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Discussion in 'Low Power Rocketry (LPR)' started by tommy, Jun 16, 2011.
I've just cracked open a new mean machine. Anything I need to know? Suggestions? Ideas?
My son and I are rebuilding his Mean Machine after a cruise missle incident.
Nozzle blow out. We included a baffle just forward of the tubing coupler in
the upper section. The "new" disconnect coupling they supply in the kit is
very nice. I had a Mean Machine back in the day and walking from the
house to the HS to launch with a 6'6" rocket was always a PITA!
Actually we ended up stretching the Mean machine by 8 inches. After
cutting off the top of the air frame to remove all the damage and get to
solid tubing we lost 9-10" of tubing (the only real damage to the rocket)
we just glued a new 18" length to the top. Inside the new section is
where we added the baffle.
I like baffles as they keep the chute and recovery system from moving
down the airframe at launch, I still use some wadding but you can reduce
the amount you use significantly. By using the baffles in many of my
longer rockets I have reduced the number of recovery system failures/
That is my 2 cents.
I replaced the stock stock motor mount and couplers with 6" long couplers I cut from a 34" I got from balsa Machine service. I also did a center break baffle. It loves F39 and F24 reload.
We had a guy in the club who painted each bt prior to assembly. He took clear 2" packing tape and lined both ends of each tube (except the motor end) inside and out. He put the couplers in per normal, put the tubes together then used 1" strapping tape (over the clear tape) to hold them together. He used the same technique to bind an interchangable 'fin can' to the motor end.
He flew two Mean Machines last launch without incident. One of them drag-raced my son's MM - both on E9-4s. My son's was 'per instructions' so it was a skosch lighter, so it won.
Definitely recommend the split in the middle. Wish that was how mine was built.
The other thing I did was laminate the fins with 110lb card stock and white glue.
Whether you choose to do any modifications or not is up to you. Keep in mind, this bird has flown stock per instructions since the Bee Gee's were on top of the charts.
Stock minus some paper on the fins for smooth paint.
Don't use the new Elmer's Glue-All when joining body tubes with couplers. Same thing applies for any yellow wood glue. These glue grab waaaay too quickly.
Epoxy will work much better than any of the above as will plain ol' white school glue so I'm told.
white and wood glue are fine as long as it's a thick layer and you work relatively fast. Make one fluid motion. If you stop and start again, it will bite and yer done.
If you like using epoxy, go for it. It will definitely give you time to play around a bit to get things exactly where you want them.
Titebond II works great for this. Nonshrinking, slippery, and doesn't grab too quickly.
On building Rowan's MM, we followed the instructions and bought a tube of Testor's Plastic Cement (they only had blue tubes, not the red ones I was used to - I've been using the runny brushon stuff for decades). We smeared it in the tubes per the instructions and stuck the plastic connector sections in.
24 hrs later, it remained well-lubricated.
We pulled the connector sections out, wiped everything clean and waited for it to dry. Then we went out to the garage, mixed up a batch of 30-minute epoxy, slid those puppies in, checked alignment and wiped down the odd dribble.
Testors in the blue has been dubbed 'smelly stuff that doesn't stick'.
I was referring to the red cardboard couplers that you use to join each pair of body tubes together. Those have always given me trouble when using anything other than epoxy. Why? Because after I join the coupler and tubes, I like to roll the assembly on a flat surface to make sure I've everything aligned properly. Gives better strength that way and saves on surface prep comes painting time.
OTOH, I've always had good luck gluing plastic parts to body tubes with the green Testor's plastic cement. I will avoid the "smelly blue stuff that doesn't stick". Thanks for the tip.
Gave my Mean Machine a first flight on a C11-3. The weak ejection did not deploy the parachute but aerodynamics were broken so the model fell into a flat glide. A D12-5 flight was far more dramatic. The model weathercocked and returned to the rangehead under full parachute. We also note that the model wobbles in flight, like a javelin tossed in a track & field event.
So, what would I need to order to make the mean machine break in the middle? I'm guessing you'll have to do away with the plastic coupler. Never built a baffle.
Thanks for all the ideas so far!
I use Ambroid on mine, liberal application, I roll them too to get everything
nice and straight, no issues here.
No you use the plastic coupler, the older version did not have the quick
disconnect plastic coupler. The plastic get glued in the tubing but not
to each other.
I meant if you wanted to make it center break for pachute deployment you would have to do away with the plastic coupler right? Then add something to attatch the chute to.
You will want to use a longer coupler too. Thoes whimpy 2in ones dont work to well (1st hand experience). Just make a bulkhead disk out of balsa or lite plywood.
So if I'm gonna do this center break, what kind of parts list am I lookin' at?
They should be in the kit, unless you have an old kit. They are black plastic
you should have a male fitting about 4" long and a female about 2" long.
And should just slide into the Body Tubes.
They also have a little vid showing prep and launch.
Give me a bit and I'll detail how I built my sons mean machine , what parts and where to get them. I'm drinkin coffee on the front porch using my phone to surf in muh sleepin pants and flip flops per my usual morning routine.
Fill me up!!! Black please!
get about a 5" chunk of balsa and turn (or cut and sand) to fit snugly inside the bts. Glue it halfway into the 'upper' section (doing your table-roll before the glue sets).
That way the NC, 2 BTs and the chunk become the effective nosecone. Use a #8 or #10 screw eye into the balsa, affix your shock cord into the 'top' of the motor end, attach it and your chute to the screw eye and you're all set.
Okay, here's how I built my son's 24mm F reload killa. I'm not going to assume your skill level as far as building so I'll be basic for everyone. I built this two years ago and 10+ flights so my memory may be a bit hazy as to a couple things so bear with me. This was an old style kit so some parts will be different than what you have.
