Towers B/C

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Crtomir
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Re: Towers B/C

Post by Crtomir » December 2nd, 2017, 6:50 am

Oh yes! You definitely need that horizontal compression piece between the legs of the base at the top of the base where they are closest together. We have been using 1/8 x 1/8 inch pieces cut from the same stock as the legs themselves for this. However, the compression force on this horizontal piece is not nearly as strong as the compression force on the legs themselves, so we could optimize it further by using a 1/8 x 1/8 inch piece of lower density than the legs.

I'm not exactly sure where our towers are breaking from. We need to take a slo-mo video to be sure. One time, it was because that horizontal compression piece I was just talking about was not cut at the correct angle to match up with the slope of the legs of the base. There was a tiny gap and eventually, the compression piece fell out. It became unattached from one of the base legs at the top of the base. Therefore, it is VERY important to get those horizontal compression pieces to fit snugly with the sloping legs of the base. Maybe we should have used a gusset or something like that. Not sure.

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Re: Towers B/C

Post by Balsa Man » December 2nd, 2017, 9:15 am

Crtomir wrote:Oh yes! You definitely need that horizontal compression piece between the legs of the base at the top of the base where they are closest together. We have been using 1/8 x 1/8 inch pieces cut from the same stock as the legs themselves for this. However, the compression force on this horizontal piece is not nearly as strong as the compression force on the legs themselves, so we could optimize it further by using a 1/8 x 1/8 inch piece of lower density than the legs.

I'm not exactly sure where our towers are breaking from. We need to take a slo-mo video to be sure. One time, it was because that horizontal compression piece I was just talking about was not cut at the correct angle to match up with the slope of the legs of the base. There was a tiny gap and eventually, the compression piece fell out. It became unattached from one of the base legs at the top of the base. Therefore, it is VERY important to get those horizontal compression pieces to fit snugly with the sloping legs of the base. Maybe we should have used a gusset or something like that. Not sure.
See post I just put up in the Wood thread - basic directions for putting together a safety cage- a way to stop/freeze everything at first failure, so you can see exactly what first failure is- where and what kind of break, with no secondary damage. High speed/slo-mo video can catch it only if where the failure happens is clearly in view, and you can't with one camera have all areas/sides of the tower in good clear view.... 8-)
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Re: Towers B/C

Post by baker » December 3rd, 2017, 9:28 am

I have a picture of a safety cage built out of 1x2 material. Is there a way to post a jpeg? It might even be something Balsa Man posted 10 years ago... Looks like a three legged Tee Pee.

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Re: Towers B/C

Post by Balsa Man » December 3rd, 2017, 1:21 pm

baker wrote:I have a picture of a safety cage built out of 1x2 material. Is there a way to post a jpeg? It might even be something Balsa Man posted 10 years ago... Looks like a three legged Tee Pee.
Wow, that does sound like my old 'safety tower' (Ver 1.0). I did post a pic (using in w/ a bridge as I recall). The problem with using a tripod like this for towers (and the reason for Ver 2.0) is that tower top is close to the top of the safety tower. Support for the load block is a single point hanger from top of tripod - it is short, and unless things are lined up perfectly, if tower starts to go, and load comes on the hanger, load block gets pulled to the side. New version eliminates that.

I share your frustration with us not being able to do attachments any more. A few months ago Bernard ....sounded like he intended to do a fix to restore the ability. I've grumbled about the need a couple of times since.....
Bernard, please, if it can be fixed, it would be much appreciated, and helpful to all.....
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Re: Towers B/C

Post by Unome » December 3rd, 2017, 1:33 pm

Balsa Man wrote:
baker wrote:I have a picture of a safety cage built out of 1x2 material. Is there a way to post a jpeg? It might even be something Balsa Man posted 10 years ago... Looks like a three legged Tee Pee.
Wow, that does sound like my old 'safety tower' (Ver 1.0). I did post a pic (using in w/ a bridge as I recall). The problem with using a tripod like this for towers (and the reason for Ver 2.0) is that tower top is close to the top of the safety tower. Support for the load block is a single point hanger from top of tripod - it is short, and unless things are lined up perfectly, if tower starts to go, and load comes on the hanger, load block gets pulled to the side. New version eliminates that.

