Towers B/C

[Random Human]

Hi all!
States is on Saturday for me and I'm very excited to compete this year. I'm hoping the tower I built for the competition can get a high efficiency.
For the legs, I used 1/8 x 1/8 wood at about 1.2 gr/36". The BS was ~28.5 grams. For my ladders and tension members, I used a combination of .3 gram and .4 gram 1/16 x 1/16 wood. The legs are braced at a 1/5th interval and the lower 3 ladders are lap joints and top 3 are butt joints. Overall, the tower weighs 6.2 grams and I didn't go for the bonus
Attached below are the pics of the tower. I was wondering if anyone had any tips for loading the tower and my possible efficiency. Also, where do you think this tower will break first? Any weaknesses in the design?
Thank you all!
https://drive.google.com/file/d/0ByNusF ... sp=sharing
https://drive.google.com/file/d/0ByNusF ... sp=sharing

I don't exactly know where it would break. Usually when you brace in 1/5 intervals, The buckling will be 10 cm(for div b) each. Your looking at a varied amount of buckling strenth (depending on leg buckling strength). I can't tell where it's gonna break, but 10 cm usually won't cut it. The tower looks nicely constructed, I expect for a high placing. Great Job!

[Random Human]

Hi all!
States is on Saturday for me and I'm very excited to compete this year. I'm hoping the tower I built for the competition can get a high efficiency.
For the legs, I used 1/8 x 1/8 wood at about 1.2 gr/36". The BS was ~28.5 grams. For my ladders and tension members, I used a combination of .3 gram and .4 gram 1/16 x 1/16 wood. The legs are braced at a 1/5th interval and the lower 3 ladders are lap joints and top 3 are butt joints. Overall, the tower weighs 6.2 grams and I didn't go for the bonus
Attached below are the pics of the tower. I was wondering if anyone had any tips for loading the tower and my possible efficiency. Also, where do you think this tower will break first? Any weaknesses in the design?
Thank you all!
https://drive.google.com/file/d/0ByNusF ... sp=sharing
https://drive.google.com/file/d/0ByNusF ... sp=sharing

I don't exactly know where it would break. Usually when you brace in 1/5 intervals, The buckling will be 10 cm(for div b) each. Your looking at a varied amount of buckling strenth (depending on leg buckling strength). I can't tell where it's gonna break, but 10 cm usually won't cut it. The tower looks nicely constructed, I expect for a high placing. Great Job!

Sorry I didn't read where u specified buckling strength to be 28.5 cm. Calculations show, 28.5 cm buckling, at 10 cm won't carry 15, but it looks pretty conservative in terms of weight, so should be getting around 10-12kg in the bucket.

[musicalwhang]

Hi all!
States is on Saturday for me and I'm very excited to compete this year. I'm hoping the tower I built for the competition can get a high efficiency.
For the legs, I used 1/8 x 1/8 wood at about 1.2 gr/36". The BS was ~28.5 grams. For my ladders and tension members, I used a combination of .3 gram and .4 gram 1/16 x 1/16 wood. The legs are braced at a 1/5th interval and the lower 3 ladders are lap joints and top 3 are butt joints. Overall, the tower weighs 6.2 grams and I didn't go for the bonus
Attached below are the pics of the tower. I was wondering if anyone had any tips for loading the tower and my possible efficiency. Also, where do you think this tower will break first? Any weaknesses in the design?
Thank you all!
https://drive.google.com/file/d/0ByNusF ... sp=sharing
https://drive.google.com/file/d/0ByNusF ... sp=sharing

I don't exactly know where it would break. Usually when you brace in 1/5 intervals, The buckling will be 10 cm(for div b) each. Your looking at a varied amount of buckling strenth (depending on leg buckling strength). I can't tell where it's gonna break, but 10 cm usually won't cut it. The tower looks nicely constructed, I expect for a high placing. Great Job!

Just to be on the safe side, I actually built the tower to 52 cms. This made each interval 10.4 cms. Thank you!

[Balsa Man]

Hi all!
States is on Saturday for me and I'm very excited to compete this year. I'm hoping the tower I built for the competition can get a high efficiency.
For the legs, I used 1/8 x 1/8 wood at about 1.2 gr/36". The BS was ~28.5 grams. For my ladders and tension members, I used a combination of .3 gram and .4 gram 1/16 x 1/16 wood. The legs are braced at a 1/5th interval and the lower 3 ladders are lap joints and top 3 are butt joints. Overall, the tower weighs 6.2 grams and I didn't go for the bonus
Attached below are the pics of the tower. I was wondering if anyone had any tips for loading the tower and my possible efficiency. Also, where do you think this tower will break first? Any weaknesses in the design?
Thank you all!
https://drive.google.com/file/d/0ByNusF ... sp=sharing
https://drive.google.com/file/d/0ByNusF ... sp=sharing

I don't exactly know where it would break. Usually when you brace in 1/5 intervals, The buckling will be 10 cm(for div b) each. Your looking at a varied amount of buckling strenth (depending on leg buckling strength). I can't tell where it's gonna break, but 10 cm usually won't cut it. The tower looks nicely constructed, I expect for a high placing. Great Job!

