Sample · BMX street 28/9

28/9 · overlapping Y star

Six Y spokes forking into a star lattice, like Wethepeople's Turmoil. On a 25T the forks leave too little room to pass the strength check, so the star is a 28T.

BMX street & park28 : 9

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Build it with your AI

Using the CheapCAD Tools connector, design a two-sprocket drive in Sprocket Designer on 081C (⅛" single-speed bicycle) roller chain, 80 chain links. Sprocket 1: 28 teeth, a sprocket; a 23.8 mm bore; spokes: overlapping spokes, 6 of them, Hub OD 46 mm, Rim Depth 6 mm, Spoke Width 10 mm; no tooth chamfer. Sprocket 2: 9 teeth, a sprocket; a 12 mm bore; no tooth chamfer. Check the design, apply any Auto-fix it suggests, then export both sprockets as STL and give me the download link.

Paste it into Claude, ChatGPT or any AI app with the CheapCAD Tools connector, and it designs this drive with you, checks it and hands you the files. How to connect your AI.

What's in this design

Sprocket 1 · 28 teeth

28T · ⅛" single speed · sprocket · bore Ø23.8 · overlapping Y spokes × 6
209 MPa peak · SF 2.41 in 7075 · rim moves 0.34 mm · 3.07 mm plate · 61 % solid

Sprocket 2 · 9 teeth

9T · ⅛" single speed · sprocket · bore Ø12
283 MPa peak · SF 1.78 in 7075; make it steel · rim moves 0.16 mm · 3.07 mm plate · 60 % solid

The link opens both sprockets and the chain in the Sprocket Designer's 3D Mode. Change the teeth, bore, hub or spokes, then download STL, STEP, DXF or SVG. Strength figures are the app's plane-stress check of each sprocket in the material it names; SF is the safety factor.

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