# Thread: help needed i am banging my head of a wall

1. ## help needed i am banging my head of a wall

hey guys a great first post but here goes

I am trying to calculate a bending moment and work out displacement and strains on a project and figures just are not working out

the design

it is 25mm long and 35mm wide and 4mm thick with a rectangular hole in the middle 17mm long and 27mm wide
so basically it is a 4mm X 4mm cross section with 4 beams and the outside dimensions as specified above.
it is basically a cantilever with one of the 35mm sides in a wall

now here is my problem if you think of this in the x plane and i exert a 10n force in the negative z direction what do i take for my i value. do i use the 4x4 cross section and double it because there are 2 beams running out. i'm completely lost

and also if ya put a force of 10 n at the most outward tip in the y direction what do i take as the second moment of are for that???????

any help will be brilliant thanks guys
andy

2. Maybe part of your problem is that you think you can clearly describe this setup using only words. I read thru it 4 times and all I can say is I am thoroughly confused. No insult meant to you, as a first time poster, but it amazes me how many folks that call themselves engineers don't fully understand rule #1 - a picture is worth a thousand words. Post your setup, your cross sections, your loading, as images. Here's the deal: words like "wide", "thick", "long", even the word "beam", they mean different things to different people.

3. JB +1

Sorry CD, I am confused too. Sketch it, take a pic or scan it and then post it here.

4. dude.jpg

here hope this goes up two forces not acting together both to be worked out seperately any help or suggestions would be great

5. ## Alternative methods

Originally Posted by confused_dude
dude.jpg

here hope this goes up two forces not acting together both to be worked out seperately any help or suggestions would be great
FYI, if you can't upload images in the future, create a flickr account and upload them there and include a link.

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