Circles, Trigonometry, Maths thing type Question

[User]

 

[Sea of vapours]

It's because a triangle where all the sides are the same length has angles of sixty degrees. So making the compasses' spacing equal to the radius means that the points you mark around the outside have to be the same distance apart as the radius and the inner angle, at the centre, will be sixty degrees. Neat, isn't it.

 

[slowmotion]

If you have the centre of the circle as one point, each pair of "tics" on the circle form the three points of an equilateral triangle. Each angle on an equilateral triangle has to be 60 degrees. All the sx tics form six such triangles. Six times 60 equals 360 degrees......one circle .

Edit: cross post with Sea of Vapours!

 

[ColinJ]

I didn't actually know that but I read the first post, thought about it, and came to the same conclusion as SoV, but didn't spot his post until I scrolled down.

Yes, that IS neat.

I like the idea of making one's own tools. I have made some which worked, and some which didn't.

 

[Aperitif]

I didn't actually know that but I read the first post, thought about it, and came to the same conclusion as SoV, but didn't spot his post until I scrolled down.

Yes, that IS neat.

I like the idea of making one's own tools. I have made some which worked, and some which didn't.

I know many people who have made themselves tools (self included)...and never recovered.

 

[Yellow Saddle]

Nice tool.

 

[subaqua]

https://www.mathsisfun.com/geometry/circle-theorems.html also helps people understand circles.

and triangles

and other quadrilaterals

have really enjoyed helping my eldest with her GCSE maths as its made me drag stuff out of the back of my brain.

 

[Levo-Lon]

No cheap cheesy tools when you get your tool making head on @User9609

 

[twentysix by twentyfive]

[QUOTE 4352312, member: 9609"]wonderful satisfaction when they do work,[/QUOTE]
Can't quite see how that worked. And did you tap that thread?

 

[subaqua]

[QUOTE 4352312, member: 9609"]I knew there was going to be a very simple explanation to this, I had got it into my head that the proof had something to do with Chords and Pi and once sidetracked I was never going to get it. Daft thing is I knew it needed to be 60 degrees and I know what equilateral triangles are - just didn't see the obvious connection



wonderful satisfaction when they do work, but I have certainly wasted much time making stuff that doesnt work. It was worth it in this case, the proper tool was going to be £18 plus 3 or 4 days for delivery. It was free to make from bits and pieces lying about in the garage, probably took me less than an hour - Pity I will only ever use it twice, the replacement BB is Shimano and I have the proper tool for that.[/QUOTE]


I welded some angle iron and a M14 nut together to make a tool for a hub on a Renault many many years ago. I watched wheeler dealers on Sunday and watched Edd China make the same for a Renault alpine hub !

 

[Andy_R]

I welded some angle iron and a M14 nut together to make a tool for a hub on a Renault many many years ago. I watched wheeler dealers on Sunday and watched Edd China make the same for a Renault alpine hub !

Just goes to show there are still some mechanics out there. They just don't work at any of your local franchises - they're all "technicians"....

 

[ColinJ]

Can't quite see how that worked.

The insides of the 6 bolts would fit into the 6 curved indents on the BB cup. I don't know what the tapped thread is for though.

 

[Yellow Saddle]

The insides of the 6 bolts would fit into the 6 curved indents on the BB cup. I don't know what the tapped thread is for though.

My guess is that the hole was in the plate before he started and it just happened to be threaded, albeit it looks like a duffed thread. He needed a hole of sorts for the end to go through and in his scrap heap was a piece of mild steel with a hole in the right place.
@User9609, am I right or wrong?

 

[twentysix by twentyfive]

The insides of the 6 bolts would fit into the 6 curved indents on the BB cup. I don't know what the tapped thread is for though.

My guess is that the hole was in the plate before he started and it just happened to be threaded, albeit it looks like a duffed thread. He needed a hole of sorts for the end to go through and in his scrap heap was a piece of mild steel with a hole in the right place.
@User9609, am I right or wrong?

Yep - got the bolts thing. It was the thread that I was wondering about....

 

[twentysix by twentyfive]

Superb @User9609 . Recycling hole saws as tapping tools