Trajectory B/C

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Re: Trajectory B/C

Post by haven chuck » June 28th, 2009, 7:47 am

Does surgical tubing stretch over time like bungee cords do? (Like does it wear out to a point where it is easier to stretch)
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Re: Trajectory B/C

Post by karatekid44 » June 28th, 2009, 7:59 am

For our trajectory device we used surgical tubing for the tension and it did not stretch out over time it was taut like the first day.
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Re: Trajectory B/C

Post by andrewwski » June 28th, 2009, 8:09 am

It will, to some degree. Any elastic material (non-springs) will deform to some degree from repeated stretching and release.

Fortunately this effect seems to be minimal with surgical tubing. I believe we used 1/2" OD 3/16" ID surgical tubing and it seemed to be consistent across all of our tests (probably 75-100 firings before competition). I'd be interested to see how many times it could be used before the results started changing (distance would become shorter).

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Re: Trajectory B/C

Post by starpug » June 28th, 2009, 8:10 am

karatekid44 wrote:For our trajectory device we used surgical tubing for the tension and it did not stretch out over time it was taut like the first day.
Then I kinda doubt it was surgical tubing unless you did very little testing because the tannish surgical tubing that you get at the hardware store stretches out over time. Might you have been using excercise tubing which would have been blue, green, red, purple, black, or some other colors?

We used 3/8 ID and 1/2 OD and that stuff had so much power it knocked the endcap off of our ABS pipe. It didn't stretch at all either but we didn't do many firings because we had such a short time to build.
Last edited by starpug on June 28th, 2009, 8:18 am, edited 1 time in total.
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Re: Trajectory B/C

Post by Aia » June 28th, 2009, 8:17 am

I perused the trajectory forum, but was unable to find any posts relating to B division trajectory scores at Nationals. Does anyone know where the scores fell for medaling in B division? My sister was wondering how her trajectory (which received 1st at State) would have stood up compared to other devices at the National competition, since she was unable to attend. Her state score (which was consistent with her other runs, both difficult and easier heights), was 6cm off the far target and 9mm off the near target.
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Re: Trajectory B/C

Post by starpug » June 28th, 2009, 8:21 am

Aia wrote:I perused the trajectory forum, but was unable to find any posts relating to B division trajectory scores at Nationals. Does anyone know where the scores fell for medaling in B division? My sister was wondering how her trajectory (which received 1st at State) would have stood up compared to other devices at the National competition, since she was unable to attend. Her state score (which was consistent with her other runs, both difficult and easier heights), was 6cm off the far target and 9mm off the near target.
I can bet you they would have 0 scores for at least the top 3 and possibly all the medalers, I heard the top 5 all hit the pin last year. Beyond that I have no clue.
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Re: Trajectory B/C

Post by karatekid44 » June 28th, 2009, 8:26 am

starpug wrote:
karatekid44 wrote:For our trajectory device we used surgical tubing for the tension and it did not stretch out over time it was taut like the first day.
Then I kinda doubt it was surgical tubing unless you did very little testing because the tannish surgical tubing that you get at the hardware store stretches out over time. Might you have been using excercise tubing which would have been blue, green, red, purple, black, or some other colors?

We used 3/8 ID and 1/2 OD and that stuff had so much power it knocked the endcap off of our ABS pipe. It didn't stretch at all either but we didn't do many firings because we had such a short time to build.
No it was the tan surgical tubing and we did a lot of testing it did not stretch.
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Re: Trajectory B/C

Post by starpug » June 28th, 2009, 8:32 am

karatekid44 wrote:
starpug wrote:
karatekid44 wrote:For our trajectory device we used surgical tubing for the tension and it did not stretch out over time it was taut like the first day.
Then I kinda doubt it was surgical tubing unless you did very little testing because the tannish surgical tubing that you get at the hardware store stretches out over time. Might you have been using excercise tubing which would have been blue, green, red, purple, black, or some other colors?

We used 3/8 ID and 1/2 OD and that stuff had so much power it knocked the endcap off of our ABS pipe. It didn't stretch at all either but we didn't do many firings because we had such a short time to build.
No it was the tan surgical tubing and we did a lot of testing it did not stretch.
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Re: Trajectory B/C

Post by karatekid44 » June 28th, 2009, 8:43 am

yes i very much say so we used doubles one short and one long on each side of the launching arm
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Re: Trajectory B/C

Post by andrewwski » June 28th, 2009, 9:20 am

There's going to be differences in different surgical tubings as well. I'd imagine the stuff from the hardware store is going to be different from the actual surgical stuff (used to replace tendons and stuff), and there's a variety of types you can get online. Some is going to deform more, some is going to deform less.

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