Instructions for Chassis Kit CK2

Ned's instructions for building a chassis and attaching a body to it.

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

Part 10: Wiring Battery to PCB

Post by Ned »

Part 10: Wiring Battery to PCB

The battery box in CK2 is long enough to accommodate a protected 10440 rechargeable battery. These protected cells have a chip on the neg (-) end, which makes the battery about .08" longer. There are several ways to connect the battery to the PCB. The best one depends upon the amount of clearance between the end of the battery box and the sides of the body and/or the amount of clearance between the top of the battery box and the cockpit. It also depends on whether or not you want to use a protected battery. Every method requires the use of a magnet installed in the battery box near the left rear wheel. This magnet helps to keep the battery from falling out of the chassis. It should be 3.0mm thick.

If you want to uses unprotected batteries, refer to Part 10 of Instructions for CK1 found at posting.php?mode=edit&f=28&t=614&p=3712

Option 1: For narrow bodies with no clearance between the ends of the battery box and the sides of the body
1. Press a 5mm dia x 1.25mm - 1.75mm thick magnet into the hole in the end of the battery box, until it is flush with the outside of the end of the battery box. Apply thin CA glue to the edges of the battery on the outside of the battery box to keep it from sliding out.

2. Press a 5mm x 3.0mm thick magnet into the hole in the side of the battery box that is near the right rear wheel. This will keep the battery from falling out.

3. If need be, cut 2 thin flexible wires the appropriate length to connect both battery terminals to the PCB as indicated in the photo below.

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4. Solder one end of each wire to a piece of steel strip about .01” x .15” x .20”. I recommend using standard lane change plate material for this. Solder the other end of each to the PCB. Do NOT try to solder wire directly to a magnet because excessive heat will destroy the magnet.

5. In the case of the negative (-) battery terminal, attach the wire to the surface of the magnet that is outside the battery box.

6. In the case of the positive (+) terminal, attach the wire between the end of the battery and the magnet. This keeps the point of connection inside the battery box. However, it does require a little more care when changing the battery. See photo above.

Option 2: For bodies with plenty of clearance between the ends of the battery box and the sides of the body
Use the same approach as for narrow bodies with the following exceptions:

1. Use a 5mm x 3mm magnet instead of a 5mm x 1.50mm magnet in the end of the battery box. Do not glue this magnet into place, until you are certain how much clearance you need inside, to change the battery easily.

2. Eliminate the installation of a 5mm x 3mm magnet in the hole in the battery box by the right rear wheel, since it won’t be needed to hold the battery in its box.

3. In the case of the positive (+) terminal, attach the wire to the surface of the magnet that is outside the battery box. This keeps the point of connection outside the battery box.

Option 3: For bodies with very little clearance between the top of the battery box and the cockpit
The key to minimizing the problem due to inadequate vertical clearance is to reduce the number of times wires have to cross over the top of the long walls of the battery box, especially the one in front. Also eliminating any wires above the PCB is essential. Use the same approach as for narrow bodies with the following exceptions:

1. Run thin, very flexible wires from the motor to the PCB through both holes in the side of the battery box.

2. Press a 3mm dia x 2mm thick magnet into the hole at the end of the battery box on the left side of the chassis and connect the pos (+) battery terminal here instead of at the other end. Eventually, after some trials, you will probably have to glue this magnet in place with CA glue applied to the outside edges of the magnet.

3. Connect the neg (-) terminal on the righthand side of the chassis. Now the wires connecting the battery to the PCB, do not have to cross each other and they don’t have to run above the PCB. Just run very flexible wires, inside and along the front wall of the box above the battery, from the battery terminals to the PCB. To do this you will have to drill a hole in both ends of the battery box in the upper corner of the box near the front wall. The diameter of these holes should be slightly larger than the diameter of your wire. Fish your wires through these holes before soldering them to the PCB. You may have to glue these wires in place after installed.

4. Use a 5mm x 3mm magnet instead of a 5mm x 1.50mm magnet for the neg (-) in the end of the battery box, since a thin magnet won’t be strong enough to keep the battery from falling out. Do not glue this magnet in place.

Option 3 does not require that insulation be stripped from a portion of the battery near the neg (-) end, since electrical contact is made at each end of the battery. However, you must be careful not to insert the battery the wrong way. Also, after inserting a new battery, you’ll have to squeeze both magnets between your thumb and finger, to make sure both magnets make contact with the ends of the battery. With the small magnet glued in place at one end, and the larger magnet NOT glued in place, this should work.


Option 4 : Spring Brass Strip Connectors
The best method for most cases may be to eliminate magnets at both battery terminals and to use spring brass strip to connect the terminals to the PCB. This also eliminates the need to remove any insulation from the battery. However, magnets in the side of the box are still needed to hold the battery in place.

1. Press a 5mm x 3.0mm thick magnet into the hole in the side of the battery box that is near the right rear wheel. This magnet along with the magnet by the left rear wheel will keep the battery from falling out.

2. Cut 2 pieces of spring brass strip about 1.0" long. The thickness should be about .007". The width should be .11" - .22". The brass strip used in many SCX slot car chassis should work fine.

3. Center a piece of strip on the outside at the end of the battery box and bend it around the end of the battery box as depicted in the picture below. Each leg of the bent strip should be about .25" long on the inside of the box.

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4. Now solder the connecting wires as seen in the following pictures. Since excessive heat will damage the ends of the battery box, you may want to remove the brass strips from the chassis to solder the wire onto the strip. Then reattach the strips to the ends of the box.

