# Need Beefy Stage Coupler

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#### RocketNut9

##### Well-Known Member
Hello:smile:
I am looking for a vendor (other then Estes) that sells the ProII Booster staging coupler or extremely strong body tube coupler for the Estes 2" series body tubes. Does any one sell these couplers? It does not have to be paper, just needs to the same size (OD/ID).

Thanks

Rocket Nut

#### dhbarr

##### Amateur Professional
If you don't mind an -external- coupler, 2in mailing tube works with a bit of elbow grease.

#### RocketNut9

##### Well-Known Member
The design (as it stands now) the coupler has to be internal.
This coupler is apart of a booster that has a 3 engine cluster. Which is the first stage for a Mammoth (Estes kit) multi stage bird. I was going to 3D print it but it is not strong enough and keep braking off. So I changed the design to match the ProII booster series staging coupler. I contacted Estes and was told that part is not available because it is stocked in China. Looking at there 2" body tube coupler it does not look as beefy as the booster coupler does.

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#### BDB

##### Absent Minded Professor
I'm going to try to 3D print your design this weekend. I was thinking about using an Estes coupler and coating it with some laminating epoxy and then sanding it smooth before installing it. I have done that for HPR couplers. It adds some weight but also makes them much stronger.

#### ActingLikeAKid

##### Well-Known Member
... or you could use the estes coupler and glass the outside.

#### RocketNut9

##### Well-Known Member
I'm going to try to 3D print your design this weekend. I was thinking about using an Estes coupler and coating it with some laminating epoxy and then sanding it smooth before installing it. I have done that for HPR couplers. It adds some weight but also makes them much stronger.
I have made some changes, so please get the update before printing at https://grabcad.com/library/3-motor-cluster-booster-1. Basically I replaced the coupler tube with a slot for a coupler. This is shown in the exploded view. The dimensions where spec by Estes as 1.926 OD, 1.869 ID+/- 0.03.

#### BDB

##### Absent Minded Professor
Whoa,that's cool!
That's why I'm heading down to the 3D printing lab at my university right now. Going to try to convince the nerds that work there that they need to let me print this. (Hopefully it's one of my students, so they can't say no to me.)

#### RocketNut9

##### Well-Known Member
That's why I'm heading down to the 3D printing lab at my university right now. Going to try to convince the nerds that work there that they need to let me print this. (Hopefully it's one of my students, so they can't say no to me.)
My printer is the CV-10. Which has a very large print volume of X=300,Y=300,Z=400. You can purchase one at https://squareup.com/store/tiny-machines for under 600. If you purchase one please mention my name. In one of those pictures, it looks like this is a 3 stage? But here https://d2t1xqejof9utc.cloudfront.net/screenshots/pics/e4aa176cd06af18754b0652a55ad7a2c/original.jpg it looks like the tops of the engine pods are plugged. Are you using electronics to light the second stage? (also how high is that getting? 3x29s can put an awful big kick on a rocket.....) The three motors are duct to a single port that's align with the next stage motor. If you look at the sectional view (5th pic in the series) you can see this duct and how it merges the three into a single exhaust port. I did this way so matter which engine burns through first it still lights the next stage. Yes using 3 F15 is one hell of a kick. Thats why I am on the hunt for an extremely strong coupler. Last edited: #### RocketNut9 ##### Well-Known Member I tried to upload a clear view to ducts but failed. So I posted it on the GrabCad. It's the 6th pic in the series of pics. Last edited: #### ActingLikeAKid ##### Well-Known Member Yes using 3 F15 is one hell of a kick. Thats why I am on the hunt for an extremely strong coupler. My gut says to use the Estes coupler to align, then wrap the joint with a couple of layers of fiberglass. Essentially you'd have an internal and external coupler. I could be wrong, but I think most of the forces there would be compressive - unless things are Going Very Wrong, you shouldn't have a ton of force trying to snap the rocket at the joint (if that makes sense) (NB: I'm not an engineer) #### ActingLikeAKid ##### Well-Known Member OK, I see the ducting now. VERY slick #### RocketNut9 ##### Well-Known Member My gut says to use the Estes coupler to align, then wrap the joint with a couple of layers of fiberglass. Essentially you'd have an internal and external coupler. I could be wrong, but I think most of the forces there would be compressive - unless things are Going Very Wrong, you shouldn't have a ton of force trying to snap the rocket at the joint (if that makes sense) (NB: I'm not an engineer) I agree fully. The coupler and compression forces is my main worry. #### ActingLikeAKid ##### Well-Known Member I agree fully. The coupler and compression forces is my main worry. I think a nice thick bead of structural epoxy at the base of the coupler should help distribute those forces. You could also add some strakes that hold the body tube in place (also that would really cool ... like if you extended the noses of the "pods" up so they go past the joint, if that makes sense) #### BDB ##### Absent Minded Professor My printer is the CV-10. Which has a very large print volume of X=300,Y=300,Z=400. You can purchase one at https://squareup.com/store/tiny-machines for under600. If you purchase one please mention my name.

