another 3D printed case extension; source of precise mechanical dimensions?

[Louis Mamakos]

I've implemented a 3D printed case extension for the PiDP-11 to increase
the depth of the case to allow for rear-panel mounted cable extensions
for USB, HDMI, etc. cables. You can find it on Thingiverse at
https://www.thingiverse.com/thing:4757068 and it was inspired by another
design also on that site. I did try printing that other one first, but
the dimensions seemed a little "tight", and I also wanted holes for the
back panel screws.. So off I went and learned a bit more about OpenSCAD
to design a part.

Well, you can render it as a single part, but my 3D printer's bed isn't
large enough for that. So you an select either the left side or the
right side to print. You then glue a couple of tabs together with
super-glue and screw the back panel on.

I fiddled around with this quite a bit (pretty much a whole roll of
filament with many versions..) tweaking the design. I ended up with a
bit more of a gap between the two halves. I think this might be because
my measurements of the horizontal distance between the two screw holes
might be off a few millimeters. Even the larger caliper that I bought
isn't quite wide enough to measure this distance directly.

I'm wondering if somewhere are the precise dimensions of the back panel
available somewhere? My part uses the locations of the 4 screws as
reference points.

Regardless, it seems to work pretty well for me so far, and feel free to
tweak the OpenSCAD code that's also been posted if you want to customize
it. Maybe change the logos and make it your own. Of course, you'll
need longer screws and maybe print some feet or something if you like.
I used to feet from the other design posted there; the holes are a off,
but "close enough" and can be made to work.

louie

[Neil Higgins]

Well done, Louie! And thanks for posting the files to Thingiverse.

It occurs to me that there should have been enough computing power in a (real) PDP-11 to drive the steppers in a 3D printer. All of the required parts for a 3D printer - steppers, bearings, thermistors, etc. (maybe even PLA) would have been around in those days. Perhaps, 3D printing either didn’t occur to anyone then, or the patents and the cost of computing held it back.

[Johnny Billquist]

I would rather guess that all the other technology that goes into a 3D
printer just didn't exist yet, back then.

Moving the head around is the trivial part. The actual printing head as
such, printing materials as well as tools to design the thing to be
printed in a reasonable way would have been more of a problem. And I
don't know about other actual bits inside the printer that might exist
which wasn't figured out yet back in the 80s.

Johnny

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Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: b...@softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol

[Oscar Vermeulen]

Louie,

Nice!

On Sun, 28 Feb 2021 at 03:21, Louis Mamakos <lmam...@gmail.com> wrote:

I'm wondering if somewhere are the precise dimensions of the back panel
available somewhere?  My part uses the locations of the 4 screws as
reference points.

Sure, attached is the back panel. Note the dimensions are in the drawing - just check the line lengths.

Kind regards,

Oscar.

[Charley Jones]

Welcome to openScad.  It’s a really great tool.  I’m Dataman on thingiverse, you can look me up. Congrats a really nice design.

Sent from my iPhone Xs!

On Feb 28, 2021, at 2:59 PM, Oscar Vermeulen <vermeul...@gmail.com> wrote:



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<paneel.svg>

[Thomas Niccum]

Hi Louie!  

I just printed out your case extension, and it looks great.  

May I ask what screw dimensions you used to mount everything to the original case?

Thanks!

Tom

[Erik Hanson]

Hello,

I printed that exact extension, it was a nice addition. The screws I ended up using are #12 x 2.5" - I believe they're an exact match for diameter and thread as the original screws that shipped with the kit. My local hardware store didn't have them in self-tapping so I went with regular sheet metal screws, and they went into the plastic just fine.

Erik

[Thomas Niccum]

Awesome, thanks!

[Louis Mamakos]

I'm glad someone has found that 3D printed case extension useful to them. I
had wondered if it was more than just me that bothered to print one out (or in
my case, about 6 variations..) It was a great excuse to buy a larger
digital caliper for measuring dimensions as large as the PiDP-11.

As I recently built myself a Voron 2.4 3D printer with a 350mm X 350mm build
area, I generated an STL file for a single print of the entire bracket. It's
been uploaded to the Thingiverse page (at https://www.thingiverse.com/thing:4757068 )
if that's of interest. Nothing else has changed. You can generate this
yourself from the OpenSCAD file by changing a parameter at the top of the file.

Louis Mamakos

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[Erik Hanson]

Hi Louis,

Somehow I didn't realize you had created the case extension, I got here late!

Thanks for the design. If I were to reprint it I think I'd make it even deeper, maybe 

another 30-40mm. Things still feel a bit packed in with usb, hdmi, power, ethernet,

and serial panel mount cables. I don't think I'd need to do it as a single piece, my

printer is 220x220 and the two pieces came out fine, I didn't even need to glue the

tabs. I'll try and get some pics up on thingiverse soon.

Erik

[Louis Mamakos]

In theory, the OpenSCAD design has the dimensions parameterized, though
there are some fudge-factors here and there. Increasing the depth is
likely the easiest thing to attempt.

Up near the top of the file at line 11 is

case_depth = 35;

which is the number you'd want to tweak. Just changing that and looking
at the preview in OpenSCAD makes me think it's doing the right thing :-)

Also, if anyone doesn't like the "d i g i t a l" and "pidp11/70" logos,
they're pretty easy to comment out at line 231 and 232.

Louis Mamakos

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[Erik Hanson]

I'm not familiar with OpenSCAD at all, sadly. I can sort of fumble through

Tinkercad for some basic things but that's it. I was thinking that making it deep

enough for a 40mm fan mount on one side and some vent slots on the other

could be useful. I just upgraded from a Pi 2 to a 4 and it runs very hot, I think

a fan would be a nice addition.

Erik

[steve...@gmail.com]

Erik,

Have you updated the firmware on your Pi 4? You may not really need the fan if the cause of your heat problem is that you've got an early version of the firmware. See the discussion and firmware update instructions here:

https://www.seeedstudio.com/blog/2019/11/29/raspberry-pi-4-firmware-update-pi-4-now-runs-cooler-than-ever/

-- steve

[Erik Hanson]

Hi,

Yes I have updated the firmware fairly recently, to get boot from USB support. The problem

isn't the Pi4 at idle, it doesn't have a chance to idle. RSX idling doesn't mean simh is idle, if

you follow. It'll chew up whatever CPU % you let it via throttle, regardless of what the guest

OS is doing.

As it is, it's not so hot that it's a problem. I have heatsinks attached but I really think when

it's enclosed a small amount of airflow from a quiet (Noctua, probably) fan would be nice,

if only for peace of mind.

-- 

Erik

[Thomas Niccum]

I just upgraded my printer to be able to print up to 400x400mm, and was able to reprint this in a single piece.  For stability, I lengthened it by 250% and now the PiDP-11 sits pretty without the wood block.

I printed it in white to match the kit's case...

On Saturday, February 27, 2021 at 6:21:14 PM UTC-8 lmam...@gmail.com wrote: