Team 323Z Design Release

[Michael_Nutt]

@technik3k

I envy senior teams - many of them already have fully functioning robots. In my corner of the universe time flows at different rate - we just got our first somewhat functional launcher prototype done.

But I can’t complain. Even though my seven-graders spend a lot of time goofing around and shooting balls at each other, there was an incredible progress made from the beginning of the season. From having no idea what torque-power relationship is a couple of month ago, they now know how to compute power losses at various axles, how flywheel’s moment of inertia affects recovery time, and why balls disperse when launched at different rates. I made sure they learned important physics behind the flywheel and finally they built a cool prototype.

Anyways, some people doubted my claim that you can launch 3 balls in one second with three motors. You may still be correct and I might still be wrong, as we haven’t built such launcher yet. However, technik jr and the team has already proven me wrong in my assumption that you would need three motors for the effective launcher.

https://youtu.be/eblm8BD93oE

In the video you will see their latest single flywheel design that uses two turbo motors in 19.2:1 external (46:1 total) gear ratio. Not only it has enough power to reach the high goal, but it rotates way too fast and keeps overshooting.

I haven’t done precise measurements, but from the crude video analysis it looks like if you feed balls at the right speed you could consistently hit target while shooting 4 balls in about 2 seconds. If you feed balls as fast as it takes it will launch four balls in a second with first three overshooting and the last one falling slightly below the target. Obviously, for it to be practical the feed rate needs to be program-controlled like 323Z does.

The purpose of this video is to show that two 393 motors provide enough power for flywheel launcher. I am not at liberty to disclose all secrets, but the main idea was to reduce the friction by avoiding large number of square axles rotating in the round holes. As you can see there are only three axles and bearing on the high speed flywheel axle are custom built out of VRC-legal parts.

I will post more details about the launcher in another thread as it matures. But for now let me just state that flywheels could be made as power-efficient as any other type of launcher if carefully built.

Thank you for posting this. I had a similar idea but it definitely would not have worked as well as this design and I did not think it could be done with just 2 motors. I just finished building a design based off of your prototype, but with a 13:1 and 52:1 gear ratio the motors would stall before it could even get up to speed, and reducing the second flywheel’s gear ratio to 39:1 would only launch 1 ball before stalling. It has two 4" wheels on the lower speed axle and two 5" wheels on the higher speed axle. Did you find that increasing the mass too much would stall the motors or do I just need to take the time to significantly reduce the friction?

Also, I know that this probably isn’t the best place to post this (since it is 323z’s thread), but since it seems that the new forum does not have private messaging, I am not sure where else to post it.