Clustering Rockets

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jake7030

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HI
My question is how do you create the motor mount for say a 3 cluster motor for o say the Mean Machine. Do you need the full version of rocksim and a type of laser cutting machine to plug it into. Thanks for any opinions or advise.
 

sandman

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HUH!!

Do you want to "make" a cluster motor mount?

Or do you want to simulate a motor mount in Rocsim?

The laser cutter thing threw me?:confused:

Making a motor mount in a BT-60 is easy...just make three motor mounts (BT-20's), glue 'em together nice and even), then glue 'em into a BT-60.

No laser cutting needed...although a household laser cutter would be a fun toy to have.

Done.

Now how do I explain to my wife all the black marks on the ceiling 'cause I was shooting flys off the ceiling with my new laser cutter:D

sandman
 

Micromeister

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Jake:
If you do a search of this forum and the low power section we have had several discussions on how to produce 3-7 motor mounts or verious size models. Including photos.
a 3-c6 cluster to fit your BT-60 Mean Machine will start with 3 3" pieces of BT-20 as motor tubes. 3- motor hooks and 2 cardstock, foamcore, balsa or basswood centering rings. the centering rings can be layed out by hand, or by using one of many computer programs. RocketCad-4 is a Freeware program with an excellent motor mounts tool, Templatewidget is another.
Rock-sim can also be used of you pay the 85.00 for the program.
 

vjp

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Originally posted by Micromister
Jake:
If you do a search of this forum and the low power section we have had several discussions on how to produce 3-7 motor mounts or verious size models. Including photos.
a 3-c6 cluster to fit your BT-60 Mean Machine will start with 3 3" pieces of BT-20 as motor tubes thee motor hooks, and 2 cardstock, foamcore, balsa or basswood centering rings.
One of the great things about the BT-60 is that three BT-20 tubes will fit just perfectly into the BT-60. So if you're in a hurry, you *can* skip making the centering rings completely. Just glue in the MMT tubes, pack some wadding tightly between the open gaps, and pour in a little 5-minute epoxy between the gaps just as it starts to warm up (indicating that it's to solidify).

It's not the most elegant way of building a cluster mount, but it's quick and easy.
 

eugenefl

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As mentioned above, 3 18mm/BT20/.736"/A-C motor mounts will fit cleanly inside a BT60/1.637" body tube. See attached picture for an example. BTW, centering rings not needed. I don't even think the ring material would fit along the outside edge of the motor tubes.
 

vjp

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Originally posted by eugenefl
As mentioned above, 3 18mm/BT20/.736"/A-C motor mounts will fit cleanly inside a BT60/1.637" body tube. See attached picture for an example. BTW, centering rings not needed. I don't even think the ring material would fit along the outside edge of the motor tubes.
Was that made with the epoxy method? Hard to tell, focus looks a little soft.
 

cydermaster

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JFlis posted an excerpt from the Richter Recker instructions in this post. Its a very clear illustration how to do the 3xmotor tubes in a body tube method of clustering.

HTH
 

arthur dent

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Yep....I used this technique to repair a balsa cluster motor mount that had been badly burned,like all the best ideas its quick,simple and effective:)
 

jflis

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Also, keep watch as FlisKits will be announcing a small family of cluster motor mount kits in the next month or so :D
 

Prowler901

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Excellent news Jim. I'll be looking out for this one for sure :)

Regards,
Todd
 

BlueNinja

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A laser cutter... Sounds fun!



Good luck with the Mean Machine. I flew mine stock today, with a D12-5.
 

Stewart32

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Speaking of Motor Mounts...

I would like to install triple 24mm MM's in a Big Daddy. Obviously, if the cluster is arranged "linearly" then I can fly on one motor in the center without adverse effect. But if I go for a "tirangular" pattern, is the same true? Will the offset thrust result in enough moment to make the bird unstable during flight? What if the spent engines are put in the remaing tubes to somewhat balance the single engine?

Thoughts?

