Alignment Debate

[spazus_maximus]

We are having a discussion pertaining to an alignment and would appreciate any input:

DAT_S(CYLINDER),1,0,0 = Primary
K-FACE(PLANE)1,0,0 = Secondary

ALIGN_SK =ALIGNMENT/START,RECALL:ALIGN_S_BORE, LIST= YES
ALIGNMENT/LEVEL,XMINUS,DAT_S
ALIGNMENT/ROTATE,ZPLUS,TO,R_FACE,ABOUT,XPLUS
ALIGNMENT/TRANS,YAXIS,DAT_S
ALIGNMENT/TRANS,ZAXIS,DAT_S
ALIGNMENT/TRANS,XAXIS,K-FACE
ALIGNMENT/END

Question:
Is it legal to level to a cylinder?

Question:
If so how can anything level with only two points? Wouldnt it spin?

[John Kingston]

What is R_FACE?
You are rotating to it. Doesn't that lock you in?

[Peter Warcholyk]

Yes you can level to a cylinder. How many levels are you measuring the cylinder at? You should try to use at least 3 levels if possible.

Pcdmis will see the cylinder as a line for the purposes of an alignment.

i) level to the cylinder
ii) rotate the plane
iii) you could pierce the plane with the line of the cylinder for an origin point.

I'm sure that others will add to this post.

Hope this helps out.

ZydecoPete

[craiger_ny]

Question:
Is it legal to level to a cylinder?

Question:
If so how can anything level with only two points? Wouldnt it spin?

Answer: Yes, perfectly legal

Amswer: A cylinder is not 2 points it is a 3D feature (think line like Pete said), that is why you can level to it.

I do question though your primary and secondary sharing vectors. Perhaps you have a drawing issue. Don't rule out the possibility that I have issues.

Craig

[#2#]

I don't like to level cylinders as it is confusing. It is less confusing for me to rotate and I am sure I've got it right that way. I believe all that level does is rotate to two axes in one step. Correct me if I am wrong.

I also don't like to rotate to planes as again it confuses me. It is much easier to level and then rotate to something else.

Edit - I deleted a bunch of stuff as I wasn't thinking straight and got stuff mixed up.

[spazus_maximus]

I guess you can..

i guess you can.

thanks anyway!

[#2#]

I'm confused... your primary datum controls two degrees rotation and two degrees of translation. Your secondary datum controls the same two degrees of rotation and the third degree of translation. You are still missing one degree of freedom.

Also, if you control two degrees of freedom with your primary datum... how do you know which degree of freedom the secondary should control since it can control the same two degrees of freedom?

[craiger_ny]

I don't like to level cylinders as it is confusing. It is less confusing for me to rotate and I am sure I've got it right that way. I believe all that level does is rotate to two axes in one step. Correct me if I am wrong.

I also don't like to rotate to planes as again it confuses me. It is much easier to level and then rotate to something else.

Wow that is wierd. You are correct though that is what is happening only make sure both rotations are consecutive. Alignments do what you tell them in the order you tell them so if anything is between the two rotations it will happen in that order and get screwy.

You don't level cylinders or rotate planes, weird. Kind of like when this guy asked for directions when I was up in the Adirondacks I pulled out a topo map and tried to show him where he was but it might as well have been in German, he just couldn't associate what the map looked like to what the terrain looked like. It's all about how our brain perceives things I guess.

Craig

[#2#]

Wow that is wierd. You are correct though that is what is happening only make sure both rotations are consecutive. Alignments do what you tell them in the order you tell them so if anything is between the two rotations it will happen in that order and get screwy.

You don't level cylinders or rotate planes, weird. Kind of like when this guy asked for directions when I was up in the Adirondacks I pulled out a topo map and tried to show him where he was but it might as well have been in German, he just couldn't associate what the map looked like to what the terrain looked like. It's all about how our brain perceives things I guess.

Craig

Did you orient your map to north? I get confused looking at a map if I don't orient north on the map with actual north (we will leave magnetic north vs. true north out of this one). I just can't mentally rotate the map for some reason.

[craiger_ny]

Did you orient your map to north? I get confused looking at a map if I don't orient north on the map with actual north (we will leave magnetic north vs. true north out of this one). I just can't mentally rotate the map for some reason.

Absolutely, orientate the map with the ground regardless of which direction you face (I give orienteering instructions once in a while). It amazes people how much better they grasp map reading once they orientate it with the ground.

[cmmguy]

If the primary datum is the cylinder, then you have to level to it(you can do the rotate- rotate if you want but it is prone to errors if done incorrectly). I dont see how you can do otherwise.

[Wes Cisco]

If the primary datum is the cylinder, then you have to level to it(you can do the rotate- rotate if you want but it is prone to errors if done incorrectly). I dont see how you can do otherwise.

I bet I could find a lot of examples in the first few programs I ever tried to write. . . LOL But if you are aligning correctly to the FCF then yes the cylinder must isolate two degrees of freedom, (whether by level or double rotate), and that must happen first before the other degrees of freedom are restricted. IMNSHO

[#2#]

If the plane can control the same two degrees of rotation as the cylinder should you level or rotate to the plane or merely use it as an axis orgin?

I guess I would level or rotate to the cylinder and then use the plane as the x-orgin only. The cylinder would be the y and z orgin. You would still be able to rotate around the cylinder - you need another datum to stop this.

[Wes Cisco]

Yes, you still need what I refer to as the "clocking" feature or datum to stop the cylinder from rotating.

By the plane, you are refering to the face? It would stop the same two degrees of freedom, but is it absolutely square to the cylinder? Even if it is, the cylinder is the primary datum, not the plane. Or as I heard it put once, "The datum is the datum and the other stuff is not!"

[craiger_ny]

I level per the drawing callout, if the cylinder is the primary on the drawing it is the primary in my program. I'm still stuck on both the primary and secondary having the same nominal vector. How the heck do you do that? I guess as long as there is no tertiary then it is fine but if there is I'm confused.

Craig