No 4407 More Errors

[JasonBModerator @jasonb]

Hobbymat was made with 3 different spindle sizes – 55, 56 and 63mm Text and drawing would seem to be based on a 55mm machine

 

Anyway the drawing would still be wrong as it shows 55mm into the 56mm chuck.

 

J

Edited By JasonB on 03/07/2011 15:59:02

[JasonBModerator @jasonb]

Is it a clock making thing or is there another reason that the OD of all the gearwheels in the clock article seem to be 10-20 thou over size using (teeth +2) *MOD?

 

Or is that why clock makers use a depthing tool rather than measure out the gear centres

 

J

Edited By JasonB on 03/07/2011 16:19:36

[JasonBModerator @jasonb]

On no I should have kept quiet about the clock. Thought I better read the text from the previous installment incase something was hidden in the text. We have , a 36tooth gear 3 times the dia of a 39T gear and again OD that are plus or minus 20thou.

 

Seems complacancy is more predominant than pedancy

 

J

Edited By JasonB on 03/07/2011 17:07:08

[adyParticipant @ady]

I don’t see what the problem is.

Everything fits together perfectly if you adapt the build as it progresses

 

Edited By ady on 04/07/2011 04:11:39

[Phil PParticipant @philp]

Posted by JasonB on 03/07/2011 16:17:27:

Is it a clock making thing or is there another reason that the OD of all the gearwheels in the clock article seem to be 10-20 thou over size using (teeth +2) *MOD?

 

Or is that why clock makers use a depthing tool rather than measure out the gear centres

 

J

Edited By JasonB on 03/07/2011 16:19:36

Jason

According to the clock wheel and pinion cutting book by J.M. Wild :-

 

For wheels the OD is (N + 2.76) x Module

 

For pinions of 6,7 & 8 teeth the OD is (N + 1.71) x Module

 

For pinions of 10,12 & 16 teeth the OD is (N + 1.61) x Module

 

That is assuming the tooth form to be cycloidal as opposed to involute.

 

Phil

 

[JasonBModerator @jasonb]

Thanks for that Phil, comes out OK using that formula, learn something new every day.

 

Jason

[JasonBModerator @jasonb]

Posted by David Clark 1 on 01/07/2011 08:52:16:

 

Fig 10

The 2.85mm hole centerline is not shown in line with the 1.75mm recess, it is clearly shown above it. Therefore we either need a height for the hole (PROBABLY 2MM) or the 1.75mm is not the size of the notches on the bearing blocks.

On the original it is clearly shown in line with the 1.75 steps.

 

Having just seen this engine in the flesh today at Guildford I can confirm thet the holes are above the 1.75mm step.

 

The engine was running very sweetly so I would suggest to anyone thinking of making this not to be put off by these drawing issues if they can all be resolved it will build into a nice piece to add to your collection

 

Jason

 

PS Drawings in 4408 look beter just need the angle for teh displacer crank in Fig 23 its shown as a strange 34+

[David Clark 13Participant @davidclark13]

Hi There

This is the drawing I aproved for press.

As you can see it clearly says 34 degrees.

It has obviously been changed by the page design software.

I will get this checked on Monday.

Probably to do with the fonts used.

regards David

 

 

Edited By David Clark 1 on 09/07/2011 14:44:55

[JasonBModerator @jasonb]

Yes could well have scanned in 84 and got 34 out.

 

Thanks, J

[blowlampParticipant @blowlamp]

I get that angle at 77 degrees by tracing over it.

 

Martin.

[JasonBModerator @jasonb]

Looks like it could also do with a dimension between the fork holes and the 4mm hole while you are at it David, as yw long teh lower arm should be without a lot of calculation

[Gone AwayParticipant @goneaway]

Is it just me or is that drawing mixing first and third-angle projections?

[JasonBModerator @jasonb]

I think its you, looks OK to me.

 

J

[Gone AwayParticipant @goneaway]

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?)

[JasonBModerator @jasonb]

Longer on the far side as the photo confirms, all 3rd angle

[Gone AwayParticipant @goneaway]

Then the lower view is wrong (or first-angle).

[JasonBModerator @jasonb]

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 13Participant @davidclark13]

Hi There

Tha angle has to be wrong or it is drawn incorrectly.

I will check with Brian on Monday.

regards David

 

[Gone AwayParticipant @goneaway]

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.

[blowlampParticipant @blowlamp]

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.

[JasonBModerator @jasonb]

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 13Participant @davidclark13]

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 CoxParticipant @ericcox50497]

.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

[JasonBModerator @jasonb]

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 13Participant @davidclark13]

Hi There

Updated dimensions.

84 is correct measured from original.

regards david

[Author]

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