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Cee-Can Slotcar Motor Building
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Motors: in this section we will discuss c-can style blueprinted motors. We use the new drag racing specialties blueprinted motors for a number of obvious reasons. First is the fact that they are a very compact motor as the endbell is shorter, stronger, cone shaped, has copper hardware and uses double overhead springs. This is important on a drag car because they need a narrow motor to fit between the tires. Drag cars do not have as wide a track width because they use a narrower style body and the tires have to be under the body when viewed from above as required by the rules and common decency. This in turn requires a narrower chassis and a narrow motor to fit between narrow frame rails. Second is the fact that our can design is the most symmetrical on the market. Another good reason is the fact that they are fast. There are some areas of the motors that we perform the following modifications and we will cover these in this article. First we would like to say that some of the following modifications are not legal in all classes in some of the governing bodies, but all the following modifications are legal in the SDRA. (Scale Drag Racing Association). Most of the modifications can be achieved with little trouble or can be performed by someone with more experience and are also aimed at reliability and longevity of your equipment.
To quote the famous engine builder Smokey Yunick "any exchange of horsepower for reliability is foolish. It does not matter how fast your motor is on the first lap, [or practice] it is how fast it is at the end of the race when it crosses the finish line. A broken motor has never won a race!" He also goes on to say that you can spend all your money on every new and trick part that comes along, but if you ignore the basics you will never be the winner. "You should really take the time to think about this because this is the best advice we have ever taken!"
The first area we will cover is the can. First of all the small axle slot goes toward the rear of the car on a sidewinder and the right of the car on an inline when viewed from above with the guide facing away from you. We enlarge the bushing hole slightly to allow the bushing or bearing to be installed on the centerline of the magnets and soldered in place. Next is the endbell we epoxy the bushing or bearing in its cup to prevent rotation and subsequent heat and vibration. We also use an alignment tool to properly check the alignment of the brush hardware and use screws to attach endbell to the can. We also use an Airgap tool to set the air gap of the motor and to locate the magnets in relation to the bushings. For epoxy we use only J.B. weld as this is a metal bearing epoxy which helps transfer the magnetism of the magnets to the can and not insulate them. This compound also works even better if it is oven cured at 150 degrees f for about 30 minutes.
Now that we have discussed what we do, we can discuss how we do it. First we mix up a small amount of epoxy: enough to do the magnets, the endbell bushing or bearing and the hardware. Then we put a small amount on the inside of the can on one side and in the center. Do not put an excessive amount, just a small dot so it will hold the magnet in place when cured. Then take a magnet and carefully push into the center of the can and then slide it up against the side of the can that has the epoxy on it, being careful not to get epoxy on the face of the magnet. Then position the magnet fore and aft so the magnet is aligned in the rear with the arch on the side of the can opposite of the small axle slot then repeat on the other side. After both magnets are installed you can install the magnet clips. These vary by magnet styles so make sure you use the correct ones for your style magnets. Once you have them installed you can move the magnets into the final position. First, make absolutely sure they are installed fore and aft correctly aligned with sides of the can. When you are sure of that take a pair of calipers and check to make sure that the tops and bottom of the magnets are the same distance apart. Next choose an Airgap tool that is the proper size for your magnet choice: usually .520-. 530.
Then put your endbell bushing or bearing on an old armature and apply a small amount of epoxy to your bushing or bearing and firmly push it into place until you feel it click into place. Next install your brush hardware onto the endbell with a small amount of epoxy on the parts facing the endbell and also on the threads of the screws, but do not tighten at this time. Then, slide your alignment tool into the brush hoods. Now, take your can bushing or bearing and slide it onto your Airgap tool, then slide the Airgap tool into the motor, then slide endbell into position and install can screws to secure endbell in position. Now you can tighten the brush hardware screws. Check complete assembly making sure magnets are still in correct position, bushings or bearings still in place, (note that can bushing or bearing is not yet soldered in place) then place motor into preheated oven (150 degrees f.) for 30 minutes.
When that is complete, remove and let cool, then solder can bushing or bearing in place. You can also install your braided shunt wires at this time if required. We like to use braided shunt wire because it is a whole lot easier to work with. Then remove the endbell and wash all parts thoroughly in hot soapy water, and dry completely to neutralize the flux. Now it is time to install the armature, first install the armature and make sure it spins and slides fore and aft easily. Make sure the armature is centered in the magnetic field and then decide how many spacers you will need on each end of the armature. Remove the armature and install spacers, reinstall armature and repeat procedure until you have the least amount of endplay possible without binding. Then install armature for the final time, now install the can screws, Mura Bigfoot II brushes, and light motor springs. Next oil lightly, and run motor on a direct current power supply at 4 to 5 volts until brushes are seated. You can tell this by looking at the trailing edge of the brush and observing the arc between the commutator and brush. (There should be an even twinkling across the brush.)