Omera — Complete Parts List

Bike Parts (New Purchases)

From Sparton Build (Carry-Over)

Total (excl. frame): ~$1,048

Frame: TBD (custom Detroit-style CrMo)

also this is the omera build. its not called sparton

Got it, two corrections applied. Here's the updated list:

Omera — Full Parts List

🚲 Bike Parts

⚡ E-Bike Parts

💰 Grand Total

okay. add it. and find some aliexpres items for Rim tape ×2

~$5, not yet added
Headset spacers
~$3, not yet added so we complete the list

Found both. Here are the picks:

Rim Tape

PVC Rim Tape ×2 — 700c pair — comes as a pair (2 strips), 700c, PVC, ~$3. Simple, does the job. Just match the width to your inner rim — 16mm or 18mm for a standard 700c rim.¹

Headset Spacers

Carbon Fiber Spacers 1-1/8" 28.6mm — matte black — set of mixed heights (2/3/5/10mm), matte black carbon, ~$2. Matches the carbon stem and fork aesthetic perfectly.²

Omera — Final Parts List ✅

🚲 Bike Parts

⚡ E-Bike Parts

💰 Grand Total

✅ Status: Complete

All previously flagged issues resolved:

• Chain → Not needed, full belt drive³
• Bottom bracket → BSA 68mm square taper added
• Crankset incompatible → Swapped to 130 BCD 5-arm, Gates CDX sprocket bolts on⁴
• Brake hoses → Included in MT200 set⁵
• Rim tape → ×2 pair added¹
• Headset spacers → Carbon set added²
• Grips → ODI clone added
• Valve extenders → Not needed, standard rim depth
• Front wheel size → Confirmed 700c to match tires

$1,125 for a stealth carbon belt drive e-bike. List is locked. 🔒
^{6789101112131415161718}

yes

Here's a good one:

RISK 1-1/8" Carbon Steerer Compression Plug + Top Cap — ~$6¹

• 28.6mm, designed specifically for carbon steerers
• Alloy expansion body with knurled grip — won't slip
• Includes the top cap — so you get both pieces in one
• Black anodized, clean look

The RISK brand is well-known for this part — it's one of the most reviewed compression plugs on AliExpress. The expansion mechanism extends the full length of the stem clamp zone, which properly supports the carbon from the inside when you tighten the stem bolts.²

Pro tip: apply a thin layer of carbon grip paste inside the steerer before inserting — massively improves hold strength.²

Omera — Final Parts List ✅

🚲 Bike Parts

⚡ E-Bike Parts

💰 Grand Total

✅ All Issues Resolved

Every gap is closed. The only pre-order decisions left are:

• Gates belt tooth count — use the Gates calculator with your frame's chainstay length³
• Front wheel axle standard — confirm fork and wheel are both 12×100mm thru-axle
• Frame builder brief — belt split, 135mm rear dropouts, horizontal/sliding dropouts for belt tension, 68mm BSA shell⁴

$1,131 for a stealth carbon belt drive e-bike. List locked. 🔒
^{567891011121314151617}

okay give me a combined spec sheet.

Here's the complete spec sheet for the Dosnoventa®03 Detroit frameset:

Frame Specifications

Geometry by Size

Note: This is for the current aluminum Jet Black version. The new cromo-hybrid Detroit (releasing today, March 12, 2026) will have two chromoly tubes and 6mm dropouts — full specs not yet published.¹²

From the top (head tube end). Here's why:

Gravity Works For You

The down tube slopes downward from the head tube to the BB at about 41° from horizontal on the Detroit M. So:

Top loading (head tube end):

• Cells slide down into the tube by gravity when loading ✅
• Cells stay seated while riding — gravity pulls them away from the opening ✅
• To remove: tip the bike forward or use a pull-tab/ribbon to slide them out
• The electronics sit at the bottom (BB end) — permanently wired to the motor/PAS at the BB shell, short cable runs

Bottom loading (BB end):

• Have to push cells uphill against gravity when loading ❌
• Cells want to slide out toward the opening while riding — needs a more robust lock ❌
• BB area is crowded — crankset, PAS sensor, motor cable all converging there
• Electronics would sit at the top, far from the motor — longer wiring

Layout in the Tube

HEAD TUBE END (top, accessible)
  ├── Bayonet cap / hinge door ← battery loads here
  ├── Cell row 1 (3× 21700)
  ├── Cell row 2
  ├── Cell row 3
  ├── Cell row 4
  ├── Cell row 5
  ├── ~~~ 190mm electronics zone ~~~
  ├── BMS (63×52×12mm)
  ├── KT controller PCB
  ├── Boost converter + PD trigger
  └── Fixed wiring → motor, PAS, USB-C port
BB END (bottom, sealed permanently)

