Sometime back in the 70's Howard Kuhn of CMR had what was called a Thrust Augmenter.

It was a pretty simple device.

a 1/2" piece of bt-20 was cut and a 1/4" eb-20 engine block was glued into the top leaving 1/4" on the bottom.

The engine was taped with masking tape on it's top 1/4" and fitted into the bt-20 so it couldn't eject itself.

this bt-20 assembly was glued inside a bt-20+ body tube such that the aft end of the engine was in line with the rear of the outer bt-20+ body tube.

the thrust augmentation tube was then made from a length of Bt-20 tube that would slip-fit between the 2.5" length of engine and the outer bt-20+.

This augmentation tube was then sealed at the bottom with a nose block which had a hole that was drilled thru its center to allow the ignition wires to come thru. This hole was plugged so no gases could escape.


The idea behind this contraption was to increase the lift off thrust ..sorta like a miniature breech launcher.

I've sketched a rough diagram showing what it looked like.


my questions are:

did anybody ever have one of these or have one of these?
Ninfingers only has the 72 and 87 CMR catalogs..... in the late 70's from what I can tell CMR came out with their piston tube launchers.

This Kuhn augmenter came out I believe sometime in the early to mid-70's.

anybody have any information, pics, instruction sheets or catalogs showing those device?

I spent all day yesterday re-reading ALL of the model rocketry magazines from 68-72 hoping to find some mention and no deal. SO the next few days I will be doing the same for ALL the Model Rocketeers from 72 thru 78....


EDIT NEW INFORMATION

In a CMR Ad in the Oct 73 Model Rocketeer, there is mention of new Thrust Augmenter coming for 1974

Geoff Landis mentions the Kuhn Thrust Augmenter for the 1st time in the 4/74 issue of Model Rocketeer.


CMR introduced their ZVPL piston launchers in March 1974 at the old Pittsburgh Spring Convention

So, this tells me the Kuhn Thrust Augmenter was real sometime previous to Oct 73.

Magazines articles back then were usually on at least a 3-month lag from publication so

perhaps it was intended as a product as early as the June-July 1973 time frame.

Geoff Landis could easily have been one of a number of beta testers for it, hence his knowledge of it.

Howard Kuhn easily would have realized that a true ZVPL was superior to a simple thrust augmented and just changed his mind, and the KTA was never released as a real product.

Howard would have known about the ZVPL piston launcher as early as March 1973 because Geoff Landis gave his 1st public report on ZVPL at the MITCON-6 which he, Howard attended.

Attached Thumbnails

 

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"Old Rocketeer's don't die; they just go OOP".....unless you 3D print them.

Terry,

CMR used to sell a Piston Launcher . . . They called it the "Boom Tube".

PDF below.

Dave F.

Attached Files

CMR - BOOM TUBE.pdf (130.3 KB, 44 views)

I still have one of those, but I need a new tube for it. The old one has borned through from over use.....

Thanks for that Dave. I had seen that before but couldn't find a copy online.

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well I think I've found the answer to my question. I was reading an old R&D report from 1984 where there is a very good description of how the CMR "boom tube" piston launcher was constructed and used. It seems that the thrust augmented idea was incorporated into the boom tube piston launcher itself. It was the way the piston launcher was attached to the motor/model combination.

I've read so much online this past week that my eye's literally were hurting......

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I recall reading either in Stine's handbook, or in MRM, about a "Wada" device. I can't recall exactly what the device was called (maybe also an augmenter). But pretty much the same concept as the Kuhn augmenter. Pretty sure though, it predated Kuhn's. The impression I got about the Wada device was it only had a short distance of the motor sticking inside of it, say 3/4" of a normal 18mm motor, so not as much "kick" as using 2.5" of a motor casing length.

I would never, EVER, trust a 1/4" wide wrap of tape at the top of a motor (as described for Kuhn's), for a safe friction fit, to prevent the motor from getting kicked out.

Actually, may have read about Wada's in an article or report by Geoff Landis about pistons in the mid-70's.

The CMR Boom Tube came after others began to develop pistons. The boom Tube had a design flaw, where it was attached to a wooden block base, with a hole in the wooden block for a launch rod to slide thru. So, the piston sat off to the side of a launch rod on a normal pad (about 1.5 to 2 inches over), rather than the piston's core rod being mounted directly to a pad. This meant every time it worked, the offset acceleration force caused it to whip to one side, due to the lateral offset of the wooden base slid over a rod. I saw those things being used on serious contest models at NARAM-16 (my first NARAM), slid over a 1/8" rod and cringed as the models often tipped off for the very reason of the side-whip.

