Industrial design — self-initiated — 2026

Datum

A Saddle Memory Collar

A solid brass seatpost collar that remembers your saddle height. Take the post out for shipping, a service or a friend’s ride, and finding that height again takes time and guesswork. With Datum, slide the post back in until it stops, and the saddle is exactly where it was.

Role: Concept, industrial design, engineering drawings, 3D and rendering
Material: Lead-free brass (C69300), machined and lost-wax cast, left to patina
Tools: Parametric geometry in Python, Three.js, Blender
Status: Prototyping

Film, 0:42 (sound on): the collar going on, then the reflector and the fender each taking the dock in turn.

Illustration of a green steel gravel bike in side view, with the Datum collar circled on top of the seat clamp — Datum sits on top of the frame’s seat clamp. Illustration.

Small numbers that matter

Riders find their saddle height over many rides, a few millimetres at a time, then lose it the moment the seatpost comes out. A strip of tape or a scratch on the post marks the spot, but neither is precise, and neither looks like it belongs on a good bicycle.

The collar sits on the seatpost, right above the frame’s seat clamp. Height is held by the post stopping against it. The pointed prow carries the single clamping bolt and sits in line with the top tube.

The collar’s prow lined up with the top tube — The prow follows the line of the top tube.

The collar’s two brass halves hinged open around the seatpost — Two halves on a hinge pin, so it fits without removing the post.

One material, made to last

I wanted an object that ages with the bicycle rather than wearing out. Every part is solid lead-free brass, machined from bar with the toolpath left visible or lost-wax cast, then allowed to patina in the same way a leather saddle darkens with use. All the fasteners are blackened stainless steel, so the few working parts read clearly against the brass.

The collar is the product. Behind it is a small dovetail dock that takes one optional add-on at a time, locked by a single M3 set screw that seats in a dimple in the collar. Nothing on the dock needs a battery.

Seatposts

Ø 27.2 · 30.9 · 31.6 · 34.9 mm

Collar

8 mm plate · 48 g at Ø 31.6 mm · one M3 bolt

Dock

Dovetail · M3 cone-point set screw into a 90° dimple

Interactive model

Turn it over

The same geometry that drives the drawings and renders, live in the browser. Swap the add-ons, open the hinge, or pull the fender apart into its layers.

Two add-ons, one dock

I kept the add-ons small and light, things a rider would leave on all year. The reflector pod is a turned brass disc around a standard 1¼ inch red reflector. The fender is a hand-planished brass blade in the traditional hammered style, polished to a mirror.

The fender’s head is a compact brass node with three tapered struts that run parallel to the seatpost up to a brass arch. The blade bolts down onto the arch through a waxed-leather strip, with four blackened-stainless shoulder bolts on leather washers. The leather cushions the thin polished blade, stops it rattling or fretting against the arch, and protects the finish; the bolt shoulders set exactly how hard it is squeezed.

Hammered brass fender blade bolted to its brass arch behind the seatpost — The fender: a 0.6 mm planished brass blade, 190 mm long, tapering from 64 to 40 mm.

Reflector pod seen from behind the bicycle — The reflector pod: 50 g, no battery.

Close-up of the dovetail dock and its hex set screw — One set screw locks each add-on onto the dock.

The fender head without its blade: a brass node, three tapered struts and the brass arch with its tapped holes — The fender head before the blade goes on: node, three struts and the brass arch, topped with a waxed-leather strip.

Reflector pod

Seen without a battery

The collar with its reflector pod, in aged brass: a standard 1¼ inch red reflector in a turned brass bezel, angled to face traffic squarely.

Brass collar with its round red reflector pod, clamped to the seatpost of a green bicycle frame

Process

Drawn from one model

I built the geometry as a parametric model in Python, so one set of numbers drives everything on this page: the engineering drawings, the interactive viewer and the Blender scenes. Changing a seatpost size or a wall thickness updates all of them together.

I checked the hinge for clearance through its full 90° swing, sized the dock so the add-ons stay put under one screw, drew the fender head as a single lost-wax casting with only its fits machined, and laid the fender blade out flat for laser cutting before it is hammered, polished and rolled.

Engineering drawing of the collar: plan, sections and dimensions — Collar, rev E.

Engineering drawing of the reflector pod — Reflector pod, rev C.

Drawing of the fender head, a single lost-wax casting: section, plan and arch — Fender head, one lost-wax casting, rev A.

Flat pattern of the fender blade with its four bolt holes — Fender blade, flat pattern, rev J.

Specification

COLLAR: Two-part, hinged · lead-free brass C69300 · 8 mm plate · Ø 4 mm pin · 47 g (Ø 31.6)
SIZES: Ø 27.2 · 30.9 · 31.6 · 34.9 mm seatposts
REFLECTOR POD: Turned brass disc · Ø 31.75 mm (1¼ in) red reflector · 50 g
FENDER: Lost-wax cast brass head and struts · 0.6 mm C260 brass blade, planished and polished · 190 × 64–40 mm · R 20 tip
FASTENERS: M3, blackened stainless steel · low-head clamp bolt · shoulder bolts on the fender
LEATHER: Waxed veg-tan strip and washers cushion the fender blade
POST CARE: Edge-broken bore; optional thin bore liner for alloy and carbon posts