3v0

Good info on the batteries. I was thinking they were more expensive.
I am not counting it out, but it is not my first choice. There is the problem of scaling it up to shoot basketballs. A bb is 1.25 lbs (EDIT: 600 grams). It would possibly take a car tire to get enough contact area to shoot it. I have not ruled it out but it does not look promising. The shooter need to fit on a robot that looks more like a water heater then a side by side refrigerator.

I am thinking of having this robot interact with people. Need to keep it from taking peoples heads off.

Could be I have champaign tastes on a beer budget

I have always wondered about disposiable champaign glasses. Sort of ruins the mood.

__________________
To control the world from your PC with USB I suggest USB Bit Wacker

3v0's Tutorials for ABSOLUTE BEGINNER
C, PIC 18F, MPLAB® and MCC18 Compiler

Pommie

That basket ball has gone from 600mg to 600Kg in less than half a day. A factor of just 1 million. I'm guessing it actually weighs 600 grams = 1 and a bit pounds.

Mike.

3v0

Gosh I see your point. Goofed twice. Fixed it!

__________________
To control the world from your PC with USB I suggest USB Bit Wacker

3v0's Tutorials for ABSOLUTE BEGINNER
C, PIC 18F, MPLAB® and MCC18 Compiler

futz

I meant to drive the robot. Obviously they're way too low geared to fire a ball.

__________________
=========================
Futz's Microcontrollers & Robotics
=========================

Krumlink

What other ways could you do it?

Flywheel
Pneumatic Cylinders to shoot it
Catapult/Trebuchet

Flywheel: With enough speed, it could shoot a ball pretty far. It would require a speed up delay (a few seconds) but then it could really kick the ball far.
Pneumatics would require expensive air cylinders, a air compressor, tubing and not to mention management for it all.
A catapult/Trebuchet would be dangerous, since it would require a spring/stretchy to pull back and fire it, besides it would be more prone to breaking.

__________________
Visit my website!
http://www.freewebs.com/electronic-hobbyist

killivolt

How about something using a crossbow mechanism. Take an old car tire cut it to the size needed to fit the ball and make the tubing large enough. Now it's just a matter of angle and pull strength.
You could shoot it from one side of the court to the other if you wanted.

__________________
Truthiness Monkeys : Obedience, Ignorance, Fear.

3v0

I found the numbers. LINK
Air Cannon.
Coil Spring. think human cannon ball.

A Catapult/Trebuchet is to bulky. A crossbow/slingshot would be smaller but not easy. Imagine what a beast the robot would be with each method.

__________________
To control the world from your PC with USB I suggest USB Bit Wacker

3v0's Tutorials for ABSOLUTE BEGINNER
C, PIC 18F, MPLAB® and MCC18 Compiler

killivolt

Based on what your link is showing when the ball is raised a human back is doing a pivot of the trunk then the ball is is flipped by the hand and the arm. what if you were able to use a leaf spring from an old truck and flip it like a plastic spoon. You would need a pivoting hand acting as a wrist about 8" from the top. ?

__________________
Truthiness Monkeys : Obedience, Ignorance, Fear.

3v0

Sounds both possible and inexpensive. A small electric winch to reset the spring. Maybe a strain gauge to determine when to stop the winch.

__________________
To control the world from your PC with USB I suggest USB Bit Wacker

3v0's Tutorials for ABSOLUTE BEGINNER
C, PIC 18F, MPLAB® and MCC18 Compiler

Hank Fletcher

What you want to do is have a have a short cylinder, slightly greater in diameter than the basketball, to rifle (roughly speaking) the ball. To power the ball, place it in a mounting that compresses a spring. The mounting will be compressed into the spring with a cam/latch. As the cam rotates, it compresses the mounting, until such a point that the cam-latch slips from the mounting, thus releasing the mounting/ball. The cam could also have a release point to set the loading of the next ball.

Spring suggestions:
- other inflated balls
- surgical tubing (using elasticity as oppose to compressed springs)
- mattress springs

positronicle

Actually, it shouldn't be too hard to design one, using not much more than a counterweight for propulsion. Some sort of jack mechanism(maybe just a stepper and linear screw for up and down?) could cock it, and an adequate solenoid could release it.I can envision some sort of stepper motor setup in order to move the counterweight closer, or further away from the fulcrum, thereby giving you a measure of velocity control. It could even automatically move the counterweight, so that each time it needed "cocked", it would be very light on your "cocker", and just have the stepper return the counterweight back to where it needs to be, in order to make the shot. Quite repeatable, I would imagine. Now that I've thought about it a little more, I believe you could probably transition(after each shot) the balance point of the counterweight to the other side of the fulcrum briefly, thereby doing away with a separate "cocking" mechanism altogether.

dknguyen

Krumlink, wiki the difference between a catapult and a trebuchet. Catapults used elastic materials. Trebuchets used counterweights and were "more advanced". One of the things they did better was they could fire much heavier louds because they weren't limited by elastic materials. If you watch the Return of the King, you can see the defending humans used trebuchets and the attacking orcs used catapults.

A trebuchet is also very repeatable because the energy applied to the projectile is always exactly the same Potential energy =mgh

__________________
Disclaimer: Avatar for entertainment purposes only.

3v0

I floated the idea of the free throw robot to teachers in various departments today. So far I have buy in from ag, votech, and the principal. We will be getting a science teacher who is said to be "scientific". He should be interested too.

The plan is to have students from each area collaborate on the design and construction of the robot. The students in the ag shop are very good at metal fab and will build the frame and related parts. The people in it votech can fabricate parts. Together they can work on the launcher, be it springs, pneumatic, hydraulic or whatever. My class will do the electronics and programming with some help from the science teacher and his students, who at the very least, will keep us honest.

I will present all your ideas to the students.

Thanks.

__________________
To control the world from your PC with USB I suggest USB Bit Wacker

3v0's Tutorials for ABSOLUTE BEGINNER
C, PIC 18F, MPLAB® and MCC18 Compiler