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Blade Inspect, developed by Mark Prinsen (Troch · Gnomon). A measuring aid, for information only and without liability: check critical values with a gauge. See What it does.

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Measuring

1Ruler edge
2Stitch
3Check & measure

Your blade's profile, from a phone video

Use your phone: slide it along the blade on a simple rig, scan the blade, and see its rocker and bend along its whole length. The video becomes one picture of the whole blade beside a ruler; every frame is measured against the ruler's own millimetres.

1 · The rig The blade on its side on a 45° angle, beside a steel ruler. The phone on a sled, looking straight down.

2 · What the phone sees From the top of the tube (where the cups are) down to the ruler and its numbers; the running edge just below the middle.

The whole blade stitched into one picture beside the ruler — **3 · One picture** Every frame stitched along the ruler, and checked against its numbers.

The rocker and bend graph — **4 · Rocker and bend** Along the whole blade, in metres or in your gauge's units.

Rocker only, or rocker + bend

The camera looks straight down and sees how far the running edge lies from the ruler, all along the blade. Which way the blade lies decides what that distance is.

Rocker only: one scan. The whole skate lies flat on its side: the boot on the table, the blade on a support (a board about as high as the boot holds it) with the ruler on the same board beside it. The camera looks straight at the blade's side: what it sees from the ruler is the rocker itself.

Rocker + bend: two scans at 45°, one per side. Turn the skate end for end for its other side. Tilted, the camera sees part rocker and part bend: one side gives rocker + bend, the other rocker − bend. Added, they give the rocker; taken apart, the bend.

Your data stays yours. Everything runs in your browser: your videos and measurements never leave your device, nothing is uploaded or shared, there is no account. The page is not even allowed to connect anywhere: its security policy blocks it. Save your scans or export the readings as a file to keep them wherever you like.

About

Blade Inspect is developed by Mark Prinsen (Troch · Gnomon). It is built on years of speed skating experience, and its measurements have been checked against real gauge readings.

Disclaimer. Blade Inspect is a measuring aid. Its results are for information only and depend on the video, the setup and the ruler; check critical values with a gauge. Blade Inspect and its developer accept no liability for any damage, injury or loss arising from using the app or from acting on its results, including work done on blades.

Hardware

What you need

A phone with a torch (flash), its camera able to focus at 10–15 cm.
A flat steel ruler, 50–60 cm: its edge is the straight line everything is measured from.
White paper under the blade, so the edge stands out.
For rocker + bend: a 15 × 15 mm aluminium angle (the blade lies on it at 45°) and an air wedge under the boot. For rocker only: a board to lay the blade and the ruler on.
A way to slide the phone steadily along the blade: a rig.

The rig

All the scan needs is a steady sideways movement: the phone at one height, looking straight down, sliding evenly along the blade. It needs about 60 cm of travel (a whole blade, a little past both ends), with the camera about 100–150 mm above the ruler. A sharp picture all the way along matters more than the lowest height: rather a centimetre higher with the camera zoomed in a little to fill the view (from the tube's top to the ruler's numbers) than so close that the focus hunts. Any setup that does that works: a phone sliding along a stack of books or your own creation, as long as the movement is steady, the height stays the same and the picture stays sharp. Rig A and rig B are two ideas, simple to build from parts any hardware store sells.

Rig A: a wooden beam with a strip of felt. Rig B: two tubes on wooden blocks with a junction box sliding along them — Front: rig A's beam, with felt where the L slides. Back: rig B, a junction box sliding on two tubes clipped onto wooden blocks.

Rig A · an L-profile on a beam

The phone lies on a sled: a short L-profile, just the beam's width, that hooks round a straight wooden beam, so the camera stays at one distance and height all along the blade.

From above: the skate with its running edge along the steel ruler (1–5 mm of white between), the ruler's numbers toward the blade, the beam beyond. The phone's sled rides along the beam, its camera over the running edge, from the cups to the ruler's numbers in view.

Section: a short L, just the beam's width, hooks round it so the phone slides at one height.

Rig B · a junction box on two tubes

A sled that slides on two tubes: quick to build from electrical installation parts, smooth, and level along the whole blade.

From above: the same skate and ruler; two tubes on blocks beyond the ruler, the junction box (the phone on it) sliding along them.

Section: the box rides on both tubes, so it stays level.

Parts

2 × steel installation tube, Ø 20 mm, about 70–80 cm long.
2 wooden blocks as feet, high enough to lift the tubes clear of the skate.
4 tube clips (Ø 20 mm) and screws.
1 surface junction box (kabeldoos), about 80 × 80 mm.
Self-adhesive velcro, the soft (loop) side.

Building it

Drill two 22 mm holes through both opposite walls of the junction box, as far apart as the tubes will be.
Line the holes inside with a strip of the soft velcro: the box then glides smoothly over the tubes without play.
Slide the box onto both tubes and clip the tubes onto the blocks, parallel.
Lay the phone on the box, camera looking straight down at the running edge and the ruler.

The ruler: flat steel, 50–60 cm, for a straight edge the length of the blade. That is straight enough. For more accuracy, a DIN 874 straightedge; it is several mm thick, so set the camera height to its top.

How to scan

The blade at room temperature for 24 hours first. Steel changes its shape with temperature: a blade just in from the cold (or the car) can measure quite differently.

Line it up

The running edge parallel to the ruler, 1–5 mm of white paper between them, the ruler's ticks and numbers toward the blade. The camera straight down, its view from the tube's top (the cups) to the ruler's numbers, the running edge just below the middle. Nothing may move while you scan.

Torch on, slide slowly

Turn the phone's torch on: a short exposure keeps the ruler's ticks sharp. Start recording, then slide the phone steadily from past the rear end to past the front, in 10–15 s, without stopping or pressing on the rig.

Upload the video

In Skates, under New scan: choose the skate, what to measure (rocker only, or rocker + bend), then the video. It stays on your device.

Check the ruler's edge

The first frame is shown with the ruler's edge found and drawn green. If it sits on another line, tap the ruler's measuring edge. Then Stitch: every frame is put together along the ruler and checked against its numbers.

Check the ends, measure

Two lines mark the blade's ends; drag them if needed (and the cups, if you mark them). Measure: the rocker and bend appear on the Skates page.

What the phone sees From the top of the tube (where the cups are) down to the ruler and its numbers; the running edge just below the middle.

The setup in detail

Room temperature: leave the skates (and the ruler) at room temperature for 24 hours before scanning; a blade's shape changes with temperature.
Paper, profile, ruler: white paper on the table, the ^ profile (a 15 × 15 mm aluminium angle, apex up) on it, a flat steel ruler of 50–60 cm beside it (steel, for a straight edge; long enough for the whole blade), its ticks and numbers toward the blade. Tape both down.
The skate: for rocker + bend, the blade's side on the ^ (45°), the running edge at its foot 1–5 mm from the ruler's edge, the air wedge under the boot pumped until the blade lies on the ^ along its length. For rocker only, the skate flat on its side (0°): the boot on the table, the blade and the ruler on a support as high as the boot holds the blade. Nothing may move while you scan.
The phone: on the sled, camera straight down over the running edge, from the tube's top to the ruler's numbers in view (see What the phone sees), in sharp focus. Torch on: a short exposure keeps the ticks sharp.
Scan: slide the sled steadily along the whole blade, from past the rear end to past the front, in 10–15 s.
Measure: in Skates, under New scan: the skate, what to measure, then the video. Rocker + bend: each skate on its left and its right side (turn it end for end), four scans for a pair; rocker only: one per skate.

New scans: which skate and side?