Ford MkIV – Scalextric vs. MRRC

by Bob Ward

November, 2017

Ford’s historic  GT40 Mk. IV only raced twice, but it won both events, Sebring and LeMans in 1967, in dominant fashion.  Too dominant, some said, and the FIA’s rules change, the day after LeMans, confirmed that it agreed.  With the big-block Mk. IV (and the Mk. II, also) banned from international endurance racing it was left to a heavily developed example of the GT40 Mk. I – the same individual car, campaigned by the John Wyer team – to win LeMans the next two years. Nevertheless, the Mk. IV’s win average in serious competition forever remains at 100%, and there are few, if any, other top-level racing cars that have equaled it.

As historically significant as the car is, it’s surprising that it has not been more extensively modeled for 1/32 scale slot car racing.  In the 21st century there have been three volume-produced models, each offered, or planned to be, in numerous liveries.  MRRC and NSR’s renditions have been around for some time, and they are now joined by a new one from Scalextric.

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NSR’s Mk. IV (above), like all NSRs, is optimized for performance and makes no pretense of being otherwise.  Its body shape is subtly stretched, slammed, and otherwise massaged for the “serious” racer in top-level competition, somewhat at the expense of scale fidelity.  This doesn’t keep it from being an impressive-looking car, not to mention by far the fastest and most adaptable of the three, but it’s not meant for the rivet counter.  It’s also a high-end car with all high-end components and the most expensive by a substantial margin.  These factors often make it less interesting to the beginning to intermediate level racer who is more scale-oriented and does not need or want to pay for the NSR’s performance.  Moreover, it’s not very useful to compare it to more basic slot cars such as the MRRC and Scalextric.  For these reasons it’s the other two this article will focus on.

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MRRC’s Mk. IV was designed and first offered for sale the better part of a decade ago.  Like most MRRC cars of recent years it’s built on the well-regarded MRRC Sebring universal chassis.   It is powered by an inline-mounted FF “slimline” motor  rated at 21,000 rpm.  MRRC Sebring-chassis cars have come at various times with either one or two neodymium traction magnets.  Our comparo car came with two, one aft of the motor and one forward, using the two snap-in magnet mounts built into the Sebring chassis.

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Scalextric’s MK. IV is all new for 2017, though it was supposed to have been out in 2016.  it was designed under the requirements of the quickly abandoned Pro Chassis initiative.  This was intended to give Scalextric an entree into the upper levels of 1/32 scale racing by making available for each newly designed car an upgrade chassis that would accept motor pods and high-end performance parts from Slot It.  The Pro chassis project never really got a chance to prove itself before it was axed.  It appears, however, that the Pro chassis-related compromises baked into their recent (and, apparently, future) car designs will be with us for a long time to come.

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One of these is the inline motor installation (in the Mk. IV an 18,000 rpm FF) which Scalextric has said is going to be standard with either the FF or the FC130 on all newly designed cars going forward.  Now, there’s nothing wrong with an inline installation, if it’s done right, for certain kinds of racing, most notably non-magnet wood track racing.  Unfortunately, non-mag/wood track racing is 2 to 5 percent of the slot car market, though its viewpoint dominates the online forums.  The other 95-plus percent races on plastic track with magnets.  And for magnet racing the best chassis arrangement is a sidewinder.  Why is that, you may ask?

First of all, it’s because a sidewinder allows the placing of the traction magnet directly under the rear axle, the optimum location for maximum cornering grip.  In addition, at the grip levels magnets allow (even stock ones, not to mention the aftermarket magnets in widespread use) the stability of the gear mesh is absolutely essential.  Two main things affect the stability of the gear mesh: the distance between the motor and the rear axle and the rigidity of the structure connecting the motor mount and the rear axle mounts.  The closer the motor to the rear axle and the greater the strength of the connecting structure, the less the gears can move out of correct mesh with each other under motor torque and the smoother and quieter the car will run.  A sidewinder places the motor right next to the axle and the pinion gear very close to the shaft bearing and connects them solidly together.  With an inline installation you have to put the magnet forward of the rear axle to clear the crown gear, and that moves the motor farther from the rear axle.

