ScrapDaddy
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AIM!! LAUNCH!!! (my Rocket CATO's)
AIM!! LAUNCH!!! (my Rocket CATO's)
10-4 Cap'in! full speed ahead! Clusters UP!
leasons learned, I need to attach the streamers closer to the ejecting back end of the model rather then the nose area of the shockcord.
its for altitude not duration if in thinking right. I have found that i stuff the shock cord into the payload section and stuff the teflon streamer into the bottom section on top of the motor. it blows it every time. im going to a launch this weekend so i should have a good chance to have some people help me track the altitude. the weather has been crazy if im working it is great out and if im off it rains or the wind is blowing way to hard to launch
I've been thinking about this for a little while. If mismatched ejection charge delay is the real problem with getting better altitudes, is there anything that can be done to fix it by the modeler?
High power rockets usually have a separate ejection charge. Is that allowed in Pee-Wee competition?
Could one of the following designs be made to work?
* Plug the ejection charge end of the motor with cardboard + superglue causing the ejection charge to go out the nozzle instead, possibly adding to thrust and giving more coasting time. Add a very simple timer+ejection charge to get the recovery device out
* Plug the ejection charge end of the motor with a fuse and glue it in so perhaps most of the ejection charge goes back out the nozzle. stick the real ejection charge on the other end of fuse, crating a longer delayed engine
* Upsize the outer body tube so you have a motor mount. Drill slots in the rings so gas can go through the back. Put a bulk head close to the ejection side of the engine with a hole in it for a fuse with ejection charge on the other side. ejection gas then lights the fuse and most of it gets kicked out the back of the rocket.
If an extra ejection charge isn't allowed, would some other mechanism to separate the body tubes work on this scale?
Maybe some combination of engine stuff above with holding the two body tube sections together with:
* a couple of electronic fuses
* regular fuse wrapped around the joint
or a solenoid to push the two sections apart?
Could any of these be made to be a net positive?
Or would any of this just be considered cheating? Wouldn't want that.
What about using a MicroMax NE motor with fuse and charge. No modification of the motor would be required.
One of the very first things everyone must realize is ADDING ANYTHING to a motor; would be considered AS "Altering the Manufacturers intended use" and as such is strictly forbidden in NAR competition.
So NO none of your first options would be allowed in competition. To be honest it's not generally allowable even for sport flights at NAR sanctioned Launches.
Plugging motors is a VERY risky thing to do. I've seen several illegal epoxy plugged D12 motors Cato so is not something I'd do or recommend others do as well.
As with all things Micro; Mass is alway the enemy. Adding anything EXTRA to a competition model has it's tradeoffs in lowering altitude. NOT a good thing. for instance I have several 2 and 3 second micro ejection timers that can be run on small SuperCap Capictors. but the added mass of these tiny electronics and ejection charge out weigh the benifit gained. The couple extra grams actually being the projected ejection time to nearly that of the normal 1 second delay.
No it's just not in the cards to add electronic ejection to a micro Altitude event. I've had these staging times designed and manufactured for use in Scale model compeititons, where the uppers stage sustainer is either T3 or T4 diameter to fit the Supercaps.
Increasing the Airframe diameter in competiton models will also decrease the expected maxium altitude achived by our models. It would be possible to go up to say T2++ (.316" OD) without doing to much harm to the achived altituded, given that our minimum diameter models are Still going up at a pretty good clip when the 1-second delay goes off. We just have to keep in mind the fact that extra diameter = greater frontal area = larger DRAG surface which always reduces altutude performance.
Doubt it would be allowed in Competition as you're still ADDING something (Fuse & ejection charge) to the motor, but more importantly "not using the motor as intended by the manufacturer".
Competition rules are pretty cut and dry when it comes to what can and can't be done with our pre-manufactured motors. The Pink Book rules are intended to level (as much as possible) the playing field for ALL who wish to compete.
Even if there is a gap of say, 2 or more millimetres between the engine and fuse? They wouldn't actually be touching/overlapping in any way. Seems like a gray area.
Say you used a ejection charge with a fuse and the engine lit it, would that be any different really then having an ejection charge with fuse, with an electronic fuse on the other end, a battery, and a pressure switch, and the pressure of the engine gas caused the system to go?
Maybe your saying though, that the whole thought exercise is infeasible by the rules, since the engine specifically was designed with a 1 second delay therefore any lengthening of the delay by any means is a disqualifying offence? I wonder how the HPR rockets work within the rules here?
Adding a separation between the motor and fuse "Should" be legal. Having the motor ignite a fuse at liftoff would also be doable. We just can't Add anything physically attached to a manufactured motors that alters or enhances the performance of said motor. It's like adding a few extra grains of BP to get a stronger ejection charge. it's simply a NO-NO!
Gap staging a fuse would certainly be a grey area; The modeler would have to disclose the intention at check-in, Showing the Gap actually exists, then reassemble the model/system in front of the Check-in and possibly RSO before proceeding to the assigned launch pad. I personally see it as an area of possible mischief on a competition range.
In no way did I say the "any" lengthening of the -NE motors .854s average delay would be a disqualifier. What I said is we CAN NOT add anything physically to a manufactured motors. It may be possible to add some form of electronic ejection system or something like it, but they will have a dramatic lowering of expected altitude due to added mass, increased frontal area drag or both.
To answer your last question: HPR rocket motors are not flown in NAR Competition at all. Largest motor allowed currently would be G's where the 1500gram model /125g propellant limits are the cut-off, no "H" motors period.
