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  #11  
Old 02-20-2021, 04:16 PM
shockwaveriderz shockwaveriderz is offline
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Quote:
Originally Posted by georgegassaway
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.


George:

Is piston tip-off caused by the piston tube/engine connection point? or does it also have to do with after release, the wind is hitting it too? either/or? or both?

TIA
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  #12  
Old 02-20-2021, 04:33 PM
shockwaveriderz shockwaveriderz is offline
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Quote:
Originally Posted by Ez2cDave
Geoff Landis . . . 1973

Dave F.


yes thank you. It was published in the MIT Con Proceedings in April 1973. I edited the original to reflect this.

I have to sit down and do a time line to keep everything straight and in correct order. !
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  #13  
Old 02-20-2021, 11:05 PM
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Quote:
Originally Posted by shockwaveriderz

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.


Speaking of FAI / WSMC flying and piston launchers, I'm surprised that George didn't mention the infamous "50-foot miss-fires" that occur when a foreign competitor's igniter fails to start the motor, but does ignite the additional flammable material inside the piston ( illegal, of course ) . . . The are commonly referred to as "Sweetened" piston launchers.

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  #14  
Old 02-21-2021, 01:17 AM
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I like the concept of this "sweetened" piston launcher.
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  #15  
Old 02-21-2021, 05:58 AM
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I was always ticked off when I'd see a piston-launched model at a WSMC "pop" up 20-30 feet, without the motor firing, due to black powder (or whatever) that had been added to the piston to make it perform better. With NO repercussions (indeed, it did not even count as a flight, they got to do it over). Saw it happen several times.

TOTALLY illegal. But nobody protested. And the RSO's that will DQ a flight if it is ignited even 1/4 second before they say "zero" in their countdown.......totally turned a blind eye to absolutely blatant obvious cheating as though nothing unusual had happened at all. (The rules do not allow the launchers to provide any acceleration that is not 100% due to the motor itself. No bungee catapults, no BP, no linear "rail guns" etc. )

Nobody on the US Team pulled that s***. If anyone had, some of their teammates would have had a talking to with them and no doubt the team manager (such as John Langford) would have a very serious discussion about not doing that again, or ELSE. Because if one team member is cheating like that, it makes it look like the whole team is in on it (and indeed I am sure the models I did see that did that, were indeed the way their teams did it on purpose. Not one person choosing to do that on their own without the rest of the team knowing or even colluding.).

But I did not recall seeing it happen at the last few WSMC's I attended. So maybe the officials did crack down on it eventually, and it stopped. Or perhaps the cheaters got better at cheating in a way that the extra BP would only go off if the motor really did ignite.

If a model using a piston popped into the air at a NARAM, with the motor not being lit, guaranteed the RSO and/or CD would be all over figuring out why/how that happened (Not acting like an oblivious referee at a 3rd rate pro wrestling match). And if the flier did purposely cheat, they would probably be DQ'ed from the entire event, previous scores wiped away. And possibly thrown out from the whole contest depending on the severity. Nothing like that has happened before, but the rules certainly would allow for such penalties.
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Last edited by georgegassaway : 02-21-2021 at 06:26 AM.
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  #16  
Old 02-21-2021, 07:06 AM
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Ez2cDave Ez2cDave is offline
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Quote:
Originally Posted by georgegassaway
I was always ticked off when I'd see a piston-launched model at a WSMC "pop" up 20-30 feet, without the motor firing, due to black powder (or whatever) that had been added to the piston to make it perform better. With NO repercussions (indeed, it did not even count as a flight, they got to do it over). Saw it happen several times.

TOTALLY illegal. But nobody protested. And the RSO's that will DQ a flight if it is ignited even 1/4 second before they say "zero" in their countdown.......totally turned a blind eye to absolutely blatant obvious cheating as though nothing unusual had happened at all. (The rules do not allow the launchers to provide any acceleration that is not 100% due to the motor itself. No bungee catapults, no BP, no linear "rail guns" etc. )

Nobody on the US Team pulled that s***. If anyone had, some of their teammates would have had a talking to with them and no doubt the team manager (such as John Langford) would have a very serious discussion about not doing that again, or ELSE. Because if one team member is cheating like that, it makes it look like the whole team is in on it (and indeed I am sure the models I did see that did that, were indeed the way their teams did it on purpose. Not one person choosing to do that on their own without the rest of the team knowing or even colluding.).

But I did not recall seeing it happen at the last few WSMC's I attended. So maybe the officials did crack down on it eventually, and it stopped. Or perhaps the cheaters got better at cheating in a way that the extra BP would only go off if the motor really did ignite.

If a model using a piston popped into the air at a NARAM, with the motor not being lit, guaranteed the RSO and/or CD would be all over figuring out why/how that happened (Not acting like an oblivious referee at a 3rd rate pro wrestling match). And if the flier did purposely cheat, they would probably be DQ'ed from the entire event, previous scores wiped away. And possibly thrown out from the whole contest depending on the severity. Nothing like that has happened before, but the rules certainly would allow for such penalties.


Here are some images of some "foreign" piston launchers . . .

Dave F.
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  #17  
Old 02-21-2021, 07:12 AM
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More . . .

Dave F.
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  #18  
Old 02-21-2021, 07:17 AM
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Yet more . ..

Dave F.
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  #19  
Old 02-21-2021, 11:46 AM
shockwaveriderz shockwaveriderz is offline
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my only response to "sweetened" pistons with BP is when does an igniter no longer become an igniter and it becomes "sweetening".....

for example, one of the issues that have always dogged piston launchers is ignition......so is it cheating or sweetening to use an electrically ignited single flash pan that has a little BP in it to ignite the motor?

What if my DIY igniter has been dipped in nitrocellulose and then dipped in a little BP, is that cheating or sweetening the pot?

what is I was to paint the nozzle area of my motor with NC and then add a few sprinkles of BP...then electrically ignite it......

where do you draw the line between what is an igniter and what is sweetening and cheating.?

George said, "Or perhaps the cheaters got better at cheating in a way that the extra BP would only go off if the motor really did ignite." <--- This is what has happened.

Maybe the FAI needs to impound the igniters and pistons before the competition like they do with the motors.

I agree that with your examples something is obviously amiss, and the fact no protest was lodged tells me even more. To not upset the applecart. To this day we don't really know what's inside the Russian or some eastern European pistons......I wonder if silicon chalking produces any gases when lit?
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  #20  
Old 02-21-2021, 12:31 PM
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Quote:
Originally Posted by shockwaveriderz
my only response to "sweetened" pistons with BP is when does an igniter no longer become an igniter and it becomes "sweetening".....

for example, one of the issues that have always dogged piston launchers is ignition......so is it cheating or sweetening to use an electrically ignited single flash pan that has a little BP in it to ignite the motor?

I agree that with your examples something is obviously amiss, and the fact no protest was lodged tells me even more. To not upset the applecart. To this day we don't really know what's inside the Russian or some eastern European pistons......I wonder if silicon chalking produces any gases when lit?


As I see it, if the "igniter" significantly adds to the pressure inside the piston, then it is "sweetening".

Of course, the only way to prove this would be to either randomly pull models off the flight line for a "tear-down inspection" of the piston and the "igniter" OR have each competitor "supervised" during prep and right up until the model & piston is placed on the flight line. If the model is taken down, for any reason, the process repeats.

Dave F.
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