Challenge for the day

tspco

Here is what I need to do, I need a spiral staircase on the outsideof a 18 foot diameter tank. Here is what I tried so far. Using the draw helix plugin, I managed to make the perfect path around the tank, then I made a step 24x12x2"(nothing special here)I then used path copy, to copy the step up the helix, which worked...kind of, the steps were not aligned perpendicular to the path (no rotation). I tried a manual approach by rotating each step 7.5 degrees, then attaching the step to the helix, well, doing this operation, 48 times did not sound like a lot of fun.
I used SDs stairmaker plugin and made a standard internal spiral staircase, which will work for the project but....not what I wanted.

TIG

Mark the center of the tank.
Make one tread/riser as a component.
Measure a tread's swept angle [using the Protractor tool, or just know if from making it].
Select the first tread and use my tool 'Grow', centered on the 'mark', with appropriate riser increments in the Z and the swept-angle around the point/Z-axis, and the number of copies needed etc...

There is a 'helical stair' example early on in Grow's thread, simply modify the values for the central newel post until it's the 18' wide tank!

Use the 'Plugins Index' to find my 'Grow'...

gilles

Here is one of my favorite: screw_1.5 ( in fact 3.0 )
http://rhin.crai.archi.fr/rld/download.php?file=screw1_5.rb

#1 draw a component of one step
#2 move it 9' on red axis
#3 select it
#4 plugins/screw
#5 pick first end: origin
#6 pick last end: the total height for one turn

in the input box

steps: number of steps per turn
turns: number of turns

note that it also works with faces or edges.

sdmitch

My solution

Draw circle with 9' radius

Using StairMaker, create a set of spiral stairs at the circle center with max/min width of 11' and angular increment of 5.73 degrees which equals 1' of arc at a radius of 10'.

Pushpull circle up to create tank.

Explode stairs and add tank to the selection

Intersect Faces With Selection

Delete everything inside the tank.

[flash=800,600:32ptw56v]http://www.youtube.com/v/tRwFJYp2f1Y[/flash:32ptw56v]

gilles

@ sdmitch,

In your solution, you do not have a single component for the steps.

sdmitch

@gilles said:

@ sdmitch,

In your solution, you do not have a single component for the steps.

and this a problem because?

gilles

If you need to modify something, it better to have just one component.

pilou

A funny method!
From the begining of the video (first 50 seconds)

A the Start : Make the inclined segment as a component : Menu Edit / Make Component
(don't exist on a right click for a line)

So when you have one spiral done

Edit the component and make a stair

So you have that your staircase
By KitoRaupp
[flash=560,315:1bxk67nn]http://www.youtube.com/v/pNTetL3Udkc[/flash:1bxk67nn]

Dave R

FWIW, doing this manually isn't difficult and the process might be useful for other things where a plugin may not work.

Make the stair component at the bottom of the helix. Copy/Rotate the desired angle and move the copy upward to align with the helix (7.5° as you mentioned before). Select the two copies and rotate/copy them 15°. Move them up. Select all four, rotate/copy 30°, move up. Repeat the process for 60° and again for 120° but for the last rotate/copy operation make two copies. Move each set of steps up as needed. That gives you a full turn of steps which can then be move/copied upward as many times as needed.

tspco

And the winner is, the Gilles technique, for ease of execution. I will try the other techniques also. Thanks guys!
I got to thinking in the real world, you wouldn't any one to fall of the steps, so I sandwiched the staircase between two walls, with an entrance at the bottom.