Saturday, April 16, 2011

HO-scale logging airships?

I was going through some old files, and came across these MacPaint pictures for a track planning tool I created way back in 1985 with my friend vp.

I was a Mac zealot back then and was especially enamoured with MacPaint. vp thought MacPaint and the Mac’s capabilities in general would make for a great track planning tool. He was certainly more prescient about this than me. I thought model railroaders would prefer using all their spare time model railroading – I was wrong, there is a niche for these sorts of tools.

The tool didn’t undergo much development because I lost interest as other activities over took it. Initially, it was meant to help plan very simple layouts: flat ones that used snap track. I came across some Pascal code I had developed (unfortunately I don’t have a way to run it any more), but we also thought of simply making a track planning font where letters and keys were replaced with different types of track that could be later cut-and-pasted into position with MacPaint or MacDraw.

I only post these fragments because I got a laugh out of the above picture with the blimps and trains that I had done as a diversion while we were fiddling with more prosaic track planner issues. I’d completely forgotten about it. With the popularity of steam punk, it doesn’t seem like the odd combination that it did at that time. Back then I was part of a team doing research into hybrid airships that could be used in forestry, so to my inner model railroader, this logging blimps meets the railroads of John Allen and John Oslon motif seemed like a natural combination. Although, I can’t account for the motivation behind the Queen lyrics and the all-seeing eye

Are functional, flyable HO-scale blimps possible? A late 1970s to mid 1980s vintage Goodyear blimp has an envelope that is 192 feet long and a maximum diameter of 50 feet. Its volume is 202,700 cubic-feet. In HO scale these dimensions would translate into 2.21 feet, 0.58 feet, and 0.31 cubic-feet, respectively. The lifting capability of helium doesn’t scale, so to figure out how much mass the model could lift is simply a matter of multiplying 0.31 cubic-feet by the static lift of helium, which is 31.5 grams/cubic-feet. It turns out the HO-scale helium inflated envelope can lift a mass of around 9.8 grams.

"Logging in steep terrain" - from the LTA-20-1 sales brochure
A similar calculation can be performed on a 1980’s vintage LTA-20-1 concept logging hybrid airship. The sales brochure states its spherical envelope has a 91.9 foot diameter. In HO-scale this becomes 1.06 feet, with a volume of 0.62 cubic-feet. Since it’s about twice the volume of the Goodyear blimp model, it also can lift about twice as much mass, which is around 19.6 grams.

"Heavy-lift emergency situations" - also from the LTA-20-1 sales brochure.
Building an actual HO scale radio controlled flying model will have its challenges given that the static lift of either of these two examples is rather small; however, if the power and control technology of this Carbon Butterfly were used, they seem to be within the realm of possibility. That indoor R/C model airplane has a total mass of just 3.6 grams, so we’re certainly in the right ballpark. Cost ? Well, I’ll swag it very, very conservatively at the cost of 2 Carbon Butterflies plus $100 for helium and some miscellaneous extras; that turns out to be around $420. Pricey, yes, maybe even too conservative an estimate, but in the zone of an expensive locomotive model; maybe it’s not too outrageous for a prototype HO-scale blimp of some sort.

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