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Drawing Projections

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David Clark 117/09/2012 15:05:42
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3357 forum posts
112 photos
10 articles

Hi There

I have stuck it.

regards David

blowlamp17/09/2012 15:15:32
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1202 forum posts
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Posted by CoalBurner on 17/09/2012 14:23:23:

Blowlamp. that is a great example of 1st angle orthographic projection, - if you coud post the same for 3rd angle I think, with the example image I posted we could put this thread to bed laugh.

cheers

CB

P.S Once resolved, maybe we could make this thread a 'sticky' - Not sure if this crappy forum SW has that ability sad

CB

In an effort to redeem myself, here's a link to the 3rd angle projection tutorial from the same site.

There's some other good stuff at the link which explains things in a way that I like.

Am I right in thinking that a good indicator of a 1st angle projection drawing is when the Plan view appears below the Front and Side views?

 

Martin.

Edited By blowlamp on 17/09/2012 15:18:07

Edited By blowlamp on 17/09/2012 15:31:07

Michael Gilligan17/09/2012 19:34:36
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14015 forum posts
608 photos
Posted by Wolfie on 17/09/2012 14:24:26:

But in Coalburners drawing the two are the same, front face, end face, top face. Whats the difference?

Okayy so its where the cone is that makes it different. The drawings are the same?

Wolfie,

I see that you are still struggling with this, so please allow me one more try:

In the diagram; the "side view" is the stable point of reference ... it's the position of the two concentric circles that varies. [ Yes, I know that sounds pedandtic, but it's important to understanding the diagram.]

The "object" is a solid truncated cone and is therefore radially symmetrical ... it is a solid of rotation, just like you would turn in the lathe. Any "side view" is therefore identical, so the trapezoid shape is infinitely ambiguous. [we neither know, nor care, if it is side, top, or bottom]

The end view [regardless of which projection we use], is two concentric circles both drawn in "solid line". We MUST therefore be looking at the small end of the object.

The only thing that remains is the location of that end view ... and that is the crucial piece of information that is provided the diagram. It defines the format for all views in the drawing.

MichaelG.

Wolfie17/09/2012 19:51:02
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502 forum posts

OK so the position of the two concentric circles in relation to the trapezoid tells us where in the diagram the side view will be in relation to the front view??

 

I can tell which is which already.

Edited By Wolfie on 17/09/2012 19:51:24

Michael Gilligan17/09/2012 20:41:13
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14015 forum posts
608 photos

So what's the problem ?

MichaelG.

Phil H 117/09/2012 20:55:32
128 forum posts
46 photos

Wolfie,

Great to see you have soted it out. Now you just need to crack 2nd and 4th angle projection and you have the full set.

Phil H

Dave Morris 117/09/2012 23:22:27
5 forum posts
10 photos

Sorry guys, didn’t mean to cause any upset but if it helps someone to have a visualisation method to help them why not?

Third angle –up the bowl, Flemings left and right hand rule for motors or generators, rhymes for remembering trig or resistor colour codes etc.

If engineering is someone’s hobby he needs confidence in his own ability to question a poor drawing, after all material is expensive and hobbies are supposed to be fun!

Dave

just found this http://www.youtube.com/watch?v=_wDpN6Zi1hE&feature=related

Edited By Dave Morris 1 on 18/09/2012 01:57:41

jason udall18/09/2012 10:33:10
2011 forum posts
41 photos

At the end of the day 1st 3rd or something freerange doesn't matter..IS IT CLEAR does.

most of the drawings I meet at work from very professional companies could be drawn to no standard at all.. but "work". some "small conpany " drawings are beauliful and complete .

and some times ( my personal pet hate) we get sent a part and say 1000 of them please....

a drawing is often just a place to hang dimentions and if it fulfils this role all is well.

PEACE

Michael Gilligan18/09/2012 10:46:08
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14015 forum posts
608 photos

Jason,

This does seem to have got rather out of hand, doesn't it.

My second note to Wolfie last night was a genuine question.

MichaelG.

Michael Gilligan18/09/2012 10:50:26
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14015 forum posts
608 photos
Posted by Dave Morris 1 on 17/09/2012 23:22:27:

just found this **LINK**

Dave,

That video is brilliant

Thank You

MichaelG.

jason udall18/09/2012 12:44:42
2011 forum posts
41 photos
Posted by Michael Gilligan on 18/09/2012 10:50:26:
Posted by Dave Morris 1 on 17/09/2012 23:22:27:

just found this **LINK**

Dave,

That video is brilliant

Thank You

MichaelG.

