MMX Piston launcher

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kruland

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Micromeister once offered to show a pictorial on piston launchers for MMX rockets.

I have built my first super simple piston launcher for 13mm using the "spend engine casing" method. I have been thinking about how to do this for MMX but am stumped by the complexity introduced by the super-tiny MMX ignitor.

Can you offer any help?

kevin
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RT1
 
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Pistons like your talking about are pretty simple to use with a 1-1/2"-2"strip of .030 to.034 gauge nichrome as your igniter.
I'm not sure if you can see it in the first photo but just at the base of the model the nichrome leads are simple hanging over the edges of the piston tube, sandwiched between the motor and the slide tube walls.

I personally don't care for this system but it is certainly the easiest way to use a piston with micros.
Just be sure to build in about 3/8" of motor overhang into your model design. That gives plenty of compression room as you install the model/Taped motor in the slide tube.

My preferred method is the micro floating head piston using pin type sockets for positive contact.
If you've joined the MicroMaxRockets Yahoo group in the file section under McCoys Micro Plans in the equipment folder is a one page plan for my floating head piston with all the needed parts. I'm very happy to say I've had 100% success rate with this piston. You do have a tiny bit of soldering needed, but it sure makes a difference when you simply plug in the igniter and KNOW it's going to have positive contact;)

MM F-Head Piston-a_Shaft-Head&Igniter CloseUp_04-18-09.JPG
 
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Kevin:
did that Help? which type Piston are you using now?

Micromeister,

Sorry I didn't respond. Yes it helped but it also confused me.

About 2 weeks ago, I built a 13mm fixed piston from an old engine, tube etc. Unfortunately, between the thunderstorms, swampy field, and general summer business, I haven't been able to try it out.

I ended up confused because I realized that I had no clue what a floating-head piston was. For the last couple of days, I've been digging up various plan to figure out the general principal. I think I now understand.

Your design is amazing but probably too complex for me at this time. I think I will first go about playing with the fixed piston, then try to convert to floating-head piston before moving forward.

Although this is off topic for MMX, I was wondering if in the floating-head designs, I should put a launch lug on the piston tube and use a rod for initial guidance. It seems that the floating head designs would have a lot of play between the support (dowel) and the tube.
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Colorado Medical Marijuana Dispensaries
 
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Micromeister,

Sorry I didn't respond. Yes it helped but it also confused me.

About 2 weeks ago, I built a 13mm fixed piston from an old engine, tube etc. Unfortunately, between the thunderstorms, swampy field, and general summer business, I haven't been able to try it out.

I ended up confused because I realized that I had no clue what a floating-head piston was. For the last couple of days, I've been digging up various plan to figure out the general principal. I think I now understand.

Your design is amazing but probably too complex for me at this time. I think I will first go about playing with the fixed piston, then try to convert to floating-head piston before moving forward.

Although this is off topic for MMX, I was wondering if in the floating-head designs, I should put a launch lug on the piston tube and use a rod for initial guidance. It seems that the floating head designs would have a lot of play between the support (dowel) and the tube.

Not needed at all.
Some RSO's may require Pistons to be used within a Tower however. I've not had that problem as my construction method keeps everything very snug.

Perhaps another drawing might help. I wish I could remember who came up with this design about 8 or 10 years ago...CRS again:( it incorporates a number of easily available telescoping brass tubes as pins and sockets. While this system works fairly well, positive contact becomes increasingly spotty as the day and flight gunk accumulates. I've modified this design floating head piston for 7.1mm(MMX),10.5, 13, 18 & 24mm options using the same plug-in connectors as one detailed in the micro-maxx piston plan. Unfortunately I have not modified the drawing with those details as yet. Hopefully this one will give a clearer picture of the moving parts of the piston.

It is the slide tube that give initial guidance to the model, the floating head simply reduces the amount of motion loss as the head hits the stop at the top of the slide tube travel. Actually reducing tip-off Chances, Floating head greatly helps maintain the inerta of the model though the slightly heavier "head" does have a some effect on altitiude. Still Floating head has been Data proven to increase piston performance by 34% and more.
Hope this helps.

Ps: If you want the full pictorial on standard Metal head pistons (the next step up for gluing a spent motor onto a dowel. or the other construction photos from the micro Floating head pistion drop me and e-mail at [email protected] I can send better res pic for there:) or download Tech-Tip 008 from the narhams.org website located in the Library section.

FH Piston-b-sm_13 & 18mm x 12in_07-08-04.jpg
 
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I'm afraid metal construction is probably beyond me right now. Small bits of soldering isn't a problem but trying to machine a metal head is way beyond me.

So I understand the physics in the previous image....

The 1/16 brass tubing inserts into the 3/32 tubing and provides support to the tube coupler. The tube coupler then supports the piston tube.

