What about a slingshot?

[Leo 1529]

i was thinking about the surgical tubing that we have laying around the shop and it came to me why not a slingshot that will shoot the NERF balls around..

does anyone think this is a viable option??

[mpob]

Originally Posted by Leo 1529

i was thinking about the surgical tubing that we have laying around the shop and it came to me why not a slingshot that will shoot the NERF balls around..

does anyone think this is a viable option??

sure a slingshot would work, but consider how long it takes to shoot 10 balls, and do it consistently, also how long would the elastic part last before it breaks and needs to be replaced.

I think you can make this work, but you'll need to test the repeatablitity of aiming and shooting......since you want to do a lot of it

--Mike

[Henry_Mareck]

i can see inconsistency and slow firing speed, and if one of the elastic pieces breaks, then its game over, man. round over, actually.

[DonRotolo]

Yes, it is a viable option.
To convince yourself that it is - or isn't - make up a test fixture. Assume the slicgshot will be pulled back somehow, and make a way to do that exactly the same each time (even if by hand), and see how well it works - distance, repeatability, and so on.

In other words, you can answer the question yourself in an hour. Try it!

Don

[Andrew Blair]

Well, the problem is going to be returning the sling after the shot. A winch and rapid release could potentialy work. It would be a far less contained system though than a flywheel, and with tensioned rubber bands flying around, rather dangerous. The fact is, no matter how much energy your ball takes from the system, you must expend much more (your entire system dumps, energy wise) on every shot. With a constant energy system (flywheel), your sytem only loses the power (with some other nominal losses), that you put into the ball. Everything else is retained, making it easier to return the system to an appropriate energy for the next shot.

[Stats]

it wont work we tried very inacurate missed more than it hit

[KenWittlief]

surgical tubing will last a very long time. It can be streached to 3 times its relaxed length repeatable without loosing strength, and without breaking

I use 100 feet of surgical tubing to launch my RC sailplane (6 foot wingspan). The tubing is at the end of 800 feet of nylon cord, and its pulled back 300 feet.

you would not want a slingshot that flaps loose like, well like a slingshot. you would want something more like a pinball machine shooter, using the surgical tubing as the spring.

the great thing about surgical tubing is you can easily double it up to get twice the force.

[meaubry]

We built a prototype of this style of launcher and others too. Seemed to me to very reliable and accurate, I suppose it all depends on how you build it. As far as surgical tubing goes, if handled properly it will work just fine. We have used this material many times for counter balancing articulating arms with zero failures in 11 years.
I believe if you created a simple prototype you would see how well it works - the difficulty is in the reload time and catch/release mechanism.

[Rombus]

Here is the issue i see besides what everyone else has mentioned:
No part of your shooter mechnaism can go outside the 28x38x60 envelope.

interesting idea, and i like the fact your thinking outside the box! Figure out a way and be unique at the competition! My big fear this season is your going to have 50% ball throwers using some form of wheel, 40% that dont have a thrower for the top goal, and 10% of "outside the ball" thinkers!

[Nuttyman54]

one possible problem here-Rule <S01> (bold mine)

If at any time a ROBOT’s operation or design is deemed unsafe by the head referee, it will receive a 10-point penalty and be disabled for the remainder of the match. If the safety violation is due to the ROBOT design, the head referee has the option to not allow the ROBOT back onto the field unless the design has been corrected. An example of unsafe operation is repeatedly throwing balls off the field at audience members, media personnel, judges, referees, etc. An example of an unsafe design is a shooter mechanism that has a large mass that is stopped abruptly at the end of travel and is at risk of breaking off the ROBOT
and becoming a projectile.

[Mark Pettit]

I think that this could be done safely and within the rules as long as your device is well enclosed for protection and as long as a human will never need to be in contact with the surgical tubing when it is cocked (stretched out).
Check out these semi-auto rubber band guns that have a rotating mechanism that releases one band at a time. In my opinion, you could make something like this to release at least a few balls in rapid succession. Re-setting the device would be a challenge, but again, I think that it can be done.

[KTorak]

I invisioned a slingshot mechanish using an air piston. The air piston could quickly set the sling shot, then by releasing the air, the rubber bands (surgical tubing) would compress, ejecting the ball. However, i've never messe with the pistons to see how quickly they release air and refill.

[KenWittlief]

Originally Posted by Nuttyman54

one possible problem here-Rule <S01> (bold mine)

An example of an unsafe design is a shooter mechanism that has a large mass that is stopped abruptly at the end of travel and is at risk of breaking off the ROBOT and becoming a projectile.

yes! that means your laucher cannot have a 5 lbs sled that the ball rides on, that slams into the frame at the end of its motion at 12M/S. You need something to absorb the impact and limit its travel (foam, another piece of surgical tubing, a spring bumper...)

the issue here is metal fatigue. Ive mentioned this several times for pnuematic shooters - you cant let a pnuematic cylinder slam its end either. Eventually the end of the cylinder WILL blow out and become a projectile.

BTW - another super positive for a slingshot type shooter. A surgical tubing launcher could be very cheap and simple, therefore you could make a robot that fires ten balls at at the same time, fires 5 pairs of two, fires them staggered at 200mS intervals... it all depends on how you load the mechanism before the match.