Just to be on the safe side, I actually built the tower to 52 cms. This made each interval 10.4 cms. Thank you!

First, it is a really pretty build; your hard, careful work shows; good precision, good detail.

Based on how the B tower I’ve been working with did at our State tournament last weekend, my guess is failure will be from buckling in the lower ladder (not the sticks right at the base- the ladder 10cm up from the base). Legs were 1.2, 36" BS measured at 37.6gr; 1/4 bracing interval; calculated braced leg strength at 4365gr; 5.9gr tower weight, meeting circle bonus

1/5 interval, ~28.5 BS at 36” should have around 5200gr braced BS w/ ladders and Xs bracing. That’s substantially over design load, suggesting legs should easily be good for carrying full load. However, our important take-away from State was that the assumption that the forces the bracing needs to handle is on the order of 1kg doesn't hold up. Our lower ladders were from 1/8”- 0.91gr/36, 36” BS measured at 20.1gr. One failed/buckled at 9260gr tower load. Still good enough to win, but well below expectation.

When you look at the BS of 1/16 vs 1/8, at the same density, the 1/8 is 16 times that of the 1/16. That’s why my concern/guess that initial failure will be in the lower ladders….. The fact that you're using 1/16 x 1/16 for your Xs (vs the 1/64 x will help- as in they will provide additional bracing against inward buckling of legs toward each other. 1/64th strips provide essentially nothing.

As we all know only too well, actual performance versus calculated performance can be surprising; better or worse. So, hopefully you’re in for a pleasant surprise; pulling for you! Do let us know how it goes.

[musicalwhang]

I don't exactly know where it would break. Usually when you brace in 1/5 intervals, The buckling will be 10 cm(for div b) each. Your looking at a varied amount of buckling strenth (depending on leg buckling strength). I can't tell where it's gonna break, but 10 cm usually won't cut it. The tower looks nicely constructed, I expect for a high placing. Great Job!

Just to be on the safe side, I actually built the tower to 52 cms. This made each interval 10.4 cms. Thank you!

First, it is a really pretty build; your hard, careful work shows; good precision, good detail.

Based on how the B tower I’ve been working with did at our State tournament last weekend, my guess is failure will be from buckling in the lower ladder (not the sticks right at the base- the ladder 10cm up from the base). Legs were 1.2, 36" BS measured at 37.6gr; 1/4 bracing interval; calculated braced leg strength at 4365gr; 5.9gr tower weight, meeting circle bonus

1/5 interval, ~28.5 BS at 36” should have around 5200gr braced BS w/ ladders and Xs bracing. That’s substantially over design load, suggesting legs should easily be good for carrying full load. However, our important take-away from State was that the assumption that the forces the bracing needs to handle is on the order of 1kg doesn't hold up. Our lower ladders were from 1/8”- 0.91gr/36, 36” BS measured at 20.1gr. One failed/buckled at 9260gr tower load. Still good enough to win, but well below expectation.

When you look at the BS of 1/16 vs 1/8, at the same density, the 1/8 is 16 times that of the 1/16. That’s why my concern/guess that initial failure will be in the lower ladders….. The fact that you're using 1/16 x 1/16 for your Xs (vs the 1/64 x will help- as in they will provide additional bracing against inward buckling of legs toward each other. 1/64th strips provide essentially nothing.

As we all know only too well, actual performance versus calculated performance can be surprising; better or worse. So, hopefully you’re in for a pleasant surprise; pulling for you! Do let us know how it goes.

Thank you for your response! So do you think it was the right choice going with 3 butt joints for the top ladders for compression and 3 lap joints for the bottom ladders to serve as tension?

[Balsa Man]

Just to be on the safe side, I actually built the tower to 52 cms. This made each interval 10.4 cms. Thank you!

First, it is a really pretty build; your hard, careful work shows; good precision, good detail.