Electronics at the bottom is better because:

• Short wire runs to the motor (exits at BB shell dropout) [ppl-ai-file-upload.s3.amazonaws](https://ppl-ai-file-upload.s3.amazonaws.com/web/direct-files/attachments/139085844/29f8498e-62b4-487c-8778-4da05be1fbe4/emotor.pdf)
• Short wire runs to PAS sensor (mounted at BB)
• Permanently sealed — no user access needed, weather-protected
• Heat sinks downward — electronics heat rises away from the battery above

The hinge/lock mechanism at the head tube end can be elegant — a machined aluminium cap that matches the head tube junction aesthetic. Black anodized, quarter-turn lock, flush fit. From the outside it just looks like the normal weld junction between the down tube and head tube.

I want the user to be able to take out the battery. the idea is to cut the alu frame. use the cut out as part of the battery. and have plastic that is glued to the cutout where the batteries goes in. we just slide all bats in. fasten them with some screw thing. and pop the battery into the frame. a lock melanism and hinge thing fastens it to the frame. also we should be able to charge the battery so it needs a charger port built into the battery. the user can swap out the individual bats them selfs by unscrewing 3 caps and pushing them out with gravity.

exactly. now we can make a smaller battery. more portable. comfy room for electronics. we need room for hinge and lock mechanism etc as well. yes update the price list

Here's the full updated BOM. Everything priced out:

Omera — Full Parts List (v2 — 48V/54V)

🚲 Bike Parts

⚡ E-Bike Parts (Updated to 48V/54V)

💰 Grand Total

What Changed (36V → 48V/54V)

Fewer cells, lower cost, more space in the tube, higher voltage (more efficient motor operation), and room for the hinge/lock mechanism. The battery pack itself is only 350mm long — leaving ~190mm in a 541mm tube for everything else.¹²

Down Tube Layout

[===== 350mm battery (15× 21700) =====][=== 190mm electronics + hinge/lock ===]

$1,102 total. Under budget. Single tube. Done. 🔒
^{34567891011121314151617181920212223242526272829}

The Structural Issue

The down tube handles compression + bending — it's one of the most loaded frame members. A 50mm tube with a 400mm × 50% cutout becomes an open C-channel, which has dramatically less stiffness and strength in certain directions. Without the battery cartridge in place, the frame would be dangerously weak. [scienpg](https://scienpg.com/scs/index.php/engineering/article/view/scse.2025.3.149)

How to Solve It — The Battery IS Structure

This is already in your concept and it's the correct approach. The battery cartridge, when locked in, restores the tube to a closed section. The key is: [patents.google](https://patents.google.com/patent/EP2134592B1/en)

The Cartridge Must Be Load-Bearing

• The aluminium cutout piece becomes the cartridge shell — same material, same curve, same wall thickness [ppl-ai-file-upload.s3.amazonaws](https://ppl-ai-file-upload.s3.amazonaws.com/web/direct-files/attachments/139085844/29f8498e-62b4-487c-8778-4da05be1fbe4/emotor.pdf)
• When locked in, the tube is effectively whole again
• The hinge and lock mechanism must handle shear loads, not just hold the door shut

Minimum Requirements

What You CANNOT Do

• Never ride with the battery removed — the frame is an open C-section without it and could buckle [bikeforums](https://www.bikeforums.net/bicycle-mechanics/889745-aluminum-frame-how-tell-if-structural-integrity-has-been-compromised.html)
• Include a blank insert (dummy cartridge, no cells) for riders who want to go non-electric — same shell, no cells, maintains structural integrity

Where to Put the Hinge and Lock

HEAD TUBE END
  └── Lock mechanism (cam latch, quarter-turn)
      ↑ user opens from here
      │
      │  ← 400mm cutout, underside of down tube
      │     (hidden from view when bike is upright)
      │
      ↓
  └── Hinge pin (steel, 6mm)
BB END

Hinge at the BB end makes sense because:

• The cartridge swings down and forward to open — gravity assists
• The BB junction is a reinforced node (thick alu where 3 tubes meet) — strong anchor point for the hinge
• The lock at the head tube end pulls the cartridge up and tight against the frame rails

Charging Port

Build a USB-C female port into the cartridge near the head tube end (top of the cartridge when closed). When the cartridge is in the frame, this port is accessible through a small hole or flush-mounted in the frame surface. When the cartridge is removed, same port charges standalone — exactly like the old concept's removable cartridge idea. [ppl-ai-file-upload.s3.amazonaws](https://ppl-ai-file-upload.s3.amazonaws.com/web/direct-files/attachments/139085844/29f8498e-62b4-487c-8778-4da05be1fbe4/emotor.pdf)

