woodworking help needed!

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BradG

BradG

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Joined
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Blackpool -UK
Hi Chaps.

I have a project on the go where i am building one of these:
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This is Little Boy, the atomic bomb dropped on Hiroshima

The metal worker in me is leaning towards sheet metal... though the more grown up side of me is telling me it will be too heavy to cart around to different places and it would be better to make it out of wood. Though I have no experience in woodwork or the machinery for it... and im guessing you dont put sheets of wood through a bending brake like you do sheet metal :biggrin:

I would even contemplate paying a UK woodworker to build the sections for me, though id welcome everyones 2 pence worth on how they would go about building it if it was them
 

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How big are you going to build it? What will its use be once built? Those certainly play into material choice
 
You have shown quite impressive pen works. But now, this! Is there a global maniac genius trapped inside that cool, calm exterior? Do you have adult supervision? How often do they let you out? Just know, everything will be alright. Give it time, give it time...

Steve
 
Hard Hat 1:1 scale, so 300CM in length, and 76CM in diameter.

lol Kovalcik, not that big :biggrin:


I will be installing electronics in it and taking it to airsoft sites where it will be used in objectives where you have to disarm the bomb or set it off etc to win. It will get pelted with plastic 0.2g 6mm BB's so i think balsa wood is out of the question. Chances are players will climb on it so id want to make it robust...
 
Hi Brad,
By day I am an exhibit builder for the local science museum so here is my answer.

For the round sections we would use Sonotube. A cardboard tube used for pouring concrete. There is also plywood called wiggle wood or bender board that could be wrapped around a frame, but it would require a lot more finish work. You can cut a pie slice out of the sonotube to make the funnel to the tail.
You might also look for a plastic barrel or tank of the right diameter and shape. I have seen plastic tanks with a similar shape as the nose cone. The plastic would be a little trickier to paint.
The interior framework would consist of plywood circles cut out on a band saw with lumber or plywood ribs.
Hope this helps.
 
Thanks Stephen, Dave

I had considered large cardboard tubing though can see it falling to bits over time as it will spend some time outdoors too.. im guessing this would be the same for sonotube.

Plywood frame and bendy board seems the best way so far
 
I would probably make the frame by steaming and bending my own thin slices then gluing them together in circular shape. As far as the outer skin either bendy board or steam large sections of plywood to bend. Or make the frame as noted and use the thinnest, lightest sheet metal I could get my hands on for the skin.
 
If you can find cardboard tubing close to the right size, you could fiberglass over it. It will be weather proof and should stand up to abuse pretty well (about like a fiberglass boat hull. Not indestructible, but pretty sturdy).

Lots of information available on using fiberglass for structural work so you won't have to reinvent the wheel.

The biggest problem (whatever you make it out of) is to make it rugged enough to survive someone climbing on it while keeping it light enough to move around without heavy equipment. Fiberglass, wood and sheet metal all start getting pretty heavy in the sizes / strength you are talking about.

You could carve it out of foam, although that might get a little pricey.

Ed
 
I agree, plywood ribs and structural foam covered with fiberglass for the body and I would go with metal and ply with fiberglass for the tail. The dolly could be aluminum or wood. All painted it will look good and be durable
 
I have done quite a bit of curved lamination. I would make a form out of plywood. Then 2 layers 3/8 of bendable plywood. Covered with a two-ply of veneer after the plywood has been glued/set. Use a glue that provides a rigid glue line. I use Unibond.

I use a vacuum bag to press the layers together. In this case, the plywood or veneer is held to shape with the form, with the lamination in the bag, and the form outside the bag.

The trick is to make sure that you end up with perfect radius. You don't want an oval bomb.

YMMV, but that is how I would make the outer panels.
 
I would say if it is going to be shot with BB's you would want to use wood so they don't ricochet off. Beyond that I'm of no help here. GL!
 
I used to make Ordnance training aids for my EOD Brethern, and we even made one likr the and the matching Nagasaki bomb. Try plastic. about 6 mm thick. Heat it up and wrap it around a form, then glue it together and paint it OD. The palstic will take sustained shots from a BB gun, paint balls, little kids, etc...
 
I have use a plywood called bender board or something like that. Its designed to bend and we have made tubes out of it before. Beyond that I will take a step back and watch.
 
30 inch PVC water or sewer pipe would be close to the size and would certainly take the climbing upon and anything shot at it , but with a wall thickness of an inch or so , it wouldn`t be light . Thinner sheets of HDPE or polycarbonate would be tough enough and could be formed , but it isn`t a trivial task .
 
My suggestion is that you cnc it out of a single aluminum billet. It wont be cheap or light but hey what else will you do with all that money. AND! (This is the best part) you can use this as an excuse to get that 5 axis turning center you have always wanted.
 
Just came to me while I was asleep ! The ideal way to make that shape is by rotational blow moulding with HDPE , but one off would not be cheap . Give a local supplier a call . He might just happen to have a stock shape that would be close . Conical bottom tanks are commonly used in a wide variety of applications .
 
I'd carve a pattern for the main body from foam and layer Fiberglass on it. Then a solvent like gasoline or lacquer thinner could be used to melt the foam out leaving the hollow body
 
I reckon you should make ( or have made ) a negative bendy mdf / cardboard template and that would become the mold for a glass fibre finished item. Lightweight, robust, durable etc,
I reckon you should have a few glass fibre contacts in the surfing, diving, boat building community of Blackpool. :)


Edit: Just seen Magic bob's earlier reply. I would just make it in two halves so you could fit the toys inside and change the battery or wind up the rubber band!! :)
 
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Thanks for all the comments guys including the witty ones :wink:

Il chew all the ideas over and see what I decide on. Some great ways suggested
 
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