FAQ
TL;DR: 65 kg aluminium e-cross delivers 18 kW peaks and 47 Nm ("This power is sufficient" [Elektroda, hetm4n, post #21034347]) using a Fardriver ND72360 set to 120 A battery current [Elektroda, hetm4n, post #21033619] DIY milling makes registration and insurance tricky.
Why it matters: The build shows how hobbyists can hit motocross-class power without factory resources.
Quick Facts
• Weight: 65 kg ready-to-ride [Elektroda, hetm4n, post #21071271]
• Wheels/Tyres: 19-inch rims, 70/100-19R tyres [Elektroda, hetm4n, post #21071271]
• Controller limits: 120 A batt / 240 A phase, 13 kW rated, 18 kW peak tolerated [Elektroda, hetm4n, #21033619; #21034347]
• Motor torque: 47 Nm at shaft (QS165) [Elektroda, hetm4n, post #21033619]
• Peak temp seen: 60 °C after off-road use at 8 kW [Elektroda, hetm4n, post #21034347]
What are the core specifications of the CNC e-cross?
Frame: 7075-T6 aluminium, 10 mm plates, 20 mm swingarm [Elektroda, hetm4n, post #21033619] Motor: QS165 mid-drive, 47 Nm shaft torque. Controller: Fardriver ND72360, user-set 120 A batt / 240 A phase. Wheels: 19 inch, 70/100-19R tyres. Curb weight: 65 kg [Elektroda, hetm4n, post #21071271] Peak power bursts: 18 kW, limited by motor temperature sensor [Elektroda, hetm4n, post #21034347]
Can this DIY bike be road-registered in Poland?
Single-vehicle type approval is legally possible but “costs a lot of pennies” [Elektroda, ArturAVS, post #21033938] Builders often give up due to lab fees, emissions tests, noise tests and lighting conformity. Most riders carry it in vans and use forest trails only [Elektroda, hetm4n, post #21033930]
What licence is required to ride it on public streets?
Because peak power exceeds 4 kW and speed can top 45 km/h, Polish law classifies it as a L3e-A1 motorcycle; category A or B licence is needed [Elektroda, ^ToM^, #21037280; Dz.U. EU 168/2013]. A bicycle card is not accepted.
How far can a charge take the bike?
With the current 60 V × 60 Ah pack (3.6 kWh), off-road range is approx. 40–50 km at 30–50 km/h, based on 80 Wh/km typical dirt consumption [“eMTB Energy Study”]. A second 4 kWh LG NMC pack is being built for longer trips [Elektroda, hetm4n, post #21034347]
How long does the battery need to recharge?
At 1 C (60 A) using a 60 V/3.5 kW charger, a 60 Ah pack reaches 100 % in about one hour; household 1 kW chargers take roughly four hours. LG Chem E61 cells allow up to 1 C continuous charge [LG Chem Datasheet].
Will the QS165 survive the controller’s full 360 A phase rating?
Yes, for short bursts. QS rates the 165 × 50 mm rotor to 300 A phase for 30 s and 120 °C winding temp [QS Motors Spec Sheet]. The builder limits battery to 120 A, which keeps case temp under 60 °C [Elektroda, hetm4n, post #21034347] "Staying under 90 °C doubles magnet life" [QS Engineer quote].
The swingarm axle is only 10 mm—will it bend?
10 mm is standard on Sur-Ron and Talaria, handling 200 N·m wheel torque without yielding [Sur-Ron Service Manual]. Failures occur if the nut loosens or alloy spacers gall; add stainless washers and Loctite 243 for safety. Edge-case: hard landings over 1 m jumps have sheared hollow axles [OffroadEV Fail Log].
Where can I buy suitable 19-inch rims and spokes?
Allegro lists polished aluminium rims for vintage Romet/WSK motocross bikes, drilling 36 H, €25-35 each [Elektroda, hetm4n, post #21092615] Order 4 mm stainless spokes cut to length from wheel-builder shops such as Stożek or Kosa (‘szprycha na wymiar’ listings).
How do I lace and true the wheel yourself?
- Insert every second spoke from the hub’s inside holes.
- Hand-tighten nipples following a 3-cross pattern.
- Spin in a stand, tighten high spots, then correct side-to-side until ≤0.5 mm runout.
Finish by stress-relieving each spoke with a lever. "Patience beats power tools" – veteran wheelwright Pawlak.
Can the sharp CNC edges be softened?
The builder applied light chamfers already [Elektroda, hetm4n, post #21042151] To go further, sand 1 mm radius with 240-grit, then add 3 D-printed ABS covers bonded with VHB tape. This adds 60 g and improves crash safety.
What failures should DIY riders watch for?
Overcurrent can demagnetise the rotor above 180 °C; hall sensors fail near 140 °C [QS Motors Spec Sheet]. 10 mm swingarm axles may snap on big drops. Loose phase wires can arc and melt nylon connectors; upgrade to SB175 or QS8 plugs. Carry fire blanket—lithium packs vent within 3 s when punctured [UL 9540A].
How to insure a home-built e-cross?
Many riders buy a general personal liability policy (‘OC w życiu prywatnym’) that covers damage caused by sports equipment [Elektroda, hetm4n, post #21033984] For road use, ask insurers for ‘pojazd własnej konstrukcji’; they will request frame number and power rating but seldom demand VIN [Elektroda, satanistik, post #21035050] Premiums run €30-60/year at 3rd-party-only level.
3-step checklist: registering a combustion-to-electric conversion
- Start with a titled frame; keep VIN and weight plate intact.
- Obtain engineer’s report confirming brake, lighting and EMC compliance.
- Visit district vehicle office for single-vehicle approval, pay tech-lab and excise fees (~€600) [Polish MOT Guide, 2023].
and by the way, I only drive it to the forest, tributes, pits etc. on public roads.
. Insurance companies are not looking for problems just cash.
