The Magic of Lane Change Plates
Posted: Thu 5. Jan 2017 02:12
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
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