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Re: Towers B/C

Posted: April 23rd, 2017, 8:55 am
by Balsa Man
musical_whang wrote:Thank you! I will definitely enjoy off-season and I'm looking forward to next year! I will come back to this forum again and keep on building knowledge about this event.

Side note, I see that Nationals in 2018 will be held in Fort Collins! Are you going to go there and volunteer or just watch some of the building events?
For sure plan on being there. Role yet to be determined. Last time I made it to Nationals was in 2005; it was a blast.
Hope your team can make it; it would be great to meet. Good luck.

Re: Towers B/C

Posted: April 23rd, 2017, 9:12 pm
by Random Human
Balsa Man wrote:
musical_whang wrote:Thank you! I will definitely enjoy off-season and I'm looking forward to next year! I will come back to this forum again and keep on building knowledge about this event.

Side note, I see that Nationals in 2018 will be held in Fort Collins! Are you going to go there and volunteer or just watch some of the building events?
For sure plan on being there. Role yet to be determined. Last time I made it to Nationals was in 2005; it was a blast.
Hope your team can make it; it would be great to meet. Good luck.
Yeah... would be an honor to meet you Len!

Re: Towers B/C

Posted: April 24th, 2017, 5:57 pm
by musicalwhang
Oh cool! I found a vid of tower performing at states
The vid was kinda taken far away but from what I see, I think that the bucket was tipping towards the person stabilizing before loading. That's why the leg on the right side was the one to break first.
https://drive.google.com/file/d/0B1BYt2 ... sp=sharing
What do you think?

Re: Towers B/C

Posted: April 25th, 2017, 5:54 am
by dholdgreve
musical_whang wrote:Oh cool! I found a vid of tower performing at states
The vid was kinda taken far away but from what I see, I think that the bucket was tipping towards the person stabilizing before loading. That's why the leg on the right side was the one to break first.
https://drive.google.com/file/d/0B1BYt2 ... sp=sharing
What do you think?
So long as the chain remains perfectly vertical, the rotation of the bucket will have no impact on the how the load is distributed to the columns. The bucket is connected to the loading block by a single chain. A tipped bucket cannot pull harder on one side of the chain than the other. ... Now, if somehow the bucket were connected to the loading block via two chains and two eye hooks, and the sand were loaded more on one side of the bucket than the other, I'd buy that the loads could be different... So what if the bucket had 2 chains connected to the same eye hook? Again, a tipped bucket would make no difference to the balance of the loads.

Re: Towers B/C

Posted: April 27th, 2017, 7:37 pm
by Juanyjose
I was in the habit of always lightly sanding structures after I was done building when bridge building was around, to try to get off another 0.2 grams or something. How significantly does this impact the structural integrity of a tower/bridge, and are 0.2 grams worth it once you get down to really low densities?

Re: Towers B/C

Posted: April 28th, 2017, 5:37 am
by dholdgreve
Juanyjose wrote:I was in the habit of always lightly sanding structures after I was done building when bridge building was around, to try to get off another 0.2 grams or something. How significantly does this impact the structural integrity of a tower/bridge, and are 0.2 grams worth it once you get down to really low densities?
Every little bit helps, especially in the highly contested tournaments, but the problem with sanding towers, is that it is probable that you end up sanding that .2 grams off the column area between where the X braces are connected.... If you were able to detail the columns to 100% efficiency, they would probably be square and smaller at the connection to the X braces and taper up to bigger and round at the exact center between the X brace connections, then taper back down to a square at the connection above. This would be done to withstand the buckling that tends to occur between connections. If you try to sand the tower after it is built, you end up taking the material from the exact wrong spots, and in all likelihood will lower your final score. You are far better to select the material you want to use as columns, then very gently, sand all 4 of the corners of each column, just enough to take the sharp edge off before beginning assembly.

In THEORY the most efficient column would be round, but that reduces the surface area used to glue the X braces to, causing additional issues, so most use square columns (with a few triangles) to get the surface area needed.

