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Strength of bar?

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viktor
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Strength of bar?

Postby viktor » Wed May 16, 2007 12:48 pm

My '05 bar had gotten worn out in the center hole, i.e the plastic had been worn out. However, I had some replaceable ones from Wipika but they were slightly larger (about 1-1.5mm) in diameter), so I drilled out the hole and put them in.
How much does this effect the strength of the bar?

BigR
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Postby BigR » Wed May 16, 2007 2:46 pm

Put a new bar in a calibrated hydraulic press and increase pressure until it breaks then compare that figure with the one you get from repeating the procedure with your drilled out bar. Empirical testing will tell you what the new strength of the bar is.

Cabrinha has some great footage of stress testing their products on their Metropolis DVD

Nino_fs
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Postby Nino_fs » Wed May 16, 2007 4:43 pm

Since your running a line through the center of the bar which connects your chicken loop to your front lines.
You really do not need to worry about the strength of the bar. Because the only weight it is holding is the load from the rear lines which is quite small.

Also if I read correctly your new bar has a 1mm to 1.5mm larger diameter than your old bar. If they are made of the same material your new bar will be quite a bit stronger. That extra 1mm adds more strength than you would suspect because it is on the outside of the bar which is being bent by the loads.

Bending is proportional to area and distance that area is from the center of the bar. So you added extra area and you added more distance. You end up gaining twice.

Basically your fine. As long as your new bar is made of materials that are at least as strong as your old one.

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cglazier
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Postby cglazier » Wed May 16, 2007 5:05 pm

Bars break. I have seen several that failed under the severe loading caused in situations like when a kite suddenly powers up deep in the power zone.

Increasing the chicken loop hole size certainly weakens the bar. Who knows whether your bar will last. You may be OK in light wind.

:wink:
Chris Glazier


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