Ogive Curve Help Needed

[sgoti]

OK, so here's the situation:

I'm trying to convert an HO (1/87) scale locomotive into something like this:

Lehigh Valley John Wilkes Locomotive

The stumbling part for me is the streamlined nose. Gil's excellent tutorial on open petal nosecones gave me the inspiration I need. I would really rather use a petal design rather than a series of small truncated cones. I'm just weird that way…

I only lack one thing: Namely, an elongated (not hemispherical) shape to scale to fit. Can I take a petal design for a half-globe (hemisphere) and stretch it vertically, or are there other considerations in creating an ogive that I'm not aware of?

Thanks in advance,

[airdave]

Ignore me if you are stuck on the petal idea...


I don't like petal domes, so I would opt for rings.
And because this loco has a headlight, its a great candidate for rings.
Its also not a half sphere dome (as you noted)...another reason to do rings.
Even at HO scale, it wouldn't be tough.

And with a little burnishing, you can get a nice rounded look.

Can you give me a diameter and length(depth) of the nose cone?

[sgoti]

Originally Posted by airdave

Ignore me if you are stuck on the petal idea...


I don't like petal domes, so I would opt for rings.
And because this loco has a headlight, its a great candidate for rings.
Its also not a half sphere dome (as you noted)...another reason to do rings.
Even at HO scale, it wouldn't be tough.

And with a little burnishing, you can get a nice rounded look.

Can you give me a diameter and length(depth) of the nose cone?

Oh, I'd still like to try this as petals, but a wise man never refuses help. Neither will I.

Let me get back with a diameter and depth. I'm still trying to determine the exact shape/look I want…

Thanks, Dave.

[maurice]

I'm still trying to determine the exact shape/look I want…

That does need to be the starting point because - in theory at least - every set of paper bits - cones or petals - are unique to each curve that might be chosen for the ogive.
You might get near enough by stretching the petals for a hemisphere - perhaps not.
Would be happy to have a try at knocking out a set of petals if given the size and shape of the ogive you want.

[Diderick A. den Bakker]

I have done a little experimenting for you - making a suitable outline for you ogive - shape is quite simple if you have Office Word.

Open a new document; > insert > shapes (not sure if these are the correct names: I only have a Dutch version here).
Now find the oval/ellipse and insert it. Find the way to adapt its size by right clicking. Of course you will have to cut the oval / ellipse in half: I would do this in Photoshop.

Even easier option:
Find the small bullet shape in stream diagrams, insert and rotate to vertical. Now adapt the sizes. Perhaps the middle example in my picture is something like your locomotive.

So much for the two dimensional outline - the rest (making the petals and so the 3D shape) is rocket science to me...

Hope this helps a little?

[Diderick A. den Bakker]

I forgot the picture:

[Diderick A. den Bakker]

Here is a second attempt. The ogive shapes can be elongated or widened quite easily in Word, perhaps also in Photoshop.

[sgoti]

Originally Posted by airdave

Can you give me a diameter and length(depth) of the nose cone?

Dave-

Diameter = 1.41 inches
Height = 1.2173 inches

I liked the profile you used for your illustration, so I rescaled that one to determine the dimensions needed.

Thanks again.

[airdave]

Originally Posted by sgoti

Dave-
Diameter = 1.41 inches
Height = 1.2173 inches
I liked the profile you used for your illustration, so I rescaled that one to determine the dimensions needed.
Thanks again.

I actually traced the shape out of that photo you posted.
then I guessed at the amount of photo angle distortion and adjusted.

Heres a PDF of the nose parts.

I'll leave it up to you to figure out your own method of glue tabs or joiners.

Might I suggest...use an extra set of ring sections #2 and #4.
Reduce them in scale (95-98%) so they fit inside.
Add tabs along both sides.
This is all you need to connect all 5 rings.

Note...I included a disc for the headlamp (actually two discs).
It appears to be recessed into a hole in the nose.
So, my part is resized to fit inside (behind the opening).

[maurice]

And here are some petal patterns in 12 and 24 petal versions.
(It's an A4 pdf but will print happily on Letter at 100%)
Dave's lamp pieces should fit.

Perhaps I shouldn't admit this but I suspect that overall you might might achieve a beter looking result using cones.