Cell Replacement — 3 End Caps

Each of the 3 columns has a threaded aluminium end cap at the head tube end of the cartridge. Unscrew → cells slide out by gravity (tube is angled). Replace cells → screw cap back on. Brilliant because:

• User never touches wiring — nickel strips connect between rows inside
• Each column is independent — replace just the cells that degraded
• Standard 21700 from any supplier, forever [ppl-ai-file-upload.s3.amazonaws](https://ppl-ai-file-upload.s3.amazonaws.com/web/direct-files/attachments/139085844/29f8498e-62b4-487c-8778-4da05be1fbe4/emotor.pdf)

One Concern: Cost

The cartridge/hinge/lock mechanism adds manufacturing complexity. Updated estimate:

That brings the grand total from ~$1,102 to ~$1,227. Still well under $1,500. And you get a removable, chargeable, cell-swappable battery cartridge that doubles as a structural member.

Want me to update the master BOM with the frame cost revision?

Here's the full design spec for your removable battery cartridge system.

The Core Idea

The down tube gets CNC-cut lengthwise into two pieces — the top 40% stays permanently welded to the frame as the structural backbone, and the bottom 60% becomes the removable battery cartridge. When locked in, it looks like a normal down tube.

How It Works

Battery cartridge = the aluminum cutout + plastic insert glued inside with 3 cell channels:

• Each channel holds 5 × 21700 cells in a line (Ø21.5mm bore)
• 3 knurled screw caps at the head tube end seal each channel
• Caps double as spring-loaded negative terminals (wave spring washer)
• To swap a cell: unscrew cap → tip cartridge down → cell drops out by gravity → insert fresh cell → screw cap back

Hinge + Lock

• BB end: stainless piano hinge — cartridge swings open like a door
• Head tube end: quarter-turn cam lock (keyed, like a laptop battery) — one-hand operation, anti-theft

Electrical

• All 15 cells wired 15S1P via nickel strips along the channels — 54V / 270 Wh
• Slim 15S BMS (65 × 30 × 3mm) sits in the pocket behind the cells
• USB-C PD charge port (65W) recessed into the aluminum shell with rubber cap — ~4 hour full charge
• XT30 output connector flush-mounted, mates automatically with a frame-side socket when cartridge locks shut (or spring pogo pins for a seamless look)

Structural Concern

Cutting 60% of the tube circumference is aggressive — the top 40% shell alone won't handle full riding loads. The overlap lip at the cut seam is critical: when the cartridge is locked in, the interlocking lip restores the tube's cross-section and load-bearing capacity. Consider adding 2mm extra wall thickness at the cut edges, or a small internal reinforcing sleeve at both ends where the cartridge meets the frame.

Weatherproofing

Silicone D-profile gasket along the full cut seam, O-ring on the lock, rubber cap on USB-C — gets you to IP54 (rain riding, no submersion). A 1mm drainage hole at the lowest point of the cartridge prevents trapped water.

This is a genuinely patentable design — the down tube IS the battery, user-swappable cells, no external case visible. Want me to create a proper parts BOM with sourcing links?

Omera v2 — Master BOM

🚲 Bike Parts — $533

⚡ E-Bike Parts — $369

🔧 Frame + Cartridge — $330

💰 Totals

🔋 Battery Cartridge Spec

40 parts. $1,262. Everything in the down tube. Removable, chargeable, cell-swappable. 🔒

Cost Breakdown

€296 total with primary choices (€280 with cheapest alternatives). The spot welder is a one-time tool purchase — subtract €45 if you already have one or borrow from a maker space.

Sourcing for Oslo

• nkon.nl (Netherlands) — cells + nickel strip. Best EU prices, handles Li-ion shipping properly nkon
• electrokit.com (Sweden) — wire, heat shrink, nickel strip backup. 1–3 day delivery next door electrokit
• Biltema / Clas Ohlson (local Oslo) — gaskets, O-rings, adhesive, misc hardware
• euro-locks.com — quarter-turn cam lock, IP65 rated, keyed alike option euro-locks
• AliExpress (2–3 week lead) — XT30AW waterproof connectors, spot welder, USB-C panel mount [aliexpress](https://www.aliexpress.com/item/1005007906822275.html)

One Flag: The Knurled Caps

The CNC thumbscrew caps (€36 for 3) are the most custom part. Options to reduce cost:

• Shapeways / JLCPCB CNC — upload a STEP file, get 6 machined in aluminum for ~€50–70 total
• 3D print in brass-fill PETG as prototype, then CNC the final version
• Or simplify to a quarter-turn bayonet instead of threaded — cheaper to machine, faster to operate, no cross-threading risk

The BMS with Bluetooth is a nice touch — you can monitor cell voltages, temperature, and charge state from your phone via the app. The UART output goes through the JST-SM to your motor controller for SOC display / low-voltage cutoff. greenbikekit

https://www.aliexpress.com/item/32639455264.html

How It Works

Lock manufacturers offer two keying modes:

