Monthly Archives: August 2015

TV Typewriter Redux

Auuugh! How did I miss these?!

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What a bummer.

As mentioned previously, the TV Typewriter was a true do-it-yourself project.  Literally all you needed to do to get going was order the plans.  The plans listed the parts and included the artwork to make your own PCBs.  Now, you didn’t have to go quite that far — Radio Electronics did offer some ‘legs up’.  They arranged for SWTPC to manufacture the boards in limited quantity.  Don Lancaster and his crew also built about 40 or so ‘surplus keyboards’ to be sold to hobbyists who didn’t want to make or hunt down their own.

Obviously I would have loved to have ‘original’ SWTPC-made boards to work with.  Would have saved a lot of trouble.  But in 2016, these are a little bit hard to come by.  In fact, I’d never seen them for sale ever on eBay or anywhere else.  And I assumed if I did come across them they’d be assembled already and ridiculously expensive.  I didn’t even bother setting up a ‘followed search’ on ebay for them, so convinced I was that they’d never be available.

And that’s okay.  The great thing about the TVT is, as I said, it’s entirely legit to make your own boards.  And that’s the thing I think that separates this project from say, an Apple I replica.  The latter will always be just that much more ‘replica’ because the original boards only came from Steve & Steve.

Anyway, regarding original SWTPC boards, I was wrong on all counts.  I don’t know how, but I completely missed an auction on ebay that offered a complete board set, untouched.  The price it went for?  A heartbreaking $39.00USD.  Ugh.  The auction has long since passed but I did manage to save some photos before it went offline:

tvtboards1 tvtboards2
tvtboards3 tvtboards4 tvtboards5 tvtboards6

Now, I suppose this is a blessing in disguise – had I managed to steal those boards, I would have faced a moral crisis about trying to assemble them, since there can’t be that many unassembled TVT boards lying around out there.  There was also the risk of assembly damage.  Evidently the marketplace did not consider these to be incredibly valuable, but for me they would be irreplaceable.  Wrecking them would be an offence punishable by flogging.

On the plus side, at least I now had a visual of what ‘original’ TVT boards looked like.  Color, texture, size.  From talking to Don, SWTPC’s involvement apparently was a while after the prototype debuted, so probably the prototype boards did not have the SWTPC logos.  But otherwise looking at photos of the prototype and the alignment of screws, switches, etc, it’s clear the prototype boards basically were the same.  Another useful bit of information – the silkscreening on the back looks more or less the same as the ‘parts placement’ templates in the plans:

http://www.swtpc.com/mholley/TV_Typewriter/page_19.pdf

That opens up the possibility that I could use toner transfer or some DIY silkscreening method to take the parts placement diagrams and transfer them to the backs of the PCBs I’m making.

The other interesting thing to note with these is they weren’t tinplated.  That kind of had me wondering about their authenticity but after consulting with ‘experts’ it appears these ought to be legit — after all, this was quite early in SWTPC’s adventures in computing.

I’ve got my eBay followed searches better tuned now but I know I’ll never see these again.  Oh well, another lesson in not making assumptions!

Kettle Valley Railway Coquihalla Sub in N Scale
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So here we are in Build an Eyebar Bridge 2.0, and I’m applying some of those lessons and new information I’ve picked up since 1.0.  Setting out, I am bound and determined above all else to keep things consistent: consistent widths for the panels, heights for the box girders.

The bottom eyebars themselves, as always, are a bit of a challenge.  As mentioned, the first time I attempted these devils I tried doing individual styrene strips – two on the outsides of the box girders, two on the inside.  However the problem of manipulating and gluing these tiny strips became readily apparent: the glue easily pulls them together, and of course getting them into place in the first place is a nightmare.  So that’s where I went to casting, first just doing it for the inner eyebars and then deciding to do it for all four. Now doing it for a second time, I really wanted to get the eyebars closer to prototype look.  On the prototype, the inner eyebars are close together, the outer eyebars are further away from the inner.  Last time I tried that I didn’t like the look of it.  With n-scale we are dealing in dimensions so small that at times it’s hard to actually see what you’ve got when you’ve scaled it right.  Anyway I ended up cutting down my original mold, the intent being to clue the eyebars in between box girders.  However after doing two panels (the first panels on each side of the bridge have lace work rather than eyebars) I discovered the width of the panels was too narrow.  The bridge is recorded as 174 feet long, including a short tail on the west end that rests on concrete footings.  There are 9 panels after that.  On site I figured out the tail was about 14 feet, so that gave me 160 feet divided by 9.  I don’t know why but my math skills really hurt me here and I ended up with panels that were about 17’ wide and would have left me with the tail end being 25’.  So I recalibrated and brought them closer to the 17.7775 feet each my calculator gave me.  But that meant having to, for the third time, make a new eyebar mold.  And since my first mold positive was now too short to fit between posts, I had to make an all new one, which is challenging.  I kept thinking about how I wanted to try to get the eyebars to have a more eyebar shape, like this:

