Bracing

Sgt Evans
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Re: Bracing

Post by Sgt Evans » February 18th, 2011, 1:27 pm

What type of bracing r u using???

sciolyswizzle16
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Re: Bracing

Post by sciolyswizzle16 » February 19th, 2011, 9:51 am

would you guys suggest using both end joints and lap joints when bracing a tower?
for example, using end joints on the horizontal pieces connecting the top of the tower and the bottom of the tower then using lap joints for the rest of the bracing?
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Forestry (2nd at regionals) (1st at states)
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12thomasal
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Re: Bracing

Post by 12thomasal » February 19th, 2011, 3:03 pm

slm, If I tilt the chimney section, does that reduce the swaying factor

SLM
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Re: Bracing

Post by SLM » February 19th, 2011, 3:32 pm

12thomasal wrote:slm, If I tilt the chimney section, does that reduce the swaying factor
No. The compression force in the chimney increases as the tilt angle increases. The sidesway of the chimney frame is directly proportional to the intensity of the axial force in the compression members: the larger the force the more the frame would displace. So, tilting a chimney frame actually increases the sidesway of the frame.

However, (1) the sidesway is very small to begin with, so it should not be of a major concern for most tower, and (2) the tilt angle is very small (in our case about 4 degrees), so its impact on the behavior of the tower is insignificant.

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Re: Bracing

Post by SLM » February 19th, 2011, 5:35 pm

sciolyswizzle16 wrote:would you guys suggest using both end joints and lap joints when bracing a tower?
for example, using end joints on the horizontal pieces connecting the top of the tower and the bottom of the tower then using lap joints for the rest of the bracing?
It can certainly be done that way. Although, you need to pay extra attention when constructing a butt joint; you need to make sure that either end of the horizontal piece is completely flat and parallel to the member it is being glued to (you want to avoid any gaps between the two pieces).

We've found that most of the time lap joints work very well even for horizontal pieces. They are easy to construct and, in most cases, their construction doesn't require a lot of precision.

sciolyswizzle16
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Re: Bracing

Post by sciolyswizzle16 » February 20th, 2011, 7:04 am

thanks SLM, i definitely will consider that
Events for 2011-2012
Forestry (2nd at regionals) (1st at states)
Chem Lab (1st at regionals) (6th at states)
Towers (8th at regionals) (10th at states)
Team (1st at regionals) (3rd at states)

yousef213
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Re: Bracing

Post by yousef213 » February 23rd, 2011, 4:11 am

on the base of the tower, or any part really,, could you skip the horizontal pieces between the x bracings, or would that weaken it significantly?
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jander14indoor
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Re: Bracing

Post by jander14indoor » February 23rd, 2011, 10:21 am

yousef213 wrote:on the base of the tower, or any part really,, could you skip the horizontal pieces between the x bracings, or would that weaken it significantly?
Probably not, especially the bottom.
Key failure mode on bottom is legs spreading out (especially on a smooth surface, common in contest test setups), increasing bending load and causing premature failure or tip over. Need horizontal members around the bottom to constrain this.

Probably not on top either unless the angled pieces are fairly horzontal anyway. Again, you want to prevent the uprights from bowing out (or in) as well as sideways, and an occasional horizontal strip is an efficient way to do that.

Note, on SLM's diagrams above, the uprights without horizontal cross bars tend to bow out, those with tend to tilt.

Jeff Anderson
Livonia, MI

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deezee
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Re: Bracing

Post by deezee » February 27th, 2011, 2:14 pm

i didnt have horizontal bracing, and I did better than when I had :) efficiency of 21
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Re: Bracing

Post by TYG » February 27th, 2011, 2:49 pm

deezee wrote:i didnt have horizontal bracing, and I did better than when I had :) efficiency of 21
Was it able to hold all 15kg?

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