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Re: Towers B/C
Posted: March 30th, 2018, 8:15 pm
by retired1
BananaPirate wrote:retired1 wrote:My computer program indicates that a ladder rung is needed at the top and the bottom with the balance X's. sometimes it will require a rung about 1/3 of the way up It mostly depends on the balsa that you are using.
just curious, if you are willing to share, what program you are using?
3dsmart. Takes a while to get used to it, but I have found it to be quite close to actual scores-barring bad glue joints or one bad piece of balsa.
Look for the student price in a couple of places. An older one is cheaper and he might let you have it for that.
Re: Towers B/C
Posted: March 31st, 2018, 3:45 pm
by cool hand luke
When you guys are saying you have a high theoretical but always break much lower, how are you calculating the theoretical? What are you using for Fe?
Re: Towers B/C
Posted: March 31st, 2018, 4:32 pm
by cheese
cool hand luke wrote:When you guys are saying you have a high theoretical but always break much lower, how are you calculating the theoretical? What are you using for Fe?
Not to be rude, but read through last years and this years forums, and you will find all the info you will need. If someone else would like to explain, go for it, but reading through the forums is the way to go.
Re: Towers B/C
Posted: March 31st, 2018, 4:41 pm
by cool hand luke
Trust me I’ve read it. I’m a civil engineer, and was trying to give some advice on how to make your results line up with your predictions. The easiest way is to adjust the Fe in rulers buckling. Len had posted earlier that he had an Fe of .55. This may be for perfectly constructed all x towers but we are not seeing this.
Re: Towers B/C
Posted: April 3rd, 2018, 4:36 pm
by MadCow2357
I've read through the whole forum, looking for density guidelines when buying balsa. I dug up Balsa Man's (may he rest in peace) explanation on why 1/8 legs are more weight-strength efficient than 3/32 and 1/16 legs, and a couple of other gold mines of info as well. But, I have not found any concrete answer to my current issue.
How to explain? First of all, I have decided to go light for the last 2 towers I will build before states. I went on the Specialized Balsa website, and looked at the "Specially Weighed" 1/16 Square Balsa sticks. I was initially preparing to just click a low density option, and hope for the best, when I came across a table of specific densities from 0.2 to 1.2 grams per 36" stick.
My issue is, I cannot determine if a certain density of Balsa is suitable for the goal that I am trying to achieve. Maybe 0.2 is way too lightweight and weak, or maybe it is considered a moderately lightweight density (what I want)? I don't know.
Maybe someone can help give me a guideline to which densities of 1/16x1/16 and 1/8x1/8 are considered lightweight, mid range, and heavy. I don't want the balsa to be overly light, and carry barely any weight, nor do I want to have a 20 gram tower that held the full load like last time (990 is a super cruddy score, even for a rookie like me
).
I am aiming for a ~8 gram tower that can carry near full load. Even a 10 gram would be fine to get gold at states (RI is not competitive). A link to a picture of my tower:
https://drive.google.com/file/d/1mcqaf0 ... sp=sharing
https://drive.google.com/file/d/10y3tuF ... sp=sharing
https://drive.google.com/file/d/17C4O9A ... sp=sharing
https://drive.google.com/file/d/1ZRe1kL ... sp=sharing
I hope I didn't make this post sound disrespectful in any way. For some weird reason, I feel like the wording of this post was a little haughty or demanding, even though I didn't mean it that way. Maybe it's just nothing...
Re: Towers B/C
Posted: April 3rd, 2018, 5:36 pm
by Cow481
Just wondering but do you guys use 1/16 or 1/16 x 1/32 for bracings in the base?
Re: Towers B/C
Posted: April 3rd, 2018, 9:22 pm
by cheese
Cow481 wrote:Just wondering but do you guys use 1/16 or 1/16 x 1/32 for bracings in the base?
I personally use 1/16 x 1/32. Some will do differently depending on if you use x-ladder of x-only.
Re: Towers B/C
Posted: April 4th, 2018, 8:27 am
by MadCow2357
MadCow2357 wrote:I've read through the whole forum, looking for density guidelines when buying balsa. I dug up Balsa Man's (may he rest in peace) explanation on why 1/8 legs are more weight-strength efficient than 3/32 and 1/16 legs, and a couple of other gold mines of info as well. But, I have not found any concrete answer to my current issue.
