Only Joules and Forces
| Only Joules and Forces | |
|---|---|
 | |
| Built By | Ian Beaver |
| Theme | The three-wheeled van from Only Fools And Horses |
| First Race | Makers Central 2019 |
| Current Status | Active |
| Motor | Vevor 2000W brushless |
| ESC | Generic 2000W eBike controller |
| Battery | 48V Li-Ion (2x 6S) |
| Transmission | Chain 9T to 74T |
| Contact | |
| View all Racer Profiles | |
Construction
Chassis uses the front crossmember from a severely crash-damaged '8mph' 4-wheeled mobility scooter which was fished entire from a skip. The front crossmember includes steering and suspension components. Bespoke mild steel sections are welded to make the front and rear of the chassis.
Front track has been widened up to the maximum allowed, to enhance stability. The front axle is positioned well rearwards - under the driver's knees - to further improve stability. The scooter's original front springs and dampers are fitted but, since the total laden weight of this hacky is perhaps only 1/3 the gross weight of the source vehicle, they don't move much in use so are unlikely to have much effect on handling.
Steering handlebars and head-tube are from a 'PUKY' child's cycle.
The single rear wheel is from the crash-damaged scooter but is mounted on a bespoke axle.
Braking is rear-wheel only by a standard cycle disk with cable caliper.
Bumpers are 12mm HDPE, removable for transport.
Theme is constructed from 6mm builder's ply, with LDPE foamboard decorations.
Powertrain
Vevor 2000W brushless motor with a 9T sprocket driving the rear axle via T8F chain and a 74T chainwheel. Rear wheel is 10" rim with 3" tyre giving an approximate dia of 16". Gearing comes to approximately 10,400 motor revs per mile. Motor's no-load speed is 4300rpm, giving a theoretical speed of 25mph - which is perhaps 20% higher than would be ideal but the limited choices of T8F gears means it is difficult to gear down further.
Electrics
Generic 2000W ESC. 12S of 10Ah hobby-grade LiPo, housed in a padded and vented ammunition box. 100A emergency switch with removable knob. Thumb-lever throttle and momentary reverse-switch mounted on the handlebars.
Performance of a Trike
The single rear wheel has some advantages and disadvantages. The obvious question is whether stability is significantly reduced when cornering, but for the most part this trike corners remarkably similarly to a four-wheeler. The worst-case instability scenario is when accelerating out of a corner, occasionally causing a wheel to lift briefly. A more significant issue is that the single rear wheel has less area on the ground and so less grip than two wheels would have, which can be a problem on very muddy circuits. On the other hand several successful four-wheelers also drive only one wheel - which will have even less weight on it that a trike's single wheel does. The advantages of a trike are that no mechanism is required to prevent the scrubbing losses and understeer associated with having a pair of wheels on a solid axle, and three wheels offer less loss through rolling resistance than four.
Driving
FatManAndRobin is quite an energetic drive. The rider's weight is best moved substantially forwards while cornering to keep the centre of mass within the widest part of the base triangle, increasing stability and maximising the grip of the steered wheels. Weight should be moved rearwards when accelerating to maximise grip of the driven rear wheel. Just as with most four-wheelers, weight should also be moved to the inside when cornering. The current driver (the eponymous 'Fat Man') is therefore grateful that races are now only five minutes duration.
Theme
All good trikes have two at the front, one at the back. Clearly, then, Del Boy's SuperVan required some minor modifications resulting in the rear window becoming the windscreen and the bonnet becoming the boot. You know it makes sense.
BOM
| Fat Man and Robin | ||||||
|---|---|---|---|---|---|---|
| GRAND TOTAL (ACTUAL) | £200.95 | |||||
| GRAND TOTAL (FMV) | £352.63 | |||||
| PART | ACTUAL COST |
FMV | QTY | TOTAL | SOURCE | |
| Accident-damaged scooter | Rascal 8mph 24V moby scooter. Wrecked. Chassis bent. Steering crushed. Transaxle snapped. Missing its electronics. And a wheel. And both brakes. And the seat. |
£3.99 | £0.00 | 1 | £0.00 | Centre Mobility, Aberaeron. Fished from skip. Paid with a box of chocs. FMVs for parts listed separately |
| Motor | Vevor | £98.57 | £98.57 | 1 | £98.57 | AliExpress |
| Controller | eBike 2kW cheapie | £27.51 | £27.51 | 1 | £27.51 | AliExpress |
| Throttle | E-bike hall-effect trigger | £8.00 | £8.00 | 1 | £8.00 | ebay: electricbikecomponents |
| Front suspension arms | Came with accident-damaged scooter. Bent but with usable parts. | £50.00 | 1 | £50.00 | Estimate | |
| Chassis | Bits and pieces of steel | £10.00 | £10.00 | 1 | £10.00 | Estimate |
| Wheels | Came with accident-damaged scooter | £0.00 | £33.00 | 3 | £99.00 | Estimate |
| Knobbly rear tyre | Generic cheapie | £12.99 | £12.99 | 1 | £12.99 | ebay: petrolscooter |
| Rear bearings | Pillow bearing blocks | £6.67 | £6.67 | 2 | £13.34 | ebay: hendersonbearings |
| Chainwheel | 74T / 8mm Mini Moto | £13.22 | £13.22 | 1 | £13.22 | ebay: carhouseuk |
| Ply for body | 6mm builder's ply 3/4 sheet | £10.00 | £10.00 | 1 | £10.00 | Davies Builders Merchants |
| Ply for seat | 10mm builder's ply 1/4 sheet | £5.00 | £5.00 | 1 | £5.00 | Davies Builders Merchants |
| Steering head | Puky child's bike. | £5.00 | £5.00 | 1 | £5.00 | Garage sale, June 2008. At the big white house, the one behind Moylgrove garden centre. |