Bracing

Locked
Juanyjose
Member
Member
Posts: 27
Joined: April 16th, 2017, 12:39 pm
Has thanked: 0
Been thanked: 0

Bracing

Post by Juanyjose » April 23rd, 2017, 5:45 pm

I'm having some trouble deciding what type of bracing to use for my tower... I've read through (some) of the towers B/C thread where Balsa Man talks about BS of sticks, and that's how you decide the interval of the bracing.

By the way, Balsa Man, (and everyone else who posts frequently here) thanks for everything you do to help out everyone, I've been reading your comments since bridges in 2015 (the start of my scioly career), I've learned a lot from you and I figured I owed you a thank you...

So: The bracing most everyone talks about, X's and ladders, is very different from what I have been doing, what I have done, for regional and states, it is like this: (No picture, cuz the computer is smarter than me, if someone can post back how to do that that would be great) no horizontal sticks (what I think you call ladders?) and not an x, but half of an x. So looking at the tower from the side it looks like zig zag. Anything below 1/12 has not really worked for me, which surprised me because when I ran the numbers, of the bs test and all, I came to the conclusion I could use 1/5 interval, which make no sense to me, it wouldn't work.

What are the pros and cons of the bracing I've been doing (lets call it zig zag) , compared to x's and ladders, or other strategies? How would I calculate the bracing I need, using zig zag? I think it's 2x as much as x and ladder, but I'm not sure.

Thoughts and comments? Thanks

Dohnnovan
Member
Member
Posts: 44
Joined: December 20th, 2016, 11:18 pm
Division: B
State: CA
Has thanked: 0
Been thanked: 0
Contact:

Re: Bracing

Post by Dohnnovan » April 24th, 2017, 1:27 am

Juanyjose wrote:I'm having some trouble deciding what type of bracing to use for my tower... I've read through (some) of the towers B/C thread where Balsa Man talks about BS of sticks, and that's how you decide the interval of the bracing.

By the way, Balsa Man, (and everyone else who posts frequently here) thanks for everything you do to help out everyone, I've been reading your comments since bridges in 2015 (the start of my scioly career), I've learned a lot from you and I figured I owed you a thank you...

So: The bracing most everyone talks about, X's and ladders, is very different from what I have been doing, what I have done, for regional and states, it is like this: (No picture, cuz the computer is smarter than me, if someone can post back how to do that that would be great) no horizontal sticks (what I think you call ladders?) and not an x, but half of an x. So looking at the tower from the side it looks like zig zag. Anything below 1/12 has not really worked for me, which surprised me because when I ran the numbers, of the bs test and all, I came to the conclusion I could use 1/5 interval, which make no sense to me, it wouldn't work.

What are the pros and cons of the bracing I've been doing (lets call it zig zag) , compared to x's and ladders, or other strategies? How would I calculate the bracing I need, using zig zag? I think it's 2x as much as x and ladder, but I'm not sure.

Thoughts and comments? Thanks
I personally would not use this approach. At my first four invitationals, I used the zigzag design(Everything was butt jointed) and the highest efficiency I got at an invitational was 668. I decided that I would switch to ladders and X's for my regional competition just to try it out, and got first place with an efficiency of 1469.
Ukiah High School '20

dholdgreve
Coach
Coach
Posts: 560
Joined: February 6th, 2006, 2:20 pm
Division: B
Has thanked: 0
Been thanked: 0

Re: Bracing

Post by dholdgreve » April 24th, 2017, 7:37 am

Juanyjose wrote:I'm having some trouble deciding what type of bracing to use for my tower... I've read through (some) of the towers B/C thread where Balsa Man talks about BS of sticks, and that's how you decide the interval of the bracing.

By the way, Balsa Man, (and everyone else who posts frequently here) thanks for everything you do to help out everyone, I've been reading your comments since bridges in 2015 (the start of my scioly career), I've learned a lot from you and I figured I owed you a thank you...

So: The bracing most everyone talks about, X's and ladders, is very different from what I have been doing, what I have done, for regional and states, it is like this: (No picture, cuz the computer is smarter than me, if someone can post back how to do that that would be great) no horizontal sticks (what I think you call ladders?) and not an x, but half of an x. So looking at the tower from the side it looks like zig zag. Anything below 1/12 has not really worked for me, which surprised me because when I ran the numbers, of the bs test and all, I came to the conclusion I could use 1/5 interval, which make no sense to me, it wouldn't work.

What are the pros and cons of the bracing I've been doing (lets call it zig zag) , compared to x's and ladders, or other strategies? How would I calculate the bracing I need, using zig zag? I think it's 2x as much as x and ladder, but I'm not sure.

Thoughts and comments? Thanks
The Zig Zag approach can and does work within certain parameters... First off, it is important that you realize that by going with a single bracing member, you are asking it to do both the compression bracing as well as the tension bracing. If you have read back through the thread, you know that bracing for compression involves the length of the piece as well as the load... the longer the piece is, the heavier it must be to resist the same load... This is not true with tension members... a 36" length piece will resist approximately the same as a 3" piece in tension (assuming no weak areas within). In an X braced tower, one member braces for tension in one direction, while the other member braces in tension in the other direction, with the ladder holding the 2 legs equal distance apart, so compression never enters into it. In the zig sag design, each member must brace for both compression and tension, while also holding the 2 columns apart. My guess is that your columns are probably fine, but it is your bracing that is failing... probably in the compression vector. This is why you have had to resort to tiers being over twice as close, and still not getting the desire results. The numbers you have run represent column buckling, and have nothing to do with bracing failure. I'd recommend that you build a tower or two as we have recommended on this site, using the Xes and ladders approach, and doing the math as you've stated, then analyze these results... I'm fairly confident that the results of these tests will be somewhere between 50% and 100% higher than the zig sag approach.
Dan Holdgreve
Northmont Science Olympiad

Dedicated to the Memory of Len Joeris
"For the betterment of Science"

Juanyjose
Member
Member
Posts: 27
Joined: April 16th, 2017, 12:39 pm
Has thanked: 0
Been thanked: 0

Re: Bracing

Post by Juanyjose » April 24th, 2017, 2:20 pm

dholdgreve wrote:
Juanyjose wrote:I'm having some trouble deciding what type of bracing to use for my tower... I've read through (some) of the towers B/C thread where Balsa Man talks about BS of sticks, and that's how you decide the interval of the bracing.