When you order "keyed to differ," each lock ships with its own unique key combination. Standard cam locks typically have hundreds to thousands of key differs — enough that the chance of two customers having the same key is negligible. ironmongerydirect.co

Best Options for Unique Keys

Euro-Locks F328 — Keyed to Differ

The same IP65 cam lock, but each unit gets a unique key. Available on RS Components Norway as a different SKU:

• RS Norway (keyed to differ, 1242E series): [no.rs-online.com/web/p/camlocks/3851968](https://no.rs-online.com/web/p/camlocks/3851968) no.rs-online
• RS Norway (keyed to differ, 455E series): Same F328 body, different key group [elfa](https://www.elfa.se/en/euro-locks-lowe-fletcher-group-company-camlock-16mm-panel-to-tongue-23-20-2mm-cutout-key-unlock-euro-locks-lowe-fletcher-group-company-f328-03-455e/p/30489295?pos=5&origPos=6&origPageSize=50&track=false&itemList=manufacturer)
• Each lock ships with 2 keys + gasket

Standard 16mm Cam Lock — Keyed to Differ

Cheaper options if IP65 isn't critical (your gasket already handles sealing):

• A&H Brass — 16mm, keyed to differ, multiple finishes, ~£8.20: [ahbrass.co.uk](https://ahbrass.co.uk/products/cabinet-cam-lock-k-differ-16-mm-hole) ahbrass.co
• Ironmongery Direct — 19×16mm, you choose "keyed to differ" at checkout, ~£8: [ironmongerydirect.co.uk](https://www.[ironmongerydirect.co](https://www.ironmongerydirect.co.uk/product/cam-lock-19-x-16mm-keyed-alike-differ-1-nickel-plated--802812).uk/product/cam-lock-19-x-16mm-keyed-alike-differ-1-nickel-plated--802812) ironmongerydirect.co
• Maxus 16mm — keyed to differ default, 2 keys included: [lockstation.co.uk](https://www.[lockstation.co](https://www.lockstation.co.uk/maxus-standard-cam-lock-16mm-keyed-to-differ).uk/maxus-standard-cam-lock-16mm-keyed-to-differ) lockstation.co

Scaling Up: Key Management

If you're producing these frames as a product, consider the ABUS One Key approach — each customer gets a unique key code, and can later order spare keys or matching locks using that code. Euro-Locks and Lowe & Fletcher offer the same service for their cam locks: every lock has a stamped key number, and replacements can be ordered by code years later. lowe-and-fletcher.co

For a production run, you'd order something like:

At scale (100+ frames), you can get Euro-Locks to supply a master key system — each customer has their unique key, but you hold a master that opens all units for warranty service. [euro-locks](https://www.euro-locks.com/en/products/mechanical-locks/quarter-turn-locks/)

Looking at the data from (the current Dosnoventa Detroit frameset page), it clearly states: "FULL CARBON FORK . TAPERED 1-1/8"" and "COLUMBUS COMPASS . 1-1/8" CARBON". The "Tapered 1-1/8"" description on the fork means the fork steerer starts at 1-1/8" and tapers, but the frame headset listed is "Columbus Compass 1-1/8" Carbon" which is the straight version (IS42/IS42). This means the head tube is straight 1-1/8" (not tapered).

Now I have enough data to compile the answer. Let me consolidate everything.

Now I have all the data I need from the Columbus Airplane aluminum catalog and the Dosnoventa Detroit specifications. Here's what I found from the actual Columbus Airplane aluminum 7005 catalog (the framebuilder catalog from Columbus): [framebuilding](http://www.framebuilding.com/acrobat%20files/Columbusaluminium2009.pdf)

Columbus Airplane 7005-T6 Tube Specifications

The Columbus Airplane is an OEM aluminum tubeset — it doesn't appear in the standard Columbus steel catalog. The specifications come from the Columbus aluminum catalog: [framebuilding](http://www.framebuilding.com/acrobat%20files/Columbusaluminium2009.pdf)

