shockwaveriderz* wrote:
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There's no doubt in my mind that Geoff Landis designed and build the 1st ZVPL, but he designed his zvpl from a piston Launcher that he had seen earlier by a person named George Helser in August 1971 at NARAM-13. At this same event, Andrew Bennet was using a similar, if NOT identical Standard type piston launcher as George Helser.
In fact, Andy Bennett presented a paper on his Standard Piston which is identical to George Helsers's Standard Piston, at MIT in March 1972.
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The “standard” piston is what I first started using. I think I first found out about it in Bennet's section’s (THOR) newsletter named “The Spotter” (which was one of the best newsletters, ever, especially for the "ditto fluid printing" age). For 13mm motor models, a BT-5 sliding upwards in a BT-20 tube, plugged at the bottom, with AR-5-20 rings peeled a bit for a proper fit
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And then there's your brass head piston launcher. I believe you got that idea from seeing a piston from a competition at the Internats?
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NOPE. That was 100% mine FIRST. I came up with it. The CMR piston was crap, really. The wrap of teflon tape over a short piece of wood dowel did not work very well. And the stranded 18 gauge type electric wires coming out of the top, to wrap around the ignitor, got very dirty from exhaust crud pretty quickly.
So, fed up with it, I designed my own ZVPL. Using K&S brass tubing 1/2” diameter, for the piston head. But the fit was too loose. So, I applied a coating of CA to the outside, which both built up the diameter, and actually held up to exhaust better. It had to be sanded a bit to tweak the diameter just right (it could have a nice slide fit). I wrapped masking tape around the support tubing that held the head, till it was the correct diamter to CA the brass tubing onto (back then, I used something like 1/4 or 5/16” OD brass tubing. Years later, fiberglass arrowshafts or graphite tubing.
The ignitor electrical ignition was solved by using two piece of 3/32” brass tubing (soldered to wires) coming out of the head of the piston, insulated to not short each other. Ignitors would have a short piece of 1/16” brass tubing slide over each wire and crimped. So, the ignitor would plug into the 3/32” brass tube electric sockets in the piston. Masking tape wrapped around both leads to help keep ignition crud from getting into the 3/32” brass. In years since, actual electronic sockets have been used, but those were not widely available to general hobbyists in the late 1970’s.
There was a plan for this brasshead piston in my club’s newsletter, “Impact”, around 1979 or so (I came up with the brasshead piston long before it was published, but do not recall just what year. No later than 1978, could have been couple of years before). I can’t find the issue it was in though. Also, our Zunofark team did an R&D report on improved brass head piston launchers at NARAM-26 in 1984 (I do not have a copy of the report). Matt Steele used brasshead pistons at the 1980 WSMC but Russia did not attend that one. So the first WSMC they attended where they might have traded for one would have been 1983 at the earliest.
Many NAR and US team competitors copied that or made their own variations. Which was perfectly fine since that was the whole point of our newsletter having the plans in it. If there was anyone else who came up with a brass head piston before I did, I’d like to know.
That was a key thing, the brass head, not so much that “brass” was a critical element (stainless steel would be better), but the plain simple fact that you could get 1/2” brass tubing at the same hobby shop you got rocket engines at (and that it did not suck like the CMR teflon tape over a dowel type of head). No need for a machinist, or special ordering some high-priced widget meant for something else.
Also when I said I was surprised that Mitiuriev found as much info as he did….this is one of those things he clearly missed - the origin of the brass head piston.
I will say, that there were many contests where I did not even use a piston. Because of complications that could happen, like tip-off, or boosting extra-fast causing a shred or early deploy at burnout. So, while I used standard pistons for a few years, it wasn't a lot. At several Alabama contests, we would have a gentlemen's agreement (not a "special rule") not to use pistons (We'd bring them but not use them unless someone else did and had a good enough flight to need to get out a piston) And so I was sort of "late" getting around to ZVPL's. Not until I learned more, and was getting better test flight results, where I felt comfortable using them more often. And ultimately "had to" up the game for NARAM flights to even stand a chance in most performance events.