ACDC
| ACDC | |
|---|---|
|
[[File:|thumb]] | |
| Built By | Vince Williams |
| Theme | ACDC |
| First Race | Scrumpy Cup 2019 |
| Current Status | Active |
| Motor | 2kw Brushless BOMA, AliExpress |
| ESC | 1500W 48v ebike Generic controller, AliExpress |
| Battery | 48V 12S LiPo (2x 6S) |
| Gearbox | None |
| Contact | @Bodgecharger |
| View all Racer Profiles | |
Background
ACDC is my second generation Hacky Racer build. I built this racer in 2020 based on all the lessons I'd learned from racing my original racer (Bodge Charger), i.e it was too tall, too narrow and too unstable. So ACDC is built to have as low a C of G as possible with a wider track than Bodge Charger giving superior handling in corners, this means I don't need to slow down so much in the corners. The chassis is 1500mm long (max allowed at the time of construction) and the width is determined by the widest I could possibly make it and still be able to roll it down the pathway at the side of my house.
This photo is of ACDC running at Fully Charged at Farnborough in 2022 where it did really well in all the races.
Construction
The chassis frame comes from a mobility scooter. The original front axle is kept, but the original back axle is binned and replaced with a new home made assembly consisting of two 20mm hollow axles mounted Left and Right side on 4 pillow bearings. Each axle has a 74 tooth drive cog and a mountain bike brake disk. I kept the original steering assembly but connected a steering shaft with a UJ from a Renault Scenic to it. Originally I bolted all the bits together to the chassis, but after the first weekend's racing when all the bolts came loose I soon learned how to MIG weld!
I bought a set of used Go-Kart wheels, hubs and a set of wet track tyres. I fitted the rear wheels/tyres as close to the body as I could to keep the racer width sensible, then I elongated the front wheel axle so the wheel to wheel width of the front axle matched that of the rear axle. This turned out well and the overall proportions ended up looking right. Because the back axle is split into two then I needed two sets of brakes, one each for the left and one for the right half axle.
The brakes are standard Mountain Bike hydraulic brakes which work great and much better than cable brakes. The only issue is balancing them both so that the operate equally together.
The motor is mounted so that it can be rotated 180 degrees to provide drive to either the LH or RH axle depending on the track direction (clockwise or anticlockwise), this means that ACDC is configured as a single wheel drive racer. This has its advantages and disadvantages, the advantage being that the car needs no diff and there aren't any steering issues like you typically get with a fixed rear axle configuration; the disadvantage is that there's usually one corner on the circuit where the wheel lifts, spins and you lose drive. But overall, single wheel drive works really well.
Motor
The motor you can see in the pictures is basically a 2kw Chinese scooter motor from AliExpress. The motor used in ACDC has been modified from the original by drilling oversize holes in the end plates to increase cooling air flow through the core of the motor; recently I've also added a wrap around heatsink that you can see in the second photo that I got from a USA eBay seller. I highly recommend getting a motor without the foot assembly if you can, or just hacksaw the foot off like I did because its made of very soft aluminium and bends when the motor is under high load, this bending ends up twisting the motor and putting it out of alignment with the drive cog and the chain will come off. Use the 4x threaded holes provided (2 in each end plate) to mount the motor securely in position.
Controller
ACDC uses a generic 1.5kw E-bike controller from AliExpress. These Chinese E-bike controllers are bullet proof, powerful and cheap. There's no reason to use anything else to drive the 2kw BOMA motor.
Batteries
ACDC uses 2x 6S 10ah Multistar LiPos from Hobbyking for races. I did try some custom 20ah EIG Li Ion cell packs in a 12s configuration, but these felt less powerful overall and the voltage sagged more than the LiPo packs. Batteries are housed in an old Ammo box mounter on the chassis, this that can quickly be removed after each race to charge the batteries up again between races. I have 2 sets of battery packs for ACDC so that one set can be ready to go and fully charged at all times while the other set is charging after a race.
I use a 2x 6s LiPo charger to charge my batteries between races. I always balance charge these LiPo packs to keep them in tip top condition.
Drivetrain
ACDC has a split rear axle, so has two independent half axles, each with its own drive cog. The gearing ratio between motor cog and drive cog depends on the drive wheel diameter and the speed you wish to achieve. Top speed isn't the most important thing in a Hacky Racer, acceleration out of the corners and torque are the main factors. I have geared ACDC to run a top speed of 20 mph, this is plenty fast enough for the short tracks we tend to use for races and is a good balance that gives decent torque and acceleration. With my Go-Kart wheels and tyres I use an 11 tooth cog on the motor and a 74 tooth cog on the drive axle to achieve a calculated top speed around 20 mph.
Awards
- Loads!
BOM
| Item | BOM Price | Notes |
|---|---|---|
| Mobility scooter chassis/bodywork | £35.00 | £25 for mobility scooter chassis and £10 for bodywork |
| Pillow bearings | £30.64 | |
| Axle shaft 25mm | £20.02 | |
| Pair of front wheel hubs | £29.99 | |
| Pair of rear wheel hubs 25mm | £34.00 | |
| Shaft collar 25mm (sprocket) | £3.12 | |
| Shaft collar 25mm (brake disk) | £- | Brake Component - Free |
| Shaft collar 40mm (sprocket) | £6.72 | |
| Shaft collar 40mm (brake disk) | £- | Brake Component - Free |
| Pair of Brake Disks | £- | Brake Component - Free |
| Pair of rear sprockets | £9.99 | |
| 8mm T8F chain | £4.25 | |
| Ammo box | £- | Free for BoM |
| Brushless 2Kw motor | £79.99 | AliExpress, bought in 2020 |
| Motor controller | £15.84 | AliExpress, bought in 2020 |
| Throttle pedal | £10.09 | |
| Steering wheel | £24.99 | |
| Steering shaft | £13 | Includes UJ |
| 2x mtb brake set | £- | Brake Component - Free |
| Batteries | £- | Batteries - Free |
| Switches | £2.00 | £9.99 for 10 |
| Seat | £10.99 | |
| Wheels + Tyres | £30.00 | £50 for 4x wheels and 2x sets of tyres |
| Total | £360.63 |
Limitations
The driver (that's me) weighs too much! No suspension. Ground clearance is only 4 cm at the lowest point, so its not suitable for bumpy fields or long unmown grass. Single wheel drive can be poor in muddy conditions (otherwise its just fine).
Resources
Twitter Account Charger @BodgeCharger
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