Helical Sweep Feature with Variable Section

[jeff4136]

I did not know it was possible and thought it might be news to others as well. Attachment is WF2 (~55 KB).

-Jeff Howard (wf2)
Sure it's true. I saw it on the internet.

 

[Heckler]

Variable Section Sweeps have been around for sometime.

Heckler
Sr. Mechanical Engineer
o
_`\(,_
(_)/ (_)

This post contains no political overtones or undertones for that matter and in no way represents the poster's political agenda.

 

[jeff4136]

> Variable Section Sweeps have been around for sometime.

Indeed they have. ;^)
But that's not a (menu: Insert ->) Variable Section Sweep.
It's a (menu: Insert ->) Helical Sweep.

-Jeff Howard (wf2)
Sure it's true. I saw it on the internet.

 

[mgnt8]

Jeff, Wow. Thats pretty awesome. Can you explain the relations a little bit more. Specifically, is the use of tan of trapar * 45 just giving you the same thing as trajpar - progression from 0 to 1?

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We, the unwilling, led by the unknowing, are doing the impossible for the ungrateful. We have done so much, for so long, with so little, we are now qualified to do anything with nothing.

 

[jeff4136]

> explain the relations a little bit more

That was sort of a doodle, playing with the shape.

Sketcher relations, for the Helical Sweep Section,
can be simplified

sd8 = .75 + 1.25 * trajpar
sd9 = .5 * d31
sd10 = start_pitch + (end_pitch - start_pitch) * trajpar

and it will solve with a linear transition in groove
depth (sd8) and distance between flight walls (sd10).

Replacing [ * trajpar ] with [ * tan(trajpar * 45) ]
alters the rate of change from linear to
slower rate at trajpar = 0,
faster rate at trajpar = 1.

(
An easy way to visualize is to create two datum curves referencing
the same CSys using the terms,
x = t, y = t, z = 0 and x = t, y = tan(45 * t), z = 0
(if you want to have a little more fun try substituting
t^(1/2), t^2, etc. for t)
)

The last tweak on (sd10) [ - .25 - .45 * tan(trajpar * 45) ]
causes the flight to taper in thickness.

-Jeff Howard (wf2)
Sure it's true. I saw it on the internet.

 

[mgnt8]

> Replacing [ * trajpar ] with [ * tan(trajpar * 45) ]
alters the rate of change

I see... I should have dug out my old trig charts. I'll never fault anyone for playing around on pro/e ever again.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We, the unwilling, led by the unknowing, are doing the impossible for the ungrateful. We have done so much, for so long, with so little, we are now qualified to do anything with nothing.