[Tropi]

TYRE TRUING
Much is written about this very important 'tuning' aspect, but listen . . .
Don't even THINK about wasting time on truing tyres unless

1. The wheels have been trued first and
2. Don't even think about truing wheels until you are sure those damned axles are straight!

If you have a bent axle, there is absolutely NO point in trying to do anything with it.
Just get a new one.
THEN check if the wheels are round and mounted true on the good axle.
Only when you have a perfectly straight axle and properly mounted, ROUND wheels is there the slightest point in even trying to true your tyres.

Of course you might very well have some trouble in locating axles that actually fit your bushings/bearings, but that's another story and that's just one of the reasons for the existence of This other thread!

As a background to this, at yesterdays' club racing, I had a choice of two brand new (box standard) cars for a particular touring car class. Neither had been run before and I had not had much time for preparation. So I gave them both a quick twirl on the faithful Kelvin Test Bench.

One very simple thing has come up in testing brand new cars on the bench and it's this. Some brand new cars are not well lubed on arrival and some not at all! Very low speed test bench running has yielded some interesting data. If I run the car at the lowest speed at which the motor will rotate without stalling and note the amperage it pulls, simple basic lubing of motor bushes, gears and axle bushes will, on average, immediately reduce that amperage by around 20%. This is a substantial saving and well worth the knowing. So that was the first procedure and the data was confirmed - around 20% less amperage on both of them after lubing, even though the gears were already greased on arrival!

The other great thing about the bench's rolling road is that at low speed, it is SO easy to see if the car is bouncing on the roller AND also to clearly view the profile of the tyre on that roller. One of these touring cars was fine, needing only a small amount of tyre truing. But the other was an abomination! While one tyre was OK, the other showed clear daylight almost pemanently between itself and the roller. It was so bad that I decided against tyre truing and whipped the tyre off. Then it became crystal clear that the wheel itself was wobbling like a drunken demented handcart. Even the centre of the wheel could be seen to be tracing an eccentric orbit. So trying to skim the wheel was a waste of time and effort, as I reckoned the axle must be bent. So I gave up on it and raced the other car. I think I finished in the middle of the pack, quite happy, lots of fun.
But practice is what I really need - tons of it!

But perhaps the most interesting thing of all was that, after the race, I gave the car with the slightly bent axle a damned good thrashing round the track. You know what? On our imperfectly smooth track, it was hard to tell the difference in handling between this and the one with the straight axles, round wheels and trued tyres! Let me tell you how this could be. It's because the traction magnets are so powerful in these particular cars that it can almost competely disguise the wheel wobble! No other possible explanation.

Pah!!!!

More ramblings when I next feel like it!

 

[550rs]

A small Tested Tip from Tamiya to Tropi's Tremendous Tome on Tyre Truing. Slightly rounding the edges of the tyres after truing them helps the car to slide more easily. The goal is to avoid steamroller tyres by putting a little roundness at the edges, so that the tyre touching the track looks like a stretched U instead of square edges.

 

[Tropi]

OK, this has nothing to do with Racing & Tuning really, but the next random synapse firing has taken place in the Tropi grey matter and this phenomenon fits in nicely with my random jottings. One day we may sort it all out into some form of master class! In the meantime, more important to get it recorded before this rare burst of energy dissipates itself into nothingness again!

On USA sites you will often hear about clear coating cars with 'Future floor wax (or polish)'.
Those guys swear by it and they know what they are swearing about.
You may have wondered what the Euro or at least the Brit equivalent is.
Whether you have or not, I am going to tell you so, if you REALLY don't want to know, close your eyes and switch off right now!

It is Johnsons Klear - the Brit name looks even more American than the American stuff!
You can buy it in pretty well ANY supermarket where it will probably be situated near to the other cleaning and polishing products. (Not my most visited area, hence the several YEARS delay in tracking the bugger down!)
500ml costs something around a quid - can't quite remember the exact figure, but it is great value for money compared with specialist modelling products.

It comes in a tall, clear plastic bottle with a blue cap.
It is a transparent liquid with a slightly milky, pearlescent sheen.
It is water based, not oil.
It is neither wax nor polish, but a tough-wearing, acrylic finishing coat.
It smells of ammonia , so use it in a ventilated area.
The kitchen is favourite because the wife may foolishly think you are cleaning the floor and, if you actually do that as well, you may find more than your car possessing a smug and sprightly sparkle afterwards - wives can be very'grateful' if treated right!

So there you have it.
The great mystery is solved!
Next inspiration will happen when it happens . . or not, as the case might be!

 

[BEEJAY7]

Tropi

I know some of the US guys think this stuff is great, but have you tried it yet?.

Regards

Alan

 

[Tropi]

Sorry, Beejay, I haven't - it's taken me so many years to find out what it actually IS that I will now have to persuade the little hands to stop shaking with excitement over this major achievement before doing anything too drastic with the discovery!
In fact, before I do, I'm going to check out some of the American experience.
Watch this space

LATER
Early feedback from Coopdevil is favourable!
Short Report

 

[Wankel Ickx]

QUOTE ...it was hard to tell the difference in handling between this and the one with the trued tyres!

Been there, done that!

But I still like to true the tyres when I get a new toy. Also do do the "U" thing.

I find that if I have followed my basic set up procedure, whether or not it has made any real difference in reality, I feel better about the car, more confident and nine times out of ten I end up with good runner.

Wobbly hubs is a different matter. Got a set of crazy hubs on one of my SCX Subarus that defy belief. They are the reason I got two of these Scoobies: I figured one would have a decent set. Glad the second one did otherwise I'd still be buying 'em!

 

[Tropi]

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!

(Who? Me?)

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

1. Select your piece of straight track and set it flat on the scale
2. 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)
3. Place your car squarely on the track.
4. ZERO the balance.
5. 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.
6. 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!

 

[Fergy]

QUOTE 50% of all racing arguments are removed at a single stroke

I think I had one while reading this...

Good read, Tropi!

The last paragraph was perhaps the best, but if one wishes to attempt magnetic measurements your method is probably as good as any I've seen. You've also highlighted the reasons why setting up magnets can be so frustrating, especially when you set up for one track and then take the car to another. With enough measurement practice though, it should be possible to make adjustments with much more confidence in the outcome.

Keep 'em coming!