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No 4407 More Errors

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Gone Away09/07/2011 17:29:36
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Is it just me or is that drawing mixing first and third-angle projections?
JasonB09/07/2011 17:37:02
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I think its you, looks OK to me.
 
J
Gone Away09/07/2011 18:38:35
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The boss in the corner is longer on one side than the other. In the top left view, is it longer on the side facing you or on the far side?
 
(And, if they're consistent, are the other two views first or third angle projections?)
JasonB09/07/2011 18:44:05
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Longer on the far side as the photo confirms, all 3rd angle
Gone Away09/07/2011 18:54:39
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Then the lower view is wrong (or first-angle).
JasonB09/07/2011 18:59:22
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Well the plan should really be above the two elevations for 3rd angle or if layed out as is then yes the boss should be the otherway round and the end of teh arm shown dotted effectively making it a view from below if you want 1st angle. But like I said in the other post I could make it from those drawings given the missing dimension and confirmation of the angle that I mentioned earlier which is what really matters.
 
Also all the other drawings in 4407 use the same layout so at least they are consistant

 

Edited By JasonB on 09/07/2011 19:03:32

David Clark 109/07/2011 19:31:23
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Hi There
Tha angle has to be wrong or it is drawn incorrectly.
I will check with Brian on Monday.
regards David
 
Gone Away09/07/2011 22:44:30
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Posted by JasonB on 09/07/2011 18:59:22:
Well the plan should really be above the two elevations for 3rd angle or if layed out as is then yes the boss should be the otherway round and the end of teh arm shown dotted effectively making it a view from below if you want 1st angle.

With respect Jason, that elevation is not described as a "plan" nor is there any compulsion in any drawing standards that I've ever come across (formal or informal) to include any specific elevations/views. Simply that sufficient elevations/views be included to completely describe the part.
 
In that case, and if this is indeed intended as third-angle, then the lower elevation would logically be interpreted as a view on the bottom of the view above it and the elevation to the right as a view of the right side. As such, they are inconsistent.
 
Yes, you may be able to make the part by scrounging around for other information but any drawing should stand alone and give enough information to make the part.
 
I sense that you don't think this is particularly important. Dimensional errors may occur occasionally even on professionally produced drawings (particularly those that are/were manually generated) but nothing else more clearly says "amateurish" or leads to more confusion, than inconsistent projection standards.
blowlamp10/07/2011 00:01:50
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As a little test, I've roughly scaled the drawing to the 50mm reference line and overlayed a few arcs and lines with their actual dimensions and some are pretty far out, as can be seen in the picture.
 
The large arc is ok, but the smaller one is not so good when compared to the theoretically correct one I've put in.
The 21mm measurement is miles out, as is the 39mm one.
 
I know we don't scale from the drawing, but it should bear a closer resemblance to reality than this one appears to.
 

 
Martin.
JasonB10/07/2011 07:44:56
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At the risk of these errors getting lost in another epic drawing standards thread could I ask that we keep this thread to the actual errors so its easier for future builders to locate corrections. Having said that....
 
Sid, the use of "Plan" comes from my construction background where the view from above is generally termed the Plan View, from the side Elevations and rarely from below would be inverted plan. What I was saying is they are consistant in as much as all the drawings for this engine in both 4407 & 4408 use the same mixed projection eg 3rd angle for the elevations with what should be the 3rd angle view from above placed below the elevations rather than above. Still could be worse, the Rina has one drawing in 1st and the other in 3rd, now that is inconsistant.
 
Martin thanks for taking the time to draw the part out and it does raise the point that without a drawing being drawn in proportion its very hard to spot if a dimension has been printed wrongly. A point for David to take up with Stavros the illustrator.
 
Interesting that the 39mm is so far out, if it were drawn the correct length then it may mean the angle is supposed to be 84deg as I suggested rather than the 77 it measures off the drawing
 
J

Edited By JasonB on 10/07/2011 07:47:47

David Clark 110/07/2011 09:15:44
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Hi There
The text says the centre bar is offset, so the 21 is probably correct.
The drawings may not be to scale.
The drawings are made from the originals and if they are not supplied to scale they will not be redrawn to scale.
The same goes for projection.
We have time to tidy up what we get, we don't have time to redraw and redesign everything.
If we did that, we would have to make another model to prove the dimensions.
regards David
 
Eric Cox10/07/2011 10:21:57
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.The 34 degree angle should be a reference dimension and the position of the 6BA clearance hole should be dimensioned relative to the X-Y axis.

Edited By Eric Cox on 10/07/2011 10:26:18

Edited By Eric Cox on 10/07/2011 10:35:49

JasonB10/07/2011 11:31:35
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I would have thought that the curved dimension line indicates that it should be an angular measurement.
 
But agree that teh hole could be positioned using teh 39mm and a second dimension fort teh other axis.
David Clark 111/07/2011 19:35:23
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Hi There
Updated dimensions.
84 is correct measured from original.
regards david

JasonB11/07/2011 20:44:42
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Thanks for that David.
 
It now raises the question regarding the length of the arm, 32 along the diagonal on the original, 39 vertacally on the mag drawing. I see this is in a darker font is this something you have added?
David Clark 112/07/2011 08:06:13
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Hi There
I added the 84 degrees, 32, the 55 and the 1 after talking to Brian.
Brian had to bend the 84 degrees to fit which is why the drawing angle is different.
The actual model is 84 degrees.
regards David
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