I will probably have to touch one before I fully understand.
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Oh man! Don't let the word Metal head scare you. we're talking about thin wall telescoping Brass tubing you see at the hobby shop all the time.
If you have a tube cutter, Mototool with a cutoff wheel or fine tooth blade razor saw, that's about the heavies equipment needed to produce these pistons. A 1/4" or larger hand drill also makes the work easier but a hand crank drill could be used.
I tapered the brass tubing for the micro piston in a plain old cordless hand drill with a metal file and sandpapers. Took awhile but worked out pretty well:).

The better 2/3rd is constantly beating me about the head and shoulders to make sure everything I do/design&construct can be built by others on the coffee or kitchen table. These pistons are in that range. I do talk about using drill bits and taps for threading stops and parts but they are Optional goodies not needed for base construction or operation.

10-4 on the 1/16" to 3/32" tube Pin&socket. the 3/32" sockets are then encased in epoxy within the coupler, making sure the epoxy stops just below the edge of the tube.

In all cases weather using a metal head (brass sleeve over built up masking tape) or floating head (coupler or smaller paper tubing with brass tube or sockets embedded) the mating parts are seperated by some sort of insulating material ( I used 1/64" plywood) between the tubes). making sure the wires are insulated all the way down the inside of the support tube. otherwise the igniter will be shorted out inside the support tube. this isn't as difficult for the larger models with 1/4" ID support tubes but it becomes critical on the micro version. Hope these photos don't scare you out of trying, they really aren't that difficult and vastly improve performance over the dowel/casing construction pistons.

e2-sm_.5in brass tube Head_07-27-03.jpg

f6-sm_Building 18mm Masking tape spacer_07-27-03.jpg

f7-sm_Masking tape buildup to Brass ID_07-27-03.jpg
 
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FYI, I did an article last year for Sport Rocketry as sort of a newbies guide to pistons, think it was the Mar/Apr issue. If you email me offline at chanstevens at gmail dot com I can probably dig up the submission (word doc) and a photo or two.

The article illustrated the difference between the traditional fixed head approach and the much more common (today) floating head, though was using the really simple externally wired version you were working with, not the internally wired one John's using. The internal is a bit more complex, slightly more work involved per flight, but I'd say I've switched to internal for more than 3/4 of my piston flights for a few advantages. What really "converted" me was a magnificent photo someone caught of one of my egg loft flights right as it separated from the piston. The photographer was oohing and aahing over the detail he caught, but my first reaction was shock and horror that my clips were in that photo, having traveled at least 36-40" along with the piston tube, a clear risk of pulling back down on the rocket leading to tip or non-vertical boost. That generally hadn't happened in my experience, but I was obviously living on the edge.

--Chan Stevens
 
I had thought that the clips would try to get pulled up. My theoretical solution to this problem was to pin the wire to the rod with enough slack for about 6 inches of extension. I thought the rocket would be able to pull off them while the volume was under pressure and piston tube still guided by the piston head.
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It's been over 2 years since Posting to this thread.
In just the past 3 months, I've re-geared to start completing many of the partical Launch Range equipment Drawings and construction photos that have been laying around half done for a decade or so.
Chief amoung them is a fairly comprehensive look at Piston Launchers from Howard Kuhn's 0-Volume piston, Team Odd-Couple's research into Floating head's in 1986 to the latest of improvements 2011-12 made to my shorter slide-tube, Positive Mill-Max contact, multi launch capable floating head versions. Some testing semi-permanent .0201" (24ga) dia. Nichrome igniters.
Two of our clubs FAI internat competitiors and I well be presenting a club Piston Launcher Info sharing photo and hands-on materials & build demo set for our club meeting January 5th. I'll be happy to share the drawing, example & demo photos for the Micro and other size Pistons from the Good old C.A.D. (Cheap & Dirty) Casing & Dowel versions, Kuhn 0-volume piston with original trapped igniter, imporved internal wired igniter, and of coarse both Tele-tubing ignitered 1985-86 style Floating head to todays positive contact socket igniter, short to very short floating head pistons.

Built & tested a Spent Casing & bamboo skewer MMX C.A.D. Piston just for fun, along with a Kuhn style MMX Metal head and an altered metal Socket Head MMX 0-Volume to see if I could find a marked difference in their operation.
As a teaser...Average beween the two igniter hook-up 0-volume piston launchers was about 8% but if the clips stayed attached and were dragged the entire length of the slide-tube to the 7" stop... as much as 28%. All these tests were done with tiny size Pico Altimeter measured.
Hopefully more nifty stuff to share a bit later in January 2013.
 
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Well here it is May already....Wow time sure flys when your having fun LOL!!!

