Tom Ramcigam (magicmarmot) wrote,
Tom Ramcigam


Well, I didn't get drunk and run naked through the streets of Des Moines
last night.

It hit 60 degrees here yesterday. The snow is gone, except for piles
where it's been plowed, but the ground cover is gone completely. I ended
up going to the gym, then coming back and working on the frames for the
Biax fluorescents. I got the inner frames figured out, which turned out
to be simpler than I originally was picturing, and is directly
expandable into a four-tube fixture (or really a 2n fixture,
though I'd probably do a practical limit at 8 tubes). And it's turning
out to be easy to put together, all square cuts and 90 degree angle
blocks that go together like a Jenga game. I suppose that if I had
access to a bigger shop I could make something that was more streamlined
and modern, but for prototypes they're just fine. And really, it's how
they work, not how they look.
I still have to design the outer frame, which will be a little trickier.
That has 45-degree cuts (ooooooh!), though I can probably get rid of the
compound cuts that I'd try to do if I was welding the frames. Part of
the concept behind these lights is the ability to make them from parts
that are readily available at Home Depot/Menards and with tools that are
fairly common. Granted, I'm using a small drill press and a cut-off saw,
but they are more for convenience than necessity.
The only downside that I currently have with these is the focus of the
reflectors. The current mounts for the fluorescent tubes are farther out
than I would like, which makes for a much broader light spread. If I
pull them back, the focus is tighter, but it means some much more tricky
I think it's probably worth doing. I just need to actually do it.

Probably more of the same tonight. I'd like to have a working light (or
at least the inner frame) working by Thursday night so I can bring it up
this weekend for show-n-tell.

The dolly trucks I'm putting on hold for a bit. Mostly because cutting
them is going to be exceptionally noisy: the cut-off saw is loud even
working on aluminum, and steel will take a lot longer. I should probably
pack the saw and the truck bar so I can cut them at home this weekend.

I'm rethinking the use of steel for the dolly frame. It would be sturdy,
but heavy as hell. I can order 6061 aircraft aluminum rectangular
tubing, but I haven't actually welded aluminum yet. Square steel tubing
I can get at 'Nards. It's only 1", but I can double it where necessary,
and welding it I can do with not a whole lot of effort. But aluminum is
easier to drill and machine.

Hell, it'll still probably be steel. It's a prototype.

Then there's the sliding wheel problem.

Dolly track is pretty standardized at 24.5" width for narrow track.
There is a wider track that is more rare, but I don't know anybody who
uses it anymore other than on big sound stages when they have big rigs.
Straight dolly track isn't much of a problem. The wheels are set at
24.5" on center, and life goes along smoothly. But when you get to
curved track, it gets a little wonky. For instance, the tightest
curvature track I've seen standard is a ten foot outside diameter. Each
track section makes up a quarter circle, so with four pieces of track,
you have a full circle with the outer track being the five-foot mark.
That means that the inner track has a radius of less than three feet
What happens when a dolly sits on this curved section of track is that
the track appears to the dolly to be a little wider. With a 36" dolly,
it's almost a 2-inch shift. And when you run a combination of straight
and curved dolly track, the dolly trucks have to be able to slide
sideways to handle this shift, as well as turn to handle the angle.
The turning part I have handled with thrust bearings, but the sliding
part I had a little problem with-- until I discovered that a couple of
miles from here is a plastics place that had a scrap piece of UHMWPE
(ultra-high molecular weight polyethylene), which is designed
specifically for extremely low coefficient-of-friction metal-to-metal
sliding joints. Think Teflon, only more slippery. It's lovely stuff.
It does mean that I have to make slots in the steel. However, I may do
this with multiple pieces with a welded crossmember rather than trying
to drill and file straight slots without having an end mill. Or if I can
find some small C-channel, it will work nicely. I could also make
sliders out of steel bar stock, which might still be the best solution.

Ah, well. Food for thought.

This morning I heard that Iowa is looking to make the "channel catfish"
as the state fish. Iowa doesn't currently have a state fish. Considering
where I have been for the past almost-a-year, I can see why. I was
thinking of lobbying for the state fish to be corn.

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