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MRRC has dealt with the shortcomings of inline motor installations a little better than Scalextric has.  MRRC, despite using a wider but shorter bar magnet, has managed to place its motor farther aft and has surrounded the motor and rear axle mountings with more and stiffer structure.  Scalextric placed the motor farther forward than it really needed to be and did not give the structure connecting the motor and rear axle mounts the heft it needed.  This makes the Scalextric chassis flexier in a place where it should be as inflexible as possible.  The net result is that in both cars you hear the sound of gear teeth not meshing right when maximum torque is being applied but you hear more of it from the Scalextric car.

In neither case does this make the car unraceworthy but, while MRRC was more or less locked into using the existing Sebring chassis for economic reasons, Scalextric could have designed their car any way they wanted.  They could have, and should have, made it a sidewinder.  It’s a shame they didn’t because their standard 11/36 sidewinder gear set (which you can’t get any more since Scalextric stopped selling spare parts) is probably the best press-on plastic gear set in the industry.  Along with the inherent virtues of their sidewinder motor/axle mounting structure it has been a big factor in making their sidewinder cars superior out-of-the-box magnet racing performers among basic 1/32 scale slot cars and outstanding race set cars that have given countless beginners an excellent start in the hobby.

And they could have made it a sidewinder, though they might have needed to make the body a bit wider than scale.  The scale width is 2.1″ or 53.3mm.  To make it a sidewinder they probably would have had to make the car about another 1/4″ or 6.35mm wider.  Yes, that would have amounted to a certain degree of subtly stretching the car a la NSR, but I’ve never been one to quibble about exact scale dimensions, especially since neither Scalextric or MRRC got the body shape perfect anyway.

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You can see in the images above that there are considerable differences between the Scalextric and MRRC cars and between both models and the full-size car. Who came closest is a question I’ll leave it to you, the reader, to decide, but the point is that since nobody’s Mk. IV body is perfect, if Scalextric had made the car a quarter inch wider and made it a sidewinder with an FC130 motor like all previous Scalextric Ford GT40 variants I’d consider that an excellent tradeoff and I’d bet only a very few people would either notice or care about the scale difference.

Here is some key information about the two cars from our testing:

Overall weight:  Scalextric – 75g; MRRC – 75g

Gross Magnet Marshal reading (weight plus magnetic downforce): Scalextric: 224g; MRRC (2 magnets) – 405g; MRRC (front magnet only) – 330g

Wheel diameter/ scale diameter:  Scalextric – 11.2mm / 14.1″;  MRRC – 12.35mm / 15.6″; Full-sized car – 15″ wheels (The diameter of center-rib slot car wheels with no outer rim effectively represents the rim diameter of full-sized wheels.  Thus, the Scalextric wheels are actually closer to 13″ wheels (2″ too small) and the MRRC wheels are about right at 15″ plus a half inch or so of rim.  This explains why the Scalextric wheels look so small and the tire sidewalls so tall, sort of like what you’d see on the rear of a top fuel dragster.  It’s worth noting that the tires Scalextric is putting on its new cars beginning this year are a real improvement in performance over the ones previously fitted.

Rear tire tread width:  Scalextric – 3/8″, 9.52mm; MRRC: 5/16″, 7.94mm

Test track best lap times (clean track, sanded stock tires): Scalextric – 3.369; MRRC (2 magnets) – 3.167; MRRC (rear magnet only) – 3.015.

With both magnets the MRRC is actually too stuck down for best lap times, though it’s easier for a beginner or a child to drive.  The Scalextric car, at 274g gross MM reading (199g net magnetic downforce) is right on the low side of the downforce range I prefer.  When the MRRC runs with only the rear magnet the downforce readings are close enough that some upgrading/detuning work with no more than tires and magnets should be enough to equalize the two cars’ lap times and also to put them on a par with other Scalextric, Flyslot / Slotwings, MRRC, and Carrera cars of similar type and era, though it may be a while before aftermarket tires to fit Scalextric’s Mk. IV appear.

The Scalextric car is digital plug-ready and comes with working headlights and taillights.  The driver’s head is badly in need of replacement by a better-sculpted one but  giving him a head transplant would not be difficult.  An MRRC driver’s head would be a good choice if you have one.

The above gripes notwithstanding, both cars are fun to drive and more than fast enough to challenge drivers of any skill level.  Both cars are well worth their respective prices.

 

 

 

 

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