test-drb April 2013

test-drb@ccmp.vtda.org

205 participants
273 discussions

Designing a replacement Alps Plotter drive gear (was Re: looking for Daisy Wheel Printer)

by bobvines00＠gmail.com

> Message: 26 > Date: Thu, 11 Apr 2013 18:49:25 -0400 > From: Ethan Dicks <ethan.dicks at gmail.com> > To: "General Discussion: On-Topic and Off-Topic Posts" > <cctalk at classiccmp.org> > Subject: Designing a replacement Alps Plotter drive gear (was Re: > looking for Daisy Wheel Printer) > Message-ID: > <CAALmimn-amKc8rMuGmaua4hqmR527STr8B30qx_TJMPKSzr_Qg at mail.gmail.com> > Content-Type: text/plain; charset=ISO-8859-1 > [snip] > > Mention of the Alps plotter reminds me that we've had various discussions > about all the plotter mechs with broken gears but we've never worked out > the details on fabricating replacement gears. I've learned a lot about > fabrication over the past couple of years, so I wanted to take another stab > at the discussion to fill in the parts I don't (yet) understand... > > So I was looking at this gear generator... > > http://woodgears.ca/gear_cutting/template.html > > ... thinking that you can't fabricate a good replacement until you > have the data on what you are replacing. I'd like to try to make > either a flat (DXF) design file or a 3D (STL) design file of a > gear replacement candidate. It's possible that with so few > leaves (teeth) and such a small size (1/8" / 3mm across the > face, 1/20" / 1.27mm shaft) that there will be fiddling for > undercut, etc., but I wanted to at least make *something* > that could be tried for good fit. > > So that web-based tool can make a bitmap image of a > gear given the right data, but my own 2D CAD skills aren't > honed enough to draft up a DXF of a gear. Is there anyone > on the list here who is good with 2D CAD and has time > to make an image of a gear? I'm fine with turning that into > 3D and seeing how things would all turn out. I still have > several broken plotters and would like to get them working > again. > > Cheers, > > -ethan Ethan, I may be able to draw up a gear like this, but like the "gear generator," I'd have to have the correct gear data to know what to draw. I'm willing to try. What specs should I try to draw a gear to? I have access to both 2D & 3D drafting/modeling software (AutoCAD & SolidWorks). Do you intend to use a 3D printer to try to manufacture the gear? I suppose these gears are spur gears with involute gear teeth. What is the pressure angle? What is the total number of teeth? What is the pitch diameter? You said the face width is 1/8-inch and the shaft hole fits a 1.27mm diameter shaft. Wikipedia (https://en.wikipedia.org/wiki/Gear) has all this info and more -- I'm pretty sure that you are interested in only spur gears right now, so you can skim over the other gear-type information on that page. Knowing the gear specs may even allow someone to go to the "small gear" catalogs and maybe even be able to select an "off-the-shelf" gear for each needed gear. It's possible. Let me know, Bob

11 years, 3 months

Computer ASCII Text Art from the 1970's

by jfoust＠threedee.com

At 09:35 AM 4/12/2013, John Foust wrote: >The Rostenbach site says the original digitized material was at >12 bits of gray, but that he worked with an 8 bit version. I'm sorry - Rostenbach says the original was 9 bits, and that he had a tape with those nine bits stored in twelve bits. - John