By the way, Balsa Man, (and everyone else who posts frequently here) thanks for everything you do to help out everyone, I've been reading your comments since bridges in 2015 (the start of my scioly career), I've learned a lot from you and I figured I owed you a thank you...

So: The bracing most everyone talks about, X's and ladders, is very different from what I have been doing, what I have done, for regional and states, it is like this: (No picture, cuz the computer is smarter than me, if someone can post back how to do that that would be great) no horizontal sticks (what I think you call ladders?) and not an x, but half of an x. So looking at the tower from the side it looks like zig zag. Anything below 1/12 has not really worked for me, which surprised me because when I ran the numbers, of the bs test and all, I came to the conclusion I could use 1/5 interval, which make no sense to me, it wouldn't work.

What are the pros and cons of the bracing I've been doing (lets call it zig zag) , compared to x's and ladders, or other strategies? How would I calculate the bracing I need, using zig zag? I think it's 2x as much as x and ladder, but I'm not sure.

Thoughts and comments? Thanks
The Zig Zag approach can and does work within certain parameters... First off, it is important that you realize that by going with a single bracing member, you are asking it to do both the compression bracing as well as the tension bracing. If you have read back through the thread, you know that bracing for compression involves the length of the piece as well as the load... the longer the piece is, the heavier it must be to resist the same load... This is not true with tension members... a 36" length piece will resist approximately the same as a 3" piece in tension (assuming no weak areas within). In an X braced tower, one member braces for tension in one direction, while the other member braces in tension in the other direction, with the ladder holding the 2 legs equal distance apart, so compression never enters into it. In the zig sag design, each member must brace for both compression and tension, while also holding the 2 columns apart. My guess is that your columns are probably fine, but it is your bracing that is failing... probably in the compression vector. This is why you have had to resort to tiers being over twice as close, and still not getting the desire results. The numbers you have run represent column buckling, and have nothing to do with bracing failure. I'd recommend that you build a tower or two as we have recommended on this site, using the Xes and ladders approach, and doing the math as you've stated, then analyze these results... I'm fairly confident that the results of these tests will be somewhere between 50% and 100% higher than the zig sag approach.
My towers break in the columns. Almost always at the top or way at the bottom of the column, and when the wreckage of the tower is analyzed, the zig zag pieces are rarely broken, but they have clearly been 'unglued', or they came off, the columns.

But, from what you said, and based on video of the towers when I test them, I would imagine not having any compression ladders would explain why the tower columns seem to be bent in weird directions after about 5 kg are put on. Not quite buckling/bowing, but like the whole column shifts over kind of

What about zig zag and ladders compared to x and ladders? Based on what you said, there would be nothing bracing for tension 'in the other direction'... what would that look like? Because there is definetly a trade off of weight, zig zag and ladder is about half as much bracing as x and ladder, that would be quite a bit less wood.

Thanks for feedback!

dholdgreve
Coach
Coach
Posts: 560
Joined: February 6th, 2006, 2:20 pm
Division: B
Has thanked: 0
Been thanked: 0

Re: Bracing

Post by dholdgreve » April 25th, 2017, 5:47 am

[quote="My towers break in the columns. Almost always at the top or way at the bottom of the column, and when the wreckage of the tower is analyzed, the zig zag pieces are rarely broken, but they have clearly been 'unglued', or they came off, the columns.

But, from what you said, and based on video of the towers when I test them, I would imagine not having any compression ladders would explain why the tower columns seem to be bent in weird directions after about 5 kg are put on. Not quite buckling/bowing, but like the whole column shifts over kind of

What about zig zag and ladders compared to x and ladders? Based on what you said, there would be nothing bracing for tension 'in the other direction'... what would that look like? Because there is definetly a trade off of weight, zig zag and ladder is about half as much bracing as x and ladder, that would be quite a bit less wood.

Thanks for feedback![/quote]

Your assumption about weight would assume that the X braces would weigh the same as the Z braces. This is incorrect. The X braces brace only against tension and therefore can be "way" lighter than Z braces that must guard against both tension and compression. Take a piece of 1/32 x 1/32 balsa, and pull it from both ends... Pretty strong, right?... Now push toward each other... You'll notice that it offers virtually no resistance against compression... Assuming you are using a piece of 1/32" piece 12" long, and in tension, it withstands 2 KG of force, you would probably need a piece close to 1/4" square to resist the same force and length in compression. Compression forces are length dependent... the longer they are, the bigger diameter they need to be. Tension braces are not length dependent... You can use the same diameter to brace 36" as you do 6" as long as all forces acting on it are tension.
Dan Holdgreve
Northmont Science Olympiad

Dedicated to the Memory of Len Joeris
"For the betterment of Science"

Locked

Return to “Towers B/C”

Who is online

Users browsing this forum: No registered users and 1 guest