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Created March 12, 2026 20:26
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frame-build.md

That's a smart move. The Detroit is the spiritual reference, but the Omera needs its own visual identity. A seat tube cutout is a strong signature — instantly recognizable and signals "this is a track-bred frame" without copying Dosnoventa's exact look.

What Makes Omera Visually Distinct from Detroit

Feature Detroit Omera
Seat tube Standard round Cutout wrapping rear wheel
Down tube Columbus Airplane ovalized 50mm round (battery inside)
Drive Chain Gates CDX belt (visible difference)
Brakes None (track) or rim Hydraulic disc
Rear dropout 120mm track 135mm horizontal/sliding
Motor None Bafang G020 (stealth hub)

The cutout + belt drive + disc brakes together give the Omera a completely different silhouette from the Detroit while keeping the same aggressive 74°/76° pursuit geometry. Someone who knows bikes would clock it immediately as its own thing. ppl-ai-file-upload.s3.amazonaws

Design Consideration for the Cutout

One thing to flag for the frame builder — the Omera has 135mm rear spacing (not 120mm track), so the seat tube cutout needs to be wider than a typical track frame cutout. The wheel sits in the same plane but the hub flanges and disc rotor are wider. Make sure the cutout clears:

  • Tire (700×25c) + 3mm each side minimum
  • Disc rotor on the non-drive side
  • Belt on the drive side

This is doable but the frame builder needs to know upfront. Want me to add this to the frame fabrication brief?

@eonist
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eonist commented Mar 12, 2026

Yes — there are proven, buyable “frame split” solutions you can design around instead of inventing your own from scratch.

What Gates Requires

Gates explicitly says the frame must have a “frame break” in the rear triangle so the one‑piece belt can be slipped in. mi-tech
They don’t care where, as long as:

  • You have at least 8 mm gap when it opens.
  • You also have a belt tensioning system (sliding dropouts or eccentric BB). 2blua

You’re already planning horizontal/sliding dropouts, so you just need the frame split.

Off‑the‑shelf frame split hardware

You can buy CNC’d metal splitters and design your stays around them:

  1. Paragon Machine Works belt splitters

  2. Dropout‑integrated split (Tout Terrain / Olsen style)

  3. Custom seat‑stay splitter services (Bike Knack, Ti Cycles)

    • Shops like Bike Knack and Ti Cycles retrofit Gates frames by cutting the seat stay and installing a machined splitter matched to the stay diameter. bikeknack.com
    • Their parts are basically a tube connector with two bolts. Good reference geometry if you want to mill your own.
  4. Veer split belt (no frame split)

What makes sense for Omera

Given your goals (stealth, clean BB, CNC dropouts, 135 mm belt hub + disc):

  • Use a dropout‑integrated split on the right side, like the Olsen RocknRollout / Tout Terrain pattern. olsenbicycles

    • Chainstay and seat stay both bolt into a two‑piece dropout.
    • Loosen 2 bolts, remove the outer piece, slide belt through, bolt back up.
    • Visually, it just looks like a chunky CNC dropout, which you already want.
  • Keep no cuts in the seat stay or chainstay tubes themselves — all the complexity is in a replaceable dropout block.

So the answer: yes, you can absolutely base your design on existing hardware. Look at Paragon’s belt‑drive splitters and the RocknRollout/Tout Terrain split dropout concepts as references, then have your own 135 mm disc‑compatible CNC dropout machined around a similar interface. bikeforums

Would you like me to sketch a right‑side dropout concept (135 mm, flat‑mount disc, belt split) you can hand to a machinist?

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eonist commented Mar 12, 2026

okay so you sanwitch the dropout module to chain stay and seat stay and lock it with screwbolts. unscrew the bolts. the gap for belt is there

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eonist commented Mar 12, 2026

omera_split_dropout

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eonist commented Mar 13, 2026

Got it — then we just mirror the function, not the look.

On the non‑drive side:

  • Same axle slot height and length as drive side, so tensioning and wheel position behave identically.
  • One solid 6 mm plate (no split), with: axle slot, brake mount (if rotor that side), and a small hole/feature for hose exit if needed. bikecad
  • Overall 135 mm O.L.D. preserved by making this plate the same thickness as the inner plate on the drive side, so dish stays simple and hub sits centered. alibaba

If you like, I can now define just the critical numbers you need to send your machinist for that non‑drive plate (slot position, thickness, axle center to stay junction, etc.) in plain text.

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