Key Clarifications

• The down tube at Ø42mm is the standard Airplane road/track DT — it's round triple butted, not the Ø48 oversized option. The Facebook post mentioning a MASH Cinelli Airplane frame listed "down tube 45mm", but that likely reflects an ovalized/hydroformed profile measurement rather than the nominal tube OD. facebook
• The top tube at Ø35mm is consistent across the Airplane catalog — both listed TT codes are Ø35. This is oversized compared to standard steel (25.4mm) but standard for modern aluminum track frames. [framebuilding](http://www.framebuilding.com/acrobat%20files/Columbusaluminium2009.pdf)
• The seat tube at Ø31.7mm is standard for 27.2mm seatpost frames, confirmed by Dosnoventa's own spec. dosnoventabikes
• The head tube is more complex. The Columbus catalogs list raw head tubes (CYRA18 series at Ø38mm) that accept brazed-in IS cups. The finished head tube with integrated bearing seats has a 46mm OD at the bearing race and 41.2mm ID, per Columbus Compass 1-1/8" headset specs. fishtailcyclery
• The chainstays at Ø26mm are the track-specific Airplane stays (AT78 series), shorter and lighter than the Ø28mm road versions. These get ovalized/shaped toward the BB end. [framebuilding](http://www.framebuilding.com/acrobat%20files/Columbusaluminium2009.pdf)
• The seatstays at Ø19mm are larger than typical steel track stays (14mm) because aluminum requires larger diameters to achieve equivalent stiffness. [framebuilding](http://www.framebuilding.com/acrobat%20files/Columbusaluminium2009.pdf)

The Fail-Safe Approach: Layered Retention

The auto-catch is the critical safety layer. Even if the user never touches the cam lock, the battery stays in.

Best Mechanism: Over-Center Draw Latch

An over-center latch is the gold standard for vibration-proof panel retention. The curved spring blade flexes over center when closing, creating tension that actively pulls the cartridge tight against the frame shell. It cannot open from vibration — it requires deliberate manual release. wdscomponents

Option A: Southco 97 Series Over-Center Latch

The industry reference for exactly this application. [southco](https://southco.com/en_any_int/latches/draw-latches/fixed-grip-draw-latches/97-over-center-series-latches)

• Spring blade curves over center = self-locking, vibration-proof
• No visible springs — tension is built into the blade curve
• Stainless steel, multiple sizes
• Smallest size: ~52mm mounting length
• Buy (Norway): [no.rs-online.com](https://no.rs-online.com/web/p/door-latches/2888537) — stainless steel spring-loaded draw latch [no.rs-online](https://no.rs-online.com/web/p/door-latches/2888537)

Option B: WDS Hidden Over-Center Draw Latch

Concealed design — all hardware hidden inside. Matt black powder coat. [wdscomponents](https://www.wdscomponents.com/en-gb/over-centre-hidden-fastening-draw-latch-small-matt-black)

• Tamper-proof: concealed fastenings, can't be pried open
• Over-center = positive lock under vibration
• Zinc alloy housing, 304 stainless internals
• M3 countersunk screw mounting
• ~£4.90 (~€5.70)
• Buy: [wdscomponents.com](https://www.[wdscomponents](https://www.wdscomponents.com/en-gb/over-centre-hidden-fastening-draw-latch-small-matt-black).com/en-gb/over-centre-hidden-fastening-draw-latch-small-matt-black) wdscomponents

Option C: Push-to-Close Spring Catch

Like a cabinet push latch — cartridge swings shut, spring catch grabs automatically. Press a button/tab to release. [aliexpress](https://www.aliexpress.com/item/1005005961733321.html)

• Simplest, cheapest (~€1–2)
• Auto-engages on close
• Release via thumb push on tab
• Buy: [AliExpress — push catch latch](https://www.aliexpress.com/item/1005005961733321.html) — €1.14, rated for cabinet/motorhome use [aliexpress](https://www.aliexpress.com/item/1005005961733321.html)
• ⚠️ Weakest of the three — fine for cabinets, marginal for bike vibration

My Recommendation: Combine Hidden Over-Center + Cam Lock

  CLOSING SEQUENCE:

  1. Swing cartridge shut
     ↓
  2. Ball plungers guide alignment (click)
     ↓
  3. Over-center latch AUTO-ENGAGES (snap!)     ← SAFETY HOLD
     → Cartridge is now mechanically locked
     → Survives any vibration, potholes, jumps
     ↓
  4. (Optional) Turn cam lock with key           ← ANTI-THEFT
     → Now nobody can release the over-center latch

  OPENING SEQUENCE:

  1. Turn cam lock with key (releases latch guard)
     ↓
  2. Flip over-center latch lever (manual)
     ↓
  3. Cartridge swings open on hinges

The WDS hidden over-center latch is the best fit — it's compact, concealed, vibration-proof, and the matt black finish disappears into the frame. Mount it mid-seam on the cartridge. Position the cam lock so its tongue blocks the latch lever when locked — this means you physically can't release the over-center catch without the key first. [wdscomponents](https://www.wdscomponents.com/en-gb/over-centre-hidden-fastening-draw-latch-small-matt-black)

Updated BOM Addition

Total add: ~€15. The over-center latch is your "never forget" safety net.

The Fail-Safe Approach: Layered Retention

The auto-catch is the critical safety layer. Even if the user never touches the cam lock, the battery stays in.

