tapered tube curvature

[Drac]

'elp me 'elp me! how do you figure the curvature for the top and bottom of a tapered tube so that when the ends of a flat piece are put together to make the tapered tube they look straight?!?! ack! brain... hurts! the top has to be 24" around and the bottom 17 1/2".

[whinewine]

'elp me 'elp me! how do you figure the curvature for the top and bottom of a tapered tube so that when the ends of a flat piece are put together to make the tapered tube they look straight?!?! ack! brain... hurts! the top has to be 24" around and the bottom 17 1/2".

Drac:

If I am correct, is this what you want to do: take a flat piece & make it conform to a tapered cylinder with the top & the bottom having the correct curvature so that when made into a cylinder everything lines up?

You can do it scientifically by using specially designed CAD programs, slide rules or asking your genius friends if they could help you.

Or you can do it the common sense way (which, btw, doesn't always work).

Take a tapered cylinder

wrap paper around it & fasten (temporarily) with tape

trim the top

trim the bottom

draw the seam line

use exacto knife to cut along the seam (cutting both layers of paper)

unfurl & you have your pattern (allow extra for the thickness of leather)

If this is NOT what you're trying to do, sorry, my bad!

russ

[Hedge]

Your pattern will be a trapezoid. The long side will be equal to the circumfrence of the large hole and the short side equal to the

circumfrence of the small hole. The distance between will be the length of the tube. Your cut seam will be made by drawing

a line connecting the ends of these lines on each side.

('suppose that's a clear as mud )

[Drac]

whinewine

that's pretty much what I wanna do. I'm a computard though so the programs won't work for me and as for genius friends, that's what this forum's for, right? *L* I'd use the "wrap around something" method but don't have anything that coresponds to the correct size. never had a prob with that method so far as long as whatever was wrapped was the correct size/shape.

hedge

yeah, that's the idea, but I need to know how to figure out the circumference size for the circles so that everything is level once cut. therein lies the rub.

[Hedge]

C = 3.14159 x dia.

(but you already have the measurements you need. 24" and 17 1/2"...right? )

whinewine

that's pretty much what I wanna do. I'm a computard though so the programs won't work for me and as for genius friends, that's what this forum's for, right? *L* I'd use the "wrap around something" method but don't have anything that coresponds to the correct size. never had a prob with that method so far as long as whatever was wrapped was the correct size/shape.

hedge

yeah, that's the idea, but I need to know how to figure out the circumference size for the circles so that everything is level once cut. therein lies the rub.

Edited March 25, 2008 by Hedge

[Drac]

hedge

hmmm... methinks I probably wasn't clear enough on the bit that I need. if you lay a properly done gauntlet flat for example, the top and bottom are curved. I need to know how to figure the size of those curves.

[Hedge]

Ahhh!! Now, I see what you're talking about. Hmmmm...I've never done that execept by eyeball. Not even sure there's a 'standard' curve

to apply. Sorry, Drac. That one's beyond my ken.

hedge

hmmm... methinks I probably wasn't clear enough on the bit that I need. if you lay a properly done gauntlet flat for example, the top and bottom are curved. I need to know how to figure the size of those curves.

[ferret]

this any help?

http://mathcentral.uregina.ca/QQ/database/...2.06/phil1.html

[whinewine]

Drac:

I think what you're gonna need to do is build an actual model. Get, or make, a hoop of the top dimension & do likewise, for the bottom. Find the corresponding height & attach connecting rods, fastened on angles (they will be longer than the height, because they go from the longer hoop on an angle to the shorter hoop- does this make sense?)...

If you can construct a model from styrofoam, in sections, using an electric knife, or a lathe-type of arrangement, where you can turn down the styrofoam to the appropriate dimensions, would work...if you want to go to all that trouble... the wraparound method is probably the most sure method of doing what you want.

good luck.

russ

[Hedge]

Good show! For some reason I got it in my mind he wanted an angle on the openings.

