Science Olympiad
Hello, I am new to this forum and know very little about RC planes. I have a question that I think many of you here may be able to answer. My son has just competed in his School's Science Olympiad and he did well. We are looking forward to next year where he will be performing in the same event and I have exhausted my knowledge on the subject so I wanted to pick the brains of the experts. I am confused by all of the new terms: KV? Turns? Pitch? Gearboxes? Its just too much to handle. Here are the abbreviated requirements for his event:
1 Build a magnetically levitate car that travels down a 3" wide track (two 4ft pieces of angled Aluminum attached to a piece of wood). We have this part taken care of. Basically put magnets on the bottom of a 3"X8" piece of balsa and also on the track so that the car levitates. Its the next one that confuses....
2. Attach up to 2 motors (35mm diam max) and props. to drive the device down the 4ft track as quickly as possible. The props don't have a size limit but the max size of the car limits the prop size to <7.5".
3. No voltage can be over 9v. NO IC MOTORS. Only brushed motors.
4. VERY important: The primary thing we are measured on is the "Vehicle score" which is defined as the weight of the car in grams divided by the time to travel down the track in seconds. Consequently, a very heavy car is a must. Our car weighed 1.5kg but we saw cars that weighed nearly 4 kgs at the recent competition! It requires a lot of "push" to get these cars moving. Our arrangement could blow a full can of Coke off of the table if placed directly behind our car (i.e in front of the pusher props).
We used this motor Electrifly T-400 and a multiplex "pusher" prop. Each motor was powered by two 14500 lithium batteries in series (they only needed to run a few runs).
My gut tells me that to increase our speed, we will need a bigget motor. I have seen some t 540 motors with 35mm diameters but I'm not sure if I need (nor sure how to choose) a motor/prop with high or low RPMs, prop with a large pitch etcetera. Most competitors chose pusher props. I attached a picture of our car.
Lastly, fear not for our safety if you want to make a recommendation. I (the coach) lost a few tablespoons of blood standing too close to those whizzing props early on in the project and the student's attitude towards the car changed drastically. We wear gloves and have a strict protocol that is followed when running the car. Thanks in advance for your help!