I share your frustration with us not being able to do attachments any more. A few months ago Bernard ....sounded like he intended to do a fix to restore the ability. I've grumbled about the need a couple of times since.....
Bernard, please, if it can be fixed, it would be much appreciated, and helpful to all.....
Attachments work for me, but that could just be because I'm a mod. You could use an image sharing site (I prefer postimage) and post the link.
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Re: Towers B/C

Post by dholdgreve » December 4th, 2017, 5:57 am

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Re: Towers B/C

Post by dholdgreve » December 4th, 2017, 5:59 am

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Re: Towers B/C

Post by baker » December 4th, 2017, 2:18 pm

Balsa Man wrote:
baker wrote:I have a picture of a safety cage built out of 1x2 material. Is there a way to post a jpeg? It might even be something Balsa Man posted 10 years ago... Looks like a three legged Tee Pee.
Wow, that does sound like my old 'safety tower' (Ver 1.0). I did post a pic (using in w/ a bridge as I recall). The problem with using a tripod like this for towers (and the reason for Ver 2.0) is that tower top is close to the top of the safety tower. Support for the load block is a single point hanger from top of tripod - it is short, and unless things are lined up perfectly, if tower starts to go, and load comes on the hanger, load block gets pulled to the side. New version eliminates that.

I share your frustration with us not being able to do attachments any more. A few months ago Bernard ....sounded like he intended to do a fix to restore the ability. I've grumbled about the need a couple of times since.....
Bernard, please, if it can be fixed, it would be much appreciated, and helpful to all.....
That's the one, April 2009. Bridge with legs. An excellent design..

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Re: Towers B/C

Post by Crtomir » December 5th, 2017, 7:29 am

Balsa Man wrote:
Crtomir wrote:Oh yes! You definitely need that horizontal compression piece between the legs of the base at the top of the base where they are closest together. We have been using 1/8 x 1/8 inch pieces cut from the same stock as the legs themselves for this. However, the compression force on this horizontal piece is not nearly as strong as the compression force on the legs themselves, so we could optimize it further by using a 1/8 x 1/8 inch piece of lower density than the legs.

I'm not exactly sure where our towers are breaking from. We need to take a slo-mo video to be sure. One time, it was because that horizontal compression piece I was just talking about was not cut at the correct angle to match up with the slope of the legs of the base. There was a tiny gap and eventually, the compression piece fell out. It became unattached from one of the base legs at the top of the base. Therefore, it is VERY important to get those horizontal compression pieces to fit snugly with the sloping legs of the base. Maybe we should have used a gusset or something like that. Not sure.
See post I just put up in the Wood thread - basic directions for putting together a safety cage- a way to stop/freeze everything at first failure, so you can see exactly what first failure is- where and what kind of break, with no secondary damage. High speed/slo-mo video can catch it only if where the failure happens is clearly in view, and you can't with one camera have all areas/sides of the tower in good clear view.... 8-)
Thanks! That's a really great idea. I never even thought about it. Now I have a project for this weekend. :D

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Re: Towers B/C

Post by Snarknado » December 6th, 2017, 6:09 am

Raleway wrote:
WhatScience? wrote:
Random Human wrote: Point is, 1kg weight tower gets u at max 17 points.... which is (no offense) nothing.. and saw a hole through a solid block of wood and what you get is 1 kg.
Ya, if you can point me to a team that scored lower than 17 points at an competition (not practice or for fun) I will be amazed!!
I believe a team had a 1.4 kg tower that hit bonus and maxed out. That's about 12 points.
sciencepeeps wrote:
WhatScience? wrote:
Random Human wrote: Point is, 1kg weight tower gets u at max 17 points.... which is (no offense) nothing.. and saw a hole through a solid block of wood and what you get is 1 kg.
Ya, if you can point me to a team that scored lower than 17 points at an competition (not practice or for fun) I will be amazed!!
Let me tell you a story.
At the 2017 IL state competition, all of my events were extremely early. I knew that competitive towers teams like Marie Murphy, North Shore Country Day, and Woodlawn were going to be testing around this time, so I headed over to the Towers room. We had already tested and wanted to see our competition. Some teams had already tested, and I was just waiting around. From the back of the room, I heard “CAN WE TEST OUR TOWER?” I turned my head aound, and there it was. A tower that was almost a meter tall that must have been made out of the biggest balsa you could find anywhere. It wasn’t a solid block of wood or anything, and the people had obviously tried to build a tower, which was the worst part. Some of the pieces were literally falling off. They went to weigh their tower at the scale, which went up to 1 kg. The evenst supervisor said, “why don’t you guys go up to the other scale and weigh your tower,” meaning the scale they used to weight the SAND. Then they started testing their tower, which despite its bad quality, would probably hold the entire weight. But it DIDN’T. It broke with only half of the sand in the bucket. At the most.
That’s the story of how we saw a tower get an efficiency of 7 or less.
I haven't done the math, but based on my experiences, I'd say it certainly wasn't even made out of balsa, and was probably either a ridiculous number of Popsicle sticks or something more like this, albeit with wood glue.
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Something like that could've been made at the last minute by someone new who hadn't read the rules.
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