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3D-printed bike accessory

Design Project 3 weeks Medium build

Design a part that fits a real bike and does a real job, model it in Fusion from your own measurements, print it, and prove it survives use. Mounts, clips, guards, holders, tools.

A black 3D-printed phone mount clamped to a bicycle handlebar, photographed close up in a workshop.

Overview

Bikes are full of small problems: a phone with nowhere to go, a light that only fits one handlebar size, a pump that rattles, a chain that flings grit at the frame, a lock that swings. Almost all of them are solved by a small plastic part that fits a tube of a known diameter or a set of bolt holes with a known spacing. That is a job a 3D printer is good at, if the part is designed properly.

You choose the problem. Measure the bike. Model a part that fits it. Print it, fit it, and use it. The assessment is about whether it works on the bike, not whether it looks good on the screen. Ideas: a phone or light mount, a bottle-cage adapter, a mudguard or chainstay guard, a tool or tube holder, a bell, a cable guide, a kickstand foot, a lock holster, a GoPro adapter, a bag clip, a reflector.

Skills needed

  • Measuring a bikeresource comingHandlebar, seatpost and tube diameters with calipers; bottle-cage bolt spacing; where cables and levers get in the way.
  • Modelling from measurements in FusionReference geometry first, then the part around it. Symmetric extrudes from the mid-plane.
  • ParametersTube diameter, wall thickness and clearance as user parameters so the same file fits another bike.
  • Designing for FDM printingresource comingOrientation for strength, overhangs, wall count, and where layer lines must not take a load.
  • Fits and tolerancesresource comingTest coupons for clamp and snap fits; 0.2 to 0.4 mm clearance is usually where a print starts to fit.
  • Fasteners and hardwareresource comingM5 bolts and nuts, heat-set inserts, rubber shims, and why you never rely on a threaded hole in PLA.

Assessment

Criterion Developing Proficient Exemplary
Brief and measurements Vague user, few measurements Named user and job, all relevant dimensions measured and recorded Brief anticipates the failure modes and the measurements cover them
CAD Works but numbers typed in Parametric; fits the bike first time or after one coupon Refits another bike by changing parameters
Print design Weak orientation, failed overhangs Oriented for strength, clean print Load path thought through; fit tested on coupons before the full print
Function Fits but loose or fragile Holds, survives a ride Better than the store-bought version for this bike
Test record None Photos and what happened Iteration shown; second version is measurably better

Deliverables

  • A design brief naming the user, the job, the bike, and the measurements you took
  • A Fusion file with parameters, plus a test coupon file for any fit
  • The printed part, installed on the bike and photographed
  • A test record showing it survived a ride, a drop, or a load, and what you changed

Materials

  • Access to a bike, yours or a shop bike, and calipers
  • PLA for prototypes, PETG for the final part
  • M5 bolts, nuts and washers, heat-set inserts, rubber strip for clamp faces
  • Zip ties and Velcro straps as fallbacks and as comparison

Steps

Week 1: Problem and measurements

  1. Pick the bike and the problem. Write the brief: who rides it, what annoys them, what the part must do, what it must not do.
  2. Measure everything the part touches. Tube diameters at three points (tubes taper). Bolt spacing. Clearance to cables, levers, tyre, cranks. Photograph with a ruler in frame.
  3. Sketch three ways to attach it: clamp, bolt, strap. Pick one and justify it.

Week 2: Model and test fits

  1. Create the parameters: tube diameter, wall thickness, clearance, bolt size.
  2. Model the bike geometry first as a reference body. Build the part around it.
  3. Print a coupon: just the clamp or bolt interface, 10 mm tall. Fit it. Adjust clearance. Reprint until it fits by hand.
  4. Decide the print orientation. Layer lines run across the part where it bends, never along the direction it will snap.

Week 3: Print, fit, test

  1. Print the final part in PETG. Clean it up. Fit hardware.
  2. Install it on the bike with any rubber shims. Photograph it.
  3. Test it: ride it over a curb ten times, or load it with twice what it will carry, or drop the bike from standing onto its side. Record what happened.
  4. Fix what broke, reprint if needed, and write up the change.

Stretch options

  • A version that fits three bar diameters (22.2, 25.4, 31.8 mm) through a parameter and a shim set.
  • Add a spring or living hinge printed in the part.
  • A two-material print with a TPU clamp face.