Extra parts used:
110lb card stock, one sheet
E length Motor tube
two Popsicle sticks
one eyelet (most commonly used for picture frame wire)
stainless steel mesh
1/4" elastic (shock cord material)
Coupler material -- www.balsamachining.com
C60-34 -- 1.592x1.524x34 inch long T60 coupler stock -- $6.00
First, I laminated the fins with 110lb card stock using white glue. If you haven't done this before, send me a pm and I'll detail it for you. I like to let fins set for at least 48 hours under something heavy to dry. I use a brake rotor from a '97 Suburban.
I replaced the standard D engine tube with an E length engine tube (yours will be E engine length). As of late, I have noticed Estes Engine tubes to be sub-par. If you think it is, either replace with thicker walled engine tube or go the El Cheapo route....Insert spent E engine and adhere two wraps of card stock with white glue. You'll need to cut somewhere around 92mm wide and I dunno how long off the top of my head. As a result, you will need to hog out your centering rings a bit with sand paper.
As for centering rings, I'm pretty sure I used the stock paper matte rings. I can't remember at this point. If I didn't, I probably hand cut 1/8" balsa and laminated with card stock. Either way I couldn't tell by looking at it. Laminated balsa is definitely a better way to go. It'll give you more material for the glue to adhere to the body tube.
The 34" coupler stock was cut into three 6" pieces. The coupler fit so nice and snug I opted to just friction fit just in case any one body tube suffered damage. This way I can just remove the body tube and replace. Mark each one at 3" to insert half way.
Good thing because my accident prone nephew knocked the lower portion over a few months ago and stepped on the fin can portion resulting in a nice crease a few inches in front of the fins. No problem. I pulled the tubes apart, jammed another 4" piece of coupler down there to straighten it out and she's good to go.
If the couplers don't fit as snug as you like, take some 1" masking tape and wrap in barber pole fashion from one end to the other. Fairly snug is good enough. You don't want to have to use too much muscle.
At this point you'll need to set the twist-lock aside unless you want to use it and put the baffle on the top of the third section. Let's assume you chuck the twist-lock and move on.
For the baffle, take a 6" piece of coupler, and mark 3". That's how far you'll insert into second body tube. Like I said, I'm going with the basics. Cut and size your popsicle sticks so you can make an "X" that will fit into the coupler flat (see picture). The bottom you can glue one piece into coupler and then the other on top. This is just to hold in the stainless steel mesh from the bottom up. Once dry, take your stainless steel mesh and stretch it out. You want it to fill the void but not be packed to tightly.
For the top of the baffle, you'll need to drill a small hole in each piece of popsicle stick to be able to thread your eyelet into. I like to dab some epoxy on both sides of the threads to lock it in place. Size fit and glue accordingly into baffle coupler.
The top half of the coupler needs to be soaked with thin CA and sanded smooth. Also coat the inside of the body tube the baffle will go in three inches as well. I dribble the CA in then wipe smooth with a paper towel. It requires less sanding. This will yield a smother surface for the baffle body tube connection. (Do not CA other couplers. You want them to bite against the body tubes.
I can't for the life of me remember whether or not I glued the bottom half of the baffle to the second body tube or friction fit. Use your best judgment but I'm inclined to think that I just friction fit.
The rest of the assembly is pretty self explanatory. Just friction fit the couplers to first and last body tubes and assemble. The nose cone was also friction fit. I ran a length of 1/4" elastic from the nose cone through the top two body tubes and then to coupler. I'm guessing about 12-14' total.
You could also fashion a bulk plate with eyelet in the top coupler to attach your recovery to. That would do away with the extra air space in the top 18" of body tube.
That's it. I hope this helps and was easy to follow. There are many, many threads on upgrading the Mean Machine. Read up, take suggestions and ultimately do what works for you and your comfort level.
Side note: Even though this baffle has worked flawlessly, I don't use the mesh baffles anymore. I have been using what I call a cold-air diversion baffle (see pic). If you go this route 13mm motor tubes will work, two in and two out.
This baffle is being used in a Quest Magnum Sport Loader my son and I are building. The bt is not much bigger than a BT60 so 13mm tubes will work for a MM if you decide to go this route.
In post #24 and photo number two...are these the dreaded flip flops you have frequently mentioned?
Thank you for sparing us the visual of yer sleepin' pants.
Yes, Sir. Those are my house flippers (not to be cornfused with slippers, I don't wear them things). Nor are they to be cornfused with my out in public or lake flippers. I reserve the beat up, stinky ones for the house. They're due for for a trip to the washer after a good bath of Clorox Cleaner with Bleach. We don't have no green stuff covering the ground out in the desert.
Don't worry, the sleepin' pants are passable in any doctors office or hospital. I have 4-5 pair of scrubs I sleep in.
Here's the view I enjoy from the front porch in the morning while drinkin' coffee in muh flippers and sleepin' pants.
We built a baffle almost identical to Cheapo's for my son's MM.
Back on topic...
El Cheapo when you say 110 lb stock do you mean something on the order of a 3x5 note card?
All my fin laminations thus far have been either standard printer paper or self-adhesive label paper.
I'd say 3x5 note cards are close if not equal to 110lb card stock. You can buy reams of 110lb card stock at Walmart, Staples, etc. BobH uses 65lb card stock for alot of his paper rockets but I haven't found it at any of the major office supply stores. I'm sure a specific paper store would have it.
For lighter rockets I use label paper where a ton of added strength is not needed. It's merely for ease in finishing the balsa but does add some strength. I'd say laminating 1/8" balsa with 110lb has greater strength than 1/8" bass wood with the bonus of less weight.
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