Doing some googling, I found this:

"Wes WADA introduced “Augmenter Tube” (essentially short “piston” without moving
parts) in his Research and Development report at NARAM-5, (Hanscom Field, Bedford,
Massachusetts, 1963)

Pretty interesting source for that quote, a very long dissertation by a top Russian FAI flier, Alexander Mitiuriev, aimed at the FAI S1 event (Altitude). It includes his compilation of history on pistons.

http://www.nar.org/wp-content/uploa...-2013-Rev-4.pdf

But it does not cover a lot of the in-between piston developments from Wada's, beyond the Closed Breech launcher dead-end for models, and then the ZVPL. As it is i'm impressed at the info he obtained and compiled like that.

In-between (early 1970's there were telescoping tube piston launchers, like BT-5 sliding inside of BT-20 (using AR-5/20 rings), a big stepping stone between closed breech and ZVPL. Telescoping were the first real pistons I used.

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George, Geoff Landis' had a report titled," The Zero Volume Piston Launcher or An Illustrated History of Closed Breech Launchers" in the May 1974 issue of Model Rocketeer. This was an expanded upon version of his MIT Con Proceedings paper," Building a Zero Volume Piston Launcher ", April 1973..

He had poor illustrations of several types of Piston launchers in both papers and in the 1st a drawing of Wes Wada's thrust augmenter from 1963. It basically looks like a piece of body tube, about the length of an engine, that has a nose block in one end of the tube. This is how I also thought it looked to me, from what I had read.

It was here that I first learned of the Kuhn Augmenter. As I posted it now appears that the Kuhn Thrust Augmenter evolved fairly quicky and with about a year became the CMR piston Launcher the "Boom Tube". The 1984 R&D report that I found described to a T the internal workings of the Boom Tube connection, and coincides with the Kuhn Thrust augmenter. It appears Howard just merged the two devices into a better one.

But recently, I got hold of a 1963 copy of the American Aircraft Modeler, and it shows a completely different design drawing by G.Harry Stine of Wes Wada's piston design.

This drawing shows the body tube/nose with an engine enclosed, sitting in a longer, bigger outer tube with the fin can and fins sitting on top of the outer tube and as the model accelerates out of the piston tube it catches the fin can/ fins body tube on the way up.

What is funny about this is, Trip Barber shows that same type of piston tube in a diagram in his January 1974 MIT Journal article, "Pressurization Effect Launchers" as a "blow-thru" piston launcher.


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.

Either way, Geoff was present at Both NARAM -13 in August 1971, and at MITCON in March 72 so there's ample evidence that he saw both Standard Piston Launchers from both people.

George had designed a piston launcher that is and was called the Standard Piston Launcher. This was a small tube inside a bigger tube, whereas the ZVPL is a big tube over a smaller tube.
There's more to it than that, the Standard piston launcher had considerable open space to fill before it would pressurize, while the ZVPL of course had zero or minimum volume to pressurize.

Geoff Landis May 1974 article shows 2 iterations of his ZVPL. It shows the first version which he also showed in the March 1974 report, but it also shows the ZVPL that we all know about today. The V1 used a string as a piston stop to prevent the piston tube from separating from the piston rod, while his V2 used a hard stop piston stop against the piston head.

The piston stop V2 model was effectively analyzed by Bauer,Prozio & Thoelen in March 1974 with their report, " Optimization of the Zero Volume Piston Launcher. "


This is just the first 5 years of Piston Tube development. I believe a Richard Essman back in 59-62 used a thrust augmented, but I'm going to have to go back and find the entry. And then I have to move forward to the mid-80's with Jeff Vincent and Chuck Weiss development of the floating head piston launcher now banned from FAI competition because it was just to **** effective and we can't have the American flyers using it to win Gold medals. (Plus it might hit somebody in the head on the way down).

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?

My plans are to develop this into an article publishable in Sport Rocketry sooner than later.

and yes George I read that piston history by Alexander Mitiuriev. That's what got me started on this in the first place because I think it's kind of strange that a Russian would supposedly know more about our American model rocket piston development history than we do ourselves, so I decided to create the definitive reference.


PS George : I have 2 photos and text from a RC BG by Bernie Biales that I want to give you for your RC BG history page. I need some place to send them to. dm me a email address?

__________________
"Old Rocketeer's don't die; they just go OOP".....unless you 3D print them.

Geoff Landis . . . 1973

Dave F.

More piston info . . .

Dave F.

Attached Files

	008b-PistonLauncherSupplement.pdf (504.4 KB, 10 views)
	008-PistonLauncher.pdf (1.00 MB, 11 views)

shockwaveriderz* wrote:



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



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.

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