Based on how the B tower I’ve been working with did at our State tournament last weekend, my guess is failure will be from buckling in the lower ladder (not the sticks right at the base- the ladder 10cm up from the base). Legs were 1.2, 36" BS measured at 37.6gr; 1/4 bracing interval; calculated braced leg strength at 4365gr; 5.9gr tower weight, meeting circle bonus

1/5 interval, ~28.5 BS at 36” should have around 5200gr braced BS w/ ladders and Xs bracing. That’s substantially over design load, suggesting legs should easily be good for carrying full load. However, our important take-away from State was that the assumption that the forces the bracing needs to handle is on the order of 1kg doesn't hold up. Our lower ladders were from 1/8”- 0.91gr/36, 36” BS measured at 20.1gr. One failed/buckled at 9260gr tower load. Still good enough to win, but well below expectation.

When you look at the BS of 1/16 vs 1/8, at the same density, the 1/8 is 16 times that of the 1/16. That’s why my concern/guess that initial failure will be in the lower ladders….. The fact that you're using 1/16 x 1/16 for your Xs (vs the 1/64 x will help- as in they will provide additional bracing against inward buckling of legs toward each other. 1/64th strips provide essentially nothing.

As we all know only too well, actual performance versus calculated performance can be surprising; better or worse. So, hopefully you’re in for a pleasant surprise; pulling for you! Do let us know how it goes.

Thank you for your response! So do you think it was the right choice going with 3 butt joints for the top ladders for compression and 3 lap joints for the bottom ladders to serve as tension?

You're welcome. Yeah, I think it might be; there's definitely some inward pressure (pushing legs together) at the top, and outward at the bottom, so that strategy makes sense. Again, best of luck!

[musicalwhang]

Hi again!

First, I'd like to thank everyone on this forum that made me do so well. Balsa Man, thank you so much for all your help, helping me understand how this event works. Just as predicted, my tower failed at the 2nd ladder. Once that broke, my whole tower went down at 9130 grams. It weighed 6.36 grams and got an efficiency of ~1435. Even though it wasn't what I expected, I still got 4th in towers at my state. I will be doing towers again next year when I'm in high school and due to how I did in my other events, my high school wants me to be on varsity next year! Our team isn't going to nationals but I've learned so much.

Thanks,
musical

[cheese]

Hi again!

First, I'd like to thank everyone on this forum that made me do so well. Balsa Man, thank you so much for all your help, helping me understand how this event works. Just as predicted, my tower failed at the 2nd ladder. Once that broke, my whole tower went down at 9130 grams. It weighed 6.36 grams and got an efficiency of ~1435. Even though it wasn't what I expected, I still got 4th in towers at my state. I will be doing towers again next year when I'm in high school and due to how I did in my other events, my high school wants me to be on varsity next year! Our team isn't going to nationals but I've learned so much.

Thanks,
musical

Congrats on 4th!

[Balsa Man]

Hi again!

First, I'd like to thank everyone on this forum that made me do so well. Balsa Man, thank you so much for all your help, helping me understand how this event works. Just as predicted, my tower failed at the 2nd ladder. Once that broke, my whole tower went down at 9130 grams. It weighed 6.36 grams and got an efficiency of ~1435. Even though it wasn't what I expected, I still got 4th in towers at my state. I will be doing towers again next year when I'm in high school and due to how I did in my other events, my high school wants me to be on varsity next year! Our team isn't going to nationals but I've learned so much.

Thanks,
musical

Congrats on 4th!

Let me echo those congratulations. You did a heck of a good job, musical; 4th at State is something to be proud of; enjoy the good feelings of accomplishment. Thanks for reporting back.

That you found the info I, and others, were able to provide here helpful feels great; you're very welcome. We've created quite a compendium here of' how to figure it out, and then how make that understanding into something real. Problem solving, like this, is a critical skill for doing science, and, as you will find as you apply what you've learned to other aspects of life, for achieving other goals in life. Its really cool your high school wants your talents for next year. Show 'em its a smart choice!

That your tower failed two thirds of the way to 15kg is, to me, good news/bad news. The bad news is, of course, you didn't get that last third. The good news is that from the understanding I've developed (and just like you, and all the other builders and coaches, what I understand keeps growing every day), it was possible to ...see with pretty good accuracy what was coming. My...private guess was it would be doing really well to get to 10Kg; that you got so close to that speaks to your high quality build.

Enjoy the off-season, and we'll talk more about towers next year.

[musicalwhang]

Thank you! I will definitely enjoy off-season and I'm looking forward to next year! I will come back to this forum again and keep on building knowledge about this event.

Side note, I see that Nationals in 2018 will be held in Fort Collins! Are you going to go there and volunteer or just watch some of the building events?