Back in January a couple Club members and I put on an in-depth Piston launcher study-Discussion, as used in NAR and FAI competitions. To that end I produced an update to my Original Metal Head Pistons Tech-Tip-008. Our update is listed in the www.narhams.org library as Tech-Tip-008b with supplimental photos and drawings.
Our discussion started and is covered in the handout from the very beginning C.A.D. (Cheap&Dirty) dowel and motor casing piston all the way through todays internal wired Mill-Max pin contact & socket, Short Slide tube Floating Head pistons for ALL motor classes 1/8A through E (MMX, 13mm, 18MM and 24mm).

Of particular interest to this group will be one of 4 iterations of C.A.D, Fixed metal head or Floating head 7.1mm MicroMaxx piston launchers.
Below are a couple static photos of these Pistons. If you'd like to build any one of these different type Pistons you'll find a detailed downloadable plan in Tech-Tip-008b.
One thing I will mention the use of Positive contact Mill-Max pin & socket contacts have made a 100% difference in 1st attempt launch reliability with ALL the internal contact type options. They actually make Piston Launching almost as stress free as common igniter hook-up flying.

4 sided Piston Display-a_18-CAD,MH-ZVPL&FLPL_12-30-12.jpg

7.1mm-a CAD-2_7.1mm x 7in Bamboo&Casing MMX ZVPL_12-06-12.jpg

7.1mm-b MH-ZVPL-1_MMX Soild Hd CAD MH-ZVPL & Stop_12-06-12.jpg

7.1mm-b MH-ZVPL-4a_MMX MH-ZVPL & 3in guide_12-06-12.jpg

7.1mm-c FHPL-1_int. wire Mill-Max socket Piston_12-06-12.jpg
 
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Just a couple flight pics of the MH-ZVPL & FHPL during fun flying last November & december. Along with a shot of a telescoping mylar windscreen.
Hope these help spark your interest.

7.1mm-c-215b2Lp08a_8thA HD FHPL & Screen_12-15-12.jpg

7.1mm-c-215b2Lpo8b_8thA HD FHPL Mid Flt_12-15-12.jpg

7.1mm-c-216glp06-1sm_8thA-PD 7mm x7in FHPL_11-17-12.JPG

7.1mm-c-216gLp07a_8thA PD, FHPL&Screen_12-15-12.jpg
 
I've managed to follow Micromeister's instructions from this thread and his Mill-Max instructions and build a workable mmx floating head piston launcher. Thanks Micromeister! :)

I had to improvise a few things and take a few guesses at sizes. I also managed to do it in such a way as to not require any soldering and I documented the endeavor along the way. I just tested it and it works well.

Please find the instructions attached. Hopefully it will be useful to others.

View attachment mmx-piston-launcher.txt

Screenshot_2014-12-14-13-59-44.jpg

Screenshot_2014-12-14-14-00-00.jpg
 
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I've managed to follow Micromeister's instructions from this thread and his Mill-Max instructions and build a workable mmx floating head piston launcher. Thanks Micromeister! :)

I had to improvise a few things and take a few guesses at sizes. I also managed to do it in such a way as to not require any soldering and I documented the endeavor along the way. I just tested it and it works well.

Please find the instructions attached. Hopefully it will be useful to others.

Not sure why you had to take a few guesses? I will assume you did not download the one page Plan provided in Tech-tip-008b? it's drawn full size so you shouldn't have had any question about sizes at all.

Looks like it should work, I am a bit concerned about not having soldered the internal 2 conductor lamp cord to the base Mill-Max connector. While whatever you did to make your connections may work for awhile but over time and especially during "the Heat of competition" such a deviation will likely cause some misfires down the road. There are only those two very small solder joints which anyone with the smallest of Soldering irons should be able to handle making our Micro-Maxx Floating Head Pistons all but Fool Proof. I say this because if you forget to install a floating head the model will still take off but will have no benifit from the piston tube... how do I know this...Because in the rush of competition I did do that myself. We can make things fool-Proof but not Damn Fool Proof LOL!!!!

For some reason your text file doesn't open correctly, the window extends far beyond the edges of the screen with no way to reduce or alter the copy layout. You might want to revise your script in a Word documents so folks can easily read it.
May be a bit Late but I'll see if the MMX Floating Head Piston pdf Drawing will upload here. Might be of help on your next one:)

View attachment c1-1c_MM FH Piston .281in X 12in Dwg-1_04-08-04.pdf

MM F-Head Piston-p02b_Mill-Max Socket in support tube_04-10-11.JPG

MM F-Head Piston-p02c_T2 F-head & Mill-Max igniter_04-10-11.JPG

MM F-Head Piston-p02d_F-Head &Igniter on support_04-10-11.JPG
 
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