How to explain? First of all, I have decided to go light for the last 2 towers I will build before states. I went on the Specialized Balsa website, and looked at the "Specially Weighed" 1/16 Square Balsa sticks. I was initially preparing to just click a low density option, and hope for the best, when I came across a table of specific densities from 0.2 to 1.2 grams per 36" stick.
My issue is, I cannot determine if a certain density of Balsa is suitable for the goal that I am trying to achieve. Maybe 0.2 is way too lightweight and weak, or maybe it is considered a moderately lightweight density (what I want)? I don't know.
Maybe someone can help give me a guideline to which densities of 1/16x1/16 and 1/8x1/8 are considered lightweight, mid range, and heavy. I don't want the balsa to be overly light, and carry barely any weight, nor do I want to have a 20 gram tower that held the full load like last time (990 is a super cruddy score, even for a rookie like me
).
I am aiming for a ~8 gram tower that can carry near full load. Even a 10 gram would be fine to get gold at states (RI is not competitive). A link to a picture of my tower:
https://drive.google.com/file/d/1mcqaf0 ... sp=sharing
https://drive.google.com/file/d/10y3tuF ... sp=sharing
https://drive.google.com/file/d/17C4O9A ... sp=sharing
https://drive.google.com/file/d/1ZRe1kL ... sp=sharing
I hope I didn't make this post sound disrespectful in any way. For some weird reason, I feel like the wording of this post was a little haughty or demanding, even though I didn't mean it that way. Maybe it's just nothing...
Re: Towers B/C
Posted: April 4th, 2018, 8:46 am
by Crtomir
MadCow2357 wrote:MadCow2357 wrote:I've read through the whole forum, looking for density guidelines when buying balsa. I dug up Balsa Man's (may he rest in peace) explanation on why 1/8 legs are more weight-strength efficient than 3/32 and 1/16 legs, and a couple of other gold mines of info as well. But, I have not found any concrete answer to my current issue.
How to explain? First of all, I have decided to go light for the last 2 towers I will build before states. I went on the Specialized Balsa website, and looked at the "Specially Weighed" 1/16 Square Balsa sticks. I was initially preparing to just click a low density option, and hope for the best, when I came across a table of specific densities from 0.2 to 1.2 grams per 36" stick.
My issue is, I cannot determine if a certain density of Balsa is suitable for the goal that I am trying to achieve. Maybe 0.2 is way too lightweight and weak, or maybe it is considered a moderately lightweight density (what I want)? I don't know.
Maybe someone can help give me a guideline to which densities of 1/16x1/16 and 1/8x1/8 are considered lightweight, mid range, and heavy. I don't want the balsa to be overly light, and carry barely any weight, nor do I want to have a 20 gram tower that held the full load like last time (990 is a super cruddy score, even for a rookie like me
).
I am aiming for a ~8 gram tower that can carry near full load. Even a 10 gram would be fine to get gold at states (RI is not competitive). A link to a picture of my tower:
https://drive.google.com/file/d/1mcqaf0 ... sp=sharing
https://drive.google.com/file/d/10y3tuF ... sp=sharing
https://drive.google.com/file/d/17C4O9A ... sp=sharing
https://drive.google.com/file/d/1ZRe1kL ... sp=sharing
I hope I didn't make this post sound disrespectful in any way. For some weird reason, I feel like the wording of this post was a little haughty or demanding, even though I didn't mean it that way. Maybe it's just nothing...
I think you would probably want to start with 1/8" x 1/8" x 36" sticks for your columns (legs) that weigh 1.2g and then start dropping down to 1.0g once you get the bracing figured out. To calculate the density, you do this:
1.2g / [(1/8)*(1/8)*(36)] = 2.1 g/in^3
To change this to lb/ft^3, multiply by 3.81 to get 2.1 g/in^3 * 3.81 = 8.13 lb/ft^3
That falls in the "Light Balsa" category (6-10 lb/ft^3) for Specialized Balsa. However, last time I ordered from them, they had run out of wood in that category. Maybe they have more now, I don't know. My guess is between the CA wildfires destroying balsa trees and the uptick in Science Olympiad orders, they might be out of stock. That was a month or so ago.
Hope this helps.
Re: Towers B/C
Posted: April 4th, 2018, 8:48 am
by Crtomir
Also, since you have a tower built and know what design you are using, then just measure the length of each piece and make a spreadsheet with the weight of each piece calculated from the weight of each 36" piece you started with. That way you can estimate the weight of new towers you build using the weight of the pieces you start with.