The Magic of Lane Change Plates

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Ned
Posts: 368
Joined: Sun 13. Apr 2014 01:02
Location: Sedona, AZ USA

The Magic of Lane Change Plates

Post by Ned »

I have been messin’ around with magracing for more than 2 ½ years. During the past week, I finally discovered the true magic of lane change plates and why properly designed, produced, and installed plates will provide more reliable and consistent lane changes for experienced as well as newbie racers at any speed, compared to any lane change design relying only on wire.

To understand the magic, take a knife, any steel knife. Or a kitchen spatula. Place the flat side of a magnet from a magracer on the blade or spatula. The ideal one to use is the 4mm x 3mm thick magnet used in the guide arm, but any will work. Now put a piece of index card or a business card under the magnet. See photo below.
https://docs.google.com/document/d/1NGp ... sp=sharing

Take a hold of the card stock and slide it around. Notice how the position of the magnet on the card doesn’t change as you move the card until the magnet reaches the edge of the knife. Once it reaches the edge of the knife, the magnet slides on the card. The magnet wants to stay within the boundary established by the edges of the knife. Put a few more pieces of cardstock under the magnet and repeat. Even with 5-6 pieces of cardstock between the knife blade and magnet, the magnet still resists going beyond the edge of the knife.

Using a .008” thick lane change plate, like those originally sold bt Wes R, I measured the lateral forces between the plate and the magnet. I taped the plate to a flat smooth surface. I then placed 2 pieces of cardstock over the plate. On top of that I placed a Ziploc vinyl bag to reduce friction between the card stock and magnet. The total thickness of the materials between the top of the plate and the bottom of the magnet was 0.025”. That represents the clearance between the top of the plate and the bottom of the magnet when the magnet in the guide arm is passing over the lane change plate. In practice with my track and cars, that distance is about 0.025”.

As best I can tell, it takes less than 1 gram of force to move the magnet laterally when it is at a level 0.025” above the plate. That 1 gram was probably due to friction. With 0.025” of clearance, it took about 21 grams to pull the magnet beyond the edge of the plate. When the clearance was reduced to .017”, the force required was about 26 grams. The smaller the clearance between the plate and the magnet, the higher the force required to pull the magnet beyond the edge of the plate, as one would expect. But it is not a simple proportional relationship. A stock magracer body weighs about 9 grams. So it takes a force 2 - 3 times the weight of a body, applied laterally and perpendicularly to the lane change plate, to pull (or push) the magnet off of the plate.

Using a similar approach, I measured the lateral force required to pull the same magnet off of a .032” diameter wire, when the force was applied perpendicularly to the length of the wire and when the clearance between the top of the wire and bottom of the magnet was .009”. (That is about the clearance in the case of my track and cars. About ½ of the 9 mils is paint.) The force required was about 30 grams. If the force required is proportional to the cross-sectional area of the wire, then a smaller .028” diameter wire would require about 23 grams. For comparison I measured the lateral force required to pull the magnet off a .020” diameter wire I had on hand, using the same clearance of .009”. The measured force was 10 grams. This data does suggest that the force between the magnet and wire is proportional to the cross-sectional area of the wire.

What are the implications for designing a mechanism to switch lanes in magracing? As I see it, when the guide magnet is passing over a lane change plate, there is very little or perhaps no lateral force exerted against the magnet by the plate, as long as the magnet is above and within the boundary of the plate defined by its edges. This implies that we can steer the car when the magnet is above the plate, with virtually no resistance exerted by the plate until the edge is reached. Once the edge of the plate is reached, considerable force is required to go beyond the edge. Assuming clearances between magnet, wire, and plate, that are typical for magracing, the lateral force to go beyond the edge of the plate is in the general vicinity of the lateral force required to pull/push the magnet off of a .032” or .028” diameter wire.

What more can we imply from this data? I think it suggests the optimal shape for lane change plates. First of all the plate should work better, if it is wider at one end compared to the other. The width at the narrow end should be about the width of the guide magnet, 4mm. There is no evidence that the magnet is attracted toward the edge of the plate, when it is completely above and within the boundary defined by the plate edges. So the plate should be long enough for the magnet to be steered over to one edge of the plate before reaching the end of the plate. This requires a plate at least 2.0” long since the minimum radius that the car can track is 9.0”. See below.

It would appear that a plate like the one depicted below would be best for slow lane changes just before very tight corners. The diagrams assume a guide wire diameter of .030".
https://docs.google.com/document/d/10jk ... sp=sharing


The white band crossing the plate represents the path of a 4mm magnet when the coil in the car is energized for a left turn while passing over the plate, from right to left. It assumes a 9” radius, the tightest possible with an original magracer. If the driver turned right instead of left, the magnet would continue straight along the top edge and continue on to the default wire. If a car were approaching the plate from either wire on the left, it would continue over the plate and exit onto the single wire on the right, without the need for any steering input.