Ditto I had planned to post that same l;ink.. . best most graphic "mnemonic" I have seen...GUYs ( and gals) you realy should bother to watch that one... not least for the " model" subject...

Wolfie19/09/2012 08:45:45
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502 forum posts

So the only difference between 1st and 3rd angle is that the various views are in different positions relative to the 'front' view.

How silly is that?? Its the same diagram, just rearranged. No wonder its confusing cos as a novice you are looking for something much more complicated.

Michael Gilligan19/09/2012 08:54:53
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14015 forum posts
608 photos
Posted by Wolfie on 19/09/2012 08:45:45:

So the only difference between 1st and 3rd angle is that the various views are in different positions relative to the 'front' view.

How silly is that?? Its the same diagram, just rearranged. No wonder its confusing cos as a novice you are looking for something much more complicated.

 

Yes

... It's rather like driving on the Left or the Right side of the road.

... Two choices, each equally valid

But it does sometimes help to know which convention has been adopted.

MichaelG.

 

P.S. There is a remarkably thorough page on Wikipedia.

Edited By Michael Gilligan on 19/09/2012 08:58:38

Versaboss19/09/2012 11:59:29
417 forum posts
50 photos

The all important words 'position / positioning' were mentioned first by TerryD (17.9./13:24), then by Keith Long (17.9./15:01), then Michael Gilligan (17.9./19:34).

Words with similar meaning (e,g, Stub Mandrel: arranged) even much earlier.

Sometimes it needs a long time to sink the simplest things into our brains,

Greetings, Hansrudolf

Edited By Versaboss on 19/09/2012 11:59:48

(name correction)

Edited By Versaboss on 19/09/2012 12:00:48

Stub Mandrel19/09/2012 21:03:42
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4306 forum posts
291 photos

Wolfie,

You question the value of knowing the projection. This example shows a front bview and two side views of a part:

conundrum.jpg

If you don't know whether this is first or third angle, you can't tell which of two possible shapes the object is.

Now think of something complex like a real car engine block, or a house... actually the simpler the part, the greater the chances of an error.

Neil

Edited By Stub Mandrel on 19/09/2012 21:04:25

jason udall19/09/2012 23:24:36
2011 forum posts
41 photos

Welll....looks like view on left of main view is wrong...but the point is correct....A knoledge of the system in use is as much a part of the drawing as any view.

 

Now try and complete the side view of the followingdrawing1.jpg

 

 

Edited By jason udall on 19/09/2012 23:37:49

Terryd20/09/2012 06:51:15
1926 forum posts
179 photos

"How silly is that?? Its the same diagram, just rearranged. No wonder its confusing cos as a novice you are looking for something much more complicated."

Hi Wolfie,

Here is a drawing of a simple component.  Projection method (1st or 3rd) is not specified. Does it matter?  Draw me a 3D sketch and post it here.

 

projection example.jpg

 

Best regards

Terry

Edited By Terryd on 20/09/2012 07:12:42

Terryd20/09/2012 08:13:55
1926 forum posts
179 photos
Posted by jason udall on 19/09/2012 23:24:36:

Welll....looks like view on left of main view is wrong...but the point is correct....A knoledge of the system in use is as much a part of the drawing as any view.

 

Now try and complete the side view of the followingdrawing1.jpg

 

 

Edited By jason udall on 19/09/2012 23:37:49


Hi Jason,

This has been covered in a another thread some time ago

 

jasons example.jpg

The first 4 possible solutions are third angle while the last is in 1st angle.

There are actually an infinite number of theoretical siolutions as the sloping face could be a curve and the central element can be either a cut out or a projection from the surfave and could be of almost any profile especially if hidden lines are excluded.

Interesting, classic example.

Best regards

Terry

Edited By Terryd on 20/09/2012 08:23:51

jason udall20/09/2012 10:38:22
2011 forum posts
41 photos

Terry.. Classic to us..new to others .. but yes .met it myself when 11....still stays with me today.

we had to also develope and build solid model ( back when that ment card knife and glue)

Wolfie20/09/2012 12:34:04
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Moderator
502 forum posts

These problems are interesting but they are asking for the side view and not where to place it so are immaterial to the original question.

I have to say that I would have thought it was blindingly obvious to put the left hand side projection on the left, and the right hand side on the right, the top at the top and so on. Who would do it any other way???

"Hi Wolfie,

Here is a drawing of a simple component. Projection method (1st or 3rd) is not specified. Does it matter? Draw me a 3D sketch and post it here."

OK no doubt I have fallen for some trick here teeth 2 but here goes, being as you haven't included the top view I appreciate thet the rear may be different to the front  (not to scale)....

 

 

Edited By Wolfie on 20/09/2012 12:36:23

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