Towers B/C

[Balsa Man]

https://drive.google.com/file/d/0B1BYt2 ... sp=sharing
Hello, so I built this partially complete tower weighing in at about 7.3 grams and I am curious as to how I should connect these two sides together without constructing a jig. How can I accurately get these two sides in place and finish this tower?

Musical_Whang here is a great video explaining the purpose of trusses, pretty much what Balsa Man said but in an actual video
https://www.youtube.com/watch?v=Uv0G4OwRWCw
Hope this helps!

Thanks for re-posting this. It IS great for visually understanding what's going on, and how bracing works.
Just a comment/correction on nomenclature, though (fm Wikipedia); bracing members are not "trusses":
"In engineering, a truss is a structure that "consists of two-force members only, where the members are organized so that the assemblage as a whole behaves as a single object". A "two-force member" is a structural component where force is applied to only two points.

[musicalwhang]

Thanks for all of your input guys!
I will be taking the suggested approach and hopefully I can test this tower over the week and see how it does. I'll get back to you guys on how well it did and possible errors in my tower design
I'm in division B and I'm not going for the bonus

[roguntur]

I have created a 10 gram tower with all 1/8 x 1/8 balsa sticks. It held all 15kgs. Our team made it to state, and I need a good way to reduce the weight of the tower to about 6.5 - 8 grams. If i replaced all of the trusses in the tower from 1/8 x 1/8 to 1/8 x 1/16 sticks the tower would weigh 7 grams. Will changing the type of stick cause the tower to become weaker? Does anyone have any other advice on how to reduce the weight?

[Balsa Man]

I have created a 10 gram tower with all 1/8 x 1/8 balsa sticks. It held all 15kgs. Our team made it to state, and I need a good way to reduce the weight of the tower to about 6.5 - 8 grams. If i replaced all of the trusses in the tower from 1/8 x 1/8 to 1/8 x 1/16 sticks the tower would weigh 7 grams. Will changing the type of stick cause the tower to become weaker? Does anyone have any other advice on how to reduce the weight?

First, welcome to the forum; you have found the place with comprehensive information on how to do what you're trying to do. It's like a textbook, but you have to dig; the info is scattered across 50+ pages (this thread, and the other tower threads). Go back to the beginning, read through; digest the posts that explain things you need to understand, skip over the.....other chatter. As you develop specific questions, feel free ask, and can get more focused answers.

Very briefly, when you say 'all the trusses'; a nomenclature note. Pieces aren't called trusses (a truss is an assembly of parts). Legs, ladders, X (or Z braces). For legs and ladders, you want square cross section. They're under compression loading; that loading at some point will cause them to "buckle." They will buckle....across the smallest cross sectional dimension. At a given stick density, the buckling strength across the 1/16th dimension will be about half that across the 1/8th dimension- so legs done this way will have half the strength of 1/8 legs, so you'd expect it to carry half the load. I can tell you, building with 1/8th (at right density and buckling strength can get you into the 8gr range (carrying full load) and with careful building and wood selection, below that.

[fdf4]

Is it a general consensus that it's "better" to have a 4 legged tower than a pyramid tower?

[Unome]

Is it a general consensus that it's "better" to have a 4 legged tower than a pyramid tower?

What do you mean by a pyramid tower? Your two descriptions seem to be the same to me.

[roguntur]

Is it a general consensus that it's "better" to have a 4 legged tower than a pyramid tower?

What do you mean by a pyramid tower? Your two descriptions seem to be the same to me.

I think he means a tower with 4 legs vs a tower with 3 legs

[Random Human]

Is it a general consensus that it's "better" to have a 4 legged tower than a pyramid tower?

What do you mean by a pyramid tower? Your two descriptions seem to be the same to me.

I think he means a tower with 4 legs vs a tower with 3 legs

Pyramid tower- a tower that looks a bit like this -> http://kidder.ca/media/catalog/product/ ... 48655x.jpg
what he means is that all four legs lean towards the center

3 sided towers could generally be "a pyramid"

When replying to this post, a questions popped up...

Would there be any issue with creating a 3 legged tower? -that's legs are using equilateral triangle (60 degrees) of sticks, how a 1/8*1/8 is a square, the legs being in a shape of an equilateral triangle?

Is there any issues with a design as such

[fdf4]

Other than more strain on the legs, if the tower is built correctly, there shouldn't be any problem with a three-legged tower. But is it generally better to have a four legged tower due to more reliability in how much it can hold?

[Balsa Man]

What do you mean by a pyramid tower? Your two descriptions seem to be the same to me.

I think he means a tower with 4 legs vs a tower with 3 legs

Pyramid tower- a tower that looks a bit like this -> http://kidder.ca/media/catalog/product/ ... 48655x.jpg
what he means is that all four legs lean towards the center

3 sided towers could generally be "a pyramid"

When replying to this post, a questions popped up...

Would there be any issue with creating a 3 legged tower? -that's legs are using equilateral triangle (60 degrees) of sticks, how a 1/8*1/8 is a square, the legs being in a shape of an equilateral triangle?

Is there any issues with a design as such

This question has already been asked/answered a couple of times this year. The main disadvantage comes in the bracing. In a square tower, the faces of adjacent legs are parallel to each other. A ladder, put between two legs sees axial loading when/if one of the legs starts/tries to buckle in toward the adjacent leg- the compressive force is straight along its long axis. With the leg faces at 30 degree angle, that same beginning of buckling puts a non-axial load on; the force is at an angle, and it acts immediately to start bowing the ladder; starting the ladder buckling. So its buckling strength is MUCH lower than if it were under axial loading; need a much stiffer (i.e., much heavier) ladder to hold against the force. The other issue is getting square load block properly centered on the top leg end triangle- so that the center, the eyebolt, is centered between the legs. If its off at all, one leg gets disproportional loading, breaks early.