General Discussion

[thsom]

I have a question since I'm new to this (building off of sj's comment slightly). When we go to check in our towers how is that done? I know it says no impound but do we bring it in earlier so they can check the mass and height and that it follows the rules? Or, do they check for everything when we bring our tower right before it is tested? I'm hoping for the second option because I have wrapped my tower in newspaper covering, tissue paper, bubble wrap, and packing peanuts but I was not able to find silica pouches and the gym we are testing in is VERY humid and i have been in it before. So, if they check for the mass, height, etc. if we have to bring it in early, then i am assuming they won't take care into putting it back into the box and it will absorb all of the moisture and cause it to fail earlier than supposed to. So, how do they do it?

[chalker]

I have a question since I'm new to this (building off of sj's comment slightly). When we go to check in our towers how is that done? I know it says no impound but do we bring it in earlier so they can check the mass and height and that it follows the rules? Or, do they check for everything when we bring our tower right before it is tested? I'm hoping for the second option because I have wrapped my tower in newspaper covering, tissue paper, bubble wrap, and packing peanuts but I was not able to find silica pouches and the gym we are testing in is VERY humid and i have been in it before. So, if they check for the mass, height, etc. if we have to bring it in early, then i am assuming they won't take care into putting it back into the box and it will absorb all of the moisture and cause it to fail earlier than supposed to. So, how do they do it?

It all depends on the individual tournament. I've seen some require early checkin, and others let you checkin right before you test. Best to ask the tournament director / event supervisor as to how it will be done.

[thsom]

I have a question since I'm new to this (building off of sj's comment slightly). When we go to check in our towers how is that done? I know it says no impound but do we bring it in earlier so they can check the mass and height and that it follows the rules? Or, do they check for everything when we bring our tower right before it is tested? I'm hoping for the second option because I have wrapped my tower in newspaper covering, tissue paper, bubble wrap, and packing peanuts but I was not able to find silica pouches and the gym we are testing in is VERY humid and i have been in it before. So, if they check for the mass, height, etc. if we have to bring it in early, then i am assuming they won't take care into putting it back into the box and it will absorb all of the moisture and cause it to fail earlier than supposed to. So, how do they do it?

It all depends on the individual tournament. I've seen some require early checkin, and others let you checkin right before you test. Best to ask the tournament director / event supervisor as to how it will be done.

Will there be any way to ensure the tower doesn't gain mass and lose strength due to the humidity (because after they checkin the tower they won't put it back in the box correctly or at all for that matter is what i would assume)? Because when it is out in the humidity of the gym, i can't think of any way to prevent the outcomes from occurring.

[jma]

If the tower holds more than 15 kg, is it considered overbuild?

[mrsteven]

If the tower holds more than 15 kg, is it considered overbuild?

well how much over? to a reasonable amount (16-16.5) it is good in my opinion in case of offset testing surface or swaying of the chain.

more than that, ya i'd say you should find a dimension or two to cut back on

[Balsa Man]

If the tower holds more than 15 kg, is it considered overbuild?

well how much over? to a reasonable amount (16-16.5) it is good in my opinion in case of offset testing surface or swaying of the chain.

more than that, ya i'd say you should find a dimension or two to cut back on

Yeah, 16-16.5 is probably a reasonable range. The taller the tower, the more suceptable to a non-level test base (or bucket sway) it will be. Bucket sway is in your control; level of test base isn't, which suggests having some level of safety factor (overbuild) is a smart idea. Is this the 8-grammer you mentioned earlier/how tall you running?

If you're overbuilt beyond a reasonable safety factor, probably easier to adjust weight downward with a desnity reduction than a dimension adjustment, btw.

[chalker]

Will there be any way to ensure the tower doesn't gain mass and lose strength due to the humidity (because after they checkin the tower they won't put it back in the box correctly or at all for that matter is what i would assume)? Because when it is out in the humidity of the gym, i can't think of any way to prevent the outcomes from occurring.

Gaining mass won't be an issue since they should weigh it as part of the check in process. The strength issue is a little more challenging. I've seen at some tournaments the supervisor let teams check in then impound a box with the tower, which would allow you to seal it up again. Keep in mind that the majority of event supervisors follow the general policy of never allowing anyone but the team itself to physically touch a tower, so there isn't any chance of inadvertent damage to it.

[jma]

Thanks, mrsteven and Balsa Man.
My 8g tower is 48 cm high, 28cm base and 20cm chimney. Besides reducing the density as you advised, I'm thinking of changing the base's braces. Some posts recomented Xs bracing without ladders, while others mentioned the ladders will keep the legs from bowing inward. What do you think of 2 sides with Xs and ladders, and 2 sides with Xs only? I saw that most of the rectangular base towers had different bracing designs between their front/back and sides but I never saw something like that on the square base tower. I was wondering if anybody had attempted that design before.

[thsom]

Chalker, or anybody for that matter. Do we have to put our school name and team number on the tower itself or is it ok to only put it on the transportation box we use?

[Balsa Man]

Thanks, mrsteven and Balsa Man.
My 8g tower is 48 cm high, 28cm base and 20cm chimney. Besides reducing the density as you advised, I'm thinking of changing the base's braces. Some posts recomented Xs bracing without ladders, while others mentioned the ladders will keep the legs from bowing inward. What do you think of 2 sides with Xs and ladders, and 2 sides with Xs only? I saw that most of the rectangular base towers had different bracing designs between their front/back and sides but I never saw something like that on the square base tower. I was wondering if anybody had attempted that design before.

You're quite welcome, jma- glad to be able to help.
Interesting thought. I honestly don't know. As I've said before, I'm not an engineer; I've just over the years absorbed some engineering understanding from various engineers, and from experience/testing. I understand how & why ladders and Xs work- with the ladders working in compression, and the Xs in tension , and we've had decent success applying, and I've described before. I've seen designs with only Xs that "work". I think the answer lies in geometry. If you look at one leg, at the point the bracing joins- you've got Xs coming in diagonally, from above and below. You can look at one X-piece as the radius of a circle, where the center (C) is the point it attaches to the bracing junction above or below the joint in question, and the arc of the circle is that described by the other end- a point on the outside diagonal edge of the leg; that radius is some distance, let's call it D. A square cross section leg is going to buckle toward one of the flat sides- its weaker in those directions than it is across the diagonal of the cross section. So, if you envision the leg where the X joins starting to buckle toward the adjacent leg- at 90 degrees to the X, what does the geometry look like? Let's ignore the bracing, and pretend its not there, and say it moves a millimeter. What is the distance from C to the outside diagonal edge of the leg, at the point the bracing joins? I believe you will find it is >D, so if the X were in-place, it would have to have stretched to allow that movement- if it doesn't stretch, the leg can't move that way. This suggests that Xs, installed with enough pre-tension so there is NO slack, will work......

So, if Xs w/o ladders 'works", it will do so on all four sides; leaving the ladders on 2 sides as dead weight. If it doesn't, 'the "it will fail at the weakest link" axiom comes into play. Time for a test. Build with ladders. Load to close to full. Under load, gently with, say, a razor saw, cut a ladder; work around the tower at that level cutting ladders.