Making paper cylinders with a ledge & full inner layer

[Leif Ohlsson]

While making the engine for the Sopwith Pup I learned a method for making all kinds of paper cylinders which might come in handy some time.

The idea was to make an almost complete inner layer for each cylinder. This should be just two paper thicknesses lower in height than the outer, original part, in order to form a ledge on which the lid of the lid should rest, flush with the surface.

The easiest way to do this is to print a double set of parts, and cut the inner parts using eye measure only. The pictures should be self-explanatory:











You may wonder why the inner layer is always, regardless of diameter, the same ca 1 mm shorter than the outer layer. Remember the old trick question: "If you spin a string around the whole Earth, and lift it one feet from the surface, how much more string will you need?"

The answer turns out to be the same as if you had spun a string around a football and then lifted it one feet - namely ca 6 feet longer, whether around a football or around the Earth.

The mathematical explanation is: Two times the longer radius, times pi (ca 3,14). Answer ca 6 feet every time.

Same thing for a paper cylinder. If the paper thickness is about 0.20 mm including glue, the inner layer is 0.4 x 3 (roughly) shorter, i.e. 1.2 mm. Try out the exact measure for your paper thickness, and way of glueing things, and keep a visual memory of it. It should apply always, regardless of cylinder diameter.

Hope this is useful for someone.

Leif

[THE DC]

Excellent thread and well illustrated.


My compliments upon your skill and ability to instruct.



The DC

[Texman]

Suweet! Wonder how that will work for my scale? Guess what I'll be trying!

Ray

[member_3]

I think I may have to start saving all your threads, Leif, and compiling them into a book called "Listen to Leif." Not only are your projects beautifully crafted but you always seem to improve on existing methods or invent new ones. Thank you for sharing.

[Leif Ohlsson]

Thanks guys - nice to hear! Tex, I fear that most of your parts wouldn't work, since we don't use parts with negative, imaginary, lengths in ordinary paper modeling.

The inner part is always 1,2 mm shorter than the outer, remember...

-L.

[Leif Ohlsson]

Rayman, sorry for slip of the mind. We have a comic strip taped to our front door, so that we won't forget:

- My memory got so bad lately I don't even remember my own telephone number when answering.
- Well, you can always just use your name, can't you?
- Names, them I'm having an even tougher time with!

- L.

[Art Deco]

Another elegant technique! Thanks for documenting it so nicely!