The three motors are duct to a single port that's align with the next stage motor. If you look at the sectional view (5th pic in the series) you can see this duct and how it merges the three into a single exhaust port. I did this way so matter which engine burns through first it still lights the next stage.
Yes using 3 F15 is one hell of a kick. Thats why I am on the hunt for an extremely strong coupler.
No luck tonight. Who knew those nerds left the 3D lab on a Friday night?! I'll try again on Monday.

Our maker space has the biggest 3D printer I've ever seen; it could print a dozen of these things simultaneously. The question is, will they let me use it?....

#### LithosphereRocketry

##### Pining for the Fjords
Not *that* much... I, personally, don't think that you need to use anything more than a standard 2" coupler. The Estes PSII parts are built to stand a G80, and you're giving it a G45. If you were clustering 3 composites (like G40s or something) I would be more worried.

#### RocketNut9

##### Well-Known Member
I have ordered form Estes there 2" tube coupler (waiting for delivery) to see it they are beefy enough for the job.

#### RocketNut9

##### Well-Known Member
Learned a HUGE thing today. The 2" tube coupler will not work as a stage coupler. The O.D, is larger then the O.D. of the Pro booster couple (supplied with the kit), making it extremely tight in the upper stage to the point staging could be questionable. Where the Pro stage coupler slips in nice and tight. With tube coupler takes a lot of work to get it to slide into the upper stage, even a lot of sanding.

So I need to find a source for the Pro stage coupler tube. Any suggestions where I might find them? Right now my only source is to buy the entire booster kit from Estes just to get the coupler.

Rocket Nut

#### LithosphereRocketry

##### Pining for the Fjords
Wait, are you trying to use PSII E2X style staging? That could be harder...

Just looked at the top of the thread and realized that the Mammoth is E2X. Then your best bet is just to get the standard PSII booster, I think...

Sorry for the confusion - I thought you wanted to just attach the coupler to the tube, rather than an E2X-style fincan. You could still use the coupler for a payload bay though...

#### Wayco

##### Desert Rat Rocketeer
Wait, are you trying to use PSII E2X style staging? That could be harder...

Just looked at the top of the thread and realized that the Mammoth is E2X. Then your best bet is just to get the standard PSII booster, I think...
The Pro series booster will only fit one F15 motor, and it can hardly lift itself, let alone a Mammoth sustainer. I occasionally fly it with my Majestic as the sustainer rocket, but only on a very calm day and off a 6 ft. rod. Rocket Nut wants to light three F15's in a custom booster, lift a Mammoth rocket, which is twice as heavy as my Majestic. Just getting all three motors lit is a feat in itself, but if this flight works, he will definitely have justified his screen name.
If I were going to make a coupler to fit, I would cut a narrow slot lengthwise in the coupler you have, fit one end inside the 2" tube, tape around it, remove it and soak the inside in thin CA glue.
[FONT=&amp] If you get the slot just right, and the sides butt up perfectly, it might be strong enough on it's own once it's glued into your booster. Paint a layer of epoxy on the outside and sand it down for a little more strength.
[/FONT]If you want to make it a lot stronger, wet out a piece of light fiberglass cut to fit inside the coupler, lay it around the inside and inflate a small balloon to hold it in place until the epoxy dries. ANY interstage coupler is a lot of work, and sanding is a necessary evil.

If you want to get the booster for $6 instead of the$10 Estes wants for it, try AC Supply:
https://www.acsupplyco.com/estes/9752_pro_series11_e2x_booster.html
They have better prices on all the Estes kits, including the Pro series....

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#### LithosphereRocketry

##### Pining for the Fjords
I was saying to use the interstage ring from the PSII booster - sorry if I wasn't clear. Of course, I've never actually seen one put together, but it has one as far as I can tell - sorry if it doesn't. Maybe I'm remembering wrong. Your method would certainly work, albeit with a lot more effort.

By the way, I like your signature!

#### OverTheTop

##### Well-Known Member
TRF Supporter
With 3D printing keep the print direction in mind. Quite often the Z direction has weaker bonding than X and Y.

I wouldn't be worrying too much about compression forces on the 3D part. Tension will be your likely weakness.

#### BDB

##### Absent Minded Professor
Our large format printer (3DP workbench) is finally operational. I'm going to try to print this thing tomorrow. It looks like the print time will be about 15 hrs. Any suggestions on settings that I should tweak? If all goes well, I'd love to fly this booster on my daughter's Mammoth next week at MMMSC.

#### RocketNut9

##### Well-Known Member
The only thing I can think of is the print supports on the bottom of the booster. They are the small post in the center an need to be remove flushed with bottom of the bottom plate between the 3 engine tubes. Please attached screen shot.

Also glue the engine retaining to the engine tubes before gluing in the engine mount tubes. Once the glue is dried then glue in the engine mounting tube so the top of the retaining is flush and tight to the bottom of booster.

#### BDB

##### Absent Minded Professor
Our large 3D printer is a piece of junk! I'll try again next week and keep you guys posted.

What happened?