Designs

[rjm]

I think you should keep the base of the tower as small as possible, while still clearing the opening. A smaller base allows the legs to be steeper. It also reduces the length of cross bracing. You will probably find that about half the weight of your towers is in the cross bracing. 16 cm x 16 cm is a good start.

I would never advise anyone to NOT experiment with a design, even a circular design. I don't think it will work, but it would be a cool structure if it does. I'd say work first on things you know and then extend that to the more exotic ideas.

Bob Monetza
Grand Haven, MI

[lllazar]

I think you should keep the base of the tower as small as possible, while still clearing the opening. A smaller base allows the legs to be steeper. It also reduces the length of cross bracing. You will probably find that about half the weight of your towers is in the cross bracing. 16 cm x 16 cm is a good start.

I would never advise anyone to NOT experiment with a design, even a circular design. I don't think it will work, but it would be a cool structure if it does. I'd say work first on things you know and then extend that to the more exotic ideas.

Bob Monetza
Grand Haven, MI

Thank you Mr. Monetza!

[Littleboy]

That is what I was planning to do.

a circular design would make it harder to put cross bracing on and would weigh more than some other designs.

[obb]

How is this bridge possible to make according to the rules?

From the 2011 Rules: The Portion of the tower more than 30cm above the test base for Division B, or more than 15.0 cm above the test base for Division C must pass through an 8.0cm diameter circular opening or hole

Then for the loading block must be a 5cm x 5cm x 2cm block.

If there has to be a hole at the top measuing at least 8cm around then how is it possible for the loading block to fit on top?

And also for you guys with wild efficienies (load supported in kilograms)^2/mass of tower.

which means scores will be in the 20s-40s

(15kg)^2/10g = 22.5 efficiency

[rjm]

The 8.0 cm hole is not part of the tower, it is a hole in a testing jig, or an imaginary circle, through which the top portion of the tower must be capable of passing. At the national tournament the tower will not be allowed to touch the circle in the jig, so don't build a force-fit. As always, it is not wise to build devices so close to the maximum sizes that you need an interpretation from a judge, you should allow a little extra clearance. There will be no problem setting the testing block on the top of the tower, you can build the top as narrow as you wish, provided the 1/4" eyebolt shank fits through it, and provided there is room for a chain below that.

It appears that the scoring scheme was revised during the summer to get the size of the numbers more reasonable, changed from grams^2/grams, or units of grams. In the 2006/2007 rules, efficiency was a unitless number. Now score is in units of Kg^2/g. The scoring scheme is idiotic.

Bob Monetza
Grand Haven, MI

[AlphaTauri]

obb, I think you're mistaken. The 8cm hole isn't a hole in the tower itself, it's that from 15 or 30 cm up (depending on division), your tower can be no wider than 8cm at the widest point(s).

Also about the scoring...I looked at my rules and that is the way it's phrased, but the relative scores are the same, only moved over several decimal places. Still, it's traditionally been in grams.





Edit: Or listen to what Mr. Monetza said.

[lllazar]

Anyone know where one could find an 8 cm in diameter circle.

[smartkid222]

If the top section of your tower is a square or rectangle, use the Pythagorean theorem to find the hypotenuse (or diagonal of the square) which would also be the diameter of the circle.

[obb]

@rjm thanks for the clarification...now i have to redo my design

[robotman]

Anyone know where one could find an 8 cm in diameter circle.

The best way i think is to use a hose clamp and get it to 8 cm using a set of calipers