Image Map Image Map
View RSS Feed

1944GPW

A good-enough replica of the ''digital' PDP11 masthead for the H960 rack

Rating: 3 votes, 5.00 average.
I recently lucked onto not one but a pair of original DEC H960 racks recently, after searching for a few years. They were interstate but I found a backloader who agreed to move them at a fair price, if I didn't mind waiting a few weeks. Now they've arrived I've thought they would look pretty nice with a pair of those groovy 1970s magenta and pink 'digital' mastheads. But they are pretty much unobtainium these days and even the plain two-tone ones with no labelling list for up to $200 USD.

So I thought about making some replicas, something that would follow the 'six foot rule'. That is, it looks good from six feet away Not having a DEC masthead of any description I of course turned to the net to see what I could find - firstly, had anyone already drawn one up I could use, or failing that could I find an image good enough to use as a background overlay for redrawing in CAD, with the aim to produce a DWG, DXF or SVG or some other form of vector output and from that a vinyl stencil. The stencil would be just the white lettering and lining which would be stuck onto a spraypainted magenta/pink styrene plastic sheet.

First off, I found the story on the |d|i|g|i|t|a|l| logo here: http://nedbatchelder.com/blog/200712...ital_logo.html
I immediately pounced on the offered postscript file which I had trouble with converting to SVG, as I thought that format might be best to cut from. I then tried the pdf version and successfully converted that to SVG using an online converter. I loaded the result into InkScape but was disappointed with the result. The path finding utility in that application generated lots of nodes that would have needed a huge amount of cleaning up to get it right, particularly the font curves. I experimented with the edge detection parameters but had no real joy, I'm just not that familiar with Inkscape.

So I reluctantly gave up on using that page and decided to draw it myself from scratch in CAD. I suppose the flip side is this would have the advantage for me that I'm not plagiarising someone else's hard work, and only using what the company itself produced and what is placed in the public domain. Firstly I needed a 'good enough' image of the masthead with preferably no perspective (if it had perspective I would have removed it used imagemagick's affine transform but that adds an extra undersirable image munging). I ended up finding a pretty good picture right on the wikipedia page for the PDP-11 here: https://en.wikipedia.org/wiki/PDP-11
Scroll down to the photo of the TU10 tape drive, click through to the raw image and it was just what I wanted.

After saving and cropping the high res image, I checked it for perspective and rotational alignment (or hopefully, lack of). It was very good with only a tiny bit of distortion: a bowing in the middle, probably a warp in the panel itself. But level at both ends thankfully, so no rotation needed.

I loaded the image into my CAD program as a background layer with a scale of one pixel per millimetre (which made the masthead 7.2m wide!) and found it fairly easy to draw over the top of, being mindful I would need to remove any distortion. Drawing the 'pdp11' was trivial. The 'digital' text wasn't too bad (mostly ellipses), but the 'a' was difficult for me to do to an acceptable standard without spending many hours on it. Since this panel is really only a 'good enough' version I compromised on the arcs and tangents somewhat, but there are a few bits to tidy up (image 3 below). At masthead size I think it would only be picked if it were next to an original one.

Now, to the lower text, 'digital equipment corporation . maynard. massachusetts'. This is a bit of an unusual font,comprised mainly of circles and hand-drawn I think - the 't's and 'r's are tweaked depending on their placement in the text. I found the lower text in theTU10 photo to be a bit too low in quality to draw vectors over, so I chose to use the image at https://hack42.nl/mediawiki/images/a/a7/Dec_footer.png which was sharper, and scale to fit back into the main drawing.

Here's the 'digital'. You can clearly see the circles used in its construction:


Now here's where I need some help. I had assumed the masthead would be the same size as an H960 3RU high filler panel. I have one, but this is too small. It's pretty evident the masthead needs to go over the top folded sheetmetal bar of the rack. If someone has an original one, I'd really like the following measurements (metric or imperial, whatever). I also would like to know of the outer edge of the masthead is a beige colour, or even silver. I can't easily tell from the photos I've found. The panel would be the inner bit with the radiused corners, the edges being a seperately cut panel which is in front of the the detailed one.



I would also like to know how deep the recess is for the front. I suspect the same as the filler panel bezel edge, about 3mm. And also the depth of the plastic backing. I think I could derive these from a CAD overdraw of a photo of a blank masthead currently on eBay. I'll get to that later though.




So far I have completed the masthead CAD drawing which I can export to DXF and SVG. After correct sizing, the next step for me is to look into those neat vinyl/paper stencil cutters such as the CriCut and Sillhouette to see if they'd do the job. Time to watch some Youtube videos on these things - how they are used, their capabilities, what they cost etc. after which I'll know 100% more than I do now

Submit "A good-enough replica of the ''digital' PDP11 masthead for the H960 rack" to Digg Submit "A good-enough replica of the ''digital' PDP11 masthead for the H960 rack" to del.icio.us Submit "A good-enough replica of the ''digital' PDP11 masthead for the H960 rack" to StumbleUpon Submit "A good-enough replica of the ''digital' PDP11 masthead for the H960 rack" to Google

Updated July 8th, 2015 at 07:31 PM by 1944GPW

Tags: dec, h960, masthead, svg, vector Add / Edit Tags
Categories
Uncategorized

Comments

  1. billdeg's Avatar
    Did you get the answers you were looking for? I have a few of the H960's.
  2. 1944GPW's Avatar
    G'day Bill,
    Yes thanks I found the information I needed from those helpful folks on cctalk. Thanks for your interest, it encourages me to get back to this project and do some more test cuts.

    Steve.
  3. ComputerGeek's Avatar
    Can you send me the CAD files please if you can. I would like to have one for my computer.