The third part of my review is looking at compatibility. And I'll start by saying that the new track system is 100% not compatible with the old track. The new sets also run on half the voltage of the old sets - 9V compared to 18V. However, there is some cross-over potential between the two systems. What I've written below is partly theoretical, but mostly based on a few things I tested last month.
Without any modifications, the differences mean that the old cars will run slowly on the new sets and the new cars will be ridiculously fast and twitchy on the old track at anything beyond half throttle (and the motors may well burn out). For other brands of HO car, their solid shoes do not work with the flat rails of the new track. I did run an AutoWorld car that I'd soldered braid to the bottom of the shoes - it ran fine, but slow (due to the 9 volts).
I did think that plugging in an old Micro Scalextric power supply to the track (to give 18V) would mean old Micro cars and other brands (with braids soldered on) would run - that seemed a simple fix. However, Hornby have very sensibly altered the power plug so that this can't be done - only the 9V power supply fits the new powerbase.
So here are a few fixes that have come up in discussions with US HO enthusiasts. However, I must stress that all these are options for dedicated slot car enthusiasts who have some electronics and car-building skills. And we can't test them until those first sets arrive in May...
1. Multi-voltage layout. The simplest option is to use a variable voltage power supply that gives settings at 9V, 12V and 18V or a fully-adjustable bench-top power supply that gives options everywhere from around 0 to 20V. The easy option is to connect the new 9V lead and plug to the adjustable power supply. An advanced-enthusiast system would be to build a custom power track and driver stations that would allow controller upgrades, a brake circuit, relays controlling track power etc etc. That would be the ultimate HO system and I think the new track is ideal for that.
2. Adding braid to other brands of HO cars. With adjustable voltage, the old Micro cars will work fine. Other brands would need either braids soldered to their solid shoes or an HORacePro Slide Guide installed. The Slide Guide acts as a miniature Scalextric guide and is designed for HO cars running on 1/32 scale track. There is also a 'Standard Track' Slide Guide that is designed for the narrower slot in HO track - I think this would be ideal for the new Micro track. I shall be getting some Slide Guides from the US to test them in May.
3. Using a replacement chassis. Using adjustable voltage doesn't solve the issue of racing 9V cars against 18V cars. However, there is a perfect solution to running other cars on 9V on the new track - the SL2 3D-printed chassis available from Shapeways. This isn't an out-of-the-box option, it has to be built and components (braid, axles, wheels, tyres, motor, gears, traction magnets) have to be sourced. So neither is it cheap. However, using the motor (and axles, gears, wheels and tyres) from the new Micro Scalextric chassis, you will have a car with almost identical performance at 9V to the new Micro Scalextric cars. Available for the SL2 chassis are body clips to fit numerous brands of HO bodies - Micro Scalextric (1994-2018); most AFX/AutoWorld/Tomy standard wheelbase cars (1970s-2019); Tyco/Mattel wide and narrow (1970s-2019); AutoWorld Super III; Tomy Mega-G and Mega-G+ longwheelbase. Plus more to come... What I will aim to do is build two (and eventually four) SL2 chassis so I can race any of my HO bodies against each other on the new track and also against new Micro Scalextric cars.
4. Using new cars on existing HO track. This would mean dialing down the power to 9V or swapping out the motor for a new one that works at 18V. The Tomy Mega-G+ cars have a similar N20 motor that was custom-made to work at 18V - unfortunately these are not readily available. Some of us would very much like to run the new cars as a school holiday race series at our club - we'd continue to use our four-lane AFX track set-up, but reduce the track voltage to 9V.
I hope that gives people food for thought. If you have any other ideas, do share them here.