Cluster Thrust VS Single Large Motor

lakeroadster

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Why not just simulate it with OpenRocket or Rocksim? Assuming the Rocksim file is accurate from Apogee's website...

22.1m/s off rod w 4x C6-7 and 14.5m/s w/ E12-6
422m Apogee w/ the cluster and 326 w/ the 24mm motor

View attachment 538406


Note to the OpenRocket folks -- Apogee had 4 individual motors which I just switched to a 4 engine cluster. For some reason it forecasts a lower speed leaving the launch rod and lower apogee. Should be the same as above, no?

View attachment 538407

Regardless, even 14.5 m/s is plenty of speed off the launch rod.

That 5 cm (1.96 inch) body tube still has me scratching my head. What the heck is it? And what would the inside diameter of the coupling tube be for that size BT?
 
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smstachwick

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My stock HiFlier XL flies really well on a D12-7, I can't imagine what altitude you could get by staging E motors. But then my stock XL might get similar altitude on an E30, but not as much fun.

OR predicts over 1600ft. Not impossible but it was a bit of a hike to recover.

A polished finish and airfoiled fins could put this well over 2000 ft.

I've gotten more paranoid these days with long burn motors. I've seen a lot of rockets take a turn right off the rod and go horizontal for long distances under thrust. I'll probably be overly cautious with mine.
Good call.

The LDRS range personnel were nervous enough with mine to declare a heads-up flight, but that was more over concerns of my staging coupler and my body tube repair. It wasn’t perfectly straight, hence my subsequent inquiry into getting straighter tube cuts here on the forum. The RSO and Pad Manager were kind enough to give me some good tips and I got a lot more from the folks here.

The rocket did end up boosting on a slightly southward trajectory over the flight line and recovered about a quarter mile south of the access road. Definitely redoing the tube repair before going for broke again.
 

heada

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That 5 cm (1.96 inch) body tube still has me scratching my head. What the heck is it? And what would the inside diameter of the coupling tube be for that size BT?
Both Aerotech and LOC sell 1.9" body tubes and couplers for them. Since this is a Quest kit and Aerotech owns Quest, that makes sense. Ask Quest (Aerotech) what the ID of the coupler is, I'm sure they know.
 

lakeroadster

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Both Aerotech and LOC sell 1.9" body tubes and couplers for them. Since this is a Quest kit and Aerotech owns Quest, that makes sense. Ask Quest (Aerotech) what the ID of the coupler is, I'm sure they know.
Thanks. :computer:


Specifications:
  • Outer diameter 1.805 inches
  • Inner diameter 1.635 inches
  • Wall thickness 0.08 inches
So.. to summarize... You can't fit (4) 18mm motor tubes into this coupler. Using a coupler as a quad motor mount will not work in this case.
 
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Ladykate

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A cluster of three C motors inside a printed can. Three new C motors aren't cheaper than a single D or single E and the E is better. But we had a lot of cheap motors collected from yard sales so we decided to burn some up. Ignition was with MJG igniters with 12 volt LIPO launch controller. The rocket was noisy and flew high. Unfortunately, on this flight, the chute failed so our test bed was kaput. Motors were bound together and then bound inside the can. Pug ugly engineering but it worked.
 

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techrat

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So.. to summarize... You can't fit (4) 18mm motor tubes into this coupler. Using a coupler as a quad motor mount will not work in this case.

Yes, but I could fit a cluster of three 18mm. With room to spare. And that would still give me a swappable motor mount. I just have to sand down my centering rings on the 24mm motor mount to fit the coupler as well. Unfortunately, "Tri-Runner" is the worst of the names I had planned. Need a better word that means three. Maybe I'll call it an "III-Runner" and use Roman Numerals (although I think Apple has trademarked everything that starts with an "I").
 

Ladykate

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How did the chute fail? Didn't deploy or ? Curious what delays the (3) motors were.


The chute failed on the third flight. The can was OK on the first two but we made a slight mistake and didn't secure them good enough on the last flight. They all left the can on ejection with no poop left over for ejection pressure. All motors were C6-5 because that was what we had. ;-} The rocket is being reprinted with less weight (cardboard tube) and positive motor clips and we'll burn up some more motors next meet.
 

lakeroadster

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Yes, but I could fit a cluster of three 18mm. With room to spare. And that would still give me a swappable motor mount. I just have to sand down my centering rings on the 24mm motor mount to fit the coupler as well. Unfortunately, "Tri-Runner" is the worst of the names I had planned. Need a better word that means three. Maybe I'll call it an "III-Runner" and use Roman Numerals (although I think Apple has trademarked everything that starts with an "I").
Triceratop...
 

Ladykate

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We named ours Cluster Faust. Drei Faust?

note: I had no input on the name or design. I was the guy who contributed the ematch and launcher for it.
 

Gemini Junkie

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While your math is not accurate I am completely with you on clusters be problematic and not worth the hassle. I have removed cluster mounts from a number of rockets including some early Estes pro-series in favor on a single mount. My own Quad-Runner was built with a single 24mm mount well before they started offering this as an option.

Absolutely build it as a single motor rocket and go enjoy it.
Clustering is more challenging but not that difficult. The show of a big cluster with all the smoke and fire is always a crowd pleaser!
1D522C50-7A9D-4284-9D95-9C102438EF4F.jpeg
 

BABAR

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Triceratop...

good name! Used it for one of the rockets I sent to NASA made of recycled books for their Earth Day celebration. Nothing wrong with recycling rocket names, either.

B058C436-70EE-45E2-B598-5814DB534CB7.jpeg
 
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