cub scout presentation

huangyhg

cub scout presentation
i'm presenting engineering to the 4th graders in my son's cub scouts tonight.  i had planned on discussing a little bit about what a structural engineer does.  i'm also going to bring in a transit and do some surveying.  i would like to have them do some kind of project also.  when i was in 7th grade, we had an assignment of supporting as much weight as we could using a single sheet of paper.  i think it had to be at least 4" high and maybe some other rules.  we only have 45 minutes though, so i'm looking for something similar but less time consuming.  also i need to keep in mind that they are 4th graders.
does anyone have any engineering experiment in mind?
thanks,
drew

this is one that i have used in the past. a variation is to but mount th e tower in a jello foundation the simulate an earthquake.
build  a tower
materials: one pound of spaghetti (uncooked), 10 oz. bag of miniature marshmallows, box of paper  clips or other light weight item, ruler or tape measure, paper for drawing designs
procedure: set the stage: students are architects and engineers who must use the materials at  hand, spaghetti and marshmallows, to design and build a tall tower that can support the  weight of a box of paper clips.
awesome idea!  that might be perfect.  i spent four years designing tall tv broadcast towers so that would fit perfectly into what i will talk about.
thanks rich
rich, one question.  how tall did you require the tower be?
total height was about 3 feet.
here's a very cool, easy one involving soil mechanics:
in a bowl, place some sand to the top or almost, and place a relatively dense "building" shaped object, steel bar or rectangular rock...
then slowly add water to the sand thereby simulating liquefaction, and watch the resulting instability occur, (think pisa).
easy, and cool.
tg
i always liked the lateral system demonstration of taking 4 popsicle sticks and put a tack in the corners to form a square shape with "pin" connections at the corners, and show how easy it is to "rack" the model.  then make another one and glue the corners to represent moment connections,make a third where you glue a sheet of paper over the whole square for a shear wall, and a fourth with thread glued to the corners to represent bracing.
explain to them where this goes in a building, what it does, and point out that you never see buildings that fall down, they alway fall over.
those little models are amazingle rigid (especially the paper "shearwall" one).  i used this method here at work to help some of my architectural coworkers
jfudo,
thanks.  were you able to get the architects to understand?  did they spec out 20lb bond paper instead of 1/2" gyp on the next project?
the guys around me are wondering why i'm laughing...
they understand, but they don't want to.  all they get out of it is that we don't need to bother with all the bracing and shear wall nonsense and just use moment frames for everything
a trip to a home under construction is a fun activity for this webelos activity pin.  i did it with both of my sons' dens (12 years apart) - it kept them much more engaged than had i done it in my den.  and i had full size construction drawings for them to look at and discuss.  quite a few parents showed up, too - and indicated they had no idea how much goes into construction.  even the developer in the group said he learned a good bit.  (unfortunately, that probably means he doesn't listen to his paid consultants!)
an easy way to demonstrate the effectiveness of a truss is to fan fold a sheet of paper, then glue the vertices to two other sheets.  use plain notebook paper and school glue from your son - the boys will have real life experience with them.  then glue three sheets of paper together like a sandwich, with the glue in a similar pattern to the "truss" section - and the same amount of glue as well.  let everything dry thoroughly.
you can then use these two props to demonstrate the effectiveness of trusses.  in turn, use them to span between two supports - and apply increasing loads until they fail.  the truss section will be much stronger - and since you used the same amount of glue on both, the shape has to be the cause of the increased capacity.
you could use this as a hands-on activity; let them compete to see whose bridge is strongest -
have fun!
those are some good ideas guys. i may be presenting to some school children in the near future and this gives me food for thought.
i was thinking about guassian elimination for the resolution of a stiffness matrix or the principles of finite elements, but these may be more appropriate!