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Discussion Starter · #1 ·
I'm fairly new to this hobby, and still finding my way. I've accumulated quite a collection of digital cars (GT and LMP), and finding intriguing differences. For example, while the Scalextric BMW, 911, Merc, and DBR9 all perform very well (track circuit times about 11-12 seconds), this can't be said for their Corvette (track circuit time about 14.5 seconds), which slews and deslots in ways that the others just don't. I've changed the braids to match those in the others, and added 10g of weight over the rear wheels, which has helped a bit, but is not the solution. I have two questions. 1. Is this the sort of variation I should expect across different cars (e.g. Corvette vs BMW) even within class (GT)? Or do I have a duff Corvette? 2. In either case, what might be the next steps towards a fix for the Corvette?

Thanks

Tim.
 

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Is it not a realistic reflection of the American car's inablity to corner? ;)
 

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I am sorry to say that this is what you will see. Even the same cars can differ a lot in performance, the motors rpm can vary a lot. Do you run magnets? Taking the magnet out will bring the cars closer, as magnet strength isn't consequent either. If the tuning doesn't work, we even the cars out by limiting power in the RMS, or play with fuel burn to compensate.
 

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Andy Player
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Out of the box, the Corvettes are like you say. With some work, they go well - especially running without the traction magnets. Mikefi at our club has put a lot of work into getting his Scalextric C6Rs right up there (and beating) the other sidewinder GT cars.

If you absolutely have to run with magnets, it's quite easy to increase the magnetic downforce of the more tail-happy cars by adding small round neodymium button magnets (eg 5mm diameter x 1mm thick N52s) on top of the existing bar magnet. By trial and error, you can end up with much closer performance.

This is what I did to equalise the downforce between the BTCC Civic and BMW 125, where the BMW's magnets sit significantly higher off the rails than the Civic's. This is the inside of the BMW...

40937360411_7162705fbb.jpg
 

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Discussion Starter · #6 ·
Thanks for suggestions - on the magnet thing, yes, I can see why serious clubbers would remove these; but my own motivation is to throw a few parties now and then for family and friends, with various formats, so for the sake of all round (ease of) fun, I'm likely to keep the magnets in. (Perhaps I'll take them out of 6 cars for a pro class, in the fullness of time). So I'll probably follow up on that magnet tip, and perhaps substitute a motor for one I'm sure is good...

cheers

t.
 

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Circuit Owner
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Some of the GTs have two magnet positions. For those that corner too well - move the magnet to the forward position - this should make them more of a challenge but not massively so. That should help level the field a bit more.
 

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David H
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In my experience across many hundreds of Scalextric cars, tyres are the greatest cause of performance difference. If you can find yourself a quantity of tyres that are from the same manufacturing batch and have been stored in identical conditions, the gaps in lap times will shrink considerably.

Magnets are the next greatest cause. I don't use them, but some years ago raced in a class that allowed standard magnets so made a contraption that measured their strength. Visibly identical Scalextric magnets differed in strength by over 30%, which is a huge and race winning/losing margin.

Motors also differ, but by far less.

One useful discovery I made when measuring magnets was the significant changes that can be made to their effectiveness by altering the shape of their magnetic field. By chance, I dropped a metal paper-clip onto a magnet that was fitted in an otherwise standard Carrera BMW M3 GT2 whilst it was sitting on my "downforce" measuring contraption. I've forgotten the precise figures, but downforce increased from around 600 grammes to 630g. A 5% improvement for the cost of a paper-clip!

Further experimentation and refinement meant 5-10% was readily available from almost every magnet in return for strategically placed metal washers, shims and odds and sods. As a result, I'd advise every rule-maker writing rules for magnet classes to specifically ban ferromagnetic ballast.
 

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Hi Dopamine,

Very interesting observation. I have four Ninco MaxiMeganes, one of which is gloriously tail happy. After much investigation my conclusion is that it can only be that the magnet is significantly weaker in this car. These have the old style "bar" magnet buried in the shell with the two slots showing the mag underneath. I've toyed with getting some newer magnets to try and balance the performance across the four cars but your suggestion has prompted me to take another look. I take it the paperclip sits on the inside of the car? I would also be interested as to how you set up a magnetic force instrument, could be a valuable diagnostic tool.

Cheers - Bob.
 

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Anything more than 150 g downforce is sad.
 

