Helix command question.

[Rob-GB]

I have used the Helix command a few times but have always had to work out the height of one complete revolution for a given radius while only needing a partial helix. This is mostly for when I design and build staircases/handrailing. The problem I have encountered is in trimming the helix to the required length, I have tried drawing intersecting lines and using solids to no avail.

 

It would be a more efficient command if one could select a given radius and from a point 'A' to point 'B' selection then have the magic of Autocad plot the line.

 

So is there an easier way to figure out the partial helix rotation from point to point (a mathematical equation I am not aware of perhaps) or a proven method of trimming the helix line to length.

 

I have looked through help files and Ellen Finklesteins Cad Bible 2010 and am still stumped. The last handrail I did was 40 something metres in length and the system crashed twice while sweeping the moulding, I only needed to draw a piece 1.6m long!

 

Any pointers gratefully received.

Regards Rob.

[JD Mather]

Don't you know the turn angle? 1 Turn 360° therefore 90° = Turn of .25

Am I missing something or do you simply need to calculate the degrees of turn as percentage of turn?

 

BTW - this is much easier in Autodesk Inventor and parametric to boot.

[Rob-GB]

Don't you know the turn angle? 1 Turn 360° therefore 90° = Turn of .25

Am I missing something or do you simply need to calculate the degrees of turn as percentage of turn?

 

BTW - this is much easier in Autodesk Inventor and parametric to boot.

 

Thanks for your reply JD Mather.

 

The turn angle was, if I remember 31°, though when I tried to get the Helix to do this the calcs must have been wrong as the line was too long. Maybe I confused my math but asking for a turn of 0.116 (I think of my head) just did not work.

 

Inventor is a great program, I have a limited access to it through my friend, most of my work requires that I deal in Autocad 2002 and up for clients as this is the cad package they use. I suspect many of the better points of Inventor will find their way into new editions of autocad. The Helix command is a massive time saver over plotting spline points if only it could be more 'user friendly' (read math dummy:wink:).

[JD Mather]

Thanks for your reply JD Mather.

 

The turn angle was, if I remember 31°, though when I tried to get the Helix to do this the calcs must have been wrong as the line was too long. Maybe I confused my math but asking for a turn of 0.116....

 

31/360=.086111 not .116

 

But here is what I do

...when I am not sure of my math (most of the time) I try to create a geometric solution and the work back and forth from my best guess at the geometry and best guess at calculations. Usually I can figure out by comparison where I had one or the other wrong.

 

Most people tend to concentrate in a particular field (like stairs). So once you have a general solution figured out it is very quick to adapt to different designs of the same general principle.

 

I think it would be worth the time to fool with the Helix command options a bit till you know exactly what to put in for any given parameters. Make sure you record your steps for future reference (I once lost an elegant general solution that I was not able to recreate for three years until one day I opened a reference book that I seldom used and found that I had stuck my notes in the book as a page marker).

[Rob-GB]

There you go I made a calculation on from the .08611 or got dispraxic.

 

I have a note book that I keep a record of things that make work easier, smarter, quicker (to coin Festools phrase) .

 

Stairs tend to be my most asked for works, due to the fact that few people either can or will do them. Prior to cad it was all hand drawn work with all dimensions arrived at geometrically (with a good deal of reference book study).

Thanks again, I will look through my post it's with all the calcs on and see where I went off course.

 

Regards Rob.