Experience?

Thanks
 

arthur dent

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Originally posted by jflis
Also, keep watch as FlisKits will be announcing a small family of cluster motor mount kits in the next month or so :D
I think i've just heard PAVLOVS bell ringing....DROOOOOOL:D :D
 

jflis

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Originally posted by Stewart32
Speaking of Motor Mounts...

I would like to install triple 24mm MM's in a Big Daddy. Obviously, if the cluster is arranged "linearly" then I can fly on one motor in the center without adverse effect. But if I go for a "tirangular" pattern, is the same true? Will the offset thrust result in enough moment to make the bird unstable during flight? What if the spent engines are put in the remaing tubes to somewhat balance the single engine?

Thoughts?

Experience?

Thanks
The off center thrust will cause the rocket to veer in the direction opposite the location of the burning motor. The higher the stability of the model the less the effect. I've seen some models like this go cartwheeling off the pad, so I wouldn't recommend it as a normal flight mode.

The Richter Recker, for example, flies stable with only 2 or 1 of the 3 burning but even with *that* beast you can see it starting to arc over and it has to have 3-4 calipers of stability...

If you want to fly your cluster as a single motor model you should either design the cluster "in-line" like this 000 or use a changable motor mount so you can switch from one mode to the other.

jim
 

eugenefl

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Originally posted by vjp
Was that made with the epoxy method? Hard to tell, focus looks a little soft.
Sorry it took me a bit to respond to this. Lotsa traffic on the boards these days!

Actually, no epoxy or CyA was used in the construction of this rocket. Once the motor mount assembly was complete I traced the three motors on a piece of foam meat tray. (Foam project board will work here as well.) I then used a compass to capture all 3 motors within a circle essentially simulating the BT60. I slid the assembly into the rocket and ran yellow carpenter's glue alongside each motor to hold the entire assembly in place. I then went back to the meat tray and cut out the 3 little triangles that are left over of what would be a centering ring. Of course, stuffing these empty areas with tissue or newpaper and filling them with yellow glue will work just as good.

I've drawn a picture to aid this explanation. See attached.
 

eugenefl

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In this picture, my 5'+ long rocket is on a cluster of 3 B6s. Only 2 ignited yet the rocket managed to maintain a straight flight. I will safely assume that even with 1 motor, so long as there is enough thrust, the rocket will fly safely.
 

vjp

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Originally posted by Stewart32
Speaking of Motor Mounts...

I would like to install triple 24mm MM's in a Big Daddy. Obviously, if the cluster is arranged "linearly" then I can fly on one motor in the center without adverse effect. But if I go for a "tirangular" pattern, is the same true? Will the offset thrust result in enough moment to make the bird unstable during flight? What if the spent engines are put in the remaing tubes to somewhat balance the single engine?

Thoughts?

Experience?

Thanks
Stewart -

I would recommend a 5-motor tube cluster configuration for the Big Daddy. One central MMT, surrounded by 4 outboard MMT's, arranged in a cross-shaped configuration with the MMT's between the fins.

In this way, you can fly in 1, 2, 3, 4, or 5 motor configurations (plugging the unused MMTs with dummy motors) and still maintain symmetrical thrust.

The Big Daddy body tube might be a little too small for 5 24mm MMT tubes though - I don't have one handy to measure here. If this is the case, though, you could still go with a central 24mm MMT and four outboard 18mm MMTs.

p.s. ditch the plastic chute for a good nylon one, and beef up the shock cord while you're at it, as well.
 

jflis

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Originally posted by arthur dent
I think i've just heard PAVLOVS bell ringing....DROOOOOOL:D :D
ain't I a corker though?? :D

Here's what we hope to be announcing before too long:

EMK2-18-60 (Two 18mm in a BT60)
EMK2-18-70 (Two 18mm in a BT70) (Motors spaced apart for the Gemini Titan)
EMK2-13-55 (Two 13mm in a BT55)
EMK3-24-70 (Three 24mm in a BT70)