Re: Towers B/C

Posted: April 28th, 2017, 12:04 pm
by Juanyjose
dholdgreve wrote:
Juanyjose wrote:I was in the habit of always lightly sanding structures after I was done building when bridge building was around, to try to get off another 0.2 grams or something. How significantly does this impact the structural integrity of a tower/bridge, and are 0.2 grams worth it once you get down to really low densities?
Every little bit helps, especially in the highly contested tournaments, but the problem with sanding towers, is that it is probable that you end up sanding that .2 grams off the column area between where the X braces are connected.... If you were able to detail the columns to 100% efficiency, they would probably be square and smaller at the connection to the X braces and taper up to bigger and round at the exact center between the X brace connections, then taper back down to a square at the connection above. This would be done to withstand the buckling that tends to occur between connections. If you try to sand the tower after it is built, you end up taking the material from the exact wrong spots, and in all likelihood will lower your final score. You are far better to select the material you want to use as columns, then very gently, sand all 4 of the corners of each column, just enough to take the sharp edge off before beginning assembly.

In THEORY the most efficient column would be round, but that reduces the surface area used to glue the X braces to, causing additional issues, so most use square columns (with a few triangles) to get the surface area needed.
So in theory it is a good idea if you do it in the right spots and don't over do it

Re: Towers B/C

Posted: April 28th, 2017, 3:23 pm
by cheese
Hey all, guess what! this is the 3000th building forum post! Wow! Also if anyone has a 3d printer and wants to print a balsa stripper, this file works: https://drive.google.com/open?id=0B4WYI ... FVySFJJUWM

Re: Towers B/C

Posted: May 1st, 2017, 5:29 am
by dholdgreve
Juanyjose wrote:
dholdgreve wrote:
Juanyjose wrote:I was in the habit of always lightly sanding structures after I was done building when bridge building was around, to try to get off another 0.2 grams or something. How significantly does this impact the structural integrity of a tower/bridge, and are 0.2 grams worth it once you get down to really low densities?
Every little bit helps, especially in the highly contested tournaments, but the problem with sanding towers, is that it is probable that you end up sanding that .2 grams off the column area between where the X braces are connected.... If you were able to detail the columns to 100% efficiency, they would probably be square and smaller at the connection to the X braces and taper up to bigger and round at the exact center between the X brace connections, then taper back down to a square at the connection above. This would be done to withstand the buckling that tends to occur between connections. If you try to sand the tower after it is built, you end up taking the material from the exact wrong spots, and in all likelihood will lower your final score. You are far better to select the material you want to use as columns, then very gently, sand all 4 of the corners of each column, just enough to take the sharp edge off before beginning assembly.

In THEORY the most efficient column would be round, but that reduces the surface area used to glue the X braces to, causing additional issues, so most use square columns (with a few triangles) to get the surface area needed.
So in theory it is a good idea if you do it in the right spots and don't over do it
As I mentioned in the quote above, the only areas accessible after the tower is completely assembled are the ares you really don't want to sand. The areas that could be sanded are buried behind the X braces. Attempting to sand these areas could very likely result in more harm than good, if you happen to know one of the braces and crack a glue joint or damage the grain of a brace. If your tower is truly competitive (less than 6 grams), the braces are so delicate, they won't take much "abuse." Far better to plan ahead, and sand the areas that should be sanded before assembly.

Re: Towers B/C

Posted: May 1st, 2017, 6:01 am
by Juanyjose
dholdgreve wrote:
Juanyjose wrote:
dholdgreve wrote:
Every little bit helps, especially in the highly contested tournaments, but the problem with sanding towers, is that it is probable that you end up sanding that .2 grams off the column area between where the X braces are connected.... If you were able to detail the columns to 100% efficiency, they would probably be square and smaller at the connection to the X braces and taper up to bigger and round at the exact center between the X brace connections, then taper back down to a square at the connection above. This would be done to withstand the buckling that tends to occur between connections. If you try to sand the tower after it is built, you end up taking the material from the exact wrong spots, and in all likelihood will lower your final score. You are far better to select the material you want to use as columns, then very gently, sand all 4 of the corners of each column, just enough to take the sharp edge off before beginning assembly.

In THEORY the most efficient column would be round, but that reduces the surface area used to glue the X braces to, causing additional issues, so most use square columns (with a few triangles) to get the surface area needed.
So in theory it is a good idea if you do it in the right spots and don't over do it
As I mentioned in the quote above, the only areas accessible after the tower is completely assembled are the ares you really don't want to sand. The areas that could be sanded are buried behind the X braces. Attempting to sand these areas could very likely result in more harm than good, if you happen to know one of the braces and crack a glue joint or damage the grain of a brace. If your tower is truly competitive (less than 6 grams), the braces are so delicate, they won't take much "abuse." Far better to plan ahead, and sand the areas that should be sanded before assembly.
Okay, thank you for the advice!