Need help on a quick tower design - outside help OK

This discussion area is for basic structure building concepts. Not intended for advanced concepts.
*Good Example: Balsa can bend with the addition of boiling water.
*Good Example: Triangle is the strongest shape for most applications of bracing.
*Bad Example: Balsa can hold X pounds under these conditions.
*Bad Example: Use this shape for this application.
Basically I want you to think a design through with the basics instead of someone else thinking through your design for you.
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dhartson
Posts: 3
Joined: Tue Mar 07, 2006 1:31 am
Location: Sunland, CA, USA

Need help on a quick tower design - outside help OK

Post by dhartson » Wed Mar 08, 2006 12:24 pm

This request will be posted shortly - thanks

dhartson
Posts: 3
Joined: Tue Mar 07, 2006 1:31 am
Location: Sunland, CA, USA

Request for help

Post by dhartson » Wed Mar 08, 2006 1:28 pm

(Sorry about that. In other forums I've used I was able to go back and revise the post.)

So, I'm looking for any ideas on the design of a tower to help my daughter. This is for a physics lab project and they are allowed lab partners and to request outside assistance because they were only given a little over one week to submit a tower for testing, and now I've learned we have to leave town Wednesday and won't return until Sunday, so there isn't any time for any experimentation on design. She's off on Monday, and will have to build the tower then.

The tower:
It must be 7 1/2" to 8 1/2" tall, a maximum of 12 grams, and must be constructed of 1/8" x 1/8" balsa sticks and any kind of glue. It must be able to slide over a 2" diameter pipe, after which the tower will be loaded with traditional weight room weights that will be slid over the pole and placed on top of the tower.

General questions:

What should the general shape be? Triangular, square, or more than four sides? The more sides, the greater the number of vertical sticks or columns that will be necessary, so that the weight will add up quickly. But, the fewer sides the longer the distances between each column, so any pieces used to cross brace will need to be longer, adding more weight.

At each corner, should an individual stick be used, or should a column of two, three or four sticks be used? Once more, weight is the difficulty, and I assume the answer will be dependent in large part by the number of sides.

I am assuming that the shorter the tower, the better.

Also, am I correct in assuming that the top of the tower needs substantial bracing around the circumference, and the middle needs more bracing than the bottom?

Then, on the bracing, since the failure is (I assume) going to come from the bowing out or in of a vertical stick or column, is there a need for triangular or diagonal bracing, or should a straight, 90 degree brace be used with a notched joint of some type that would hold against a tendency to bow out and would also brace against a tendency to bow in? What type of joint would be optimal?

My daughter, Kat, is planning on using over the counter "super glue" to attach pieces together since she probably won't have time to use glue that would require clamping and curing time; also, while we live in L.A. , there isn't time to order a specialty glue for delivery. Is there a commonly available brand or type of glue that would be better?

Technical rules:
Any kind of joint is evidently OK. There are some specific don'ts, particularly no continuous contact of over 1" between two crossing sticks, and no laminations are allowed. In addition, except for the crossing of two sticks just mentioned, there can be no more than 1/8" of contact at any point; if two sticks are placed in parallel, then 1/8" square blocks could be used between them to hold them together, but there must be more than a 1/8" gap between each such block, particularly if there is a third or fourth stick used to form a column. Finally, if there is a corner (like the corner of a log cabin), there is a maximum of four members in the joint structure.

Any help, thoughts, or rough sketches would be greatly appreciated. Thanks!!!

David
hartsonlaw [at] usa.net
818/352-9916 (fax)

dhartson
Posts: 3
Joined: Tue Mar 07, 2006 1:31 am
Location: Sunland, CA, USA

Concerns over "outside help" rules

Post by dhartson » Wed Mar 08, 2006 1:58 pm

I received a well considered and kind PM from a member of the forum that expressed a concern over the possible violation of "no outside help" rules in the competitions in which most members of the forum are probably involved.

So, I understand that my request for help is contrary to the rules of these competitions, which is a world entirely new to me. It appears that the competitions are designed to promote creative thinking through a process of "trial and error", and, obviously, outside help would be counterproductive to that process. So, the rules make sense.

In my daughter's situation, because they have very little time, there is no time for substantial trial and error. I think the project is intended as a quick introduction to the concepts involved and will lead to a class discussion of which designs were most effective.

I posted my email address and fax number, so that should help to allay any fears that I am involved in an effort to circumvent any rules. It would not be difficult to identify me through public records and thereby identify the "cheater" if that is what I am doing.

It is clear to me that much of what I would like to know would be apparent from the observation of just a few structures being placed under a load. Issues such as glue type, the best design of joints, etc., must be easily discovered through trial and error, or with simple observation. I'm sure any individual or team covers a lot of ground overcoming any learning curve at the time of their first competition. This just doesn't happen to be a hobby for us, and we don't have the luxury of time, so we'll just take the best ideas available and take our best shot. Hopefully it will hold the min. 50 lbs necessary to get a passing grade . . .

So, I understand any reluctance to help, but I still hope that someone may offer some ideas. Thanks.

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ClarkInMI
Posts: 123
Joined: Fri Oct 07, 2005 12:55 pm
Location: Grand Rapids, MI

Outside Assistance Impact

Post by ClarkInMI » Wed Mar 08, 2006 3:24 pm

David,

It isn't just that the person receiving outside assistance (OA) is subject to penalties, under OM rules the person (or team) guilty of passing on that OA is also subject to penalties. Good luck to your daughter, Kat, on what sounds suspiciously like a basic OM structure problem.
ClarkInMI

geraldatwork
Posts: 7
Joined: Fri Feb 10, 2006 3:33 pm

Post by geraldatwork » Wed Mar 08, 2006 4:39 pm

I can't give you an exact design but this should not be that hard. In Science olympiad people build towers 20 inches high with a bottom span of 8 inches and come in under 10 grams which generally do fairly well at regional competitions. They have to hold 33 lbs. At states the towers come in 8 grams. You are on the right track using CA or super glue as it dries in seconds. So your daughter should be able to build a structure in an hour or so. Wait maybe 30 minutes to an hour then test it. If you give this project 3 or 4 hours you should be able to come up with a design that works after trial and error. Your first towers may tumble but you will see the problems and fix them. Or you can start heavy and reduce weight. Basically a good tower builder would probably be able to build a tower like this in 3 or 4 grams. Just look outside at some towers to get you started. This is rambling as I dont have too much time.

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