Cross Supports

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.
Post Reply
User avatar
amh
Posts: 32
Joined: Sun Mar 07, 2010 2:56 pm
Location: Greenville,DE

Cross Supports

Post by amh » Thu Mar 18, 2010 8:32 pm

I am an expirienced balsa builder, but have not done alot of expirimentation with extremely light balsa wood for cross supports. Are cross supports intended to connnect to the columns to stabalize them without actually taking any actual pressure? Or are they designed to take pressure when the balsa column wants too bend, but is held in by the cross supports? Also, how could one determine if a structure broke in the columns or the cross supports? Sometimes the cross supports are completely smashed and i don't know which one broke first.

User avatar
Solodex
Posts: 383
Joined: Wed Oct 12, 2005 10:28 pm
Location: Lebanon, PA
Contact:

Re: Cross Supports

Post by Solodex » Fri Mar 19, 2010 7:32 am

amh wrote:I am an expirienced balsa builder, but have not done alot of expirimentation with extremely light balsa wood for cross supports. Are cross supports intended to connnect to the columns to stabalize them without actually taking any actual pressure? Or are they designed to take pressure when the balsa column wants too bend, but is held in by the cross supports? Also, how could one determine if a structure broke in the columns or the cross supports? Sometimes the cross supports are completely smashed and i don't know which one broke first.
"Cross supports" (bracing) serve several specific functions in a structure. There is several basic resources on the web that you can refer to for more information. Diary of A Balsa Goddess is a good source for information about the function of bracing. Look in the tutorials section. Virginia Odyssey of the Mind also publishes a guide with useful information.

Do some basic research and you will have your answer. If you are mathematically inclined, look up Euler's buckling theorem and start studying. That one equation will open doors in terms of design.

Regards,

Nate

User avatar
amh
Posts: 32
Joined: Sun Mar 07, 2010 2:56 pm
Location: Greenville,DE

Post by amh » Sat Mar 20, 2010 1:11 pm

Nate, thanks that information really helped me. I haven't figured out euler's buckling formula yet.

User avatar
tortuga
Posts: 104
Joined: Fri Oct 07, 2005 8:28 pm
Location: Pittsburgh, PA

Post by tortuga » Wed Mar 31, 2010 12:58 pm

i would also recommend video taping your tests. when a structure breaks, it can often be so smashed up that you have no idea where it broke. if you have a decent digital video camera, you can aim it at the structure during the test, and then go on your computer and go frame by frame. my camera shoots 30 frames per second, and I can almost always see exactly when and where the structure failed
Ah, I'd love to wear a rainbow every day,
And tell the world that everything's OK,
But I'll try to carry off a little darkness on my back,
'Till things are brighter, I'm the Man In Black.

User avatar
amh
Posts: 32
Joined: Sun Mar 07, 2010 2:56 pm
Location: Greenville,DE

Post by amh » Thu Apr 01, 2010 7:14 pm

I tried that two days ago with an HD camera. I'm not sure how many frames per second it is, but all i could see was which direction it broke in. Also, I can't figure out euler's buckling formula, could anyone explain it?

User avatar
Solodex
Posts: 383
Joined: Wed Oct 12, 2005 10:28 pm
Location: Lebanon, PA
Contact:

Post by Solodex » Fri Apr 02, 2010 5:41 am

amh wrote:I tried that two days ago with an HD camera. I'm not sure how many frames per second it is, but all i could see was which direction it broke in. Also, I can't figure out euler's buckling formula, could anyone explain it?
You must figure it out for yourself. To explain it would give too much away and might breach into OA realms. However, to make sure you are using the right formula, the one on Wikipedia helps. It is the first formula on the page in the second section. Also, to help you out, you can essentially ignore K.

User avatar
tortuga
Posts: 104
Joined: Fri Oct 07, 2005 8:28 pm
Location: Pittsburgh, PA

Post by tortuga » Fri Apr 02, 2010 10:17 am

if you're using an HD camera, it should be a high enough FPS to see the actual break. you'll have to get the video on your computer, and use an editing software that will allow you to go frame by frame. if you have a mac, ivideo is great for this. if not, there's lots of free software online that will get the job done
Ah, I'd love to wear a rainbow every day,
And tell the world that everything's OK,
But I'll try to carry off a little darkness on my back,
'Till things are brighter, I'm the Man In Black.

User avatar
amh
Posts: 32
Joined: Sun Mar 07, 2010 2:56 pm
Location: Greenville,DE

Post by amh » Fri Apr 02, 2010 11:45 pm

oh thanks. Yeah I do have a mac, I'll give i a try.

Post Reply

Return to “Bridges & Towers”