HO scale blimps revisited

The post HO-scale Logging Airships continues to be the second most popular at this blog. I started to wonder what it would cost to buy the parts to build one of those little blimps. When I went to the Plantranco site to cost out the parts I was pleasantly surprised to see that they now sell a nano-blimp R/C toy that looked just the right size for an HO scale layout. Naturally I immediately ordered one. It's proving harder for me to learn how to fly one of these things than I expected. That’s not a reflection on the item, just on my inept flying skills.

Basically, the kit consists of a very well engineered propulsion module, a radio control unit with joysticks, and some balloons and miscellanea. All you need to do is charge up the propulsion module, tape it to the bottom of the balloon, add some ballast to make the whole thing neutrally buoyant and you’re ready to fly. It goes together easy and works just fine. The only extra things you need to buy are some AAA batteries and helium. I bought a small tank of helium at Walmart that is marketed for filling children’s party balloons.

{A sketch of a one-person spherical airship I did back around 1985. Its envelope is very optimistically small for something getting its lift from helium.}

When I was at Walmart buying helium I also picked up a pack of white, ‘helium-proof’ balloons since the ones in the kit are coloured and marked with the seller’s brand. I wanted the balloon to look more like the LTA-20-1’s envelope.

I’m a horrible flyer and am still trying to get the hang of the controls. I don’t play video games, so I’m probably climbing some steep learning curve hand-eye coordination wise. Also, I find it a little difficult to get the blimp to be neutrally buoyant. Again, more practice is probably what’s called for.

This thing seems to have lots of potential and once I get the hang of flying it I’ll post again to try and elaborate on using it as a potential OO, HO, or N scale free-flying blimp.

LTA 20-1 poster

Of all the LTA-20-1 memorabilia I have, this is my favourite. It shows the vehicle in its most positive light, and makes something that is essentially a big spherical bag of helium look rather svelte and technically feasible as a flying machine. The signature in the lower-left corner says: R. C. Beaussard. He or she has done a good job on this picture.

R/C models and computer simulations of this vehicle clearly demonstrated that it was highly maneuverable. Turn on a dime? No problem. Those engines could be vectored and throttled, so lots of different types of motion was possible. The other cool thing was that it made use of the Magnus Effect – hence the company’s name, Magnus Aerospace – to create additional lift for carrying stuff. Its helium-filled spherical envelope was mounted on an axle, which in turn was slung across that huge curved wing-yoke structure. Spinning the sphere opposite to the vehicle’s direction of flight – that is, if some super villain dropped you on the top of the sphere while it was spinning, you’d find yourself clinging for dear life while the sphere’s rotation tried to fling you back into the blimp’s wake J - created aerodynamic lift. So, you got aerodynamic lift from spinning the sphere, and static lift because it was full of helium.

The problem was that maneuverability and the unusual way of creating aerodynamic lift came at a high price. If I remember correctly, its lift-to-drag ratio – L/D in aerodynamics-speak – was always somewhere between 0.9 and maybe 1.1 at best, but usually a little below 1. When a 747 is cruising around, it has an L/D of something like 17, and a sailplane has one of maybe around 50. Drag is the cost of creating lift, so if you can get 17 units of lift for 1 unit of cost, or 50 units of lift for 1 unit of cost, that’s pretty good, but 1 unit of lift for 1 unit of cost makes me scratch my head. For a small, scale model flying over a model railroad layout this wouldn’t be much of a problem since when the batteries died, the beast would just be left floating around in the house until rescued, but for the real-McCoy, this could be trouble.

But, lift cost aside, I still like the way it’s depicted in this poster.

400 posts; 1 about blimps

Time flies. The latest post in the E. L. Moore series was #400 for this blog. 400 posts – well, 400 and 1 counting this one. I can hardly believe it. I know that for many blogs, 400 isn't that many, but it seems something like a milestone for me. Google’s stats say the blog has had 36,767 hits up until now, so that’s an about an average of 92 hits per post. In fact, though, the hits aren’t sprinkled evenly over all the posts; some have had a lot more than others, some a lot less, and some have been special favourites of roving spam-bots :-)

From the high hit count, and Google stats showing searches for variations on the phrase ‘HO scale airships’ that lead visitors to the blog, the post called HO-scale logging airships? has been the 2nd most hit over the years. In it I talked a little about an airship called the LTA-20-1 that was being developed in the mid ‘80s, and speculated on how an HO-scale radio-controlled flying model might be built. The real-McCoy was being designed to do things like aerial logging, lifting de-railed freight cars, and assisting with pipeline construction. For a while I was a wet-behind-the-ears junior engineer on the project with a minor role doing some flight dynamics analysis. Unfortunately, a full-scale flying prototype was never built, but it did leave me with some interesting memorabilia -now stuffed away in dusty boxes down in the basement. Here’s a scan of the project’s promotional brochure.

These days I look at it as I was participating in a rather unusual art project.

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.