Best Mechanism: Over-Center Draw Latch

An over-center latch is the gold standard for vibration-proof panel retention. The curved spring blade flexes over center when closing, creating tension that actively pulls the cartridge tight against the frame shell. It cannot open from vibration — it requires deliberate manual release. wdscomponents

Option A: Southco 97 Series Over-Center Latch

The industry reference for exactly this application. [southco](https://southco.com/en_any_int/latches/draw-latches/fixed-grip-draw-latches/97-over-center-series-latches)

• Spring blade curves over center = self-locking, vibration-proof
• No visible springs — tension is built into the blade curve
• Stainless steel, multiple sizes
• Smallest size: ~52mm mounting length
• Buy (Norway): [no.rs-online.com](https://no.rs-online.com/web/p/door-latches/2888537) — stainless steel spring-loaded draw latch [no.rs-online](https://no.rs-online.com/web/p/door-latches/2888537)

Option B: WDS Hidden Over-Center Draw Latch

Concealed design — all hardware hidden inside. Matt black powder coat. [wdscomponents](https://www.wdscomponents.com/en-gb/over-centre-hidden-fastening-draw-latch-small-matt-black)

• Tamper-proof: concealed fastenings, can't be pried open
• Over-center = positive lock under vibration
• Zinc alloy housing, 304 stainless internals
• M3 countersunk screw mounting
• ~£4.90 (~€5.70)
• Buy: [wdscomponents.com](https://www.[wdscomponents](https://www.wdscomponents.com/en-gb/over-centre-hidden-fastening-draw-latch-small-matt-black).com/en-gb/over-centre-hidden-fastening-draw-latch-small-matt-black) wdscomponents

Option C: Push-to-Close Spring Catch

Like a cabinet push latch — cartridge swings shut, spring catch grabs automatically. Press a button/tab to release. [aliexpress](https://www.aliexpress.com/item/1005005961733321.html)

• Simplest, cheapest (~€1–2)
• Auto-engages on close
• Release via thumb push on tab
• Buy: [AliExpress — push catch latch](https://www.aliexpress.com/item/1005005961733321.html) — €1.14, rated for cabinet/motorhome use [aliexpress](https://www.aliexpress.com/item/1005005961733321.html)
• ⚠️ Weakest of the three — fine for cabinets, marginal for bike vibration

My Recommendation: Combine Hidden Over-Center + Cam Lock

  CLOSING SEQUENCE:

  1. Swing cartridge shut
     ↓
  2. Ball plungers guide alignment (click)
     ↓
  3. Over-center latch AUTO-ENGAGES (snap!)     ← SAFETY HOLD
     → Cartridge is now mechanically locked
     → Survives any vibration, potholes, jumps
     ↓
  4. (Optional) Turn cam lock with key           ← ANTI-THEFT
     → Now nobody can release the over-center latch

  OPENING SEQUENCE:

  1. Turn cam lock with key (releases latch guard)
     ↓
  2. Flip over-center latch lever (manual)
     ↓
  3. Cartridge swings open on hinges

The WDS hidden over-center latch is the best fit — it's compact, concealed, vibration-proof, and the matt black finish disappears into the frame. Mount it mid-seam on the cartridge. Position the cam lock so its tongue blocks the latch lever when locked — this means you physically can't release the over-center catch without the key first. [wdscomponents](https://www.wdscomponents.com/en-gb/over-centre-hidden-fastening-draw-latch-small-matt-black)

Updated BOM Addition

Total add: ~€15. The over-center latch is your "never forget" safety net.

text
     FRAME (top 50%, welded)
    ╭─────────────────────╮
    │    lip    lip        │
    │  ○   ○   ○          │  ← 3× 21700 triangle pack
    │    ○   ○            │     fits in 43.5mm envelope
    ╰─────────────────────╯
     CARTRIDGE (bottom 50%, removable)

Geometry (Detroit-Inspired, Not Copied)

The Detroit runs 74° HT / 76° ST / 382mm chainstay — aggressive pursuit geometry. Your Omera keeps the same spirit but the 50mm downtube is wider than Detroit's 42mm Columbus Airplane tube, so the frame silhouette will already look distinct. That fat downtube is the design identity. [ppl-ai-file-upload.s3.amazonaws](https://ppl-ai-file-upload.s3.amazonaws.com/web/direct-files/attachments/139085844/e4366386-60b4-4746-a0f8-1aad86b7378e/fixie-dream.pdf)

Down Tube — The Main Event

This is where almost everything lives. 581mm center-line length (M size), 50mm OD, 47mm ID, 1.5mm wall. [ppl-ai-file-upload.s3.amazonaws](https://ppl-ai-file-upload.s3.amazonaws.com/web/direct-files/attachments/139085844/e4366386-60b4-4746-a0f8-1aad86b7378e/fixie-dream.pdf)