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David H
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I would also be interested as to how you set up a magnetic force instrument, could be a valuable diagnostic tool.
Here's my downforce measurer. Not pretty, but it works. It's composed of three elements:
1: The wife's kitchen scales.
2. A rigid aluminium baseplate to which are screwed wooden side blocks, which in turn have a steel crossbar screwed to them. The crossbar is mounted in such a way that its height can be precisely altered using shims and is sufficient to allow the scales to fit underneath without contact. It has a hole in it for the car's guide. The hole must be large enough so that no part of the car or guide touches the crossbar.
3. A smaller piece of aluminium plate which sits on the scales and onto which are placed wooden blocks that, when in situ on the base, exactly match the height of the upper surface of the steel crossbar.

My primary aim was to make the measurer rigid enough to withstand the forces of Carrera magnets and to give consistent readings. Whether the steel crossbar accurately mimics the magnetic attraction of a track rail is debatable, but the readings the measurer gives are very consistent with how magnet adjustments affect a car's on-track performance.

Away from the base assembly, place the smaller aluminium plate, central wooden blocks and car onto the scales and zero them. Then reassemble it all on the base; the reading shown on the scales is the magnetic downforce.

The Scalextric BMW here is fitted with its standard brown bar magnet which, despite being substantially weaker than modern neodymium magnets, still produces a whopping 94g downforce. For modern Scalextric cars fitted as standard with the thickest neodymium magnets, I've occasionally seen readings of over 700g. Everyone has their own taste, but cars stuck to the track by that much aren't for me.

By far the best set-up tweak for magnet cars is to position the magnet as close to the rail as possible, usually by truing the tyres down until the chassis is almost scraping the track. The downforce difference between having a magnet 1mm above the rail rather than 1.5mm is substantial.

I take it the paperclip sits on the inside of the car?
Yes, the ferromagnetic ballast used to tweak the magnet's magnetic field goes inside the car, touching the magnet or very close to it. In Carrera cars, I had good results by placing one of Carrera's standard rectangular magnet shims at an angle on top of the magnet so that it also touched the can of the motor. Sometimes two shims were better than one, sometimes a round washer had better results. Experimentation is the key.

The contraption.
magnet measurer 1.jpg

Zero with car on scales.
magnet measurer 2.jpg

83g. The car's weight.
magnet measurer 3.jpg

Ready for measuring downforce.
magnet measurer 4.jpg

94g. The amount of magnetic downforce.
magnet measurer 5.jpg

Anything more than 150 g downforce is sad.
In my book, traction magnets are sad full stop, but the solution is simple: remove them. Harder to deal with are motors with high magnetic downforce. The cars which are fastest in standard form on my track are Avant Slot Mirage GR8s and Spirit Peugeot 405 Silhouttes, both of which have highly magnetic motors. Fun for a handful of laps, but thereafter a bit dull.

The best place for magnets.
magnets-01.jpg
 

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David H
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In Carrera cars, I had good results by placing one of Carrera's standard rectangular magnet shims at an angle on top of the magnet so that it also touched the can of the motor.
It was a long time ago and I've just remembered that Carrera cars are inline, so I couldn't have touched the magnet and the motor with a shim and must be mistaken about the car used. Having thought about it, I'm pretty sure it was a Scalextric Camaro that I did this to, as one of the magnet classes I was racing in was Trans-Am using Scalextric and Pioneer cars, which are sidewinders. Whatever car it was, the principle is the same for any car with a traction magnet: experimentation. There is a good gain to be had.
 

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Circuit Owner
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I agree with the no magnets preference. Tyres are critical without magnets and gluing, truing and lightly oiling rubber tyres gives cars enough grip to compensate for lack of magnets. Yes lap times are slower but the playing field is far more level. Magnet cars give little warning on the edge of adhesion and just let go too quickly to catch - non magnet cars break their grip more slowly and you can catch it and recover traction far more easily. Scalextric rubber responds well to a drop of 3-in-one oil rubbed onto the contact surface of the tyre 24 hours before you race.

I appreciate that newbies find non-magnet racing far harder BUT you can turn down the voltage in most cases (or limit power in digital systems).

But if you insist on magnets then sort out your Corvette tyres and consider swapping magnet positions and swapping magnets between cars until you get them as evenly matched as possible (a great excuse to spend a few hours on the track!!!)
 

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Dopamine, thanks for the detailed reply, I see how your scales system works and is very clever! Of course, it's not an absolute measurement but it does allow relative downforce to be evaluated which will at least allow me to explore the Ninco Megane issue. It's very kind of you to take your time to detail your approach and again, thank you.

Cheers - Bob.
 
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