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Square Holes In Rims


rab shropshire
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do i not need to cut them out using a dremel and a small cutting disc or anything like that

how lomg is ages lol I have plenty of time on my hands as i am of work for 2 weeks

not sure, but you'd have to cut every hole, then file the corners so there rounded, I'd just leave it to be honest, or buy a new rim if you're that bothered.

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It takes a LONG time, if you use a file you need to make sure it is a good sharp one, Dremels can be ok, but not usualy strong enough. The other way is to drill the corners and then drill randomly and then reoved the aterial thats left with a file, as it will be quicker due to there being less material.

If you are me however, I use a illing machine, actualy did another rim today, took me about an 1.5hrs to square hole a rim from the std rim, the rim was a DX32 and the holes were 24 x 32mm, I have also single walled it and drilled the sidewalls, the rim started at 783g and it is now 515g, thats with eyelets too!!

Adam

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It takes a LONG time, if you use a file you need to make sure it is a good sharp one, Dremels can be ok, but not usualy strong enough. The other way is to drill the corners and then drill randomly and then reoved the aterial thats left with a file, as it will be quicker due to there being less material.

If you are me however, I use a illing machine, actualy did another rim today, took me about an 1.5hrs to square hole a rim from the std rim, the rim was a DX32 and the holes were 24 x 32mm, I have also single walled it and drilled the sidewalls, the rim started at 783g and it is now 515g, thats with eyelets too!!

Adam

We're not all lucky enough to have access to a milling machine :P

But yeah, you'd have to have a pretty decent dremel to actually get anywhere, and for the cost you might as well just buy a new rim

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even if the edges are all smooth, square holes still act as stress concentrators surely?

I'm aware having rounded corvers/edges helps, but isn't this the reason hatches etc on naval boats are typically elliptical/round?

Correct me if i'm wrong but the stress concentrators were first identified on battleships, when the gun size meant the firing shockwave passing through the ship was splitting the steel at the edge of sharp cornered deck hatches??

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even if the edges are all smooth, square holes still act as stress concentrators surely?

I'm aware having rounded corvers/edges helps, but isn't this the reason hatches etc on naval boats are typically elliptical/round?

Correct me if i'm wrong but the stress concentrators were first identified on battleships, when the gun size meant the firing shockwave passing through the ship was splitting the steel at the edge of sharp cornered deck hatches??

Then again, a gun is pretty powerful, especially one on a ship, so it might still destroy round-cornered rectangle holes.

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The highest profile case of failure from square edges was the De Havilland Comet, the first jet airliner made (And one of the best looking designs in commercial aviation). Thanks to the plane flying higher than other commercial planes of the time causing greater pressure changes, incorrect sealing on the windows and inaccurate stress concentration factor data, cracks formed at the window corners and eventually caused a number of planes to break apart in mid air. http://en.wikipedia.org/wiki/De_Havilland_Comet

If you're really worried about it look up formulae for stress concentration factors around holes and compare the round hole and square hole cases, but once you have a smooth radius rather than a sharp corner, the rim is pretty unlikely to fail. Also even if it does it'll probably be as likely to bend or fold on a landing due to reduced stiffness than crack at the corners of the rim holes. There's also every chance the peak stress in the rim is at the spoke hole anyway... I wouldn't do it because I'm just not that bored :)...

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