I’m not sure if these have been asked, but it’s something that sparked my attention.
Is attaching two motors to one moving part a power hog? I have a part that requires a bit of torque, and I had a gear ratio that was strong yet tended to slip and went wicked slow. I know that adding two motors on the same axile (both moving the same direction, yet on opposing ends) will add quite a bit more power like I needed, but I was wondering if in the heat of the competition this would drain tons of power too quickly, hence making me use 80,000 batteries over the tournament just to add some power to one part. I figure that since the time to move the part and the stress on one motor is less, as long as its done right it could be counted as perfectly equal, if not better.
I have the radio kit, and dont have funding nor intentions to buy VEXNet right now. Whenever I use radio, the robot has clean code and all but gets jittery for no reason (sometimes I wont even move the joystick and it would spazz out for no reason). I know not to keep the radio around metal, but I’ve had it in the straw guide, etc. and it still jitters. Are there any tips on how to remove the jitters and increase reliability?
Think of it as a physics problem: you have a mass that you are trying to move a certain distance. This requires a certain amount of work to be done. Let’s call this work “WORK”. So, to get a motor to produce WORK, you can either run it at higher current (increased wattage with a power source with fixed voltage), or add another motor. With two motors, each motor will have to generate WORK/2, or half the power. Depending on some factors like heat loss, friction in the motors, and how efficient each motor is at different RPMs, using two motors may use LESS total power than one motor alone. Generally speaking, in VEX robots I advise my students to either reduce their gearing or add another motor if a mechanism with one motor struggles to achieve its work. In 2009, three of our teams (417, 418, and 575) added two extra motors to their drive train to increase rate of turn. Total power used probably didn’t change much, but all three went from speedy, slow-turning robots to speedy, turn-on-a-dime robots. Watch 575 in this video: http://www.youtube.com/watch?v=aIsQckNv9zM.
And keep in mind that if you hit stall current on a motor you are sucking LOTS of power, so it is definitely better to use 2 motors operating mid range than one motor struggling.
Word, we’re lucky these motors don’t burn out as easily as the VEX DC motors. But Mr. Folea is right, like always.
Are you using 6 motors on that drive? It’s REALLY fast.
Don’t worry about battery drainage. In 07-08, we had 10 motors which were all taking decent amount of strain during the competition. Make sure you use a fresh battery before each round and I’m sure you’ll be set.
You want to MAKE SURE this not a code problem, use a tether, or the little yellow cord, to control your robot directly with your controller without the radio. If these tests are good, then I would try different frequency crystals, and if THAT still doesn’t work, see if you can get your hands on another radio kit. And as for it not being around metal…I mean it’s fastened to metal, and more often than not, my team just loops the receiver antenna cord around a vertically mounted bar…hasn’t failed yet.
Also, try using a dead zone for your joysticks if you are experiencing over sensitivity.
Check the antenna wire for any scratches or open wire. We have found some instances where a damaged antenna severely affected reception quality.
The receiver cable itself might be bad, but this is unlikely. If this is the case, the robot will either be dead, or completely alive. It won’t jitter either way.
Last try - if you have a programming kit, try coding the robot to run from the Rx2 port (I’m assuming this is a single-remote robot). This approach fixed one of our reception errors.