OK, this one will probably complete the ongoing process of temporarily draining out the dregs from the vast Tropi pool of random thought, in order to make room for colossal quantities of cholesterol inducing Christmas cheer!
TESTING MAGNETIC DOWNFORCE
One of my early Christmas presents to myself was Bob Schleicher's book, "Slot Car Bible". It's a jolly good read and I recommend it to any slottist, because there is something there for almost everyone.
Off topic to start with, but it IS my topic and I can do whatever the hell I want with it, OK!
Sod off, all pedants!
In this book, among many other fascinating subjects, you will find a detailed and illustrated "How To" on adapting Scalextric's Pacer to other makes of track.
Bob says of Pacer,
QUOTE "This may be the most important accessory for anyone racing at home".
I wholeheartedly agree!
I really needed to say that and I feel MUCH better now - thank you!
Back to the original topic.
I spent some time reading Bob's article on
How to make your own magnetic downforce scale
(Note to Bob and his publisher - you can't find this article in the alphabetical index under Magnetic, Downforce, OR Scale - not very helpful when trying to find it again!)
The book devotes 5 pages of text and photographs to the subject and yet it is very difficult to figure out exactly what you are aiming to do and how and why. Once you finally do understand the principle, you wonder why it seemed so obscure at first, but it certainly does. This is only the first difficulty.
The actual construction demands a lot of time, patience and first rate workmanship AND it requires you to effectively destroy one complete section of track for each make of track that you want to run on (and therefore to check with the scale). In addition, due to the nature of magnetism, the results obtained with this 'scale' will be quite variable, depending entirely on your workmanship in building it. If you build another one or use someone else's, the results will almost certainly be different. The reason is that tiny variations in distance between magnet and rail have a hugely disproportionate effect on the downforce. Actually, it IS proportional, but proportional as in the mathematical square. There are other good reasons too, but you will read about them in my 'dummies alternative' to Bob's more sophisticated device. Precision factory-built versions would be much more consistent but, again, you will eventually discover why this might not matter much, if at all.
There is a much easier way to check downforce IF you have access to a suitable scale/balance/weighing apparatus. It requires ZERO workmanship, ZERO construction skills, destroys ZERO track, and requires almost no time to set up. These plus factors are intended to make it more appealing to some of us! I'm not going to produce a detailed 'how-to', but just to lay down the dead simple basic principles that 'YOU' may then adapt to your circumstances and availability of scales.
The simplest apparatus is a small, digital platform scale, although it could probably be adapted to a spring suspension scale and other types too. The scale's platform needs to be big enough to set a standard straight track section upon, although it can be considerably smaller than the whole track section. I would suggest that the scale should be capable of weighing around 1 kg or more and to an accuracy of 1 gram. Accuracy less than 1 gram is utterly irrelevant. In fact, even 10 grams may be accurate enough, as you will soon discover, should you try this out.
End of waffle - now down to business
- Select your piece of straight track and set it flat on the scale
- By any means, temporarily but firmly, attach the track to the platform. By far the simplest method is a weight on each end of the track. (a rock, a small book, your granny, depending on what comes to hand and the capacity of the scale)
- Place your car squarely on the track.
- ZERO the balance.
- Gently and slowly lift the car, vertically, straight up from the track while watching the scale readout. The car magnet will naturally try to lift the track but it is firmly held down to the platform. So now the magnet will try to lift the platform as well as the track attached to it. As it does, the scale readout will show NEGATIVE numbers.
- Note the highest number (lowest negative - let's not get into semantics here!) shown on the scale readout. That is the magnetic downforce of THAT car on THAT piece of track.
That's all there is to it - could it be simpler?
Now for a few notes, based on my rough experiments of some time ago and you may want to add your own. Please do, as I don't know everything (though you may be forgiven for thinking that I think I do!) and my aim is just to share knowledge and experience.
If 'you' can improve or add to it, I want to know - we all do.
The knack is in lifting the car squarely and evenly, while reading the negative weight at the same time. You WILL get different results each time you do it. Practice and you will develop a more consistent technique. You may sensibly wish to average several results. The extremes of those results will show you, vividly, just how much magnetic assistance does vary on the track.
You will also quickly find that it REALLY matters how parallel the car is to the track rails, which is an extremely 'hits-you-between-the eyes' indicator of just how much the magnetic attraction can vary on a fast moving car doing its business on the race track! NOW you know why it's so hard to get consistent track behaviour AND why tiny slides so often transform into almost instantaneous offs, with absolutely NO chance of recovery.
In addition, the rail height on track does vary
(though some makes vary much worse than others) and you will almost certainly get different readings if you do not replace the car in exactly the same place each time. That last one can be simply overcome by marking the track. But does it really matter? After all, your entire circuit will display this frightening unpredictability - another indelible illustration of the unreliable vagaries of magnetic assistance!
If you put in the effort, over time, you will gradually develop a reasonable picture of the magnetic variations between different makes of track and you will equally see the unavoidable variations in exactly the SAME make of track, possibly even on the very same piece! You will find much more variation in the more flexible track, such as Scalextric classic (due to warping and inconsistent manufacture & assembly) and you will find MASSIVE variations displayed by 'trick-track', mainly due to its severe lack of flatness, but also due to magnetic dead spots in crossings. This dead spot factor could play absolute havoc with all those lane changes in digital circuits!
You might very well decide that it would be more meaningful to do the tests on a curved section - after all that IS where the magnet is most needed.
Wow, doesn't life get complicated!
Have you noticed something here?
All this mind-numbing blurb about variations in the TRACK and we haven't even faintly touched on the damned magnet in a car!
But, you are intelligent chaps aren't you?
Once you have refined your test technique and been suitably gob-smacked at the incredible inconsistency of the track, you can settle down and start playing with the ungodly magnets in the cars for yourselves!
Please let us know how you fare in this quest.
At the end of it all, you will have learned quite a lot and may even intelligently conclude that magnetic assistance is so inconsistent that it actually ruins the FUN aspect of fair and evenly matched slot racing
by turning it into a magnetic nightmare.
Is it really worth all the bother and argument?
You see, if you simply remove the magnets altogether, this entire article is instantly rendered redundant (3 cheers from the now brain-dead!) and about 50% of all racing arguments are removed at a single stroke.
Worth thinking about!