EMK-5-124-413-70 (5 motor cluster, One central 24mm with Four 13mm)

See the attached pix
 

powderburner

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Jim, I'm going to have to order some of those when you get 'em in stock.
I would also encourage you to carry solid bulkheads out of the same material. I have often run into the need to create a pressure bulkhead, or a weird custom centering ring. I don't like the 'universal' centering rings with all the pre-cut punchouts, because they are weak, and they are impossible to work with if the hole(s) you want to cut are off-center. It would be a huge help to have a source for well-cut solid blanks.
Please give it some thought.
 

vjp

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Originally posted by jflis
ain't I a corker though?? :D

Here's what we hope to be announcing before too long:

EMK2-18-60 (Two 18mm in a BT60)
EMK2-18-70 (Two 18mm in a BT70) (Motors spaced apart for the Gemini Titan)
EMK2-13-55 (Two 13mm in a BT55)
EMK3-24-70 (Three 24mm in a BT70)

EMK-5-124-413-70 (5 motor cluster, One central 24mm with Four 13mm)

See the attached pix
Jim - Have you thought about offering upgrade MMT kits for popular designs like the Fat Boy? I just drew up a turbocad layout for a BT-80 CR with (1) 24mm central "E" and (3) outboard 18mm mounts which I was going to get laser cut. While doing this, the thought crossed my mind that cluster upgrade kits might be a great way to breath extra life into popular kits like the Fat Boy.
 

Stewart32

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Jim,

Will the motor mount kits be sold as a bag of parts, or will they be pre assemled? The variety looks great by the way.


Stewart
 

cydermaster

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Originally posted by Stewart32
Will the motor mount kits be sold as a bag of parts, or will they be pre assemled?
I doubt very much that they'll be pre-assembled - Jim doesn't do pre-assembled. Theres no merit in just popping a pre-fabricated motor mount into a body tube, and pouring glue over it.
 

eugenefl

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Originally posted by cydermaster
I doubt very much that they'll be pre-assembled - Jim doesn't do pre-assembled. Theres no merit in just popping a pre-fabricated motor mount into a body tube, and pouring glue over it.
Agreed...

Er, I'll take one of each motor mount assembly....uh, make that two. :D
 

jetra2

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Originally posted by eugenefl
Er, I'll take one of each motor mount assembly....uh, make that two. :D
Three of each for me please! :D

I REALLY like that 5 motor cluster in the BT-70, and the 2x13mm in the BT-55...I have a rocket that needs that MMT!

Jason
 

jflis

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Originally posted by Stewart32
Jim,

Will the motor mount kits be sold as a bag of parts, or will they be pre assemled? The variety looks great by the way.


Stewart
They would be kits with all the parts and instructions. Once you get to know me (and FlisKits), you will realized that I am a great fan of having *you* do the work. Not because I am lazy, but because I want *you* to learn as you go.

There is no greater satisfaction, beleive me.

VJP: As for upgrade MMT kits for popular designs, well nothing quite *that* specific. But we will continue to grow our offering of cluster motor mount kits (ideas for combinations are welcome via email ([email protected]) but we make no promises). That way the modeler can choose the motor mount that best suits their needs whether it be to scratch build or to upgrade.

I wasn't expecting quite this kind of a response. Based on your feedback here, I will get right to work on these things. thanx.

jim
 

Prowler901

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Great stuff Jim! Those look awesome. I think I have a plan for each one of them :D Looking forward to their release. Fliskits sure does have some great things coming our way. :)

Regards,
Todd
 

eugenefl

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I certainly think that the rings alone fill a HUGE gap in the rocket product community. NO ONE sells cluster mounts unless it's a custom order! NO ONE I tell ya! Low power rocketry may never be the same. We're all greedy and hungry for more power. I don't care if you're into MMX or no-bigger-than-E9s, you're going to at some point have the urge to cluster the motors! Christmas is going to be fun this year!
 
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