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Please contact me by PM, if you find a mistake in the instructions or have a suggestion for improving them.
Ned
Posts: 368
Joined: Sun 13. Apr 2014 01:02
Location: Sedona, AZ USA

Part 11: Mounting Body to Chassis

Post by Ned »

Part 11: Mounting Body to Chassis

Before attaching the body to your chassis, run the chassis around your track several times. Make sure it is performing well before mounting the body to the chassis. The body will substantially affect the handling and cornering of the completed car. If you encounter problems, you need to know if it is with the chassis or with the body.

With an effective bumper, usually 2 regular steel screws, attached to motor pod in the rear, and one attached in the upper suspension beam in front, along with 3 magnets glued to the body, are enough to hold the body to the chassis. If need be, you could use 2 screws and magnets in front, 2 in front of the rear wheels and 2 in the motor pod. Use the quantity and length of screws appropriate for your body.

Size # 2 screws of various lengths work well. They have a diameter of .086”. They cannot be stainless steel. I recommend using larger magnets glued to the body rather than the 3mm dia x 2mm magnets used for the stock chassis. Magnets having 4mm - 5mm diameters, and 2mm - 4mm thick should work fine. The photo below shows 5 different lengths of screws, from 1/4" to 3/4". The 3 shorter lengths are most often used for 1/32 cars. The 3 flat head screws are stuck to 3 different size magnets. The flat head screws provide the most holding power to the magnets.

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The height of the body can be precisely adjusted relative to the frame and wheels, by turning the screws. The wheelbase can also be precisely adjusted by loosening the screw in the motor pod, sliding the pod, and re-tightening the screw.

You will have to fabricate a bumper or make some provisions to prevent the body from sliding back relative to the chassis upon crashing, as well as sliding forward. You will also have to devise something to prevent the body from shifting sideways, especially in front. Each case is unique.

The photos below show an example for a 1998, Mercedes CLK-LM.

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In this case quite a bit of the cockpit had to be removed. The black bumper was made from the bumper plate for a stock magracer and attached with screws. It prevents the body from sliding back relative to the chassis and also prevents the body from sliding left or right in front. The piece of white plastic glued to the body behind one of the magnets in the rear, prevents the body from shifting forward.

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The case of an SCX 2006 Chevrolet Montecarlo slot car is shown below.

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I used the front portion of the slot car frame as a bumper and glued it to the body after removing the nubs with a Dremel tool.

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Then I glued 3 cleats on it to keep the body from sliding back, left, or right. Two pieces of black plastic glued behind one of the magnets in the rear, along with the 3 screws and magnets, completed the system to hold the body in place.

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Very little of the interior was removed in the case of this Montecarlo. After building this car I learned that a connector socket on the PCB is not needed, unless you want to reprogram the module on the PCB. The connector is the white rectangular object with 7 small electrical pins. It is located between the screw used to attach the PCB to the frame and the bank of 4 dip switches on the PCB. Some cars were shipped without this connector socket. In some cases this connector interferes with the cockpit. Since I do need these connectors, I removed one when building another car.

Please contact me by PM, if you find a mistake in the instructions or have a suggestion for improving them.
Ned
Posts: 368
Joined: Sun 13. Apr 2014 01:02
Location: Sedona, AZ USA

Part 12: Troubleshooting

Post by Ned »

Part 12: Troubleshooting

1. Inadequate clearance between magnets in the box on tie rod and the steering coil
  • a. Remove paper from the end of the steering coil.
    b. Reduce the thickness of the end of the plastic coil bobbin by sanding.
    c. Sand down the bracket molded into the frame for mounting the coil.
2. Car runs intermittently, stops for no apparent reason and won’t start
  • a. Make sure you have good electrical connections between the battery terminals and the wires going to the PCB.
    b. Try using a different transmitter/controller to determine if the problem is with the car or the controller.
3. The front wheels bounce up and down on the track.
  • a. Remove the wheels and tires and sand down the tires until they are perfectly round and cylindrical. Round/bevel the edges of the tires slightly. (A magracer will never run well with out-of-round front tires.)
    b. Smooth the track surface if it is rough and bumpy.
4. Lane changing is unreliable or car changes lanes without any steering input
  • a. Make sure tires are perfectly round.
    b. Reduce the clearance between the guide magnet and the track surface.
    c. Make sure there is no bump in the track surface in the 18” prior to the lane change plate.
    d. Make sure there is at least 18" of straight track guide wire leading up to the lane change plate
5. Car loses guide wire when steering wheel is turned too soon before approaching a lane change plate.
  • a. Reduce the clearance between the guide magnet and the track surface.
    b. Increase the gap between the magnets on the tie rod and the steering coil.
    c. Replace the 5mm dia x 3mm thick magnets on the tie rod with 4mm dia x 3mm thick magnets. Make sure that each magnet is glued down into a corner of the box on the tie rod, to maximize the distance between these magnets.
6. Car tends to lose the wire going around tight corners (10”- 11” radius) even at slow speed. (I recommend a minimum 10” radius for track corners.)
  • a. Turn chassis upside down and verify that nothing is preventing free smooth movement of the guide arm from swinging, from full left to full right. Make sure the front wheels don’t touch the body anywhere.
    b. Verify that when fully cocked, the car can turn within a 20” diameter circle, without the body and also with the body. (To do this, tape the wheels in the fully cocked position and run the car on a smooth table top, without any steering input from the controller. Measure the diameter of the circle made by the car.)
    c. Make sure that the 3mm dia x 2mm thick magnets in the frame near the guide magnet are NOT protruding below the bottom surface of collar around the magnet on the bottom of the frame. It may help to recess these magnets up to .03”, which would make the top of the magnet almost flush with the top surface of the base frame.
Locked