Make yourself a Magnet Master

How DO they do that??

Make yourself a Magnet Master

Postby wixwacing » Thu 08 Jun, 2017 6:02 pm

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298.5 and no mistake!


I have been an exponent of non magnet racing for more than fifteen years now and as each year goes by I feel more strongly about the disparity that magnets create at the race track. No matter how balanced you try to make the racing there are usually one or two racers who have become SCM’s; in becoming such a creature, a Jekyll and Hyde conflict takes over and a ‘win at any cost’ mentality becomes prevalent leading to that slippery slope almost of no return where surreptitious modification and devious practice are common.


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Handy pocket size 127 x 106 x 19 m.m.

Mini Pocket Scales


In non magnet racing it is very difficult to usurp the rules as it can become immediately obvious to all when modifications like motor swapping have been carried out, especially on the more sweeping tracks. I have heard tell of a significant southern racer actually re marking Plafit motors to sustain his place at the head of the pack. But apart from this, talent is the greatest skill required to succeed at non magnet racing, as scrutineering, diligently applied, will detect any slight of hand practices.


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Scales placed under magnet area where possible


Traction magnets are a different story, some magnets, like SCX, are on full display and any tampering is blatantly obvious to the alert scrutineer. Many other makes have their magnets buried in the bowels of the model, and nothing short of a chassis strip down will reveal their fidelity or otherwise. So the perpetrator has comfort in the thought that it will be almost unlikely they would be detected; and if suspected, his vociferous protestations should calm the angry mob!


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Having been a race organizer for several years I have grown wise to the level and type of rule bending which goes on, even in non magnet racing; and as such, I have always run events to a strict set of guidelines. On the most recent of occasions, races where run over successive heats and after the final heat, the first three models home would be scrutineered according to the guidelines. Any model which falls short of compliance is removed from the results and remaining contestants are moved up a notch until three compliant models fill the top three spots (a bit similar to ‘parc fermé’ in F1). It sounds a bit long winded but believe me, once contestants know you are serious, they soon tow the slotcar line, and future scrutineering becomes a doddle!


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So, getting back to the more difficult aspect of scrutineering magnet racers in a timely fashion, there needs to be some sort of magnetic attraction measure. The number and location of magnets in a model can usually be established by sweeping a screwdriver across the underside of the chassis. This will tell you where magnets are located, but to detect ‘double stacking’, the strength of the magnet requires a special piece of equipment; in this case a device popularly known as a ‘magnet marshal©’ is readily available on several of the ethernet market places.


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Attractor bar with wooden ends glued in place.



These devices do a good job in telling you more or less the amount of magnetic downforce being generated by the model under test. In doing so, it can be compared to other models and a generally acceptable ‘downforce’ can be established for the class being tested. Also, it will tell you which models do not comply to the rules. All this comes at a price which leads me to the original point of this article, being, parity on the track. What price is acceptable to the race organizers?


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Attractor bar glued to casing


Well, where you can get them, they start about US $100.00 plus freight. Not bad value considering the arguments they could settle! But there is an alternative For about Au$30.00 you could make your own! So stay tuned…….and read on!


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Platform construction, all PVA glued and braced


When I first decided to build this device, the first thing I needed to know was the dimensions of the measuring device (from here on called the ‘scales’).This would determine the overall dimensions of the casing and platform. An hour or two on eBay saw a potential candidate come in at Au$10.00 plus free postage from Hong Kong! not bad since local postage for any parcel is $7.60, the catch being it probably would come by surface mail and that would take 30 days or more! But it was an ideal size AND there was a choice of weight ranges, 0 - 0.5 kg, or 0 - 2.0 kg for the same price!


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Attractor bar fitting



While waiting for its arrival, and based on its on-line dimensions I went as far as I could designing and building the casing and platform. Another decision was what to make it from? 0.5 m.m. plastic card was the first option, but that isn’t cheap, so I settled for 3.0 m.m. MDF. It takes PVA glue well, and being a box type structure should be resistant to rough handling. So MDF it was and off the drawing board onto the workbench we went.


