How legal are tension springs?
 

We were thinking that tension springs would put more force out per inch of movement than surgical or latex tubing. After searching the rules multiple times and checking the list of legal and illegal parts, tension springs are not mentioned. In order for our initial shooter idea to work in the least amount of space, however, we need to use them. Anybody know if they're legal, or if theres another springy material that would work just as well?

Thank you on behalf of Team 2191 Flux Core.

Re: How legal are tension springs?
 

I believe they are definitely legal IF they are slack when the robot goes on the field and/or is disabled. The stored energy rule is designed to prevent a robot from being handled while significant amounts of energy are stored in components creating an obvious safety hazard.

Re: How legal are tension springs?
 

Tension springs are legal. It up to you to properly apply them. The robot inspector can decide that the design utilizing springs is unsafe. Unsafe can be springs, exposed propeller blades, exposed shooter wheels, ETC.

[T12] refers to springs on the robot.

[R34] Non-electrical sources of energy used by the ROBOT, (i.e., stored at the start of a MATCH), shall come only from the following sources:
A. compressed air stored in the pneumatic system that is legal per R79 and R80,
B. a change in the altitude of the ROBOT center of gravity,and
C. storage achieved by deformation of ROBOT parts.

[R34-C] is commonly known as a spring. It can be compressed/tensioned at the start of the match.

Re: How legal are tension springs?
 

If there is no rule against them, then they are legal. (There is none).

Keep in mind, however, that surgical tubing can provide as much force as you need it to - just keep adding bands of surgical tubing. That is why it is so wonderful to work with. If you want to used springs over tubing, then I'd prototype with tubing to find a rough spring force constant and verify it with a little math. Otherwise you'll be spending a lot of money on springs.

Re: How legal are tension springs?
 

Tension springs are specifically permitted as an energy source on the robot - energy from "deformation of robot parts" refers to surgical tubing, springs, etc.

Re: How legal are tension springs?
 

I don't think that tension springs are necessary. Surgical tubing is essentially the same thing, but with a feel-good squishiness that will make your life better. Plus, it's free in the KOP!

We did a quickie catapult test yesterday using two loops of surgical tubing stretched 2 feet. It launched the ball with about 4 feet of loft. By doubling up the tubing, we should be able to get the necessary height on our next try.

Re: How legal are tension springs?
 

If it's not mentioned, it is probably legal. In this case:

(Emphasis mine.)

So yes, you can use a spring.

Re: How legal are tension springs?
 

Pro safety tip: put a string through coil springs that is tied off securely on the robot frame. This will help prevent the spring from jumping out and killing an inspector if it snaps.

Re: How legal are tension springs?
 

Surgical tubing is certainly workable; however, you will find that over time it will degrade in performance and you will have to tighten it or replace it. Probably fine for one regional, but an actual spring will remain much more consistent over time.

Re: How legal are tension springs?
 

my team 1108 was one of the few that built a catapult for rebound rumble in 2008 and we started and ended with coiled steel springs running it. We made surgical-tubing springs and tried them for a while but they stretch over time, they oxidize and where they're fastened, they tear. Steel springs had no degradation. I think we were able to get more energy into a smaller space too.

At first when we installed the coils, we thought they would require a cable down the middle like on your garage door, but no one ever mentioned it.

Note that one of the 'bots' on the game-introduction video visibly has a compression spring catapult.

I think we'll end up with metal springs again, but I can't say that for sure now. Also, air springs a possibility.