Bracing Pattern

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Re: Bracing Pattern

Post by Crtomir » April 25th, 2018, 1:01 pm

M017 wrote:I recently tried doing a tower with the P1 type bracing from the Wikipedia. It cut about 1 gram from our tower and it held about the same, also arranged it so there aren't any empty spots. Has anyone else tried this type?
What is P1 type bracing? I don't see it on Wikipedia.

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Re: Bracing Pattern

Post by jgrischow1 » April 25th, 2018, 3:18 pm

Crtomir wrote:
M017 wrote:I recently tried doing a tower with the P1 type bracing from the Wikipedia. It cut about 1 gram from our tower and it held about the same, also arranged it so there aren't any empty spots. Has anyone else tried this type?
What is P1 type bracing? I don't see it on Wikipedia.
I think he's referring to this https://scioly.org/wiki/index.php/Tower ... :_Bracings

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Re: Bracing Pattern

Post by cheese » April 25th, 2018, 3:40 pm

dholdgreve wrote:FWIW, I agree that having the top smaller than the bottom of the upper section is a good idea... but not for the same reasons cited... You can't state categorically that the legs will bow inward just because the top is smaller than the bottom of the chimney... It depends on what is happening between those 2 points. If the columns have a slight (1 mm) bow outward, that is all it takes to set the predisposed direction of the buckling. They will now bow outward, putting the bracing and ladders in tension, a very slight inward bow will predispose to compression. If you do a perfectly vertical SFPD, you will find that most columns will have a "preference" as to which way they intend on bowing under load. Mark this edge and factor this into your build. Also keep in mind that every time you add a ladder, you effectively separate the column into individual stacked columns. This can result with a sort of harmonic wave sort of pattern. Lets say you have 7 tiers of bracing, the middle tier (tier 4) may be predisposed to bow outward, forcing the tiers above and below (3 & 5) to bow inward, thus forcing tiers 1 and 7 to also bow outward. Each Ladder will in effect, function as a fulcrum,
Never really thought about that, I will keep that in mind as I do realize that when doing SFPD, there is always that side that wants to go.
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Re: Bracing Pattern

Post by MadCow2357 » April 25th, 2018, 3:42 pm

M017 wrote:I recently tried doing a tower with the P1 type bracing from the Wikipedia. It cut about 1 gram from our tower and it held about the same, also arranged it so there aren't any empty spots. Has anyone else tried this type?
I have used P1 bracing for my last 5 towers. I find P1 bracing easier to build than x bracing. :?:
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Re: Bracing Pattern

Post by Crtomir » April 26th, 2018, 4:37 am

jgrischow1 wrote:
Crtomir wrote:
M017 wrote:I recently tried doing a tower with the P1 type bracing from the Wikipedia. It cut about 1 gram from our tower and it held about the same, also arranged it so there aren't any empty spots. Has anyone else tried this type?
What is P1 type bracing? I don't see it on Wikipedia.
I think he's referring to this https://scioly.org/wiki/index.php/Tower ... :_Bracings
Okay, thanks. Evidently, we have been using the P7 bracing pattern for the bottom base part and the P5 bracing pattern for the top chimney part. This is for Div-B though. We have been scoring over 3000 at the last few competitions.

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Re: Bracing Pattern

Post by MadCow2357 » April 26th, 2018, 7:58 am

Crtomir wrote:
jgrischow1 wrote:
Crtomir wrote:
What is P1 type bracing? I don't see it on Wikipedia.
I think he's referring to this https://scioly.org/wiki/index.php/Tower ... :_Bracings
Okay, thanks. Evidently, we have been using the P7 bracing pattern for the bottom base part and the P5 bracing pattern for the top chimney part. This is for Div-B though. We have been scoring over 3000 at the last few competitions.
The wiki mentions that other bracing types like P7 "v" bracing do not usually score as high as other towers with different bracings. Why did you guys choose P7 for the bottom part? It would seem like the ladders would break in the middle because of the diagonal members transferring significant amounts of force onto the ladder members.
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Re: Bracing Pattern

Post by Crtomir » April 26th, 2018, 11:38 am

MadCow2357 wrote:
Crtomir wrote: Okay, thanks. Evidently, we have been using the P7 bracing pattern for the bottom base part and the P5 bracing pattern for the top chimney part. This is for Div-B though. We have been scoring over 3000 at the last few competitions.
The wiki mentions that other bracing types like P7 "v" bracing do not usually score as high as other towers with different bracings. Why did you guys choose P7 for the bottom part? It would seem like the ladders would break in the middle because of the diagonal members transferring significant amounts of force onto the ladder members.
Good question!

If you can, try to download the "Truss Me!" app: http://www.scientificmonkey.com/software.html
That's probably the easiest way to play around with different bracing patterns. You can do that in "Freestyle" mode. It's only 2D, but you can learn a lot. (Good for Mystery Architecture too!)

What you want to do is construct a trapezoidal tower base (just 2D remember). The main legs will be bigger (thicker). You will need a tension piece at the bottom and a compression piece at the top. You will find that with the P7 "V" bracing, you can get the braces to be really thin and have almost no force on them. They are effectively zero-force members. That means you can make your braces super thin and light and still have them do what you need them to do.

You can experiment with all sorts of bracing systems to see which one you like. You will enjoy watching this video comparing bridge truss systems https://www.youtube.com/watch?v=oL-39NZJmhI

See how thin you can make the members and hold all the weight. The app will tell you which member is most likely to fail and roughly how much force is on each member and if it is tension (red) or compression (blue). The darker the color, the more force.

There is a "Challenges" section which is fun to play as well.

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Re: Bracing Pattern

Post by stevepilot » May 10th, 2018, 6:47 pm

I just tested a tower with a P7 base, and found that the ladders towards the middle of the base bowed significantly and broke quite promptly. Have you also observed this? I used 1/32*1/16 for the ladder and 1/16*1/16 for the "crosses"
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Re: Bracing Pattern

Post by M017 » May 10th, 2018, 8:12 pm

stevepilot wrote:I just tested a tower with a P7 base, and found that the ladders towards the middle of the base bowed significantly and broke quite promptly. Have you also observed this? I used 1/32*1/16 for the ladder and 1/16*1/16 for the "crosses"
If I ever do ladders I do 1/8 pieces on butt joints. Try to use thicker pieces like 3/32 and put it on the inside of your columns

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Re: Bracing Pattern

Post by M017 » May 10th, 2018, 8:20 pm

Crtomir wrote:
jgrischow1 wrote:
Crtomir wrote:
What is P1 type bracing? I don't see it on Wikipedia.
I think he's referring to this https://scioly.org/wiki/index.php/Tower ... :_Bracings
Okay, thanks. Evidently, we have been using the P7 bracing pattern for the bottom base part and the P5 bracing pattern for the top chimney part. This is for Div-B though. We have been scoring over 3000 at the last few competitions.
I had a 1628 tower with p1 on top and all x's on bottom, expecting a 2100 score at nationals because we went from 11.5g to 8.8g
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