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Platform slides under bar when scales are removed



The main principle to achieve was to get the model sitting on a non magnetic platform which would rest on the scales plate; and to simulate the track rails, a piece of steel should locate centrally under the model with the emphasis on it positioning under the model’s magnet location. This should ideally be flush with the platform top. Most in-line models have their magnet located between the rear axle and the motor; no problem. Sidewinders and anglewinders usually have the magnet located in front of the motor at about half way up the model. Ninco in-line long can motors have the magnet located in front of a point half way up the model and some models have two magnets, one about the centre and the other behind the motor, like Carrera for instance. So the attractor bar needs to cover all these areas at least. In my case and for ease of construction I decided to mount a 3.0 m.m. thick mild steel strip the length of the base. This strip needed to be fixed to the casing as it will be holding the strip stationary compared to the platform, there should also be a visible air gap around the attractor bar and the platform


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Assembled



Once the scales arrived I could get on with final assembly. The starting point was to make the platform which the model sits on. The MDF was cut carefully to size and the three sided base was glued. The sides were assembled using some square aluminium tube as support. PVA glue was applied to most of the length of the base except for 10 m.m. at each end. These spots had a drop of superglue applied to them. The sides were matched up around the alloy box section and held for twenty seconds or so while the super glue dried. This holds the sides together while the PVA is drying and allows minimal handling of the glued parts.


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Components


The platform was constructed using similar techniques and the model surface received a couple of braces under each side to prevent sag at some time in the future. All glued joints had a fillet of PVA on the inside just to give it a bit more strength. When dry, the attractor bar was glued into position. This position was established by partially assembling the base and marking on the side plates the top of the model platform. These lines would be used to align the attractor bar. The bar had hardwood quadrant type end pieces at each end superglued in place while the platform was held in line with the marks. The top of the base was trimmed to size and the whole was tidied up and sanded flush.


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Rear side



First test was to place the platform into the base, lift it, and then slide the scales underneath the platform. When lowered onto the scales, and if you have measured correctly, the platform top should align with the top of the attractor bar ‘et voila!’ Time for testing!


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Zeroing body weight (tare)



Firstly it needs to be zero’d. This is done by placing the model to be tested across the platform. The platform sides will stop the model touching the attractor bar, this will prevent giving a false reading. The initial display will be the model’s actual weight; we want to remove this from the end calculation so the zero button is pressed while the model is still in place. This will zero the display. The model is then carefully lifted from the platform. The guide is carefully engaged in the left end of the slot until it touches the end, the model is then lowered down onto the platform. The display will now be reading the actual amount of downforce being produced! Mission accomplished!


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Alloy square tube and clamp



So there you have it; a lick of paint and you could fool your mates! There are a couple of things to watch out for; firstly, the scales need to sit centrally under the model’s magnet position to avoid an inaccurate reading. There are several small ‘feet’ on the underside of the scales in the form of small plastic domes. These were odd heights and caused the scales to rock when sitting on the casing base. The centre feet were sanded down and this fixed the rocking. And, it is important that the scales are zero’d completely before each test. If in doubt, remove the model, switch the scales OFF! and start again. The best results are obtained by having the scales as directly under the magnet position as possible. Too far to one side will cause the scales top plate to tilt and give an inaccurate reading.


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Centre ‘foot’ sanded down to eliminate rocking



The ‘Magnet Master ©’ is of a fairly robust construction and with moderate handling should last a while. Another aspect of the device is that it can be used not only for detecting fraudulent magnets, but it can also be used as a set-up tuning tool, to trim existing models and match magnets and a whole lot of other slotcar things, your imagination is the limit!

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If you would like further information or clarity on some point, PM me this board or email me at pwix@yahoo.com
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When I'm not racing slotcars,
I'm out in the back yard, burning food!!

When I win, it's because of my talent, not my car or my controller!
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wixwacing
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Re: Make yourself a Magnet Master

Postby wixwacing » Mon 26 Jun, 2017 1:46 pm

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357 grams downforce! Not bad for a muscle car!


After using the magnet manager for a few days it was obvious there where a couple of niggling teething problems. Firstly, it took far too long to zero when the ‘TARE’ button was pressed, more importantly, there was a use for the manager for setting up NON MAGNET! models…Mmmmmmm….? Trust me!

The first problem took a bit of time but was simple enough. In the building stage some of the sides and the base where not completely flat. Probably due to the fact that the MDF may well have had a slight curve in it from where it had been leaning against something for a while. I have already explained how the scales tipped in their rest position, and some sharp handiwork got the scales sitting firmly, without moving, on the base.

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Some sticky label cushions in the corners to overcome platform rock


Unbeknownst to me, the base was also distorted on its underside where it sat on a flat surface like my work bench. This was allowing the base to ‘hover’ on opposite corners and any slight movement allowed the scales to not zero. The solution here was to sand down the opposite corners which were causing the scales to hover!

So, now we have the base flat on the bench, and the scales flat in the base, zeroing was now not an issue. The best position for all models also needed to be determined. The sales are very accurate and you can place an object on any part of the weighing table and it will not differ from place to place, this negated the need for the magnet or wheels to be exactly over the centre of the scales.