For high speed lane changes on straights or those before curves with radii greater than 12”, a plate 2.5” long, with otherwise identical dimensions, would probably work better. A gap of .10” to .16” between the end of a plate and the end of a wire should work fine.

A plate like the one below would give the driver 3 options; left, straight, or right.
https://docs.google.com/document/d/1wY7 ... sp=sharing

I suspect that any thickness of steel from .004” to .008” should work for a lane change plate, if it is installed so that the top of the plate is recessed the appropriate distance below the top of the guide wire. If the plate is .008” thick, it should be installed so that the top of the plate is consistently about .020” below the top of the wire. A thinner plate would have to be installed higher, resulting in less clearance.

When designed, made, and installed properly, lane change plates have 3 major advantages over lane change designs without plates.
1. Cars can run clockwise or counterclockwise on the track.
2. Cars will continue onto a lane, and not loose the wire, even if the driver turns the wrong way. This is very helpful for people learning to drive magracers.
3. Lane change plates allowing the driver 3 options, left, straight, or right, are possible.

Keep in mind that for lane changes to be extremely reliable, the front wheels of the car cannot be dancing left and right as they pass over the plate. In other words, the car must not exhibit any frontend shimmy when crossing the plate. Also note that frontend shimmy will probably cause more problems with long plates than with short plates.

Tin plated sheet steel .008” thick, (Ref: MKS254) is available at http://www.greenweld.co.uk/acatalog/Sho ... e_197.html
It works well for lane change plates. I suspect that this is the material that Wes R used to make his plates.
Similar material is available from ACE Hardware in the States.

.004’ thick x 1/2 “ wide steel tape with adhesive on one side should also work. It’s available at
http://www.bfplasticsinc.com/pc_product ... AB85B32F09
kiklo
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Re: The Magic of Lane Change Plates

Post by kiklo »

Looks like I have to reconsider my 'non' use of LCP...... :-)

Any thoughts of if the gap between the LCP and wire is needed ?
Racing Regards

Kim K.
BriG
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Joined: Wed 10. Aug 2016 00:44
Location: Bethlehem, Connecticut USA

Re: The Magic of Lane Change Plates

Post by BriG »

Ned is making perfectly good points here.

I recently set up my first track utilizing the gap lane changes, and while they all work properly, they do not prevent the car from exiting the wire if the wrong steering input is made, and I found that at lower speeds, they are not reliable and can allow the car to go beyond the selected lane and cross the wire intended to be picked up. This second fault I just happened to notice while operating a car at lower than normal racing speeds, and during a race it probably wouldn't be a factor, but it is still something that would probably not occur if using a lane change plate.

I think that once we all see how the new cars are set up, we will all ultimately know the compatibility of the new and old cars with the lane change plate and how it will need to be configured in the track to work with both chassis. And if that doesn't happen there's going to be a great divide between the old and new, which I don't think anyone would want to see happen.

I'm sure in the end it will all work out.

Brian
Ned
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Joined: Sun 13. Apr 2014 01:02
Location: Sedona, AZ USA

Re: The Magic of Lane Change Plates

Post by Ned »

kiklo wrote: Any thoughts of if the gap between the LCP and wire is needed ?
I’m not certain, but I suspect that the size of the gap between the end of a wire and the end of a plate is not important as long as it is not too long. I definitely would not make it longer than the diameter of the guide magnet, 4mm. I suspect that a gap of 2mm would be better than 4mm. If this gap is too long, the car could crash if the driver turns the wrong way. It might also crash if going to slow. Now that I've thought more about it, I doubt that any gap is needed between the end of the lane change plate and the end of the guide wire.

I think that the distance between the infeed wire and the alternate outfeed wire is much more important. My drawings incorporate a gap of .10” between the end of the infeed wire and the end of the plate. The gaps are also .10” between the end of the plate and the ends of the 2 or 3 outfeed wires. This implies a gap of 2.20” between the end of the infeed wire and the end of the default straight ahead outfeed wire. The distance between the infeed wire and alternate outfeed wire is slightly larger, since it runs at an angle.

Wes originally proposed a lane change plate 35mm (1.38”) long with a gap of 5mm (.20”) between the infeed wire and plate. He suggested gaps of 2mm (.08”) between the outfeed wires and the end of the plate. That results in a distance of 40mm (1.57”) between the ends of the infeed wire and outfeed wires (compared to my 2.20”). He also suggested a space of 2mm (.08”) between adjacent outfeed wires.

See http://www.magneticracing.com/track/track.html

Later he suggested increasing the gap between the infeed wire and plate for high speed lane changes. This of course, when using a constant size lane change plate, has the effect of increasing the distance between the infeed wire and the alternate outfeed wire, which I contend is the important variable.

