tardis roundel reference

[Theta Sigma]

Excellent work Tony!  One question though, you said:

The first diagram shows the revised positions of circles with the diameters drawn to match the dimensions determined by Theta Sigma.

I'm not seeing this drawing.  Did you intend to post something that looked like my drawing with the center points and radii of the arcs?  If not, can you produce such a drawing? 

If it's not possible, I can always import your drawing into the CAD program I use, and adjust my drawing to match yours.

I make my formers by printing out the drawing on a shipping label, and then sticking it to the brass sheet.  I use a small punch on the arc center points to mark them into the metal, then drill out the arcs using the proper size bits and a drill press.  The rest is carefully cut using a scroll aw with cleanup using a file/sandpaper as needed.

I'm not sure how much it could cost to have a machine shop CNC the former, but if not cost prohibitive, they would need a CAD drawing of the former to work from.

[tony farrell]

Hi,

I can really only use Microsoft's "Paint". Whilst I've used a conversion program to accurately convert actual dimensions into pixels, the problem with 'Paint' is that you can only draw the results full pixels (i.e., no fractions of a pixel).

To get round this, I drew the diagram at twice full size. But, even then, a circle with a few thousandths of an inch diameter might result in a drawing of a circle with an odd number of pixels as its diameter. So - for example - one of the circles I've drawn has a diameter of 21 pixels; therefore, Microsoft "Paint" wouldn't allow me to accurately identify its centre-point i.e., I would have been forced to mark the centre-point at either ten or eleven pixels rather than ten-and-a-half pixels.

I tried to create a drawing at four times actual size but, when I tried to print it out at 25%, there was too much loss of definition so, I was forced to compromise and to create a drawing at twice actual size and print that out at 50% which fortunately resulted in a clear (usable) image.

As I say Theta Sigma, I have used the diameters of the circles as specified by you, it is only their positions which I have altered. Unfortunately, I can't help you with any CAD drawing you might need. (Just in case the forum's software has caused any distortion or slightly resized it, if you want to let me know your contact details by private message, I can e-mail you my drawing.)

T

[Theta Sigma]

Truly impressive work using only the "Paint" application, Tony!

I will import your image into my CAD program, and alter my drawing to match yours!  I'll post my revised version as soon as I can.

[Theta Sigma]

Tony,

I imported your drawing into my CAD program at half-size.  I was able to modify my drawing to match up, and came up with the following overlay.  I have switched over to metric measurements, and rounded off to the nearest 0.5mm.  

I am having trouble reconciling the established 8mm difference between the flange and the center disc on your drawing.  As you can see, there is a significant departure between the two drawings (by ~4mm) on the flange height when I specify the 8mm difference.  Thoughts?

[Theta Sigma]

Now if I drop the height difference between the flange and center disc down to 4mm, everything seems to fall into place.  The measurements taken by Karsten also line up when rounded to the nearest 0.5 mm.  These agree with my partial casting as well.

If we can get concurrence on this drawing, I will add more dimensions to fully constrain it.  After that, I can extrude it in the CAD program to produce a 3D roundel shape for us to marvel.

[tony farrell]

Blimey, you did that quickly!  

Below, I've taken the liberty of re-scaling your revised drawing so that it is the same size as mine (i.e., twice actual size). For comparison, my drawing has been placed underneath yours and I've then overlaid my drawing on top of your revised version:



As you can see, we have an almost exact match. In truth, any slight discrepancy is down to how I've drawn mine (as I tried to explain in my previous post, Microsoft Paint only allows the use of full pixels).

The second thing to say is that these roundels were designed by Barry Newbery and were designed to be fitted through holes cut in the original wooden Control Room's wall panels. Now, on the Season 15 Tardis plans, these pre-existing wall panels were re-utilised and the plans for the Season 15 Control Room specify that the new wall panels were to be made from 19 mm thick blockboard to match the pre-existing ones.

We can therefore state with a high degree of certainty that the depth of the outer 'wall' of the roundel was 18 millimeters which matches what you and I have both drawn.

Now, I'm not a gambling man (the last time I had a bet was a pound on Red Rum to win the Grand National in 1977) but, on this occasion, I'd be prepared to put my neck on the block and state that between the three of us, we've come up with screen-accurate dimensions for the Newbery Roundels!  

Thanks once again to you and Karsten for your help and I'm looking forward to seeing a render!

T

(Edit - note to self: learn how to spell 'National' correctly! DOH!!)

[Theta Sigma]

Awesome!  This next part might take me a while.  My current drawing is under-constrained with 74 degrees of freedom.  It will take a while to fully constrain the drawing, and usually I get down to like 1-2 degrees of freedom and can't find where I need to put the contraints.

[karsthotep]

this is excellent news and great work by Tony and Theta,  I am glad I could contribute to the effort.   I really want to take a crack at this with a former and some modeling clay.   Would it be possible to have a CAD drawing made up for a former, we could get that uploaded into shapeways for a print out.  I don't want to try and cut it out by hand. 

[tony farrell]

It was a team effort Karsten! 

I too would be interested in a 'former' for the Newbery Roundels. However, I'm afraid a suitable CAD drawing isn't something I could do.

Theta Sigma seems to have the necessary 'know-how' so, I guess we'll just have to be patient.

T

[Theta Sigma]

I am down to 19 degrees of freedom on the CAD drawing from 74.    The process of exactly marking each vertex and arc radius is painstaking.  The drawing is so busy at this point, you can hardly see the profile.  I hope to have something soon to share.

[karsthotep]

Kevin,  no worries man we appreciate that you are doing it.  i still want the full CAD so I can see if there are any reasonable 3D printing options for something of that size.  Prices are always coming down so always worth a check, but that is neither here nor there,  take your time we get it when we get it,  thanks again.

[Theta Sigma]

Well, I have the full drawing done, and here's the render.






I am tweaking the former drawing still, but it should be done this weekend.  

One last item I would like some discussion on before I finalize the drawing.  Do we think this area is flat as Tony has drawn it, or does it become slightly concave as I have drawn it here?  Feeling the partial casting I have tells me that it has a concave feature.  Now I feel like a pervert.  

[Theta Sigma]

Another closeup picture of a roundel that leads me to believe there is a concave section.  Notice the shadow.

I also fear we may have over-smoothed parts of the profile effective muting sharper features such as the wide flat-ish section about 1/3 of the way in from the mounting flange.  Thoughts on sharpening these on the drawing?  Any moulds made of plugs will, by nature, automatically mute some of the sharper features.  I don't think we want to go overboard with the softening when making a plug.

[tony farrell]

 

One last item I would like some discussion on before I finalize the drawing.  Do we think this area is flat as Tony has drawn it, or does it become slightly concave as I have drawn it here?  

I haven't drawn it as flat - I've drawn a slight concave at that point - don't forget what I said about Microsoft's Paint and the fact my diagram is twice actual size because of the limitations of 'Paint'.

T.

[karsthotep]

Looking great Kevin, can't wait to get that cad file