Nando's Little Boy Atomic Bomb Cutaway

[cdavenport]

I have upscaled Nando's Little Boy, available at ECardmodels, to 1/6 scale, making the model 18.9" (48.0 cm) long with a diameter of 4.667in (11.9 cm).

I plan to turn the bomb casing out of steel and burnish it, just like the real article.

Internal/external bomb components, based on intelligent conjecture (not mine) will be made from an amalgam of paper, cast paper, plastic and other metals.

I printed Nando's original model parts to roughly 1/6 scale and used them as the basis for my original Autocad drawings. I found the speculative cutaway on Wikipedia.

Nando was generous enough to send his original side/top views so that I could verify my drawings. The second photo shows the overlay of his design on my CAD drawing. As it turns out, his drawings are absolutely invaluable so that I can incorporate important surface details on the steel portion of the model.

Thank you, Nando, so very much. You are a real gentleman!

I hope to have all the drawings complete by this weekend so that I can start turning metal next week!

[mbauer]

What version of autocad lt do you use?

I use ACAD 2002 Lt to do all my models.

Mike

[cdavenport]

I have a really old version of AC Lt. But, it serves me well enough for my needs. I have been thinking about going back to school to upgrade my skills to the new version....definitely expand my design capability!

[cdavenport]

I've been working all day and making a little progress.

I've been drawing and then erasing loft lines so that I can define the outlines of the gun. I'll separate the gun from the drawing and dimension it so that I can turn it on the lathe. Each of the different colored hatched area represents a specific part of the gun.

The writer of the article was nice enough to dimension the gun and uranium elements which matched ever so nicely with the scale drawings that Nando and I developed separately.

Off to the right, I wrote in the gun/U235 nomenclature so I could have it readily at hand as I drew.

BTW, U235 looks so much like lead, that I plan on using sheet lead for the projectile/target elements.

[Leif Ohlsson]

Charles, just a little bit of nitpicking in the interest of promoting an intuitive understanding of the metric system:

18.9" = 48.0 cm (for a quick check in your head, 2.5 x 20 = 50)
4.667" = 11.9 cm (for a quick check in your head, 2.5 x 5 = 12.5)

You multiply with 2.54 to go from inches to cm. Or 2.5 if you do it in your head.

So, your model in 1/6 scale would be rougly 48 cm length by 12 cm diameter. Which translates into full scale roughly 3 m x 70 cm. Which makes sense to me, I suppose, vaguely remembering photos of the original. One-and-a-half times the length of a very tall man, and as thick as I could not quite get my arms around.

Similarly, if you live with the metric system in your head, and you wish to make quick sense of dimensions like 3/8" or 1/16", you approximate one inch to equal 24 mm (instead of 25.4 mm). This way 3/8" easily converts to 3 x 3 = 9 mm in your head, and 1/16" to 3 / 2 = 1.5 mm.

The key is that your fraction system seems to be built upon increments of 1/2, 1/4, 1/8, 1/16, 1/32, 1/64 - which is why, when doing this kind of quick conversion in your head, you really want one inch to be 24 mm since that is divisible by 2, 4, and 8 (plus 3 and 6 of course, which however is of no use for converting your fractions).

That's how I learnt to live with fractions of inches ever since my first encounter with Aeromodeler fifty years ago. Made me appreciate calculus and worked wonders for my ability to do calculations in my head...

I still have to practice using the full stop (.) instead of a comma (,) when writing numbers in English. What complicates things is that neither the onboard computer calculator, nor my drawing software will accept that, since the system is set to metric standards. But I can live with that.

Like I said, nitpicking.

Leif

[cdavenport]

Like I said, nitpicking.

Leif[/QUOTE]


Not at all. I use a calculator. I just made the mistake of dividing instead of multiplying! Thanks for catching that. I'll see if I can make corrections.

[cMags]

Fixed your math in the original post - thanks Leif!

[cdavenport]

Originally Posted by cMags

Fixed your math in the original post - thanks Leif!

Thank you cMags!

[nando]

My compliments for the ambitious and challenging project.
I hope that you will not encounter problems coupling the parts that you are designing with enlarged parts of my model.
I designed my model not for this purpose, and it will be interesting to see how much it will be usefull in your project.
At 1/24 scale we can forgive some mistake, but at 1/6 the mistakes become important.

Good luck, my friend

Nando

[Kevin WS]

Charles, did you ever finish this?