I believe that a space of only 2mm (.08) between adjacent outfeed wires, as Wes originally suggested, is much too small. It’s only ½ the width of the guide magnet. I think that a gap of 5.5mm (.22”), as indicated in my drawings, would work much better. If you think that a gap of 4mm between adjacent outfeed wires is adequate, then you could make your plate about .32” wide instead of .39”, at the wide end. You could also make it a little shorter. (I’m leaving that for you to calculate.)

I continue to believe that a 2.0” plate of the shape and size of the one described in my original post and installed as clarified here, should provide excellent results for slow to moderate speeds, as in the approach to a very tight turn. For very high speeds, a plate of the same width, up to 2.5” long, should provide slightly better results. Instead of increasing the length of the gaps between the ends of the plates and wires for high speed lane changes, better results will be obtained by increasing the length of the plates.

Plates are easy to cut from .008” thick tin plated steel sheet (the original standard) or from the steel lids for Ball canning jars, which are .007” thick, including a rust proofing coating on both sides. The thinner .007” plates have to be installed about .006” higher than those that are .008” thick. Thus the clearance between the bottom of the guide magnet and the plate would be .006” less, but the magnetic forces would be the same.
Ned
Posts: 368
Joined: Sun 13. Apr 2014 01:02
Location: Sedona, AZ USA

Re: The Magic of Lane Change Plates

Post by Ned »

I found a new source of material to make lane change plates for those living in the States. It's .008" thick. The product is made by K&S Precision Metals of Chicago Il. It's sold by ACE Hardware among others.
http://www.acehardware.com/product/inde ... Id=3693093
WesR
Posts: 371
Joined: Fri 21. Dec 2012 17:37

Re: The Magic of Lane Change Plates

Post by WesR »

Hi Ned and all, Good to see continued interest and activity on the Forum and that Magracers are still getting enjoyment from the hobby.
Re. lane changing, the plate system is undoubtedly the best and pretty much 100% reliability can be achieved but I accept that good accuracy in construction is necessary. I spent quite some time considering pre-built lane change sections but, like sectional track, they would limit the freedom of track layout to some extent.
Another factor affecting lane changing is of course the weight of the front of the car on the front steering coil magnet and also the grip of the front tyres.
I appreciate the having only vac formed bodies and plastic wheels/tyres is not to everyone's taste but it does enable 100% lane changing which we had on our Linford circuit.
However, keep working on it!. Regards to all, Wes
Ned
Posts: 368
Joined: Sun 13. Apr 2014 01:02
Location: Sedona, AZ USA

Re: The Magic of Lane Change Plates

Post by Ned »

For an update concerning the length of lane change plates for a chassis using 2.4ghz RC gear and a steering servo mounted between the front wheels see
http://magracingforum.com/viewtopic.php?f=5&t=694
kiklo
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Re: The Magic of Lane Change Plates

Post by kiklo »

Hi. I have been thinking..... sort of. I'd like a lanechangeplate that could be used for both directions. Why ? Because I'd like to make my track with different characteristics.

Like std Macracing one way and kind of BLST system when turning around. (best lane system).

This is what I'm going to test.
mag-lane-change3.jpeg
mag-lane-change3.jpeg (32.56 KiB) Viewed 17362 times

Normal direction as the arrow points.

In stead of the plates we use today, I intend to use only wire as those plates is kind of hard to come bye.

The BLACK markings is an example of an normal Y split, one inn and 2 out. normal line is straight.
The BLUE and black is one in and 3 out with normal line is taking the left out. Blue overrides black lines.

I have included 'fences' using wire to keep the car within the lane change. I hope this will work running the opposite directions as well.

I'll test.
Racing Regards

Kim K.
Ned
Posts: 368
Joined: Sun 13. Apr 2014 01:02
Location: Sedona, AZ USA

Re: The Magic of Lane Change Plates

Post by Ned »

Lane change plates are easy to make from any steel plate .006” to .010” thick. The side of a tin can (the kind used for soup and fruit) could probably be used. Cut to desired shape with tin snips. Then roll flat with some kind of roller. Rolling pin (used for rolling pie dough) or wallpaper seam roller both work fine. The thicker the plate the deeper it has to be recessed into the track. If the plates are not rectangular, but more triangular in shape, they work well in either direction.
kiklo
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Re: The Magic of Lane Change Plates

Post by kiklo »

I have just tested my new lane change plates. It seems to work as expected. Slightly changed from the drawing.

I have an adjustable sliding, pressure holding unit. To change default path, I slide it towards the entering side of the plate to relieve pressure.
Then I can move the loose wire to the desired linepath and slide the 'holder' back to pressurize the end to engage.

Do not look at the finish. Still have to plaster and paint.
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Racing Regards

Kim K.
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