Elevated Bridge B/C

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Littleboy
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Re: Elevated Bridge B/C

Postby Littleboy » May 24th, 2010, 4:00 pm

what state are they from

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Re: Elevated Bridge B/C

Postby tennisgal » May 24th, 2010, 6:32 pm

First of all, I would like to thank RJM for aiding me the second time at Nationals. I truly appreciate his kindness and willingness to help those who do not have a partner. It was nice to have someone helping you during a stressful time knowing they won't mess up your bridge. So thanks again.
Second, Congrats to all competitors, especially the team from Pennsylvania, which I barely beat. In my opinion, that margin was too close for comfort. Such intense competition.

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Re: Elevated Bridge B/C

Postby rjm » May 24th, 2010, 7:07 pm

Glad to help. I helped three or four teams where the competitor had no partner; all I offer to do is steady the bridge or bucket while the competitors set up and load. It is our opinion as judges that the point of the competition is to see how well your bridges perform, not to see whether teams can cope with the testing apparatus. I don't believe such help gives any kind of advantage to a team, we are really correcting a problem caused by the testing apparatus. We will only do exactly what the competitors ask and no more.

One of the inherent problems with the sand hopper testers is that the flow of sand sets up movement in the bucket which can have disastrous effect on a structure. It's bad because it puts a competitor at a disadvantage if he or she is testing alone, and it places the team member who is steadying the bucket close to the bucket, block, and structure when they break and so there is more exposure to the possibility of being hit by wood or even the block. I don't think it's extremely risky, but it's there. Often we advise kids to let go of the bucket after about a third of the sand is in, because it becomes very stable, but sometimes kids have inadvertently pulled the bucket off center and letting go causes a swing.

On the plus side, the sand flows completely out in 23 to 25 seconds with a smooth, constant flow with the gate wide open. We time the testers at the beginning of the day to make sure there is nothing wrong with the sand or the chute, and we want to be sure all testers work the same.

Bob Monetza
Grand Haven, MI

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Re: Elevated Bridge B/C

Postby lllazar » May 24th, 2010, 7:26 pm

First of all, I would like to thank RJM for aiding me the second time at Nationals. I truly appreciate his kindness and willingness to help those who do not have a partner. It was nice to have someone helping you during a stressful time knowing they won't mess up your bridge. So thanks again.
Second, Congrats to all competitors, especially the team from Pennsylvania, which I barely beat. In my opinion, that margin was too close for comfort. Such intense competition.
Hey are you the girl from Wichita? Nice job at nats, i was actually watching you test...i was talking to your coach while you were testing and he said your bridge was 7.23 grams, but i guess the humidity that day added .1 grams...i hate when that happens -_- And did you do the bridge alone througout the season or did ur partner, if you had one, have other timing conflicts? It was nice of rjm to help you out...for state, i actually didn't have a partner so i asked a teammate who had a free time slot at the bridge time and he had calm hands so it went well...

Btw was ur bridge all balsa? Congratulations again at nats...i wish i could have competed, o well :(

And rjm, since ur a judge for bridge, maybe u know about the balsa event next year? The general con-census on the forum has been Towers, can i get the opinion of a sci oly official? :)
2011 Season Events~

Fossils (Regionals ~1st) (State ~6th)
Towers (Regionals ~1st) (State ~3rd)
Helicopter (Regionals -3rd gahhh) (State ~5th)
Wind Power (Regionals ~1st) (State ~3rd TIERED!)

Hooray for getting everything i wanted?

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Re: Elevated Bridge B/C

Postby nejanimb » May 24th, 2010, 8:33 pm

First of all, I would like to thank RJM for aiding me the second time at Nationals. I truly appreciate his kindness and willingness to help those who do not have a partner. It was nice to have someone helping you during a stressful time knowing they won't mess up your bridge. So thanks again.
Second, Congrats to all competitors, especially the team from Pennsylvania, which I barely beat. In my opinion, that margin was too close for comfort. Such intense competition.
Congrats again to you - I was very glad to meet you. Your bridge was fantastic - well designed and it seemed extremely intricate.