11 years, 3 months

Designing a replacement Alps Plotter drive gear

by bobvines00＠gmail.com

On Thu, 11 Apr 2013 21:29:30 -0400, Ethan Dicks <ethan.dicks at gmail.com> wrote: >>> Mention of the Alps plotter reminds me that we've had various discussions >>> about all the plotter mechs with broken gears but we've never worked out >>> the details... > >> I may be able to draw up a gear like this, but like the "gear >> generator," I'd have to have the correct gear data to know what to >> draw. > > Understandable. If I had more numbers up front, I would have given them. > >> What specs should I try to draw a gear to? I have access to both 2D & >> 3D drafting/modeling software (AutoCAD & SolidWorks). >> Do you intend to use a 3D printer to try to manufacture the gear? > > I do not. I was contemplating trying to laser-cut some out of Delrin sheet, > something I did not have access to the last time this conversation made > its rounds. As before, FDM printers do not have the resolution for such > a tiny part, and other technologies (sintered powder or UV-cured resin) > are likely to be too brittle, especially with such fine features. > I didn't really think so (for the same reasons), but I haven't kept up-to-date with today's additive manufacturing capabilities. >> I suppose these gears are spur gears with involute gear teeth. > > As far as I know that is true. > >> What is the pressure angle? > > I do not know. > >> What is the total number of teeth? >> What is the pitch diameter? > > I do not know without digging out a printer to check. I used to have > 4MP close-up pictures (taken with my gear in 2003 back when > Electronic Goldmine was surplusing the bare Alps printer mechs > for a few dollars) but I don't know exactly where those photos > are at the moment. My best approach right now would be to > drop one on a high-res flatbed scanner (1200 dpi) to get a > reasonable "to scale" picture, but I don't have a gear in front > of me at the moment (I do have them in town). > If you find the photos or make the scans, please send them. If possible, scan the gear next to something with a known scale such as a 6-inch machinist's scale or equal. >> You said the face width is 1/8-inch and the shaft hole fits a 1.27mm >> diameter shaft. > > That's what I've scraped from previous conversations about this > gear. I now own a micrometer so with a gear in hand, I have > a chance of confirming that to better accuracy. > >> Wikipedia (https://en.wikipedia.org/wiki/Gear) has all this info and >> more -- I'm pretty sure that you are interested in only spur gears >> right now, so you can skim over the other gear-type information on >> that page. > > *nods* > >> Knowing the gear specs may even allow someone to go to the "small >> gear" catalogs and maybe even be able to select an "off-the-shelf" >> gear for each needed gear. It's possible. > > I think we (the cctalk community at the time) looked into that and nobody > had such tiny gears with so few large teeth in their catalog. Sounds like a "non-standard" gear. I can see why you (cctalk) couldn't find one in a catalog. > There were > calls to remove a gear and make castings (most gears are already broken > making that difficult) or using a lathe to make a fresh brass gear, etc. > Someone apparently did take a stab at a homemade brass gear but > declared it too expensive to warrant starting up a small run. Perhaps > hobby CNC has evolved to the point now where one could do a gear > with less labor and make an individually cut gear easily enough to > justify selling it for around $5. Or not. The hobby CNC world seems to have drastically increased in popularity in the last few years. A lot of the (mostly) guys are retired now and *may* be willing to make a small run for a reasonable cost just for the challenge. We'd still have to be able to give them full specs so they can program their machines. I recommend we wait on approaching the hobby CNC community until the gear specs can be determined and you have a go at the prototype with the laser. > > If I have a DXF or EPS of the face of the gear, I can see if the laser > cutter can make an approximation out of Delrin for nearly free (I just > spend a few minutes when I'm already working on a run and as long > as I don't work past the quarter-hour billing tick on the tool, the time > is already paid for by the other job). I'm not positive that this will > work, but the cost is so low that it's worth a stab. Just need the > silhouette to scale and I'm good to go. > > -ethan Go ahead and measure what you can and send me the dimensions & photos/scans. I'll see what I can put into DXF or EPS format for you. Bob

11 years, 3 months

Computer ASCII Text Art from the 1970's

by jfoust＠threedee.com

At 06:06 PM 4/11/2013, Mike Loewen wrote: > Internet sources state that the "Mona by the Numbers" image was done on a plotter. There is some info and a few links at the bottom of this page: >http://rostenbach.com/mona/mona.htm Yes, that's the one. I hadn't seen digitalmonalisa.com before. It is owned by a Andrew Patros. Does anyone recognize his name and know why he made it? At first I thought he was selling prints. It says "Mona by the Numbers" was reproduced on a "diazo printing machine." In the PDF on the site, it also says "Peterson used his EYE [a flying spot scanner] to scan a 35mm slide of the Mona Lisa, and then, using a specially designed character set, played the scan back onto a 30 inch Cal Comp plotter. The 30 inch monochrome playback sparked a mini collecting frenzy all over the country." The Rostenbach site says the original digitized material was at 12 bits of gray, but that he worked with an 8 bit version. Nelson's "Computer Lib" says each spot was 100 levels, which makes me wonder if he wasn't misconstruing "percents" as levels. So as I understand it, diazo was a copying technology that made copies of the original plotter print. Does that account for the faded orange color of the surviving prints? <http://www.vintchip.com/DOCUMENTS/monanumbers/mona.html>http://www.vintchip.com/DOCUMENTS/monanumbers/mona.html has a nice closeup of the bottom of an original. That site is kept by a Greg Barber. I'd love to get an original. Does anyone recall them ever coming up for sale? Barring that, I'm tempted to recreate it in Illustrator so vector reproductions could be made. - John

