Surgical tubing issues

[jijiglobe]

Our team is using surgical tubing to power our catapult . After a couple hours of testing our surgical tubing seems to be losing power. Is there any way we can avoid this problem (such as stretching the tubing less) that a team knows of or a good alternative to surgical tubing that won't be ruined easily? Thanks in advance people.

[Mike Betts]

Originally Posted by jijiglobe

Our team is using surgical tubing to power our catapult . After a couple hours of testing our surgical tubing seems to be losing power. Is there any way we can avoid this problem (such as stretching the tubing less) that a team knows of or a good alternative to surgical tubing that won't be ruined easily? Thanks in advance people.

Surgical tubing looses its elasticity if it is subjected to cold. We had a tubing issue at a cold venue once and had to heat the tubing with a hair drier before every match.

BE CAREFUL! Overheating has its own set of negative issues...

[Chowmaster4695]

We knew this was going to be a very big issue for many teams this year, so we decide to use the better alternative; springs. We are using one 1000lb 5 inch diameter spring with 15 inches of free length and a 12 inch diameter puck. We highly recommend this because of its consistency and power.

[Phyrxes]

Depending on how you have your surgical tubing set up it may be "easy" swap to go to exercise bands.

While a bit more of a challenge to deal with due to wall thickness they do come in distinctive force ratings when stretched to twice their original length.

[WeJohnFriedIt]

Originally Posted by jijiglobe

Is there any way we can avoid this problem (such as stretching the tubing less) that a team knows of or a good alternative to surgical tubing that won't be ruined easily?

Team 1466 is using a similar system, and we have had success just loosening the tubing when we don't need to shoot. If that doesn't help, you may want to use something easily removable like S-hooks to attach the tubing.

[BBray_T1296]

Surgical tubing works best if not stretched more than 2x its length. It is supposed to retain its structure longer.
Also, if you have a bundle of tubing, they may rub against each-other (especially during rapid retraction) and wear in that way

Other than that, I would leave it to normal wear and tear. A couple of hours is not unreasonable for something like elastic tubing. Maybe just bring enough to a regional for 3-4 replacements?

[rcmolloy]

I wouldn't say that your surgical tubing isn't losing power but more on the side that you're having the tube elongated out of its clamp. This would decrease winch elongation and therefor the force to shoot. What you might want to look into doing for your surgical tubing is clamp it using a capstan. It essentially uses the friction around a corner, cylinder, or any surface to relate to clamping force.

Here's the wikipedia page about it all!

http://en.wikipedia.org/wiki/Capstan_equation

[nxtmonkeys]

U can also use more if u have it.

[david cobbley]

Our team ordered the black tubing from Mcmaster mostly for aesthetic purposes but they appear to hold their elasticity longer than those supplied in the kop, we will probably change them out once or twice during a district though to be on the safe side.

[Lil' Lavery]

It really depends on how much you're currently stretching your tubing. Once stretched far enough, any material will begin plastically deform (permanently stretch) rather than elastically deform (stretch and then return to original length). Once you pass this yield point, each stretching cycle will cause a slight amount of permanent deformation, resulting in longer (and thinner) tubing, which will be stretched less in the future (thus resulting in less force). One solution to get the same amount of force would be to use more (or thicker walled) tubing, with each band stretched less. Another would be to periodically replace the tubing with new tubing.

[ice.berg]

Our team is using 5/16" OD 3/32" wall surgical tubing. We found a force calculator online for surgical tubing and found that most surgical tubing is most efficient in the 300% stretch range. We then based our design around that.
As for the lifespan of the surgical tubing we have found it is good for about 100 shots, but only because of the small nicks and cuts it had in in because of some sharp pieces on our robot. After replacing the tube, we compared an old piece and a new piece and found that the old piece only stretched an extra inch after about 100 shots.
We do know of the issue of temperature, being from Minnesota this is definitely on our minds as outside temps are just a little bit different from the inside temps... So we just make sure the robot is properly warmed up before we start testing and practicing.

The force calculator can be found here: http://www.primelineindustries.com/tools.html