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Optimum rear tyre position


I decided to mark a point where all models back wheels needed to align with just to add a datum point for all models. Firstly, I established a fixed point on the base for the scales to remove any ambiguity in measurement. The scales were set a bit to the left of the right base side so that the bottom of the scales didn’t ride up on the fillet of PVA glue I had applied to strengthen the base. Once happy I scribed a line along the base in line with the left edge of the scales. The scales will be aligned with this mark from now on, and also, the back of the scales should be touching the rear stop.

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The new non magnet patform, glued throughout with super (c.a.) glue


Taking one of my longer models and sitting it on the platform with the guide as far forward as it can go, I marked a spot where all rear tyres are now required to align with to maintain accuracy.

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Non magnet model weight


The second issue is less of an issue but more of an extra function. Those of us who race non magnet models know the importance of getting the model ‘balanced’. For this I have created a second platform which only carries the rear of the model, the front being supported by the guide on the attractor bar. I like my models to weigh around about the 45% / 55% mark front to back. i.e. 45% of the models weight on the front guide / wheels and 55% on the rear.

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Scale left hand alignment mark


The model can be set up quite easily by first zeroing the scales. The model is then laid on its side across the weighing platform. The scales should then be reading the models weight (see illustration). The model can then be placed on platform with its guide in the slot and the rear tyres as close as possible to the mark. This will give the weight on the rear tyres. A simple maths subtraction calculation will give the weight on the front axle. Having these figures you can then calculate the percentage load on the front and rear.

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Rear wheel / axle weight 67.0 grams. (67 ÷ 1.03 = 65.0 %)


I also like to use the magnet manager to set up initial magnet strength for a whole range of models, taking out the guesswork and negating over magnetizing of new and regular models. I have found that in setting up new models, a model with regular width urethanes (Rally/touring cars) will perform well with a magnetic down force of 225/250 grams on most plastic tracks, and with lower and faster models with rear tyres 10 m.m. < , a lower setting can be applied, say 175/200 grams. Fast Sedans like Trans Ams and modern NASCARs will probably need 300 grams + for best performance. Track technicality will also creep into the calculation.

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Not touching right side


A fast sweeping track is less demanding on magnets than twisty, turney tracks. But remember, too much magnet will bog the model down and you also run the risk of overheating the motor. I have seen guys running models with in excess of 1000 grams of magnet. They don’t win often. Hopefully a ‘balanced’ model will result. But I am sure there will be further uses for the ‘Magnet Manager©’ in due course

So that’s about it, and I’ll bring you updates as and when they occur; but at this moment the only extra needed is a shiny coat of paint, Mmmmmmmm?

Let me know how you get on!
Image

When I'm not racing slotcars,
I'm out in the back yard, burning food!!

When I win, it's because of my talent, not my car or my controller!
User avatar
wixwacing
Marshal!!!
 
Posts: 1888
Joined: Thu 10 Jul, 2008 8:22 pm

Re: Make yourself a Magnet Master

Postby wixwacing » Tue 18 Jul, 2017 4:51 pm

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As mentioned in the previous post, all that was left to do was give the new toy a lick of paint, I had a part used spray can of a gunmetal colour and decided that would be the way to go; so after primer, undercoat, gloss and clear lacquer, all that was left to do were the fancy bits i.e. the new name in the form of a decal. I got three sheets of A4 clear water slide ink jet decal paper from ebay and proceeded to finalize the logo in Microsoft word.

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Test sheet

Once happy with the design I then printed off several sizes onto plain paper and cut out the sizes that looked promising, and offered them up to the platform face. A couple of colour changes and a test print determined the finished article; then came the need to print off the design on the decal paper.

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I positioned the design at the bottom of the A4 decal sheet as this would leave the rest of the paper free for another decal another time. Once printed it was cut out and given a coat of clear acrylic lacquer. The following day it was applied to the platform and the day after that it had its final coat of clear acrylic.

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Non magnet balance platform

So, another job jobbed and if I don’t mind saying myself, quite tidy and effective. But I cannot take all the credit, A gentleman known affectionately as “Wal” from our local race group inspired me with his Mk 1 magnet tester and after some design alterations the Mk 2 was born!

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Note that I have built this for 1:32 models only. For 1:24 you will need to upgrade dimensions as required. So now it’s time for you guys to rush down the local hardware store and stock up on 3.0 m.m. MDF!
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When I'm not racing slotcars,
I'm out in the back yard, burning food!!

When I win, it's because of my talent, not my car or my controller!
User avatar
wixwacing
Marshal!!!
 
Posts: 1888
Joined: Thu 10 Jul, 2008 8:22 pm


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