Pictures of ours (from this year and last) are now up in the image gallery.

http://gallery.scioly.org/categories.php?cat_id=66
Harriton '10, UVA '14
Event Supervisor in MA (prev. VA and NorCal)

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Re: Elevated Bridge B/C

Postby jander14indoor » May 25th, 2010, 3:44 am

Towers next year for sure, probably new scoring equation, still efficiency, more emphasis on weight held.

New score equals weight held squared over mass of bridge. Still max 15 kilo load. Goal is to motivate students to get closer to 15 kilo capacity.

Jeff Anderson
Livonia, MI

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Re: Elevated Bridge B/C

Postby eta150 » May 25th, 2010, 4:20 am

YES! that's awesome!
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Re: Elevated Bridge B/C

Postby bridgebuilder25 » May 25th, 2010, 7:23 am

That really is great. I've been wanting them to do that for a while.
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Re: Elevated Bridge B/C

Postby tennisgal » May 25th, 2010, 7:37 am

First of all, I would like to thank RJM for aiding me the second time at Nationals. I truly appreciate his kindness and willingness to help those who do not have a partner. It was nice to have someone helping you during a stressful time knowing they won't mess up your bridge. So thanks again.
Second, Congrats to all competitors, especially the team from Pennsylvania, which I barely beat. In my opinion, that margin was too close for comfort. Such intense competition.
Hey are you the girl from Wichita? Nice job at nats, i was actually watching you test...i was talking to your coach while you were testing and he said your bridge was 7.23 grams, but i guess the humidity that day added .1 grams...i hate when that happens -_- And did you do the bridge alone througout the season or did ur partner, if you had one, have other timing conflicts? It was nice of rjm to help you out...for state, i actually didn't have a partner so i asked a teammate who had a free time slot at the bridge time and he had calm hands so it went well...

Btw was ur bridge all balsa? Congratulations again at nats...i wish i could have competed, o well :(

And rjm, since ur a judge for bridge, maybe u know about the balsa event next year? The general con-census on the forum has been Towers, can i get the opinion of a sci oly official? :)

Yep, I'm the girl from Wichita and thanks. I actually have competed alone in this event since mid-Sophomore year (I'm currently a Junior, becoming a Senior). Because other partners have not been able to put the same amount of time in the event as I have, my coaches did not think it would be fair to have both of us in the event. So, I haven't had a partner since State 2009.
No, my bridge is not all balsa. It's a mix of balsa and bass. :)

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Re: Elevated Bridge B/C

Postby Balsa Man » May 25th, 2010, 9:27 am

Well, congratluations to the top 10 in both divisions - very well done; and particularly to the top 3 in B and top 4 in C; very, very well done!
Why top 3/top 4? You get an interesting picture when you run the average of top 10 scores, and then look at results as a percentage of the top 10 average.
Not surprised to see B efficiencies about 15% ahead of C; B span is 78% of C (=less wood), truss forces in B a bit higher (= stronger/denser wood); 15% makes sense.
While there's a notable gap in C from 4th to 5th, 5th thru 10th fall off less rapidly than in B - building experience/skills showing, perhaps.
And as a percent of top 10 average, the winners in both divisions essentially dead equal

Div B % of AVG
1- 2734 147.0%
2- 2409 129.6%
3- 2104 113.2%
4- 1926 103.6%
5- 1872 100.7%
6- 1671 89.9%
7- 1602 86.2%
8- 1438 77.3%
9- 1422 76.5%
10- 1415 76.1%
AVG 1859.3

B Avg to C Avg 114.6%

Div C % of AVG
1- 2379 146.7%
2- 2012 124.0%
3- 2005 123.6%
4- 1837 113.2%
5- 1360 83.8%
6- 1347 83.0%
7- 1339 82.5%
8- 1332 82.1%
9- 1306 80.5%
10- 1304 80.4%
AVG 1622.1

So, on to towers next year. Like the new scoring approach, if that's how it comes down.
Again, congrats to all.
Len Joeris
Fort Collins, CO

