Juice

I'm using AutoCAD 2000 to help me figure out where to cut holes in the fuse formers where my pull pull cable will pass through. Take a look at the attached picture in [link=http://www.rcuniverse.com/forum/m_4928269/anchors_5031930/mpage_4/anchor/tm.htm#]TF P-40 Build Thread, Post #: 78[/link] to see what I've done already.

I have already modelled the rudder post, the rudder control horns, simple 3D polylines for the pull-pull cables, and the servo arms. I have all the information and the ability to figure out everything I need. Actually, I think what I've done is overkill, and this is now more of an excercise in the advanced features of CAD.

What I'm doing now is:
1) Rotate the rudder (with control horns) to its maximum deflection.
2) Move the rudder end of the cable polyline to the new location of the control horn.
3) Rotate the servo arm so that the connection point is close the the new position of the servo end of the cable polyline.
4) Rotate (more like pivot in 3 dimensions) the servo end of the cable polyline, without changing it's length, closer the the connection point on the servo arm
5) Do steps #3 and #4 a couple more times until the servo end of the cable polyline and the connection point of the servo arm are close enough.

This procedure is never exact. It accurate enough for practical purposes, but that's not the point. I want to be exact.

Does AutoCAD have features to make this easier? Anchor points? Object properties? I want to be able to just rotate the rudder, and then the control horns, cable polylines, and servo arm move accordingly.

Thanks in advance.
Juice

dmcmike

My Feedback: (14)

Autocad doesn't do that.. you could copy the object and rotate it, but that's about it.

dreadnaut

My Feedback: (5)

Actualy, AutoCAD does not have a ''now think for me" icon. It is, however, an awsome geometry calculator if you know the trick to it.

The first illustration shows the neutral position control geometry. In the second picture, I rotated the control surface and pushrod 20 degrees.

Now I drew two circles (in red) depicting the path of travel of the servo output, and the free end of the pushrod. Now we need to rotate the hole on the servo wheel to the point where the two red circles intersect. Do not eyball it! There is a very precise way to do this.

Command: r { hit the enter key}

ROTATE

Current positive angle in UCS: ANGDIR=counterclockwise ANGBASE=0

Select objects: 1 found { select the pushrod}

Select objects: { hit the enter key once to indicate that you are done selecting objects}

Specify base point: _cen of { select the center of the hole on the control horn}

Specify rotation angle or [Reference]: r { typing ''r'' ->enter puts you in the ''reference angle'' mode}

Specify the reference angle <0>: _cen of Specify second point: _endp of { select the center of the hole on the control horn again, then the free end of the pushrod}

Specify the new angle: _int of { select the intersection of the two red circles}

Repeat the proceedure to rotate the servo wheel.

CoosBayLumber

My Feedback: (1)

I am getting lost here. Cannot find the appropriate image to which you are mentioning. A date/time would be handy, for the one which comes up with your feed has little to do with tail feathers fromn this viewpoint.

And the little drawing an mentioned by Dreadnaut has an error in it. Don't know about you, but cannot locate any prefabbed control horns that do not have a base set at anything other then 90 degrees around here. Would like to find a DuBro or C-G number for the item shown there. In the example the control horn is shown to be 90 degrees to centerline, not the surface. This affects a few things.


Wm.

Dr1Driver

Buy a control horn of the type you want, measure it, and draw it, saving it to a wblock. Use ortho rather than 3D. AutoCAD is not a user-friendly 3D platform. AutoCAD will do the drawing and calculating, but you must do the designing and thinking. [8D]

Dr.1

dreadnaut

My Feedback: (5)

It's called a schematic representation. The intent is to explain the rotate with reference angle function. That much is free. If you want me to devote the time to creating an accurately scaled drawing of a DuBro fitting, it will cost you.

As far as affecting a few things, setting the control horn so that the pivot is at some angle other than 90 degrees will induce differential. I used to do this the elevator with slope gliders before the days of computer radios (more down than up). If you want to build differential into a surface, you can use this technique to establish the desired geometry.

I beg to differ. The following is a 42" yak for E-power. I will be building a plug in two halves. I lofted all of the formers in about four or five hours.