Anyone have tips for dual engine rockets?

[CoolRockets]

I’m trying to make a realistic Gemini titan rocket, this is my first time with multiple engines. Any tips please?

 

[Cape Byron]

What sort of tips? Clustering? Who makes cluster mounts for LPRs?

Qualman make a nice range of centering rings for dual motor clusters.

http://www.qualmanrocketry.com/Rings BT Multiple.html

 

[CoolRockets]

I mean clustering, igniting the engines, and engine mounts.

 

[BABAR]

Use a 12 volt power source.

Leave a loose length, say 2 feets, of igniter lead that can ascend up the rod with the rocket, possible attached to a dowel off to the side. If the engines don’t ignite simultaneously, this gives second motor a few more milliseconds to light before lead pulls off.

Ideally use powerful enough motors that flight is safe and stable even if only one lights.

Swing test fully loaded (motors and chute and wadding), clusters tend to be tail heavy..

Good motor retention, don’t use friction fit. If one motor ejects then the second might decompress through the first now open mount

Have fun

Wishing you two straight trails!

 

[teepot]

Balsa Machining has CR's for clusters. 24mm x 2 and 3, 29mm x2. I use igniters from Quick Burst. And a 12 volt car battery.

 

[BigMacDaddy]

I use a high-amp 3S Lipo and have no issues igniting 2x engine clusters. I just twist the leads for the two engines together and connect the clips to either side.

 

[CoolRockets]

Thank you for the advice, I will show pictures/video of the Gemini flight.

 

[astronwolf]

That rocket in the photo is definitely a cluster.

 

[lakeroadster]

View attachment 546602I’m trying to make a realistic Gemini titan rocket, this is my first time with multiple engines. Any tips please?

Thanks for including that photo. Your rocket reminds me of making rockets back in high school shop class, circa the mid to late 1970's. Good times.

I've always launched using a regular automotive style 12-volt battery, and always used a clip whip for launching more than one motor.

 

[BigMacDaddy]

If we are sharing our two-engine cluster pictures...

 

[CoolRockets]

Cool rockets


The official cool rockets remark from the, CoolRockets

 

[smstachwick]

Most scale models of rockets with multiple engines are best done with a single, higher-thrust motor. After you spend a lot of time getting the paint and decals to look pretty, you generally don’t want complex internals that present additional opportunities to go wrong.

Take, for example, Apogee’s 1/70th scale model of the Saturn IB. It flies on a single F or G motor to anywhere between 400 and 1200 ft.

https://www.apogeerockets.com/Rocket-Kits/Skill-Level-5-Model-Rocket-Kits/Saturn-1B-1-70th-Scale
But if you insist on going for a cluster, voltage is your friend!

 

[CoolRockets]

At some point I want to make a 5 engine paper Saturn v, the Gemini is a sort of test going in chronological order , Gemini to Apollo

 

[BigMacDaddy]

There are a couple of situations where a pair of engines outperforms many other options -- for example, 2x A10 engines or 2x D12 engines have a ton of lifting power for their weight...

 

[CoolRockets]

Hmmmm, interesting

 

[BigMacDaddy]

Pair of A10-3 engines have max lift of 170g and weigh 15.8 grams. Compare that to a C6-3 which has a max lift rating of 113g and weighs 24.9g or a C11-3 which has a max lift rating of 170g and weighs a whopping 32.2g. Only 18mm engine that Estes puts out with a higher max lift rating is the C5-3 which is rated to lift 227g but weighs 23.6g. A pair of D12-0 engines can lift 792g and weigh under 82g. Compare that to an F15-0 which has a max lift rating of 539g and weighs 94.1g. Obviously max lift is not everything but I tend to build odrocs with lots of 3D printed parts and nose weight so they are heavy.

Here is my fully 3D printed Pogo on a pair of mini A-10 engines... took off like a bat out of H@!!...

 

[CoolRockets]

Wow, that’s incredible. I did not know that those engines could lift that much.

 

[Cape Byron]

Wow, that’s incredible. I did not know that those engines could lift that much.

The Estes mini motors are underrated by a lot of modellers. Personally, I love 'em!

 

[Grog6]

BMS makes multi tube mounts 2-4 motors; I used some of the 4-way ones on my Nike Herc model.
That one needed thru tube fin mounting, lol. It was a cool shred on 4 D12-5's.

 

[CoolRockets]

Cool

 

[Cape Byron]

Forthcoming Two-Up kit on two A10-3Ts. Lots of fun to be had with small clusters. Not expensive to fly either.

 

[sriegel]

Check out the Firewire Mini igniters by MJG.

 

[bad_idea]

I cluster black powder motors with MJG black powder starters held in place by Scotch poster putty (the latter being a tip I learned on this forum).

 

[BABAR]

BMS makes multi tube mounts 2-4 motors; I used some of the 4-way ones on my Nike Herc model.
That one needed thru tube fin mounting, lol. It was a cool shred on 4 D12-5's.

So….definition of too much of a good thing?