(not good at multi-tasking...like breathing and thinking at the same time! )

this any help?

http://mathcentral.uregina.ca/QQ/database/...2.06/phil1.html

[Drac]

ferret! dude! I think that just might be what I needed. we'll all find out before too long. thanks!

whinewine

that's what I tend to do when I have the time and materials for it. I'm better at thinking that way than semi-abstract 3d type stuff.

hedge

not good at multi-tasking? I have enough probs single-tasking! *L*

[tonyc1]

Drac, there is a formula for this, what it is I don't know, but a friend of mine who is an engineer did some patterns for me a few years ago told me all about it but of course I forgot! I do remember he said that you need a set of trammels to do the drawings.

Tony.

[Spider]

Hey Drac,

For some reason I thought it was something like this.

Have your top dimension's straight line (24) find the center and draw a line 1/2" down. Draw your bottom line (17 1/2) find the center and draw a line 3/4" down. The end of the lines you drew down will be your midpoint for your radius'. I think I saw this on a tut. for making arm bracers. What do you think?

[bcurrier]

Have your top dimension's straight line (24) find the center and draw a line 1/2" down. Draw your bottom line (17 1/2) find the center and draw a line 3/4" down. The end of the lines you drew down will be your midpoint for your radius'. I think I saw this on a tut. for making arm bracers. What do you think?

Should be close enough for most purposes. It all depends on how precise you need to be.

Bill

[ferret]

just a thought, do you have plastic plant pots over there? could save doing all that jometree stuff

[whinewine]

just a thought, do you have plastic plant pots over there? could save doing all that jometree stuff

yeah, that would work IF you can find 2 of the right size. put them bottom to bottom, then cut off one bottom to make the height correct, glue together & you have the proper top & bottom curvatures. wrap the cardboard around the top & bottom, tape, trim top & bottom & then scribe the center joint line & cut down the middle. good one, ferrett!

[BillB]

Alternative B: Go down to the local Motorcycle Shop, buy a pair of gauntlet gloves that are close to if not what you what, disassemble and use as a pattern.

[Drac]

bill

only problem with that is I'm not doing gauntlets. just used 'em as a reference to be more clear about what info I needed. it's for a special project. and nope! not gonna say what until it's done. you can't make me. nosiree bob! my lips are sealed!

[Beaverslayer]

I'm pretty sure with a few well placed electrical devices we could get some info outta ya....LOL

It's stuff like this that makes you shake your head for not paying more attention in math class. I'm with Bill, I've spent a fair bit of money on things just to tear em apart, I've got a "Long Riders" coat that I payed $350.00 for, and still have not found the time to make it out of leather...one day soon.

Ken

[Drac]

well, the one site didn't help after all. couldn't figure out where they got one value. did find this one though! http://jwilson.coe.uga.edu/EMT725/CarlCone...utionPaula.html

at the bottom of the page is a link to a spreadsheet that figures it out once you put in certain values which you'll have already if you're gonna do one of these. looks like it'll work. I should know in the day day or two. w00t!

[BillB]

If the intent is to have a set of leather cuffs similar to the gauntlet on a set of gauntlet gloves, and you want to make the edge closest to the elbow a curve, then the line that is drawn on the flat template can be anything some a simple arc to a parabolic to a hyperbolic curve depending on the amount of curve one wants to have one the final project. Some of the old Western Gloves used in shows had an extreme curve on them. In some cases I have simply started with some heavy drawing board, and started making prototypes. A lot easier to cut and a lot cheaper than leather.

[mikeymoto]

I'm pretty sure the page mentioned previously (http://mathcentral.uregina.ca/QQ/database/QQ.02.06/phil1.html) does answer your question.

In your case you know the diameter of the upper and lower "rings" of your "cuff" (or whatever your mysterious project is. You also need to choose the length of your project, which I don't think you mentioned. This is arbitrary and can be whatever you want it to be.

So let's say for the sake of example that you are making a cuff. The smaller hole (the wrist end of the cuff) is 7" in circumference, the larger hole (where the forearm enters the cuff) is 10" in circumference, and the length of the cuff is 8".

What you need to know is where to put the center of your compass to draw the two arcs on your flattened pattern which, when folded, will produce circular openings of sizes 7" and 10". Right? So what you need to determine is the radius of the two entire circles on the pattern, parts of which will be the arcs that when folded make the circular openings.

Doing the math on that web page, you find the from a center point, the diameter of the small circle is 18.699" and the diameter of the large circle is 26.713" and your project patterm uses 21.45 degrees of the circles you just drew.