Hey Guys i had a dealer contact me in regards to a customer that replaced some armatures in a couple of his slot cars. I have written below my findings and I en...courage you to read through them. These types of issues are common and should be avoided. Hopefully my explanations below will help you enjoy the hobby even more then you already do.
Notable issues (excessive heat within 10 laps)
Car #1 Viper V1
1) Passenger side traction magnet was installed backwards. This causes the chassis to bow and binds the arm when the car is on the track. When magnets are installed backwards the chassis is tweaked and no longer usable. Witness marks on the magnets indicated this was a issue before the arm was replaced as well.
2) Rear bushing is a stock G+ bushing. The inside diameter of these is too tight and does not allow the chassis to flex without binding up the arm which results in heat build up. This is exaggerated when the magnets are installed backwards. If you wish to use stock bushings i would advise you to ream them to .062”
3) Gear mesh is too tight causing heat build up. On a Super Stock its ok to have some play, They like to be free.
4) Endbell contact tabs “AKA Bunny Ears” were smashed due to improper installation. We recommend using a small slot screwdriver or the Viper motor installation tool to prevent the ears from being smashed. This applies to any endbell and any car that uses a endbell. See pictures on the viper website showing how the tool is used. It makes assembly a breeze.
5) Endbell had absolutely zero break in on brushes. This is a major one that applies to any DC motor. All endbells/motors need to be broken in before running on the track. This endbell appeared to be installed and run without any break in. There was only about 10% brush contact on the commutator. This will lead to excessive heat on and drastically reduce the power output and life expectancy of the armature. If you do not have a brush break in tool you can do it the old school way and run the car on 5 or 6 volts for roughly 5 hours or until you see 75 to 80% break in on the brushes. If the brushes still have a hourglass pattern then they will require additional break in time. I can't stress this one enough.
6) It appears that brand new sponge tires were installed. Brand new sponge tires are extremely tacky and have the same effect on the cars as driving around with the emergency break until they are scuffed/broken in. I recommend scuffing the tires in on the bench at 5 or 6 volts. You can use a piece of paper or brown paper bag to run back and forth on the tires. I do this until the rear axle setup rolls freely across the table. If scuffed in on the track i would expect to see higher operating temps until they are scuffed in.
Conclusion for car #1 is that all of these factors contributed to the higher then normal operating temp (10 to 20 laps) No armature would survive these conditions if raced continuously. I replaced the chassis at no charge, I checked the armature and although it got hot it wasn't run long enough to do any long term damage. I trued the commutator and broke in the brushes 100%. I also installed a Viper Bronze bushing which come with the proper size bore. The ears on the endbell were reworked and now provide 80% of the contact that a new one would. Electrical contacts were cleaned and checked. Car was reassembled and sounds like a dentist drill. Note: Rear tires need additional scuffing to be 100% race ready. All this done at no charge
Viper Scale Racing