Lakeroadster's Lifting Rocket

lakeroadster said:

I am at a loss? Why don't manufacturers sell "plugged" booster motors?
.... and why does NAR having an issue with us "plugging" a booster motor in order to address an obvious issue?

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Money is the main reason manufacturers (Estes) aren't currently making plugged motors ( or at least very limited selection, A10-P are the only ones I know of), they have limited uses in rocketry and don't seem to sell well, a single run may take years to sell ( just a guess without data on how long it takes to sell).

As for plugging motors it comes down to " they aren't tested in that configuration" so if something occurs NAR insurance and the organization are not liable, the safety code states

"2. MOTORS.I will use only certified, commercially made model rocket motors, and will not tamper with these motors or use them for any purposes except those recommended by the manufacturer."

Plugging boosters, what have you tried and what works?

I'll post this in the "Propulsion" forum.

There is an efficient rather inelegant solution. Whatever motors you do not want to participate in ejecting the chute, plug the forward ends of their MOTOR MOUNTS. Let them eject and free fall. Black powder motors are completely biodegradeable, so although you should look for them and pick them up if you can, not a big deal if they get lost. Can put little streamers on them if you feel otherwise, mainly just to make them easy to FIND, not needed for any safety purpose.

Ejecting some of your motors, say two of three, also slightly lightens the load on your parachute.

BABAR said:

There is an efficient rather inelegant solution. Whatever motors you do not want to participate in ejecting the chute, plug the forward ends of their MOTOR MOUNTS. Let them eject and free fall. Black powder motors are completely biodegradeable, so although you should look for them and pick them up if you can, not a big deal if they get lost. Can put little streamers on them if you feel otherwise, mainly just to make them easy to FIND, not needed for any safety purpose.

Ejecting some of your motors, say two of three, also slightly lightens the load in your parachute.

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You sir are wreckless! I want to hang with BABAR.

I'm thinking a D12-3 bouncing off your head wouldn't be pleasant, nor "compliant" with NAR rules.

Also the ejected motor / streamer may get hung up on, or rip the fins off of, the rocket. Keep in mind the rocket will still be traveling at a very high rate of speed.

Of course if these slip fit motors didn't light... they would likely fall out at lift off.

I think a bench test of a plugged rocket is in order.

lakeroadster said:

You sir are wreckless!

I'm thinking a D12-3 bouncing off your head wouldn't be pleasant, nor "compliant" with NAR rules.

Also the ejected motor / streamer may get hung up on, or rip the fins off of, the rocket. Keep in mind the rocket will still be traveling at a very high rate of speed.

Of course if these slip fit motors didn't light... they would likely fall out at lift off.

I think a bench test of a plugged rocket is in order.

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Not at all reckless. BP engines will tumble recover, and motor eject is routine. A falling tumbling D is unlikely to cause any greater impact than a tumble recovery complete rocket with a standard engine casing. Per Der Micromeister, ejected E's have also been used at NAR sanctioned NON competition events. I have been using D engine eject routinely for Heli's and Air Brakes with no problems with falling casings. It is a courtesy to spectators to call a heads up. Having watched many D12 casings fall (although I haven't intentionally stood under them!) they might surprise someone but wouldn't hurt them.

Engine eject may be RESTRICTED under certain launch conditions (high fire danger). Same restriction used for Sparky motors. Note that an unstable rocket that "landsharks" or otherwise comes to earth with engines still under thrust or during delay charge would actually be a much higher fire risk. To me this is a much greater concern with a cluster rocket if all motors don't light, and those that do are insufficient to reach sufficient altitude for safe deployment.

Engine eject is also compliant with NAR rules for NON-competition rockets.

Properly friction fit motors shouldn't "fall out" at launch.

Regarding whether the ejected motors MIGHT impact fins, I hadn't thought about that. I kind of doubt it, the estes engine "shotgun" ejection charges would likely clear the fins, but you are correct that I can't be sure. One way that would be sure would be to use a slightly longer delay on the ejected motors, example Central D12-3, open canted motor C6-3, ejected motors C6-5. Should be under chute before motors eject. I would review with open rocket or other simulator however to make sure altitude would still be "way up there".

I would say being wreckless is high praise for someone who flies rockets (and especially odd-rocs).

Oy, don't get me started. Well, lets do...

You can epoxy a thrust ring on but can't put epoxy in the ejection cavity. If epoxying a plug in the ejection end of a -0 is bad, I'd think wadded up tape or anything else that really contains the blow through would also be considered a modification. I have used dog barf and wadded tape but also have been blessed to fly with MDRA where the epoxy plugs are allowed.

BTW, if you don't plug a -0 in the cluster and plug it well, if you have a cato, there is a good chance the -0s will ignite from the wrong end. Toasty.

IMO, any plugging is better that falling motors. I got hit by an AT E15 SU that accidently got ejected from MY rocket. It left a nice 3/4 moon welt. You could even make out the ejection port. Ouchie. Glad it didn't bean be or anyone else for that matter.

Aside: "pendulum" describes the design not the mechanism of stability. Make sure you only is good starters in your pendulum clusters. And make sure you wiring isn't subject to being snagged by those pendulum-mounted fins. Using your launch controller as an extension of the pendulum is a bad idea (first hand knowledge).

You can check with AMW and see if they still have a bunch of D11-Ps....

Didn't want to wrongly quote Der MicroMeister.

https://www.rocketryforum.com/threa...e-eject-at-naram-and-nsl.148164/#post-1818190

post 17

"In non-contest Sport flying 1/8A through G motor single use casings...are perfectly legal to eject and fall free without any attached recovery system.
Personally I like to add a small streamer (about one round around the casing) to motor over D12's. "

John (AKA Der MicroMeister) is my go-to go for all things NAR related (and just about everything else, too!)

lakeroadster said:

Spent some time today on CAD working on a scratch build.... I'm calling it a "Lifting Rocket".

