SlotsintheCity.com EXCLUSIVE First Preview!
Back in September 2014, I got the chance to examine and test-drive pre-production examples of a number of Slot.it models – now, finally, I’ve managed to get my hands on another of them; one of the first 4WD Audi R18 e-Tron Quattro models released.
The CA29a arrives in the recently-updated Slot.it packaging – the new colour scheme and larger cut-outs certainly set the model off nicely. The bare, matte-black, finish of the car looks menacing, adding contrast to bright details such as the headlight clusters and chromed roof panel. The tampo printing is clean and sharp, just as we’ve come to expect from Slot.it – even the smallest logos are solid, bright, and precise. The body is almost an entirely different moulding to the 2011 R18 TDi, and appears to have been reproduced as faithfully as the scale allows. Every complicated little spoiler, vent, duct, and winglet has been replicated to achieve a highly-detailed bodyshell – and, there are many more than on the CA24-series models – the only possible downside being that, as it’s made up of so many parts, it feels a little more fragile than Slot.it’s usual offerings.
Certain smaller details stand out over larger ones. I particularly like the fact that the inside surfaces of the wheels on this model have been painted black – it sounds minor, but it really adds contrast to the spoked insert and creates the impression of depth in the hub. Also, the bulky aerials have been replaced by thinner, shorter, versions and even the wiper blade is different – a very fine photo-etch… great stuff.
…on to the mechanics!
Technical milestones at the 24 Hours of Le Mans are nothing unusual for Audi: the brand with the four rings has always consistently used the endurance classic to race new technologies – TFSI, TDI, VTG, ultra lightweight design, and this, the e-Tron Quattro, are all examples of the brand’s pioneering spirit in motorsport. [Joest Racing]
All of which makes the 2013 Audi R18 e-Tron Quattro a fitting scale platform for Slot.it to launch their own pioneering new system – clutched, belt-driven 4WD. In prototype form, this car and its clever drivetrain debuted at the 2014 DiSCA Slot.it oXigen Le Mans 24 Hours at Henley-In-Arden, UK. Now, 12 months later, as the entrants lined up for this year’s DiSCA event, the production CA29a lined up for inspection on my bench!
…so, how does the Slot.it 4WD system work?
Well, the principle is rather simple: a clutched (one-way) bearing in the hub of each front wheel transmits only positive torque, letting the wheels turn freely with almost zero power loss whenever they need to spin at a lower speed than that of the axle they’re attached to. In practice, the system allows the inside front wheel to spin freely while the model corners, overcoming the dreaded understeer issue common to many standard 4WD slot cars – and, on straights, it reduces the front wheels’ friction drag to zero, thus reducing power losses to just whatever the toothed belt causes, which isn’t much. As a result, whenever the front wheels can provide any traction, they do! [Maurizio Ferrari, Slot.it]
Slot.it appear to have outdone themselves by cramming so much into a 1:32 scale chassis – or, at least, down one side of it – it would certainly have been more convenient to integrate this system with an inline configuration, after all. The anglewinder setup of this Audi does make things a tight fit; the belt sits perilously close to the pinion, and the overall width of the model means running a wheel and tyre combo any wider than 8mm is likely to be out of the question. But, interestingly, there’s little else to suggest that this model wasn’t originally designed to be used with this 4WD system – for example, it uses the same CH74 motor pod and CS24t-60b chassis as designed for the 2WD models and, impressively, the belt passes alongside the strengthening rib on the chassis and through the tiny gap between it and the EVO6 mounting lug on the motor pod. When I applauded Maurizio on this foresight, he assured me in his usual modest style that it wasn’t so – it was a purely fortuitous; a ‘happy accident’!
Slot.it’s own instructions for their 4WD system are clear and thorough, detailing not only how the system fits together, but also another clever design feature – the front wheels both make use of the same type of directional bearing, so there was no need to add to the cost of the 4WD system with a bearing unique to each wheel. In fact, the only expense you’ll need to make in order to maintain your purchase is for a pair of special pliers for the ‘Seeger rings’ (circlips) employed to hold the front hub assembly together.
The pulleys are attached to the hub (both axially and radially) by the normal grub screw in the wheel itself – this keeps them locked in place to provide drive from the 110-tooth belt. The front pulley is one tooth larger than the rear one, which ensures that the front axle spins whenever the rear one does, but always slightly slower – so, as Maurizio explained earlier, it’s only in the event that the rear wheels break traction that those clever clutched bearings in the front hubs ‘engage’ and the car becomes truly 4WD; basically, it’s rear-wheel-drive with an independent front axle when cornering, four-wheel-drive under heavy acceleration. The best of both worlds? I’m very much looking forward to putting this system to the test on-track… more on that in the next instalment.
Any concerns about the belt pulling the front axle to one side under power have been addressed with the simple addition of brass bushings to the front axle – for some time now, Slot.it chassis have been manufactured with a small groove in the front axle carriers for exactly this reason, but this is the first model to have them factory-fitted. As you’d expect, the front axle now spins as precisely as the rear and with very little play – and, although there is a small amount of additional drivetrain ‘drag’ present from the extra parts, I expect this to loosen up after a some running-in time.
Components for the 4WD system have been available separately for a short while now, ready to be retro-fitted to many models from various brands to good effect – the only limiting factor is the length of drive-belts available. Further, Slot.it have teamed up with Hornby/Scalextric to work on a number of rally car models; in combination with a new range of replacement chassis, it’s an obvious use for such a system and a welcome collaboration for many racers who are excited to see such high-performance components improving products offered by other manufacturers.
Available in stores: 29th April 2015
Once again, I’d like to say a big thank you to Maurizio at Slot.it for showing me his 2014 Henley-In-Arden entry back in September, and for making arrangements so that this production version was made available to me so quickly.