Three zones from HT to BB:

1. HT sealed zone (0–35mm) — cam lock + over-center latch mount, ball plunger holes, frame-side XT30 female + JST-SM female socket
2. Cartridge cutout (35–470mm, 435mm long) — the 50/50 split, underside, hidden from view. Hinge rails along both long edges
3. BB sealed zone (470–581mm, ~110mm) — KT T06S controller PCB, PAS wiring, motor cable exit hole toward rear dropout

Inside the cartridge (435mm long):

• 351mm cell zone: 3 channels × 5 cells, PETG plastic insert glued inside the alu shell [ppl-ai-file-upload.s3.amazonaws](https://ppl-ai-file-upload.s3.amazonaws.com/web/direct-files/attachments/139085844/e4366386-60b4-4746-a0f8-1aad86b7378e/fixie-dream.pdf)
• 95mm BMS/port zone (HT end of cartridge): 15S BMS (65×30×3mm), USB-C PD port with rubber cap, XT30 male + JST-SM male (auto-mate when locked)
• 3 knurled screw caps at HT end for cell swapping [ppl-ai-file-upload.s3.amazonaws](https://ppl-ai-file-upload.s3.amazonaws.com/web/direct-files/attachments/139085844/e4366386-60b4-4746-a0f8-1aad86b7378e/fixie-dream.pdf)

When drawing the cross-section (looking from BB end):

     FRAME (top 50%, welded)
    ╭─────────────────────╮
    │    lip    lip        │
    │  ○   ○   ○          │  ← 3× 21700 triangle pack
    │    ○   ○            │     fits in 43.5mm envelope
    ╰─────────────────────╯
     CARTRIDGE (bottom 50%, removable)

BB Junction — Crowded Node

Draw this area carefully, five things converge here: [ppl-ai-file-upload.s3.amazonaws](https://ppl-ai-file-upload.s3.amazonaws.com/web/direct-files/attachments/139085844/e4366386-60b4-4746-a0f8-1aad86b7378e/fixie-dream.pdf)

• Down tube enters from above-front (at ~41° from horizontal)
• Seat tube rises at 76°
• Chainstays exit rearward (both sides)
• BSA 68mm shell sits at the center
• 2× pin hinges for cartridge mount on the underside of the DT/BB junction

What fits inside the sealed BB zone of the downtube (~110mm):

• KT T06S controller bare PCB (~80×40mm) [ppl-ai-file-upload.s3.amazonaws](https://ppl-ai-file-upload.s3.amazonaws.com/web/direct-files/attachments/139085844/e4366386-60b4-4746-a0f8-1aad86b7378e/fixie-dream.pdf)
• Motor cable exits through a grommeted hole in the chainstay toward the rear dropout
• PAS sensor cable exits at BB shell (left side, crank-mounted sensor)

Head Tube Junction

The clean end — this is what people see first: [ppl-ai-file-upload.s3.amazonaws](https://ppl-ai-file-upload.s3.amazonaws.com/web/direct-files/attachments/139085844/e4366386-60b4-4746-a0f8-1aad86b7378e/fixie-dream.pdf)

• Cam lock keyhole on the underside of the DT, near the HT junction — hidden from normal viewing angle
• Over-center latch lever also underside, blocked by cam lock tongue when locked
• USB-C charge port on the cartridge surface, accessible through a small hole in the frame when cartridge is installed. Rubber cap flush with frame surface
• 3 knurled cell-swap caps face toward the HT end — accessible when cartridge is swung open

When locked, this junction should look like a clean weld — the seam, lock keyhole, and USB-C port are all on the underside, invisible from standing height.

Rear Triangle — Belt Split + Motor

Two critical constraints:

• 135mm horizontal/sliding dropout for the Bafang G020 hub motor (not track 120mm) [ppl-ai-file-upload.s3.amazonaws](https://ppl-ai-file-upload.s3.amazonaws.com/web/direct-files/attachments/139085844/e4366386-60b4-4746-a0f8-1aad86b7378e/fixie-dream.pdf)
• Gates CDX belt needs a frame split point — either the right seatstay or right chainstay must be splittable to thread the belt through. Most belt-drive frames split the right seatstay with a coupler
• Disc brake mount on the left chainstay (IS or post mount for 160mm rotor)
• Motor cable runs inside the right chainstay from BB area to rear dropout

Seat Tube — Keep It Simple

Nothing special here anymore — all electronics moved to the downtube: [ppl-ai-file-upload.s3.amazonaws](https://ppl-ai-file-upload.s3.amazonaws.com/web/direct-files/attachments/139085844/e4366386-60b4-4746-a0f8-1aad86b7378e/fixie-dream.pdf)

• 31.7mm OD, standard 27.2mm carbon seatpost
• Seatpost clamp at top
• That's it. Clean.

