade Inspect measures the whole running edge at once. A sheet of paper's factory edge is the straight reference; a phone filming slowly along the blade is the measuring instrument. The frames are stitched into one picture along the paper's edge, the gap between the paper and the running edge is measured in every frame to a fraction of a pixel, and from that profile it gives the readings a Marchese or SCP gauge would give, anywhere along the blade, and the radius. Both sides of a skate, with the angle each side leans at, separate the rocker from the bend.

Everything runs in your browser: the video is not uploaded anywhere. Free to use; made by a short track skater.

How to set up and film

· seven steps
1 Paper A sheet of printer paper (A4, or A3 for a long blade) flat on the table. Its factory edge is the straight line everything is measured from.
2 The blade along the edge Lay the skate on its side so the running edge lies along the paper's edge, 1–2 mm from it over the whole length. The smaller the gap, the better.
3 On its side The skate rests on two places: the running edge and the side of the boot (green). The blade leans at an angle α.
4 The angle Take a photo of that same view: along the blade, at ground level. In the app tap two points on the ground (green), then two along the blade (red).
5 The phone on a box A box or a stack of books beside the skate, the phone flat on top, its camera just over the running edge, looking straight down, 10–15 cm above it.
6 What the camera sees The blade along the picture, the running edge and the paper's edge near the middle (red line), in focus. The blade about a third of the height.
7 Slide Slide the phone on its box slowly along the whole blade, from past the rear end to past the front end (5–8 s), and back. By hand: keep the wrist still, move your whole body.

Your four measurements

One video per side: each skate lying on its left side and on its right side. Choose the video in its card; the result lands in the right place.

The blade from the back of the blade (the middles of the cups)
Measure an angle from a photo

A photo along the blade (end on). Tap two points on the ground, then two points along the blade's side.

Rocker and bend

From both sides of a skate and the angle each side leans at: a side measures rocker·cos α ± bend·sin α (the bend's sign flips with the side). Angle 0 (upright, filmed from the side): pure rocker. Gauge, smoothing and places as set in the profile.

Measure both sides of a skate to see its rocker and bend here.