How to make an accurate and consistent turret for this projectile competition?

[sauravp]

Summary:: What propelling mechanism can get me most consistent shots?
Compressed air, spring powered, rubber band powered or any other

Hello, I am a high school student participating in a local competition where I have to make a turret.
Here are the rules:
1) The projectile has to fall in a cup.
2) the cup should be at least 2 metres away from the turret.
3) the one with the most precise shots win.

So my plan is to make a ring of cups around the turret. For rotation I am using a stepper motor so no worries there,
but can anyone help me to make it precise like what mechanism should I use to get consistent shots. I am pretty serious for this competition so any help would be appreciated.
I don't have access to a spring or a shop where I can get one so either tell me a way without using those or how to make them aswell.

I am new here so sorry for any errors or mistakes.

 

[Baluncore]

1) The projectile has to fall in a cup.

Welcome to PF.
What is the projectile? How much does it weigh?
Do all projectiles weigh the same?

 

[sauravp]

Welcome to PF.
What is the projectile? How much does it weigh?
Do all projectiles weigh the same?

first of all thankyou for replying.
Projectile can be anything and to be very honest I haven’t given much of a thought on the projectile as I was thinking about the turret only.

but for now it will be spherical. The current idea is to use those jumpy/magic/rubber balls(weight would be less than 20gms atm) they are good as far as accessibility but they are pretty heavy for 28byj stepper I guess (when taken 5-6 at a time).

also if I take 1 ball it is not true that the other will have the exactly same mass. But almost same can be handpicked.

so a projectile recommendation would also be helpful.
Sorry, I should have added it before, my bad.

 

[Baluncore]

so a projectile recommendation would also be helpful.

I would suggest you use live hungry white mice, that you have trained to find food in cups.
Alternatively glass marbles, selected by weight, would be repeatable.

 

[sauravp]

I would suggest you use live hungry white mice, that you have trained to find food in cups.
Alternatively glass marbles, selected by weight, would be repeatable.

Glass marbles final.

 

[anorlunda]

Summary:: What mechanism can get me most cons

I don't have access to a spring or a shop where I can get one so either tell me a way without using those or how to make them aswell.

I don't understand. What propels the projectiles?

 

[sauravp]

I don't understand. What propels the projectiles?

That is what I am asking for, best way to propel it to get consistent shots
Here are a few options
1) compressed air
2) rubber bands
3) spring powered

any other Ideas would be appreciated.

PS: I edited and corrected the summary

 

[berkeman]

You only mention a turret, which will presumably pivot to fine tune the azimuth for your shot, correct? BTW, you mention using a stepper motor, but perhaps you should look into micro-stepper motors as well. You will get much more resolution on your azimuth angle with a micro-stepper motor setup.

You didn't mention if this mechanism will be single-shot loaded by hand, or multi-shot loaded by some mechanism on the turret. Which is it? For a launch mechanism by hand, you could look into spring-loaded (or rubber-band powered if you have no springs) catapults. With some experimentation, you can come up with a calibrated launch arm position scale that shows you the range your shot will travel.

https://www.flinnsci.com/catapult/ap7788/

Oh, and I don't think I'd use hard rubber super balls or even glass marbles for the projectiles. It seems like you will want something that will deform or stick to the surface when it lands, rather than bounce away.

Come to think of it, since this is for a school competition, there must be written rules and directions, right? Can you post a copy of those please?

 

[hutchphd]

It strikes me that golf balls are manufactured to be identical in flight.

 

[anorlunda]

You are not the first high school student faced with this project. Here are some links to other students who posted the same question. You may be able to learn from them.

https://www.physicsforums.com/threads/accurate-projectile-launcher.287967/
https://www.physicsforums.com/threads/air-cannon-physics.282353/
https://www.physicsforums.com/threa...o-air-pressure-to-launch-a-projectile.773745/
https://www.physicsforums.com/threads/high-school-science-fair-railgun.373566/
https://www.physicsforums.com/threads/floating-arm-trebuchet-calculations-and-predictions.374581/
https://www.physicsforums.com/threads/spring-constants-and-balances.201703/
https://www.physicsforums.com/threads/physics-problem-projectile-motion.468529/
https://www.physicsforums.com/threads/how-to-find-tension-in-a-spring.404018/
https://www.physicsforums.com/threads/projectile-motion-lab.636710/
https://www.physicsforums.com/threads/air-cannon-school-project-firing-paper-projectile.855698/
https://www.physicsforums.com/threads/onager-designs.284933/
https://www.physicsforums.com/threads/trebuchet-competetion.263089/

 

[sauravp]

@berkeman , @anorlunda thank you very much for spending your time to answer the question.

there must be written rules and directions, right?

All they told me I told you. They did showed some examples and some had a simple trebuchet and others had a cannon mounted at an angle
And i will be using a spring/rubber power canon mounted at an angle, it will be like a tripod joint so that I can choose different angle(by hand only).

It seems like you will want something that will deform or stick to the surface when it lands, rather than bounce away.

I will demonstrate on grass so glass marbles will not bounce much and also i just might use those disposable paper tea cups as a container.

You didn't mention if this mechanism will be single-shot loaded by hand, or multi-shot loaded by some mechanism on the turret.

The mechanism will be single shot and will be loaded by hand each time to shoot.

I want to know in what ways can I fine tune the turret, is it by simply changing the angle of canon, or trying different rubber bands or pulling the striker and then releasing it at different length what should be the first priority and how much consistent will i be able to land my shots with such mechanism.

i want to know this before I buy the tools and spend my budget and then realize that the mechanism is limited and I can't do anything about it.

 

[anorlunda]

How many test shots are you allowed? How many contest shots are you allowed?

I would choose a styrofoam ball, because they don't go far, if they go in the cup they won't tip it over, and if they land near the cup, they won't roll far. I would use the same ball over and over again.

I also suggest a bungee cord rather than a rubber band because the bungee has a longer lifetime, and its tension and speed may be more repeatable. You shouldn't need a big budget.

We could continue giving many tips, but the project is for you to design it, not to get strangers on the Internet to do it for you. (Think of Tom Sawyer ). So how about you suggest how to select the materials, construct, aim and calibrate, and anchor, and test your cannon? We can comment on your design.

 

[sauravp]

I'll make something and then reply back in a few days with some images and all.