One of the challenges with replicating something you’ve never seen in person is getting the details right. In my modelling of the Kettle Valley Railway’s Coquihalla subdivision, I had a problem: the railway didn’t exist anymore. Not the line, scarcely a single building remained. All I had to work with were old photographs and the say so of others. In that situation, you gradually learn to pick out details. How to deduce sizes and distances in photographs using objects with known dimensions. It’s detective work, and quite honestly, I enjoy it.

Now, we’re not quite so far gone with the TVT prototype. The real thing does still exist. I could, if I wanted to, go and see it; however it’s a 2 day drive in another country. And I just don’t have time. Now, fortunately, the prototype’s current owner is the Computer History Museum in Mountain View, California. And they are nothing if not thorough in their catalog of their collection. They had record of the rough dimensions, and had some great frontal and overhead shots. Further, I was fortunate to get in touch with Dag and Chris from the museum, who were very helpful in providing some critical photographs, like this one of the back of the TVT unit, an angle no other photographer bothered with:

I knew the case was made of wood, but that sliver of silver at the bottom of this picture shows was appears to be metal. Which would make sense, since that’s what my TVT2’s motherboard is mounted to. I’m not sure what the screws at the back are holding up; because the case is screwed shut and the museum understandably doesn’t want to risk damage taking it apart, that’ll probably remain a mystery for the forseeable future.

Here’s a kind of side shot Dag was kind enough to send:

It’s hard to say for sure with just pictures, but I’m thinking the wood is probably hardwood — maybe fir or oak. Could be pine too but it looks too dense. I don’t see any screws attaching that wood support in the front to the sides. It appears Don routed into the side pieces wood and then secured the front ‘beam’ with either screws that are hidden inside or maybe glue. Probably I’ll go with No More Nails or something like that with maybe a couple of inside screws. Is the front a 2×4?

I asked Dag if the measurements on the museum’s website were fairly accurate, and he went above and beyond and got another museum staffer to measure the unit again, particularly the wood sides. It turned out that the dimensions were pretty correct, the side wood being 4.25″ high by .75″ thick, the length of the side pieces being 13.125″ at the bottom and 12″ at the top (Don cut the ends on an angle) the entire unit being about 11.75″ wide. Perfect! Now I was ready to cut wood. I got my hands on some 1×5″ fir, which actually measures 1×4.5″. I’ll trim off .25″ inches and then cut to length, and then cut my angles.

Nice! Now I have something tangible!

Now, I know the width is 11.75″. So factoring in for routing on each side, I figured the pieces on either side of the keyboard needed to be about 11 inches. I felt pretty confident they were 2x4s, and I had some 2×4 cedar around. Now I had this:

Cool! But… it doesn’t look quite right. The 2x4s just seem a bit too big. Looking at how much space is left in the back, there doesn’t seem like there’s enough room to fit the TVT boards in there. Drat. Something’s wrong. I need to figure out how big those front and middle pieces are.

Aha! An idea. A trick I learned from using air photos and a large format printer to very precisely model a segment of railway.

First, I took the above shot the museum had. It appeared to be more or less directly over top. I then print screened and copied into Photoshop, cropped it, and then set the image size to the known length and width dimensions. From there, I printed it at that exact size to my Designjet 450c. Voila!

A (roughly) life size printout of the TVT prototype.

I then took out my MDS keyboard and checked the measurements. The keytops are .75″x.75″. Sure enough, my large photo also measured the same. Great. I can trust it. Now I measured those two wood pieces. They come out at just over 1″. So I’m guessing these are 1″x4″, not 2″x4″. That’s going to necessitate a trip back to Home Depot, but at least I know now before I go and router some rather expensive wood ($28.00 for 8 feet).

More progress tomorrow!