You know, I had a post planned for Christmas. I had it half-written. All I needed was an hour or so to polish it off….and then wham!
We were derailed by ‘Le Grande Project’. You see, we’d been asking the kids, particularly C, ‘what do you want for Christmas?’ for a while now. And received the dreaded shrug. Variations on ‘is there anything you really want?, elicited similar responses….until three days before Christmas. Yes. Three Days. That was when he wrote his letter to Santa. And oh boy, what a letter. Go have a look at it. Go on. It’s no particle accelerator, but – oh boy!
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| Letter to Santa Page 1 of 4 – Le Grande Project |
The cars and trucks, somewhat plausible…19 Tanks? 100 pistons? 200 pieces of steel girders? And on it went. It was only after prompting that C decided that Santa might need a few words (i.e. like Dear Santa, this is what I want for Xmas) along with the blue-prints…
…poor Santa had run afoul of ‘Le Grande Project’.
You see, C’s new passion of the moment is …bridges. Thinking about them, watching TV shows (a la Big, Bigger, Biggest – Bridges), playing computer games about them, planning them and building them with anything to hand. The problem was, the things to hand, were in his mind, not quite good enough.
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| K’nex Bridge Kit + Instructions |
It started off simply – block building with his sister J. Then he moved onto his K’Nex Bridge building kit – he’s been working through the designs in this kit for a while now – theirs and his own designs.
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| K’nex Bridge |
Build a bridge, photograph it, and film it under stress when an earthquake hits. Rinse. Repeat.
But you see, it’s not versatile enough. He’s played the computer game Bridge Project to death. He’s completed 47 of 48 levels, and trust me, these are real engineering challenges – using limited materials – wood, steel, cables, pistons, and then tests to see how much the bridge can endure: cars, buses, tanks, earthquakes and windstorms. He’s learned about stress and strain, learned how to make Warren trusses and suspension bridges. Learned about carrying capacity, and how spectacularly gravity can collapse the (deliberately) poorly designed bridge…
..and that’s where Le Grande Project started. You see, he didn’t just want to make it on the computer. Oh no. He wanted to make bridges for real.
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| Spaghetti Bridge pieces – all just a little too imprecise and non-reusable for C. |
So we started looking around for how to scale model bridges to test the strength of various designs. And stumbled upon spaghetti bridges. These are the bridge-models used in wonderful competitions, and is often used in University engineering courses. So off we went to the supermarket and bought packets of spaghetti – lots of spaghetti. Then hours of slowly gluing pieces together – layer on layer.
Then it was time to put it all together – with marshmallows. And we discovered that marshmallows are very tasty – but pretty hopeless at holding up a spaghetti bridge. Alas.
So now Santa was tasked with finding something bridge-like for Christmas. That was real: with steel and wood; iron and pistons. Santa and his helpers had a wonderful time laughing maniacally and pulling their hair out in awe and frustration. Reality had flown out the door a long time ago and started doing wheelies down the driveway, in a large leopard-print suit…
After a fruitless day looking at hobby stores with the kids, (inspiration where are you?) I sent a desperate call out to the forums – (Thankyou to everyone who responded!) – and we had a plan. A DIY model bridge – from basic materials. And my poor DH spent a very long day trawling the whole city going from craft shop to hobby shop, to hardware stores…until enough ‘scale’ items had been found. Hours later, Santa could be very proud of his helper!
He had a haul of:
- 12mm x 12mm wooden dowel,
- multi-sized paddle pop sticks,
- matchsticks in various sizes,
- ridiculously small nuts and bolts,
- a special mini-drill bit (9/64″ or 3.57mm),
- a couple of hinges (for pistons),
- and lots of PVA wood glue.
Thankfully, C decided that Santa did it right, despite the lack of steel. (After explaining our lack of welding and drilling material able to cut and rivet steel, and no garage to store it in, he decided that was acceptable.)
And so began construction of Le Grande Project. I mean, what else do you do between Christmas and New Year? DH and C have spent hours designing and putting together their bridge.
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| Drilling holes in Paddle pop sticks for trusses: 4mm hole for 3mm screws recommended |
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| It’s not as easy as it looks – slow and steady, or you get split paddle pops. |
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| C and DH putting together a roadbed of paddle pop sticks and wooden dowel |
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| Showing the side – with the holes in the dowel to attach the trusses |
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| Upside down roadbed, showing it’s construction |
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| Roadbed from on top – all neatly lined up. |
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| Almost there… |
And now the dreamed up bridge is in C’s own hands….and we may get a few moments before we’re hit between the eyes with another Le Grande Project…impossible managed!
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| Le Grande Project, so far…more spans planned! |
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| Under load. |
So, where to from here? What great ideas for bridge-building and learning have you found out there?
It's hard to get, but have you seen "Steven Caney's Ultimate Building Book"? It is a brilliant resource to help me work out how to help my son make his ideas into reality (though there are no tips in there for his human-sized wedge-tailed eagle silently operating surveillance flying suit).
We also have a book called "Bridges – Amazing Structures to Design, Build and Test" by Johmann and Rieth, which is simpler.
Thanks for that – I haven't seen the Steven Caney book before but it sounds like our kind of book! I think I'll also try and track the other one down. I love the idea of the eagle surveillance suit, it sounds like crazy fun – has he actually tried to make it yet?
No … he has talked about it for hours but we haven't found a starting point. It has led to lots of reading about the history of flight. December was not a good month for him to need me to don the science mentor hat. He has no idea about materials. We watched clips of wing suits but he wants a silent propulsion method, not just a glider. I am so out of my depth and our most likely mentor just moved 10 hours drive away.
