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Whistle Spindle Comparisons


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I had the idea to try skinny spindles for rockets, here is the data that I gathered.

Spindle Specs Here

heres a few more details.

1. All motors used the same propellant, hot hot hot Sodium Salicylate whistle.
2. All motors were pressed to the same loading pressure, about 8000 pounds on the composition.
3. All motors were lit the same, with a J-hooked piece of visco inserted into the core, just a bit.
4. All motors were pressed and lit in the same environmental conditions.

drum roll please

Slim Pickins

Apple Bottom Jeans

Fatty McGoo

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  • 2 weeks later...

Thank you for sharing your research.

I also did some comparisons, but without a force gauge this is really not very telling. Small 10mm motors with 36mm spindles and benzoate fuel where used. Because I once wanted to make BP motors in that small size, I also got a Spindle for that. My tubes are very short, so I had to choose the same spindle length but of course it had to be slim to get the right ~3.2mm diameter.

When I compared 3.2mm BP and 5mm whistle spindle in flight, with generous sandballast, there was no noticable difference.
I course this is an absolutely unscientific method though i think a big difference would have been visible.

But judging from it anyway, I'd say the exact shape of a whistle rockets spindle are not very important(within certain range). Length makes a difference of course.
And that's also how I interpret your results. Any objections?

One interesting fact is missing in this comparison:
How much fuel is burnt in each test?
If every motor gets exactly the same length of fuel above the spindle, one could also judge which design is most efficient.

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Its hard to know what is going on without data, if I had flown three identical headers with these, I would have concluded incorrectly which one was the best (based on how they looked/sounded when burned). Data is king, but I appreciate your experience.



I also have a hunch that the type of whistle is important, I will be running these tests again and again with different propellant arrangements.



I will be sure to measure fuel burnt on the next iterations- Somehow I looked over that detail.

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