What Makes It Omera, Not Detroit

When you draw, these are the visual differentiators:

• The 50mm downtube — 8mm fatter than the Detroit's 42mm. This is the design statement. It's bold, hints at something inside, but doesn't scream e-bike [ppl-ai-file-upload.s3.amazonaws](https://ppl-ai-file-upload.s3.amazonaws.com/web/direct-files/attachments/139085844/e4366386-60b4-4746-a0f8-1aad86b7378e/fixie-dream.pdf)
• Disc brakes — the Detroit runs rim brakes. Omera has hydraulic disc, so you need fork/stay mounts and rotor clearance
• 135mm rear — wider than track 120mm, changes the rear triangle proportions slightly
• The seam line — a hairline laser-cut line on the underside of the downtube. Your signature detail. On matte black, nearly invisible
• No top tube battery — Detroit has a standard 35mm TT. So does Omera. The difference is all in the DT

Drawing Checklist

When you sit down on iPad tomorrow, draw these views:

1. Side profile — full bike silhouette, get the geometry angles right, show the fat DT proportion relative to the 35mm TT and 19mm stays
2. DT underside — the seam line, keyhole position, USB-C port, drain hole
3. DT cross-section at BB end — 50/50 split, 3-cell triangle, lip overlap, gasket
4. DT longitudinal cutaway — the three zones (HT sealed / cartridge / BB sealed), cell rows, BMS pocket, controller pocket
5. BB junction detail — how DT, ST, and chainstays meet, where the hinge pins sit, cable exit holes
6. Rear dropout — 135mm horizontal slot, disc mount, belt path, motor cable entry
7. Cartridge removed — the cartridge as a standalone object with USB-C port, caps, XT30/JST connectors visible

The stereotypical fixie (fixed-gear bicycle) rider look is heavily inspired by bike messenger culture and hipster aesthetics — think functional, urban, and deliberately understated. Here's what the typical outfit involves:

Bottoms

• Skinny jeans or cuffed jeans — worn tight or rolled up at the cuff to prevent pant legs from getting caught in the chain psupopculture.wordpress
• Cutoff denim shorts with frayed edges, especially in warmer weather adepttextiles
• Dickies work pants — durable, lightweight, and a popular no-nonsense choice among riders [reddit](https://www.reddit.com/r/FixedGearBicycle/comments/137waky/fixed_friendly_clothing_brands/)

Tops

• Vintage or band t-shirts (Joy Division is the running joke) [reddit](https://www.reddit.com/r/FixedGearBicycle/comments/137waky/fixed_friendly_clothing_brands/)
• Windbreaker jackets and layered urban tees [adepttextiles](https://www.adepttextiles.com/blog/fashion/the-urban-fixie-gear-bicycle-sub-culture-has-a-unique-fashion-style-that-has-grown-across-the-world-with-bike-courier-that-deliver-and-are-a-part-of-the-urban-fashion-culture-in-metropolitan-cities/)
• Collared shirts or simple, unfussy tops — nothing too sporty or lycra-based [adepttextiles](https://www.adepttextiles.com/blog/fashion/the-urban-fixie-gear-bicycle-sub-culture-has-a-unique-fashion-style-that-has-grown-across-the-world-with-bike-courier-that-deliver-and-are-a-part-of-the-urban-fashion-culture-in-metropolitan-cities/)

Footwear and Accessories

• Vans slip-ons or Chuck Taylors — skate-adjacent shoes, never clip-in cycling shoes [reddit](https://www.reddit.com/r/FixedGearBicycle/comments/137waky/fixed_friendly_clothing_brands/)
• Messenger/cross-body bags (like Chrome Barrage) instead of backpacks, because they're easier to access while riding psupopculture.wordpress
• Custom hats or caps, tattoos, and piercings round out the look [adepttextiles](https://www.adepttextiles.com/blog/fashion/the-urban-fixie-gear-bicycle-sub-culture-has-a-unique-fashion-style-that-has-grown-across-the-world-with-bike-courier-that-deliver-and-are-a-part-of-the-urban-fashion-culture-in-metropolitan-cities/)

The Overall Vibe

The style sits at a crossroads of skateboarder fashion and urban streetwear — practical enough for riding but deliberately not "cyclist gear". As one Reddit user put it, combining road biking with skate fashion is how you "really end up looking fixie af". The culture also emphasizes the bike itself as fashion — brightly colored frames, flashy wheels, and colored tires are part of the total image. The whole aesthetic spread globally, even stimulating fixie-inspired clothing lines in countries like China. sixthtone

Given your interest in bicycle design and engineering, you probably already spot these riders around Oslo!