Hmm. That's a tricky one. You might need to find a good engineering textbook on the Mechanics of Materials, or if you're talking about designing objects to be stream-lined, you might need to look up fluid dynamics. Most University's with a good Mechanical Engineering Faculty will have a wind tunnel – which they generally love to show off on open days. If you live near one, you could try contacting them to organise a tour. There are probably a number of good free textbooks online –
Classroom Aid website
seems OK, as does this textbook. For more basic stuff on engineering, my DH (who is an engineer) reckons the German Wikipedia sites are quite good – much better than the English ones for engineering topics, as they're moderated – and you can just translate them with Google translate. Or there's always Kahn Academy for high school level material, it's OK too. I hope that helps 🙂 . I might be able to find some other resources…. What level of science / math is your son up to?
From my DH: A few questions and considerations that may help your son developing a solution. These notes are the result of about a half hour of thought, so apologies if you have already moved beyond this point.
Firstly, what would your like your design to do? Replicate the mechanical motion of an eagle's wing in flight…conduct a solo flight for a number of seconds/minutes/hours…take off and/or land…fly from stationary…operate at 0dB or less…carry a load of 50kg…an artificial eagle that would be at home with the owl in Blade Runner? Keeping in mind I am more of a software and electronics person, my understanding of flight is that you have to overcome the basic problems of lift and propulsion. If this is to be a person powered device, then you will run into a few problems, mostly around the design of the human body (bone density and muscle distribution for land based movement) compared to a bird's construction. To compensate for this, you need mechanical aids, which usually also means a more dense power source and a means of turning it into work. These all add weight and noise.
Mechanical exoskeletons generally generate a lot of noise when amplifying motion due to the use of motors, but there may be some advances in this field that could point you in the direction of quieter aids. The SmartBird project runs through the design considerations for how to mimic bird flight in a robot, as do Ornithopter designs.
For quiet flight, the two existing systems consist of blimps (lighter than air lift with quiet propulsion system) and gliders (falling with style). Gliders are a pretty good idea as birds also make use of thermals to sustain flight with minimal energy use. But man-made ones are fixed wing devices that are considerably less efficient than a bird. A blimp has significantly less mobility but is a much safer option as lift and propulsion are solved separately. You might be able to combine a blimp with some of the ideas from devices like the Slocum glider or the AirFish. …
(continued…)
For materials that would work, it really depends on the payload. Assuming you want to move about 50kg, then you will start to run into challenging problems of strength vs weight. Aerogel is certainly an interesting material that is strong under compression and very light, but I have no idea if it would handle bending loads sustained in flight. Composites are fairly common in racing bicycles, sailing boats and military aircraft as they are strong and much lighter than metal, but they are not cheap and difficult to inspect for wear. Wood is probably no longer suitable for the loads but I am happy to be wrong about this. Plastics would be great for small models but is unlikely to suit people loads.
You can either try for simulation or experimentation to test the design. Simulation can be very difficult to get reliable results from, especially with exotic materials and structures, and experimentation can be expensive and/or dangerous (but fun). If you can, go with the Mythbusters approach of small scale tests first. And if you can get access to a wind tunnel, then you should be able to get better information as to where to make improvements. For a wind tunnel, try your local university. Car design companies usually also have them. And you should even be able to build a good enough one to test small designs (like this for example ).
I hope this helps a bit, and I would be very curious to see how the build goes.
That helps a LOT. Thankyou so much for the thought you guys put into those suggestions! There is more than enough there to keep us interested and progressing with this for a while now. I just didn't know where to start. I am thrilled to have a way to move forward. We (DS9, and I, in refresher mode having forgotten most of what I used to know, with DD8 tagging along for whatever interests her) are learning basic physics and chemistry, around upper primary/ lower secondary level. DS is probably moderately-highly gifted, 2E with dysgraphia. He is more of a dreamer than doer, so it's hard to say whether this project will go ahead or only live in his ideas book for now. Either way, it sounds like a long-term project, and we will learn a lot along the way.
I appreciate your responses so much. DS will be thrilled to know he isn't totally limited by my lack of knowledge (I hadn't even identified what we needed to know to progress … it just all seemed to big and with too many unknowns).
DS recently started using SketchUp to model some of his designs. I will go through your questions with him to refine the purpose and functionality of what he has in mind. … cont.
You wrote: "Keeping in mind I am more of a software and electronics person, my understanding of flight is that you have to overcome the basic problems of lift and propulsion. If this is to be a person powered device, then you will run into a few problems, mostly around the design of the human body (bone density and muscle distribution for land based movement) compared to a bird's construction. To compensate for this, you need mechanical aids, which usually also means a more dense power source and a means of turning it into work. These all add weight and noise."
That was basically the same conclusion we reached last year, at which point I left him to read books on flight, we watched You Tube clips about wing suits, Myth Busters, then got sidetracked with other projects about robots and war planes.
In maths, he's between Grades 5 and 8 (late primary to early high school), with various strengths and gaps. I love maths and science and find it a lot of fun, but have to work hard at it to understand, so online resources, books, and local Uni resources will be important in future years to help DS learn what he needs. I find it quite a challenge to find what's possible amongst all of DS's ideas, and don't wish to limit him to my comfort zone, but just listening once he gets going on a thread takes all the energy and time I can find. Reading articles like yours (such as le grande project) inspires me to dig a little deeper and keep trying. Thanks again!
No Problem. If you have any more questions, please feel free to ask! My DH got quite a buzz talking about 'such an interesting question' 😀
I shared your replies with my son on the weekend, and he was thrilled that you took the time to help him! We clicked all the links and I was able to jot down his thoughts as we talked. It was very special. He has also been able to refine the purpose of his project and has identified some areas for further research (one of which includes buying an ornithopter model!)
Thanks for giving us some pieces of the puzzle. I will share a link here if I get time to write on my blog about it one day.