Best Way to Tie Off Surgical Tubing
 

Hello CD world,

We are planning on using surgical tubing this year for our launching mechanism. We have been tying the surgical tubing in knots, but with the extreme stress we are putting it under the knots are slipping bit by bit. I was wondering if any people with a lot of experience with the stuff could advise us and other FIRST teams on the best way to tie the stuff. I have seen a few posts mentioning zip ties and hose clamps, but can't be certain if there is any trick to securing this stuff.

Thank you

Re: Best Way to Tie Off Surgical Tubing
 

The method that the teams I have been on is to use zip ties to hold them together. The trick is to stretch the surgical tubing so that the zip tie is tightened when the tubing is as thin as it will be so it doesn't slip.

Re: Best Way to Tie Off Surgical Tubing
 

Using zip ties with a zip tie gun ensures that they are tight. Pretty easy to find one relatively cheap.


http://www.uline.com/Product/Detail/...A&gclsrc=aw.ds

Re: Best Way to Tie Off Surgical Tubing
 

Hose clamps might be the way to go for a COTS component. The ability to have them adjust tensioning with minimal effort is a solid way to go. Also, replacements for new surgical tubing in the same clamps would take much less time than with zipties.

The only issue I could see with them is that they would be too sharp and the recoil might sever the tubing which would drastically increase performance overtime. However, adding some material to reduce the catching of that edge can certainly be done.

In addition, clamping the tubing after a point where it has attained some friction is much better than to the final stretched position.

Edit: Apparently the end of my third sentence was cut off.

Bolt two flat blocks together. Sandwich the surgical tubing in between.

Re: Best Way to Tie Off Surgical Tubing
 

Zip Ties work great. We have put lots and lots of stress on our surgical tubing and the Zip Ties have not shown any real weaknesses.

Re: Best Way to Tie Off Surgical Tubing
 

What Cory is getting at is make a capstan of sorts;
http://en.wikipedia.org/wiki/Capstan_equation

Wrap the surgical tubing a few times around something and the clamping force required afterwards is a fraction of the loaded tension.

Re: Best Way to Tie Off Surgical Tubing
 

In 2011 when we balanced our arm with tubing, we doubled back the tubing about six inches and installed several zip ties, pulling them all tight with pliers. The system never slipped, just be sure those zip ties are TIGHT.

Re: Best Way to Tie Off Surgical Tubing
 

What kind of knot have you been using? We haven't had any problems using a euro death knot. Also, you can reduce the load on whatever joint you use by using more individual strands in parallel.

Re: Best Way to Tie Off Surgical Tubing
 

Don't tie knots in surgical tubing, they are nearly impossible to remove. Zip ties work just when you pretension the surgical tubing, and are much more easily removed when compared to knots.

Re: Best Way to Tie Off Surgical Tubing
 

What's wrong with the obvious way?

(do NOT lubricate)

Re: Best Way to Tie Off Surgical Tubing
 

I agree with the zip tie solution. Knots can be incredibly difficult to remove, plus, in my experience, creates wear on that point of the tubing due to the tension of the knot itself, making it weaker as time goes on.

Re: Best Way to Tie Off Surgical Tubing
 

We have also been using the "Pre-stretch, ziptie really tight" method for years.

Re: Best Way to Tie Off Surgical Tubing
 

Can anyone provide pictures of their zip tie surgical tubing method?

Re: Best Way to Tie Off Surgical Tubing
 

I concur with the multiple ziptie method. One way we've used to prevent pull-out is to insert the largest set screw you can into each open end of the surgical tubing. You may have to work it a little bit to get it in all the way. Then when you ziptie your tubing in place, make sure at least one ziptie is across the set screw area of the tubing. The threads act as a bit of a hose barb feature to resist slippage.

Good luck to all this year!