Chevy Monte Carlo ARC Pro lap counting fix

[woodcote]

I really like the Scalextric Chevrolet Monte Carlo and Ford Thunderbird. They are big and tough and perfect for digital racing. However, the Monte Carlo has a problem counting laps on the ARC Pro powerbase in digital mode. This is something Dr_C has looked at both theoretically and in practice.

The Monte Carlo counts laps perfectly in the analogue mode of ARC Pro - and also with ARC Air, ARC One and other Scalextric analogue lap counters. It is only the digital mode of ARC Pro which is a problem - and I do find that it counts laps reliably on Red, Green and Blue but does miss some laps on Yellow, Orange and White. Basically, the higher the ID number (the colours furthest to the right on the powerbase), the greater the risk of missing laps.

The two-step lap counting mechanism involves a black coloured guide breaking a horizontal sensor in the track (used in analogue mode and with ARC Air and One). In digital mode, the powerbase then needs to know what car ID has crossed the line. A second vertical sensor immediately searches for the car ID via the digital chip's LED. This second sensor is a set distance behind the first and there is a very short window of searching for the ID. In practice, Dr_C has found that the optimum performance for the second sensor is when the rear edge of the guide to LED distance is in a range between 6mm and 14mm (10mm plus or minus 4mm) - and the absolute maximum is 24mm.

I measured the gaps on both the Thunderbird and the Monte Carlo. The T-Bird is right on the money at 10.6mm. The Monte Carlo is 23.86mm, right on the limit - which explains the issues with lap counting.

 

The easiest fix I've come up with is to wrap some black PVC electrical tape around the guide so it trails back to 10.6mm in front of the LED - marked with the gold dot on the picture below...

 

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The tape does add extra width to the guide and - if you will be permanently modifying the car to run exclusively on ARC Pro digital - you could sand down the guide a little on both sides to compensate. I haven't found problems on any of my Scalextric Sport track pieces (including Radius 1s), but the tape does clearly rub. If you have any track pieces that have been bent and the slot closed up at all, the wider guide is likely to get stuck and the slot must opened out again or you risk damaging the digital chip if you gun the motor to get past the blockage.

The first thing to do is to remove the braid plate. Then cut a long length of black PVC tape and attach it - one side at a time - to the guide blade, the bottom of the tape just above the slot for the braid plate and then stick the ends together at the trailing end. It is important the tape is wrapped tightly around the front of the blade...

 

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Then trim the tape level with the bottom of the guide blade (or top when the car is up-side-down!) and cut at the back in line with the gold dot marking 10.6mm from the LED...

 

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Then re-fit the braid plate, which will require looping it over the tape extension at the rear of the guide...

 

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We are then ready to race and count laps!

 

There is another issue with the LED being so far back which the guide extension will not solve. This impacts on both lap counting and lane changing. The LED must be directly over the slot to trigger the lane changer and lap counting sensors - any sideways movement of the rear wheels (out of a corner, fishtailing on a straight etc) will move the LED off the centre line - and the further back the LED is positioned from the guide pivot, the further off the centre line the LED will be. Slot.it suggest a maximum distance of 35mm from the guide pivot to the LED and the Monte Carlo is 33.4mm, the T-Bird only 20.14mm.

What this means is there must be at least one half straight between the exit of a corner and either a lane changer, pit entry or the ARC Pro powerbase - otherwise LED and sensor will not line up. This is good practice for any digital track design and running any digital cars. A full straight is even better - especially if running cars without traction magnets. The Monte Carlo will be more susceptible to missing sensors than the T-Bird, so that is important for the drivers to remember.

[Andy P.]

Excellent woodcote! Thanks!