It can be flown with a single 24 mm motor.. or a canted cluster of (3) 18 mm motors.

I'm still working on this... I want to add a payload section at the bottom that locks to the body tube in place of the 24 mm motor.

It would be neat to have multiple motor options and payload configurations.. all retrofitted onto the Lift Rocket

I've added stiffener rings and struts to make it as "durable" as possible.

View attachment 369807 View attachment 369808 View attachment 369809 View attachment 369810 View attachment 369811

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That’s so Cool! I just built and flew something similar, with multiple configurations.

neil_w said:

I would say being wreckless is high praise for someone who flies rockets (and especially odd-rocs).

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Lol, don’t I wish!

Daddyisabar said:

Put your canted motors as far forward as possible. If three ejection charges are too hot just reinforce the tube above the mount or plug a 0 delay motor or two with a nice glob of epoxy. All you need for the motor mount is an old centering ring and a few drops of superglue. There is more than enough surface area on the body tube to get a strong and durable superglue bond on the motor mount tubes. Drag most any asymmetrical payload up attached to the rear end. Tell the RSO the pendulum theory is still good. Put some cool looking fins way up front. Most folks don't know that you have one of the most stable rockets at the launch. It being kinda funny looking keeps up the scare. Just need all three motors to light. Love tractor motors. So much more fun to pull than to push. Not many do it, but you can fly what you like, Ekranoplans, Stukas, worms, dragons, or just pull up silly payloads. So it is not conventional in construction or bends some rule, but it works and is not boring. Keep up the good work.

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lakeroadster said:

Spent some time today on CAD working on a scratch build.... I'm calling it a "Lifting Rocket".

It can be flown with a single 24 mm motor.. or a canted cluster of (3) 18 mm motors.

I'm still working on this... I want to add a payload section at the bottom that locks to the body tube in place of the 24 mm motor.

It would be neat to have multiple motor options and payload configurations.. all retrofitted onto the Lift Rocket

I've added stiffener rings and struts to make it as "durable" as possible.

View attachment 369807 View attachment 369808 View attachment 369809 View attachment 369810 View attachment 369811

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Hey! Attached are pics of a multi-configuration Rocket I designed with open Rocket. I’ve flown it twice - once mated with a glider, once mated with a smaller rocket. It is designed to lift other rockets and gliders, and it has the option to launch the latter as a “third stage,” as the second stage has two 18mm mounts. First stage takes a D12-0.

Any suggestions? I’m new to this, so any input, or tips, would be great!

I knew I had seen the "Strap That To The Bottom Of The Rocket" look before...

Ah ha!

I guess karma dictates I order the "correct' nose cone.

lakeroadster said:

I guess karma dictates I order the "correct' nose cone.

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Actually, that's a Gemini capsule. Here's a Mercury:
https://www.erockets.biz/semroc-balsa-nose-cone-bt-60-3-0-capsule/
Great thread. I shudder to think what you and Coach Steve could come up with if you put your heads together. Cheers.

Thanks Kurin... I'll have to update my CAD model to the that one.

Speaking of CAD... making some progress on the drawings. Here's where I'm at as of today... not finished though.

lakeroadster said:

Finished building the CAD model of the lifting rocket. I came up with a way to attach some external parachute chord mounts for the recovery bay, and external strut mounts for the cargo bay.

See detail B below. Basically it's quan. (6) 1/8" plywood centering rings that are notched to trap a 1/4" nylon lock nut, then the rings are glued together.

Should be hell-for stout.

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What (computer) program is this???

Jonathan 7 said:

What (computer) program is this???

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AutoCAD Inventor

That motor mount is going to be a work of art and science! Can't wait to see the build!

Finished up the drawing package today, ended up with 19 sheets.

I changed the fin design, basically changed the 2 outer ply's, increasing their size to help strengthen the entire fin.

Next up is to make a few changes to the Open Rocket models to ensure the model is accurate... then by materials from BMS.

Here's sheets 10 through 19...

Updated the Open Rocket simulations... all systems go..

lakeroadster said:

Finished up the drawing package today, ended up with 19 sheets.

I changed the fin design, basically changed the 2 outer ply's, increasing their size to help strengthen the entire fin.

Next up is to make a few changes to the Open Rocket models to ensure the model is accurate... then by materials from BMS.

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Hey... is it possible to get a Center of Pressure in Inventor?

I am jealous of your CAD skills .

OverTheTop said:

I am jealous of your CAD skills .

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I know, righ?

Jonathan 7 said:

Hey... is it possible to get a Center of Pressure in Inventor?

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Not that I am aware of. There may be some 3rd Party Software add in's.

I use Open Rocket just to get a feel for the CP. If the caliber is to close, add nose weight just to be safe.

lakeroadster said:

Not that I am aware of. There may be some 3rd Party Software add in's.

I use Open Rocket just to get a feel for the CP. If the caliber is to close, add nose weight just to be safe.

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Wise. I suppose, if you can measure centroids, you could set up equations for CP? I’m not really familiar with Inventor.

Jonathan 7 said:

Wise. I suppose, if you can measure centroids, you could set up equations for CP? I’m not really familiar with Inventor.

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Centroids would just be an application of the cardboard cutout method which is......rough (at best) for models more complex than a standard 3 or 4FNC

Nytrunner said:

Centroids would just be an application of the cardboard cutout method which is......rough (at best) for models more complex than a standard 3 or 4FNC

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Agree, but for a quick, rough idea of your CP, it’s not bad, if that is possible to do. In other words, if you can do equations in Inventor, than you can do anything OpenRocket or Rocksim can do, probably with more precision.