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| Volt-Crane-O | |
|---|---|
| Built By | Chris Stubbs |
| Theme | Liebherr Mobile Crane |
| First Race | EMF 2024 |
| Current Status | Active |
| Motor | 6x Hoverboard 6.5″ Hub Motors |
| ESC | 3x Hoverboard PCB |
| Battery | 48V 12S3P Li-Ion/LiPo (2x 6S) |
| Transmission | Direct hub motor |
| Contact | @emfroamer |
| View all Racer Profiles | |
Background
Volt-Crane-O is a scratch built, 6 wheel drive, 4 wheel steer, fully functional miniature crane.
The theme is based around a Liebherr 6 wheel mobile crane.
Construction
The chassis is constructed from wood, mostly 2x4. Fixings are mostly wood screws, except the use of M6/M8 bolts where additional strength or rules compliance is needed (bumpers).
The body is also constructed from a lightweight wooden frame, panelled with thin plywood.
Steering uses two M8 threaded tie rods to connect the pitman arm to the trailing spindle arms. The steering column is 25mm bed frame offcut with socket set articulating joint. There is a second pitman arm on the steering column at 90 degrees to produce a back and forth steering linkage to the rear axle, which is then translated 90 degrees again using a pivot to drive the rear tie rods. The steering angle of the rear axle is approximately 1/3rd of the front steering angle, because the rear/mid wheelbase is approximately 1/3 the front/mid wheelbase. No real thoughts were given to steering geometry and the handling is somehow "fine".
The steering components are mostly constructed from offcuts of bedframe, steel angle welded to make U section, or 4x30mm flat steel bar.
Powertrain
Volt-Crane-O utilises 6x 6.5″ 350W hoverboard motors, fitted with 4.10/3.50-5 tyres. Regenerative braking is extremely effective if configured correctly, however one motor has been fitted with a mechanical brake from a Xiaomi M365 scooter to comply with the rules.
Power is delivered to the motors using 3x original hoverboard PCBs running a fork of EFeru’s FOC firmware (links at the bottom). A higher current limit is applied to the rear motors to aid traction given the awful weight distribution. Throttle is applied in torque mode, controlled from aliexpress hall effect pedals via an Arduino.
Traction power is supplied by either 2x custom 6S3P Samsung 30T 21700 Li-Ion battery packs, producing 48V total. Each pack contains a 60A DALY BMS, or 2X 6S 9500mAH CHNL Lipos. Another 6S4P Li-Ion set using reclaimed hoverboard 18650’s also exists for testing and running around, but does not perform well enough for racing.
Other Features
The crane boom can be raised and lowered, extended and retracted (2 sections), and the winch/hook raised and lowered by a control panel below the steering wheel.
The boom itself is constructed from 3 telescopic sections of 18mm plywood, running on internal/external 608 skateboard bearings or homemade tubular bearings at each end.
The winch is a 12V caravan/boat trailer winch rated for 900kg.
All other actuation is driven by drill motors with their attached two speed (low gear) gearbox and chuck, which drives an M12 nut along a threaded rod. Opposing bearings are used to take the axial forces rather than relying on the drill. The boom raise/lower rod drives a nut attached to the elbow of an old monitor mount, which in turn raises the boom.
Power is provided by a dedicated 3S lipo.
The boom is lowered in to a cradle and secured directly to the chassis using the steel cable during racing. It fits within the envolope of the body/bumpers.
10 strobing orange hazard lights, 6 orange chasing LED beacons, 2 white headlights and 2 red brake lights illuminate the track for night racing.
An Arduino logs all hoverboard and control telemetry locally via SD card.
Awards
- EMF 2024
- 3rd place overall.
- 1st place Moxie.
BOM
| Item | Cost |
|---|---|
| Tyres | £32.64 |
| HBs | £40.00 |
| Winch | £40.00 |
| M12 rod + nuts x3 | £16.11 |
| Drill motors | £11.66 |
| M12 rod bearings | £2.94 |
| 2x4 frame | £11.44 |
| 38*63*2.4m wood | £6.72 |
| Ply boom | £18.12 |
| Boom bearings | £2.40 |
| Body frame wood | £6.80 |
| Panelling ply | £3.40 |
| Steering UJ | £1.90 |
| pedals | £7.86 |
| Winch controls | £2.44 |
| steering wheel | £8.27 |
| Wire | £8.00 |
| IP Enclosures | £11.86 |
| Seat | £0.00 |
| Limit sw | £0.50 |
| Paint | £15.00 |
| Crimps | £3.33 |
| Eye hooks | £2.79 |
| Washers | £1.54 |
| Nuts | £5.00 |
| V monitor | £5.06 |
| Drag chain | £4.22 |
| Limit indicators | £2.25 |
| Voltage reg | £3.00 |
| Control PCB | £32.00 |
| Brakes | Excluded |
| Brake Spacers | Excluded |
| Haz lights | Excluded |
| Winch isolator | Excluded |
| Isolator | Excluded |
| Lighting controller | Excluded |
| Fuse box | Excluded |
| Total | £307.25 |
Limitations
Steering wheel snapped off.
Sluggish on mud/grass.
Heavy (100kg).
Happily pops 30A fuse if accelerating too hard/long.
Resources
Twitter Account @EmfFRoamer
The Hoverboard firmware, Arduino code, and CAD on GitHub
Remote control Pi code on GitHub
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