That could work if it gets through Check-in. Sounds like it's time to stop talking and start flight testing. Actual flights results never match simulated results generally 10-20% lower. Most of the actual flight results currently available have this particular event will top out around 18o - 208feet +/-.
Assuming you're using a standard .049 x 12" launch rod to calculate your sims the numbers seem about right. Actually the BTC's would be flying from floating head pistions with Non-Standard materal minimum diameter model airframes. Personally I've topped 200feet with this type 1/8A payload model while the Standard models were designed to be qualifiers so even novice flyers could enter these payload events.
Good to see others are looking at flying this provisional event. Hopefully if we get enough clubs flying 1/8A Payload it will be made a permanent event.
I might take a stab at it if I can dig up the appropriate parts and figure out the appropriate fuse/charge.
Another idea thats been kicking around the back of my head is a chemical means, rather then electrical or pyrotechnic. I really think it would be funny to use tiny mentos and diet soda. but I wonder if baking soda/vinigar would work as an ejection gas generator with a pistion/pin replacing the fuse.
LOL!
I haven't tried it on anything this small. Would have to make or create some sort of waterproof capsule so as not to burst the body-tube but Acid/Base reactions would certainly create enough CO2 to easily pop a nose cone. Not sure if it would be enough behind a small piston to push out a streamer but it's certainly not beyond the pail
Been flying Pill bottle/35mm film can Alka Seltzer & water CO2 rockets with the Grandkids for a few years now. They create enough pressure to pop the bottle 15feet in the air pretty quickly on a 1/4 table of alka seltzer. Baking soda/vinegar would be a stronger (faster) reaction.
Nice rockets.
I was thinking the piston would go the other way. The piston head would be at the bottom of the rocket right on top of the engine. it would have a rod that would go through a bulkhead and then pop a bag at the top causing the chemicals to mix. The real trick I think would be getting the delay right. After popping the bag, you'd want 2.5+ seconds before the nose popped. baking soda + vinegar might be too quick. Maybe an elephants toothpaste variant of hydrogen proxide and dry yeast would be slow enough. How long does the alka seltzer and water take to really start going?
Another thought I had yesterday is using gravity as an altimeter. put the liquid at the bottom and the powder at the top, in a couple of tiny cups, and just after apogee the rocket flips and the liquid gets up to where the powder is. This way, you wouldn't have to time the reaction at all. It should be as fast a reaction as possible in that case.
For the alka seltzer, can you use a solid pellet or do you have to powder it? If it could be solid, that might be easier to deal with. Just cut/shave down a piece to fit perfectly into the tube.
Do you think a coat of Elmers glue down the inside of the body tube would be enough waterproofing?
The mercury in a mercury switch used for staging is not thrown forward. The mecury is an object in motion and it stays in motion. The rocket decelerates because thrust ends and air drag and gravity are the only forces left acting upon it and the mercury keeps moving, so the even though everything is still moving forward, the rocket is slowing down a bit while the mercury keeps moving at the same speed so that the mercusy switch housing and the contacts on the front end approach the liquid mercury and make contact completing the circuit.
The liquid does not slam forward, it keeps moving. The rocket appears to slam backward, even though it is still moving forward because it is slowing down relative to the liquid mercury.
https://en.wikipedia.org/wiki/Newton's_laws_of_motion
The Physics is of coarse exactly correct; Just simpler to explain as described.
Whatever Liquid is chosen Will Indeed be slammed into the rapidly slowing, Not "Slowing down a Bit" model causing the condition as described. Weather the liquid hits the contacts or the contact hit the liquid is Totally immaterial to this process. We both know this condition occurs in Less then a second after burnout so for all intent and purpose your post is a Difference without Distinction. The major Point being the liquid would NOT stay in place until the model arcs over at apogee as suggested. My apologies for not wasting a bunch of time beating around the bush doing a complete physics lesson to explain why the idea in question would not work.
Ok. I completed a first test with failure. But learned a few things along the way...
I built a Fliskits Tiny Triskelion earlier and had the inner material from one of the engine centering rings left over. It made a perfect end cap. I then cut out about 1 inch of T2 and super glued on the end cap. I then filled it up pretty good with Elmers glue to coat the inside, let it dry a bit, wiped out the excess, and then let it dry the rest of the way. This piece weighed 0.3 grams. I then used some more T2 to cut a cylinder out of a alka seltzer tablet. On some spare alka selzer, I tested super glue to see if it would react. It does not react, and glues nicely.
So, I filled up the tube with water, put a small ring of glue around the top of the cylinder, and topped it off with the alka seltzer. The whole capsule came in at exactly 1.0 grams and it looks to be water tight. At least for several minutes. I still have it and see no water damage.
I carefully took a T2+ tube with two nose cones, and slid the finished capsule inside, replaced the nose cone, and then tested it by turning it on its side, and then counted. After a minute of counting, It was a clear failure since it would never be in the air that long. I took it a part and saw that it hadn't gotten much gas out yet. After another minute, I could see gas escaping between the tablet and the tube, so it eventually started working. I'm wondering if I used too much super glue. Also, I did not thin out the alka seltzer cylinder. It was the full tablet thickness. Probably too thick. I also after the fact realized I didn't sand down the nose cones at all, and I think they were probably on way too tight to do a good test.
So, in summary, the good:
* Building a capsule out of T2/paperboard worked.
* Water proofing with Elmers seems feasible.
* The weight is correct. 1 gram.
To be figured out:
* alka seltzer or alternative. alka seltzer seems to be too slow a reaction.
* if not alka seltzer, how to keep the powder and liquid separate. Will the cylinder method still work for baking soda or whatever?
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