Efficiencies

[sciolyswizzle16]

wow, that's really good!
my school was suppose to go to that invitational, but unfortunately we couldn't due to the "snowstorm".

[sj]

Thanks!

[SLM]

Yeah, I had a 9.7 gram tower that held all 15 kilos so a 23.1 efficiency.

Congratulations on your success at Towers and your other events.

Out of curiosity, how much time have you been spending on your events since the beginning of this SO season?

[lllazar]

Just got new wood a few days ago, after revising our base design and testing today our 8.2 g tower held all the weight, 27.4~

I speak from experience, plan out your design and building method first before you even build a tower, i don't think we'd be getting anywhere close to this high without an accurate jig and consistent building technique. The design honestly isn't that important as far as placing at state goes (now at nats, definitely...design is paramount, how else would they get lower than 5 grams )

[hpfananu]

Congrats! We just had an invite and I'm not sure what happened but our tower that was 16.5 g (not specialized wood yet) wasn't able to hold the weight. I'm thinking it was because while bracing, we tried to straighten the tower and that may have put a lot of stress on it. We had a tower of the exact same design not nearly as straight holding approximately 18 kg and this one holding 6.5 kg. Do you guys think this could have been it or some other factor like wood? We've been using a foam board but no actual jig yet, but this time we're planning on using that paper jig that NC SO has a video of. Any other jig recommendations? Thanks in advance!

[sj]

Yeah, I had a 9.7 gram tower that held all 15 kilos so a 23.1 efficiency.

Congratulations on your success at Towers and your other events.

Out of curiosity, how much time have you been spending on your events since the beginning of this SO season?

Probably about 15 hours a week.

[soccerkid812]

What wood sizes and wood weights did you use for the 9.7g tower or any other tower?

[dholdgreve]

As I understand it, Solon brought 2 Division B towers to the Northmont Invitational last Saturday. Both weighed between 5 and 6 grams. One held the entire load. the other did not... Very impressive for the first invitational of the year!

[lllazar]

Wow, very impressive, i wonder how that would relate to div c (the efficiencies would be lower but it can't see too much of a differential).

[old]

I'm sure this is a relatively stupid/simple question, but is there a certain way you all pour in the sand. If a lever system is used to let the sand fall in, would you want to go slow, then faster, then switch back to slow? Letting the sand in slow seems like it would make your tower sustain the weight for longer times, but faster streams seems a bit all of a sudden.

And if there is a manual sand system, then I would assume you would try to pour the sand around the bucket evenly, so there are no mounds, and try to do it as quick as possible?

It makes no difference if the sand is evenly distributed in the bucket as the attachment to the bucket and tower are both flexible.
As to what speed you should pour the sand you have two conflicting considerations. You want the tower to have to support the sand for the minimum time possible, which would suggest a fast pour. But the sand is falling some distance from the outlet of the "lever" system so it will have some velocity by the time it hits the bucket. when the sand hits the bucket it must quickly decelerate which requires an opposing force from the bucket (and therefor the tower). The faster you pour the greater the force needed to decelerate the sand. F=change in momentum / change in time. So if you pour 1 KG/sec. of sand at 4 M/Sec. (a reasonable speed for a 30cm drop to the bottom of the bucket) you have a change in momentum of 4KG M / Sec. sq. which is a force of 4 newtons. This force is equivalent to the tower carrying an additional 400 grams of sand while you are pouring. If you slow down to 0.5 Kg of sand per second the equivalent mass carried drops to 200 grams. If you run a constant pour speed that would reach 15KG in 2.5 minutes your tower will be effectively be carrying an additional 40 grams the entire time you are pouring.