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Re: Elevated Bridge B/C

Postby nejanimb » May 25th, 2010, 9:55 am

Thanks BalsaMan! I saw Poudre got something back in the 50s... Are you privvy to what happened? I would guess that's a Tier 2...
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Re: Elevated Bridge B/C

Postby Balsa Man » May 25th, 2010, 12:17 pm

Thanks BalsaMan! I saw Poudre got something back in the 50s... Are you privvy to what happened? I would guess that's a Tier 2...
Uh, yeah, that's a big 10-4 on the Tier 2 for Poudre. I was really sorry to hear about it. They are our big cross-town rival, but once State's done, we're always glad to help them for nats. We made our jigs/tools available, and broken regional bridge to see construction detail. Went through wood specs for each of the pieces, passed on some wood left over. We also passed on the height gauge, span gauge, and clearance block I'd made for Regional & State Bridge judges to use - which I know were accurate. From e-mail with their coach, and a very brief phone discussion with their builder:
After building, a) when they got there, it had a significant weight gain (fm 12.4 to 13....1 or 2) b)they checked height with a ''cheap" ruler, read it as too tall, sanded a fair amount off the top, and still measured 20.05 at check in, and weren't allowed to withdraw/sand to fix-Tier 2. The top sanding apparently thinned the top enough to cause it to fail at around 8.7kg. What I don't know is why they didn't do leg end sanding (as opposed to top side) - unless they put the main tension members on a bit low, and didn't have room. The MTMs are the only piece the jig doesn't ....."lock-in"; there are only marks for alignment. One of the tricks on this design I'd alluded to, but hadn't spelled out, is putting the MTMs on pre-stressed. On an aluminum bar with little ears, both strips get put on one end, then you pull 11kg of tension (which stretches them about 1.3mm), and glue the other end down. They twang like guitar strings. That bar with the MTMs on it slides onto the underside, and you glue where it crosses the "main joint." When you cut the MTMs outside the ends of the bar, it pulls the sides in, putting in the unloaded deformation I'd discussed earlier. A definate possibility they didn't push it far enough up when building.

I was very happy about how the girls from Preston (Jr High from Fort Collins) did in B -13th; their best event. It was a B-configuration of our last year's bridge; same basic tooling approach.
Len Joeris
Fort Collins, CO

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Re: Elevated Bridge B/C

Postby nejanimb » May 25th, 2010, 12:25 pm

Gotcha. Shame about Poudre - very unfortunate. We were extra, extra conservative on staying within specs; at least a couple millimeters at all sides. Are you still thinking you'll put up pictures of your design? It's cool that the image gallery is now populating itself with more photos with everyone being done.
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Re: Elevated Bridge B/C

Postby Balsa Man » May 25th, 2010, 12:53 pm

Gotcha. Shame about Poudre - very unfortunate. We were extra, extra conservative on staying within specs; at least a couple millimeters at all sides. Are you still thinking you'll put up pictures of your design? It's cool that the image gallery is now populating itself with more photos with everyone being done.
Yes on the pics. I'm going to ask my (more digitally proficient than I) son to do that this weekend. The gallery is becoming both a great resource, and a neat history - do want to have our part in it.

We ended up a little less conservative on clearances than intended when the jig was built; <1mm on height, about 2/3 mm on block clearance, and about 1.5mm on span; didn't appreciate the amount of structure bowing the pre-tensioned MTMs and leg TMs put in; kinda humped it up....
Len Joeris
Fort Collins, CO

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Re: Elevated Bridge B/C

Postby smartkid222 » May 25th, 2010, 1:54 pm

Towers next year for sure, probably new scoring equation, still efficiency, more emphasis on weight held.

New score equals weight held squared over mass of bridge. Still max 15 kilo load. Goal is to motivate students to get closer to 15 kilo capacity.

Jeff Anderson
Livonia, MI
woahhh. so that means that the #1 Div C bridge:
1. 6.19, 14725, 2379
under that equation would have an efficiency of 35,028,372
?!?
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