Hello,
I thought this would be a suitable place to discuss the issue of " Magnetic Traction of Motors" in respect to our Proxy events.
Is it important
not if your running only on wood tracks only perhaps, but we are not, often at least half of our "Host" Rounds are carried out on Plastic track with metal contact rails.
What is the effect of Motor generated magnetic fields on Traction
well actually quite a lot, depending on orientation of the motor in the car, how it's located within the chassis or how high or low it is from the track surface. In my opinion having a motor magnetic force capable of generating enough force to lift 5gms of weight. Is equivalent to allowing you to reduce your ballast weight by 5gms and getting the speed benefit of not having the car carrying the additional weight.
Why do some brands make motors with higher magnet force than others
Usually the magnetic field in a motor is there to drive the armature and hence the motor speed or amount of Torque, loose magnetic force in a motor and your speed will dramatically drop off. This I seen a lot in old 60's Slot car motors which can be re-magnetised or magnets replaced to restore previous motor performance.
The wider question is why do some brands make excessive magnetic force for their motors, some do out of need because the type of slot car racing requires much higher speeds. but others I suspect is seen as a way of getting people to buy their motors to effectively say "their motor gives improved performance" as a result of increased motor magnet traction on home based tracks. However I have yet to see any brand openly declare their motor Magnetic Force in a specified manner. Hence the problem we have now in terms of deciding what is and what is not acceptable if running cars in a proxy on metal rail tracks ?
Testing Motor Magnetic Force field.
I decided to buy an instrument for measuring this characteristic purely on selfish grounds. To see what advantage I could use this knowledge for, lets face it I am not one of those racers with the human inbuilt gift of competition racing, my brain just seems to work slower than others (hence the indecision in setting the rules some times) and my response reflects are definitely slower in my old age
at least that's my excuse.
So I try to understand anything that will help my cars to run faster
"without me"
SRC Test Equipment (LMS Medidor Magnetico)
Initially I made the assumption that Magnetic force must increase when the motor is running, but having made measurements with cars running and static, the problem is that a running car mostly causes vibration and "the car moves along the bar" , so trying to get a direct comparison with moving cars is really difficult and variable. And in effect from the results there is really no difference (at least when motors are fitted into cars). Perhaps motors testing on their own without the car maybe different, I shall check this when making my "List of eligible motors"
So why use it now for the proxy - "ignorance is bliss"
When I started running these proxy's I was not actually aware of "magnetic traction" as being "a real issue", and I certainly did not have any device able to measure it until last year.
And I had not anticipated using it until running the EIS Proxy last year. It was whilst testing that great Slot it Ferrari 152M of Savage GT, frankly I was surprised how well it ran compared to it's rivals, but more importantly I noticed something "Strange" about the way it ran on my track.
It would struggle to gain speed initially and then as the running proceeded the car was running faster and faster, and then even with my DS controller fully depressed the car would just run perfectly smoothly round my track "without showing any signs of coming off ! "
This is of course the same as what I get with my Standard ASV Scalextric car fitted with traction Magnets, so the "penny dropped" and I thought I would test his car on the SRC instrument. Well I got a measurement of 10.6 gms negative deflection, whereas my Scalextric car was 11.12gms.
Now I should point out that even when I asked for the motor to be changed in the proxy, that superbly built Ferrari 512M continued to be a dominant top running car, so how much was the benefit of the "Magnetic Traction overall ? " to be honest I really can't say.
Pandora's box
The problem is now that I am testing cars as a matter of course, I have to assume that the "Magnetic Traction Effect " is a performance related benefit.
So I have make a judgement based on the normal range of measurements for all competing cars.
What is the "Excessive Magnetic Traction" Limit ?
No one has told me this, I have seen in some other rules that it is the "Cogging effect" when the gears are difficult to move, of the motors quoted in those rules of prohibited motors is the BRM Super Evo motor, so I bought one and measured it on the SRC, recorded 55 gms negative deflection. I have not tried to fit in a car and run it, but I suspect that at this level the car would probably remain stationary
or even run upside down as fast
But in my mind the limit should be mainly relative to the other motors fitted in all the other cars. So if we have a general range of between 0-2 gms of negative force for 43 cars, then 6, 8 or 11 is excessive.
In this latest example on the track the De Tomaso of Brumos RSR does show similar degree of "Strange track behaviour" and with my throttle fully depressed the car could not be de-slotted. Now that is most likely to be because Brumos is a fantastic at setting up cars and is nothing to do with "Magnetic Traction" he had no idea that the motor he bought had a high level.
And I would say that the track effect is less severe with his car, than with the Ferrari as I have not really seen too much initial resistance on "start speed"
But I must assume that there could be some advantageous effect if the motor is 3X the normal Magnetic force of the other highest level motors used in the competition.
If you asked me to put an actual figure on it, I would say 5gms of Magnetic force measured in situ fitted in a car. This would equate to not having to fit 5gms of ballast in a car.
The measurement on the instrument is 8mm between the motor and the balance, most cars sit only 1.5mm or less from the track surface, so in reality the Magnetic traction benefit is much greater than the 5grms measured. But we know that all these things are relative and traction due to tyres and other factors makes the complete package.
In reality after last year, I would put good money on Brumos RSR De Tomaso car running at the same speed with an alternative 25k rpm motor in it, as we might see...... but I must be seen to police these events the best way I can and try to ensure we have an even playing field.
Now I have a whole load of motors to check out for the next proxy
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