11 years, 3 months

Computer ASCII Text Art from the 1970's

by craig＠solomonson.net

I ran across some old computer art from the 1970's while sorting through some old boxes in storage. It seems like nearly every computer lab and room had a few posters hanging on the wall. As I recall, Snoopy was probably the most popular subject along with "space stuff." I just had to piece these old posters together and see what I had printed back in 1981. It turns out that at least 2 of them were from the Princeton University Computer Center Clinic and done by Samuel P. Harbison in 1973. The third one of the Golden Gate Bridge is huge (8 ft. wide and 6.5 ft. tall) and no credits were given. Here are some photos of them for those that are interested: Golden Gate Bridge (with a PAA airplane) - 96" x 78": http://www.solomonson.net/computers/GoldenGate.jpg One Giant Leap (man on the moon) - 40" x 33": http://www.solomonson.net/computers/GiantLeap.jpg The Moon - 59" x 55": http://www.solomonson.net/computers/Moon.jpg

11 years, 3 months

Designing a replacement Alps Plotter drive gear (was Re: looking for Daisy Wheel Printer)

by ethan.dicks＠gmail.com

On Thu, Apr 11, 2013 at 4:20 PM, Tony Duell <ard at p850ug1.demon.co.uk> wrote: >> One of those 4-colour pritner/ploters using the Alps mechanism. Everybody >> >and his dog sold them at some poitn -- Tandy CGP115, Commodore 1520, >> >there was an Atari oen, a Sharp one, theOric printer, etc. > > But that little Alps unit is somewhat odd, and IMHO deserves a place i na > colleciton of hard copy peripherals. Mention of the Alps plotter reminds me that we've had various discussions about all the plotter mechs with broken gears but we've never worked out the details on fabricating replacement gears. I've learned a lot about fabrication over the past couple of years, so I wanted to take another stab at the discussion to fill in the parts I don't (yet) understand... So I was looking at this gear generator... http://woodgears.ca/gear_cutting/template.html ... thinking that you can't fabricate a good replacement until you have the data on what you are replacing. I'd like to try to make either a flat (DXF) design file or a 3D (STL) design file of a gear replacement candidate. It's possible that with so few leaves (teeth) and such a small size (1/8" / 3mm across the face, 1/20" / 1.27mm shaft) that there will be fiddling for undercut, etc., but I wanted to at least make *something* that could be tried for good fit. So that web-based tool can make a bitmap image of a gear given the right data, but my own 2D CAD skills aren't honed enough to draft up a DXF of a gear. Is there anyone on the list here who is good with 2D CAD and has time to make an image of a gear? I'm fine with turning that into 3D and seeing how things would all turn out. I still have several broken plotters and would like to get them working again. Cheers, -ethan

11 years, 3 months

New Flip Chip PCBs

by dm561＠torfree.net

A couple of folks on the VCForum talking about making new flip chip boards: http://www.vintage-computer.com/vcforum/showthread.php?36190-New-flip-chip-…

11 years, 3 months

PDP 8 components file for spice

by jws＠jwsss.com

The discussion thread about the flip chips had a discussion about a spice model. there is a file missing and I wonder if anyone knows where it might be found thanks JIm .INCLUDE ../PDP8/PDP8_COMPONENTS.cir

11 years, 3 months

Who might want my collections (but not yet!)?

by ard＠p850ug1.demon.co.uk

Since my father passed away a couple of months ago I have been giving serious thoguth to making a formal wil myself (when my father was around, he would have known who to contact about various things). My first ;'choice' is to give everything to a personal friend who has been on this list. He shares enough of my interests that he will realise what is valuable and what is perhaps not so valuable. But the problem is tha said friend is about the same age as me, and it is not certainn he wil loutlive me. Of course if he passes away long before me, I can producve a new will, but it is worth putting a clause in the one I am currently writing to say what happens if he is not around. Now, as well as my classic computers there's also cmaeras, books, tools, test gear, other electronci stuff, etc. I would rather leave everything to one person/orgnaisation (rather than say 'the classic computers go to <a>, the tools go to <b>, etc) or worse still 'I leave my PDP11/45 system to <foo>', etc. In the latter case if I have, say, swapped my 11/45 for an 11/790 at some point then <foo> gets nothing, even though it was probably my intention that he would get the 11/70. In the former case, there could be disputes as to what category certain things fall into -- is the 'Datacopy 300' (an early digital camera that needs a classic PERQ to run it) a 'classic computer peripheral' or a 'camera', for example. Does anyone have any serious suggestions for an organisation (and yes, I am considering computer museums here, no matyter what I may have said i nthe past) who would be prepared to take the lot and pass on that which was of no use to them to other organisations or enthusiasts? -tony

11 years, 3 months

Computer ASCII Text Art from the 1970's

by jfoust＠threedee.com

At 12:39 PM 4/11/2013, Sam O'nella wrote: >http://www.vintage.org/exhibit99.html has a better picture of it from the >now CHM. "Better" as in that one is 320 x 240 pixels and mine was 122 x 184? :) - John

11 years, 3 months

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test-drb April 2013