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1/4 inch bottle rocket CATO


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#1 Tim1877

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Posted 28 September 2017 - 05:55 PM

So I broke down and bought a 1/4 in rocket spindle and about half of my rockets Cato I m using plain black powder for fuel granulated with alcohol and no binder through an 8 mesh screen hand ramming with a raw hide mallet. Some of the rockets go 75 feet high others explode 2 feet after launch any ideas?
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#2 pyrokid

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Posted 28 September 2017 - 11:44 PM

8 mesh seems like a large particle size for such a small rocket. It seems like this could pose problems for the creation of a solid fuel grain without faults. I would try making a few with mill dust to see if particle size has an appreciable effect on reliability.

 

Are the rockets nozzleless? How much control is there over increment size? It could be that large increments cause insufficient fuel compaction.



#3 NeighborJ

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Posted 29 September 2017 - 02:29 AM

What fuel ratio are you using? Tooling model? Charcoal type?

I've made some powder which just can't be used for rockets, even nozzleless. The tiny motors can be quite forgiving but it is possible to make too hot of a mix.

#4 mikeee

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Posted 29 September 2017 - 11:18 AM

You can always add more charcoal to buffer your fuel mix.

Sometimes you need to make several motors and test the fuel mix and adjust until you get consistent results.

This usually requires precise measurements with a scale and recording the results with each motor made and test.



#5 Mumbles

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Posted 29 September 2017 - 11:39 AM

The other question is what type of tubes are you using?  Bottle rockets are VERY forgiving as far as fuel goes.  I doubt that it is inherently too hot.  You can press whistle all the way up the core burner tooling.  

 

If you using some of those red spiral wound tubes, you may want to look into getting or making a support sleeve.  To me, it sounds like the wall is splitting or something causing the case to weaken in some instances.  I'll try to find the source, but there are some real high quality bottle rocket tubes around for the Super Bottle Rocket tooling sets.


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#6 davidh

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Posted 29 September 2017 - 01:38 PM

Are you using a very consistent amount of clay in your nozzles? Think it through.



#7 Tim1877

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Posted 29 September 2017 - 03:28 PM

I'm using 75-10-15 BP that has been ball milled for several hours the charcoal is pauliwania it makes great lift I use the little stainless spoon set so my fuel increments are the same. Mumbles I think you could be on to something because I notice the walls of the tubes get weak once in awhile I thought I was just ramming it to hard not really sure how hard to hit the rammer would think a few decent wacks would put enough pressure on a 1/4 inch rammer. As far as nozzles I'm using benonite that has been ground to a fine powder in a blender not sure how much to use to make a good nozzle they look smooth and solid to me
Tim

#8 OldMarine

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Posted 29 September 2017 - 05:22 PM

I hand ram ½" rockets and when ramming I hold my mallet halfway up the handle and use my wrist to swing it. This gives a more gentle blow to keep me from screwing up my tube. I tried a lighter mallet but that led to catos galore.
I still use 8 whacks but they're not as heavy.
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#9 Tim1877

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Posted 29 September 2017 - 06:57 PM

So I eliminated the nozzle completely everything else the same except a little liter mallet blows and I had no Cato out of 10 rockets,only thing I noticed is the rockets aren't as powerful without the nozzle but they are acceptable.
Tim

#10 chuckufarley

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Posted 29 September 2017 - 08:24 PM

Nice job! After you get the feel for ramming them nozzleless you can always start experimenting with using a nozzle again, if you want more thrust.

#11 Tim1877

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Posted 29 September 2017 - 08:54 PM

That's exactly what I plan on doing just have to figure out how the nozzle affects the rockets
Tim

#12 davidh

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Posted 30 September 2017 - 05:11 PM

If you use more clay in your nozzle, the core is effectively shorted, you get less pressure, and you are less likely to have a cato. I suspect the ones that blew up had a shorter "nozzle core".



#13 Tim1877

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Posted 01 October 2017 - 05:12 PM

If you use more clay in your nozzle, the core is effectively shorted, you get less pressure, and you are less likely to have a cato. I suspect the ones that blew up had a shorter "nozzle core".

You hit the nail on the head after some trial and error today I dialed in the exact amount of clay to use. I know 1/4 rockets aren't a big deal to most people,but I would like to thank the people who helped me learn hopefully be moving up to bigger rockets soon.
Tim

#14 chuckufarley

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Posted 01 October 2017 - 05:46 PM

Glad you got it working! Those little rockets are fun. When Im bored and dont want to get involved in a project, I just bang out a few of those Sbr's just for something to light. Always puts a smile on my face!

#15 Oinikis

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Posted 02 October 2017 - 04:59 AM

What type of CATO'es arr you experiencing? Do the plugs pop out or does the tube rupture?
I feel the need, the need for speed.

#16 Tim1877

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Posted 02 October 2017 - 02:49 PM

The tubes burst right in the middle
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#17 dagabu

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Posted 05 October 2017 - 07:17 PM

If you use more clay in your nozzle, the core is effectively shorted, you get less pressure, and you are less likely to have a cato. I suspect the ones that blew up had a shorter "nozzle core".

 

Uh, wait, what?

 

Yes, with a bottle rocket set you can reduce the pressure by adding more dead and useless weight. BUT that is not the direction you should be going. Try LESS clay and make a smaller nozzle instead. In a 1/4" bottle rocket, a 1/4" nozzle is all you need, just long enough to get past the taper on the spindle. 

 

Here, take a look. This is Caleb's set. See the radius, the taper for the pseudo-bell at the end of the spindle? Right where it starts to straighten is where your nozzle should stop. This allows the nozzle to erode and enlarge if the pressures become too great for the nozzle clay. 

 

s915033251272547339_p6_i3_w640.jpeg

 

Lets move on to the tube itself. A 1/4" ID tube needs very little pressure to consolidate the BP. Think about tapping, not hammering the tooling with a plastic hammer. A 1/4" rocket only has 0.049 square inch of area and reduce that by half if ramming around the spindle! .0245" of area leaves you with about 300 LPI on the area you need to ram.

 

Tap, tap, tap!

 

Try that once and see what you get.


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#18 dagabu

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Posted 05 October 2017 - 07:18 PM

Oh, increments! No more than 1 ID per increment. You will get consolidation and a solid, no soft space grain that way every time! 


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#19 OldMarine

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Posted 05 October 2017 - 07:40 PM

I haven't tried the SBRs yet and would like to do so. Might be fun to try BP boosted with whistle and put them on the ACME. 

Edit: Just ordered the ¼" set from Caleb and 3" tubes from Cannonfuse.com.


Edited by OldMarine, 05 October 2017 - 08:06 PM.

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#20 dagabu

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Posted 11 October 2017 - 07:44 PM

I haven't tried the SBRs yet and would like to do so. Might be fun to try BP boosted with whistle and put them on the ACME. 

Edit: Just ordered the ¼" set from Caleb and 3" tubes from Cannonfuse.com.

 

I would like to see that! 


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