Maths Question

[craig51]

Heres one for you all.

I have a VERY heavy base used to hold up a table umbrella for when its sunny. The base has a round hole for the umbrella to lock into.

I want to use this base as part of a bird feeder, as it wont be blown over the place etc.

Is there a way to work out what size of square wood would fit in a round hole if I knew the diameter of the hole????

Ie if the diameter was 10cm, then the piece of wood couldnt bebigger than 6cm x 6cm.

 

[AndrewSchofield]

I think you can do the following:-

Square the diameter of the circle (so 10cm dia squared would equal 100)

Divide this by two ( = 50)

And then find the square root of this (=7.07)

Square piece of wood 7.07cm x 7.07cm would fit inside a 10cm dia hole.

I'm pretty sure thats correct??

 

[Shytalkz]

Bit long-winded

Diameter/1.414 is much quicker

 

[AndrewSchofield]

Ok, Ok, well played Shytalkz - sometime its nice to take the scenic route though!

 

[jefoss]

cement into the ground

 

[stevebamford]

Try a round bit of wood ?

Just a though

 

[^woody^]

Using Pythagoras, the diameter of the hole is the hypotenuse of a triangle with two other equal sides - which are the length of the sides of the square timber.

So square the diameter, then divide this by 8 to get the length of the side of the triangle/side of the timber

 

[craig51]

Cheers all for the help.

MY GF however thinks if i measure from the left top corner to the bottom right corner (cross section of wood), this should be equal to the diameter of the hole, so i would buy a pice of wood with a slightly shorter cross-section that the diamter of the hole.

Is she right???

 

[2scoops0406]

How about a slightly oversized piece of wood that is slightly tapered ?

 

[^woody^]

Is she right???

No, GF's are always wrong.

The wood needs to be the length of a chord of the circle, which is less than the diameter

 

[Shytalkz]

Using Pythagoras, the diameter of the hole is the hypotenuse of a triangle with two other equal sides - which are the length of the sides of the square timber.

So square the diameter, then divide this by 8 to get the length of the side of the triangle/side of the timber

So that's 100/8 = 12.5: uhurrrrrrr somehow, you've made a side longer than the hypotenuse teehee.

 

[big-all]

no good getting a bit of wood that just fits in you need a bigger contact area

the small contact area of a corner will soon compress and loosen off causing it to lean or move

in this instance a 3" post at 76mm would be perfect by the time youve wittled away the corners to fit you will have around a 10mm contact area that will be less likly to cause problems

 

[Shytalkz]

Ah but Big, now you're changing the question!

 

[Bilioustrumpstaine]

You can't put a square peg in a round hole.

 

[gcol]

Throw the base away and just make a cross foot out of timber. Oh and while you're at it.... give your Doris a back hander for speaking without being spoken to.