I am going to try to enter a T-Jet race toward the end of the month. In looking at the tech specs for the car I saw that the Dash Chassis, top plate, and arm and most parts are allowed. So, I thought I would try to enter with a mostly T-Dash car and see how it compares. So I started going through my T-Dash 2.0 chassis looking for the best armatures and will hopefully prep two cars for the race. In the rules it allows for balancing the arm either by adding epoxy or by removing material from the heavier armature stack. I will do the latter. If your interested in how I balance an armature then please read on...
Of course the first thing I do is try to find the most electronically balance arms. By this I mean those that have the closest Ohm reading between the three armature stacks. Once I have narrowed that down I then work on the physical balance. To start the process I take my sharpie marker and mark the stacks with no marking, one mark and finally two marks. Below is a picture of the stack with no marks.
The next picture show the one mark. Notice the black mark on the right side of the arm stack in the picture.
The next picture show two black marks on the end of the stack
Once the armature is marked I then mount the armature into the balancer. If you would like to see how I made the balancer you can click here. When mounting the armature into the balancer I put the arm between the two magnets and turn the caliper until both magnets are just lightly touching the two ends of the armature shaft. See picture below to include the caliper reading. You will notice the caliper reads about 0.6465... half way between 0.646 and 0.647.
I then back the caliper off about 0.001 and 0,0015 of an inch this usually allows the armature to spin the most freely. You can experiment yourself and see what I am saying.
I then use a straw to spin the armature... take a look at the video below.
When spinning the armature I keep track of which marked stack goes to the bottom and how many time. If I have another stack that goes to the bottom that helps me determine where I notch or remove material from the arm stack. Below you will see how many times I spun the armature and which stacks went to the bottom 0 = no mark, 1 = 1 black mark, and 2 = two black marks
You will notice that the stack with no marks ends up on the down side 7 times and the stack with 1 mark ended up on the bottom 1 time and the stack with 2 marks did not end up on the bottom on any of the 8 spins Given the results I will remove the material from the stack with no marks and I will remove the material from the center of the stack. Should the stack with 1 one mark end up on the bottom a couple of more time I would remove the material from the 0 stack on the side closest to the 1 stack.
After I remove the material by notching with the Dremel I then spin 8 to 10 times and see that the arm is balanced and that no one stack consistently goes to the bottom. Finally I then clean up the dremel cut with a Jewelers File.
Hopefully some of you will give it a go!! Practice on some bad armatures first. It's a combination of Science and Art!! Good Luck!!