Current Vex Project

Completely ou of curiosity please post your current vex design here (even FTC).
plz describe in some detail (i.e. drivetrain, wheels, gear ratio, mechanisms, purpose, etc.)
i understand if you want to keep your methods or special mechanisms a secret just please don’t say that on this thread (kind of mkaes it boring and that kind of argument has been started in other threads)

My robot that i am building now is for FTC.
It is my first robot that i have ever built (i have tried different designs previously for FTC but never went through with them)
if has 2 all-purpsose wheels and 2 knobby wheels
1:4 gear ratio drive train
runs on 2 motors to move the robot
uses eight 48-teeth gears
eight 12-teeth gears
four 24-teeth gears
two 84-teeth gears
uses power pack
has one bumber sensor (so far!)
as 2 motors with a 1:7 gear ratio each for a 1:49 total gear ratio that act as a shoulder joint for an arm
1 motor with two 12-teth gears connecting to two 24-teeth gears and two 12-teeth gears then to two 24-teeth gears for creating a 1:9 gear ratio
elbow is just a 8" chassis bumper
gripper is a angle gusset with standoffs for fingers
also a motor attached to an angle gusset with standoffs for fingers
it has a couple of chassis angles in the back for a counterweight
go to minirobotics.blogspot.com for pictures

im working on a vex (duh) that will be able to climb ropes
the climbing gears, [2] run on a 12-60 radius
2 motor drive
right wheel connected straight to motor
left wheel connected straight to motor

when the robot comes up to the rope it wil spread the gears out,
this way i wont have to push the rope through then when it has gotten to the rope it will close the gears, pinching the rope.
the gears will spin, counter-clockwise liftinf the vex up

it has a ultrasonic sensor Im not sure why i put it there but ill find a use for it
it has a bumper sensor that will make is stop if the tension is overwhelming to vex

sounds pretty cool, when you said 12-60 radius you meant 12-60 gear ratio right?

I’m new here, but here’s the first project I’m trying:

It’s a Prize wheel, like you’d see on gameshows or in Vegas. ( or here: http://images.google.com/images?hl=en&q=prize+wheel&gbv=2)

My plan (feel free to poke holes in it):

  1. Player presses bump sensor to start the process off
  2. A Motor spins the Prize Wheel by engaging an attached gear with a gear on the wheel’s axle
  3. Servo lifts motor to disengage it from wheel gear (so the wheel can spin freely)
  4. After X seconds (when the wheel has stopped), the servo lowers the motor to engage the wheel gear again so the process can repeat.

I’d like to be able to read the result of the wheel using the Vex as well, so my plan there is to use the line following kit like so

  1. Line up the three line sensors at different distances from the center of the wheel, on the back. (fixed, not attached to the wheel)
  2. Draw semicircles on the back of the Wheel, lining up with the sensors, so that each “slice” on the front of the wheel has a unique set of semicircles on the back.
  3. Read the semicircles as a binary string. I figure with three sensors I have have up to 8 “slices” on the prize wheel
  4. Notify the player of a win or loss through lights and/or sounds. I don’t think I have anything in my vex kit that can do this. Maybe I’ll spin a wheel with streamers attached or something.

I’ve only built the starter bot with Vex, so I’m not sure if any of this is possibly, really.

sounds cool, its defintely possible but why dont you attach the motor directly (or a 2:1 drive train for toque depending on weight) to the wheel and instead of using line followers i think optical encoders would be easier and take less code

can you post pics when your finished plz?

First, thanks for replying, basicxman. I’m dying to talk about this with someone, but the Mrs. is shockingly uninterested. :slight_smile:

I thought about the optical encoder idea as well, and I think you’re right, it would probably be a lot less code. But for it to work, I’d have to start the wheel in the same position each time (so I know how far it’s traveled), correct? But now that I think about it, that’s not such a big tradeoff for a lot simpler function, so maybe I will give that a try first. I am in a bit of a time-crunch (this is for a halloween costume next week), so this is probably the way to go.

Regarding hooking the motor up to the wheel, do you think that would put a lot of drag on the wheel once I stop powering the motor? I’d like it to have a nice “slow-down” period. Maybe I’ll experiment with that first, as that sounds a lot easier as well.

Mounting the motor that way might also help with another idea I was thinking of: cheating. If I have time, I might try to force the wheel to stop on a “lose” slice for some people, perhaps by holding down a button they can’t see on the back while the wheel spins. Even if it doesn’t look super-smooth, I think it’d be worth it. (In fact, it might be funnier if the wheel is about to stop and then suddenly gains new life to stop on a losing slice). But that opens up a lot of complication, so I’d be surprised if I get around to it in time.

Thanks for the suggestions! I’ll make sure to post how it turns out.

my brother is very uninterested in robotics too
for the slow-stop you can use a for loop (do you have a programming kit?) that slowly deincrements the motors speed value (0…255)
and if that doesnt work or your not satisfied you can have a mechanical stop thats just a motor hooked to a flat bar or something that stops it

if you want to do the ‘trick’ thing where it slows down then speed up it would be easy…just raise the speed in programming with another for loop

Currently I’m working on a tank-like device. But instead of having two loops of tread on either side, it has four loops of tread, one loop for each wheel. That part is done. Now I’m trying to construct the turret (out of two servos. . aye). The turret needs to rotate 360 degrees, as well as go up and down.

I wanted to use bevel gears included in the advance gear kit, but I don’t own it. I have a mounting system for rotating it, but it doesn’t hold together very well, and doesn’t go 360 degrees due to it being powered by a servo. So I’ve gone back to the drawing board to figure out some other way of doing things. I’ve been thinking about using two wheel drive instead of four wheel drive, but would that complicate things?

Suggestions welcome.

And just a tidbit, this is essentially a Vex remake of a Lego set. A cookie to the person who knows which set. :slight_smile:

As promised, here are some photos from my prize wheel project I mentioned above. It turned out great. As suggested, I used a motor directly on the axle, and the optical encoder to try to “cheat”.

See it in action here: http://www.youtube.com/watch?v=BKDoC9c9jTo&eurl=http://www.kevincooney.com/archives/000154.php

Read more here: http://www.kevincooney.com/archives/000154.php
motor.jpg
wheel_final.jpg

Read more here: http://www.kevincooney.com/archives/000154.php

Impressive.:wink:

Very nice. A unique way of using VEX.

Read more here: http://www.kevincooney.com/archives/000154.php

VERY cool. Thanks for sharing.
I made sure to pass this one around the office.

Regards,
John

thats awesome! i guess this is a bit late but to save money you could have put a tab or nail or something on each section of the wheel and make it hit a limit switch, have the program count the times it hits the limit switch :smiley:

Wow, wish I had thought of that, as the wheel I was trying to imitate has pegs like that. Oh well!