o——o   instead of like how I had them in my model ———

The problem is, those round ends make the casting process difficult.  I could cast the individual eyebars one at a time, but then I’m in for a world of pain with tiny, extremely fragile parts.  The advantage of keeping things square is it means I can assemble a complete section of eyebars as one piece, and cast it as one piece without having to worry about having awkward spaces the alumilite casting mix won’t reach or release from properly.   I did do a bit of reading on two piece molds but concluded it would be much too difficult for an amateur like me to master, if it could be done at all.  And again, the beauty of n-scale is that everything is so small anyway that you can relieve yourself of having to get that nut and bolt crazy if you want to.  Especially in black paint, nobody but the pickiest will notice.   So I decided to leave them as rectangular on the ends.  Each eyebar casting will be wide enough to be glued into the center lines of the posts at each end.    I also made the inner two eyebars closer together to more closely fit the prototype.  Now I just have to tear apart, again, the two panels I started on, respace them, and hopefully tomorrow my new eyebar mold will be ready and we can get down to business!

Kettle Valley Railway Coquihalla Sub in N Scale, Uncategorized
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I’ve been working on my pin and eyebar bridge for my Coquihalla canyon scene on and off for months.  Much of it has been guesswork – the actual place (now a park) was closed for a while due to a rockslide that damaged one of the original bridge footings – and with guesswork comes mistakes.  Details missed.  And some things you just can’t figure out from pictures, like the width of the deck.  Some things I deduced, but even then I didn’t trust my numbers, because you tend to remember things being much larger than they actually were.  I was doing my best though, not having the opportunity to get into the field, and I think it was coming pretty close.  However new photos, especially a few aerials from the talented photographer Andrea Coughlin, kept coming up with info that contradicted what I thought I knew.  The eyebars that rise diagonally from bottom left to top right of each ‘panel’ in each truss I thought were oriented one way the whole length.  Nope.  Midway through the bridge on the 5th panel they switch directions.  Also discovered that the east end of the bridge features lacework rather than eyebars, just like the west end.  I still didn’t see anything that answered my question about whether there was any sort of reinforcement under the bridge deck where the rails would be. Along the way I was learning a lot about processes for creating such tiny parts.  I discovered rather than installing all four bottom eyebars for each panel painstakingly with styrene (which loved to warp and get stuck to one another with glue), I could just cast them as one piece.  I started thinking, man, if I had known all of this before, I could have been more consistent.  In changing techniques on the fly, I ended up with bridge panels that were not even width, nor even height.  The variation is slight and not that noticeable, except to me.  And I am the one I am doing this for.  Darn!  I needed to get to the canyon

So I went back to Othello and I thought, okay, if I notice any more inconsistencies with this bridge, I’ll give a thought to doing a Version 2.0.  Why not?  Then I can apply all I learned.  I eagerly measured the deck width, which in pictures seems quite wide, but in reality is a skimpy 12.5 feet across. I also discovered that the plate girder the ends of the ties rest on has another beam of some sort running parallel to it that the ties were also resting on.  Oh, and that there is nothing beneath where the rails would be.  Just the ties themselves, and the odd crossbeam.  the ties are literally supported at their ends.  That’s it!  Wow.  Those ties must be strong.  The bridge is definitely kind of an odd design: most pin connected deck trusses I’ve seen have one truss per side, but this one has two.  One gentleman speculated that it might be that the bridge, in being recycled from another location due to WWI steel shortages, might in fact have been double tracked in its original configuration, or perhaps had been longer, or two separate bridges.  Interesting to contemplate, although I’m not sure why you’d need to combine two bridges in a space where you only needed one.  Perhaps the Coquihalla canyon is one of those places where you want to put off repair and upgrades as long as possible?

I learned enough there to now proceed with redoing my model of bridge, which had progressed almost to the point of painting and joining the two double trusses.  That’s okay, this will give me an opportunity to put into practice a lot of what I learned as I went the first time.  And I can use my first attempt as a stand-in for the ultimate bridge, so I can finally get the scenery done in there.

One thing about the canyon – it never ceases to amaze me how utterly beyond description it is.  Superlatives don’t cut it.  It blows my mind early 20th century railroad builders managed to put a railway through here.  With 19th century tools!  Also each time I return I find new visual cues and features I end up adding to the model.  I’ll probably be doing that forever, always working just another inch closer to perfection.  I’m very pleased with how it’s come out so far – especially considering I had zero knowledge of modelling going in.  I wanted the Coquihalla canyon in my office, and darn it, I think I may be close to having it!