delay comp

[MadMat]

Does anyone know of a cast-able delay comp for Rcandy? I experimented with adding charcoal to Rcandy to create a slow burning comp, but up to the percentage where it became crumbly it didn't slow the burning much at all, in fact at lower percentages it actually seemed to speed up the burn.

Edited September 10, 2015 by MadMat

[AAF]

add baking soda to the mix

Edited September 11, 2015 by AAF

[MadMat]

Any idea on the percentage of baking soda? Actually, the fact that a small percentage of charcoal sped up the burn of the Rcandy makes me wonder if the standard 65/35 mix isn't a little oxidizer heavy. I suppose I could calculate the stoichiometry of Rcandy to see what percentages produce a completely balanced mix.... but I'm lazy

Edited September 11, 2015 by MadMat

[Andres1511]

I calculated it once when I was bored in Chemistry class, 65/35 is pretty accurate. I don't remember the exact ratio, and I don't remeber where I saved the calculation... I'm sorry.

Start with 5% sodiium bicarbonate, keep experimenting until you found what you needed.

[Mumbles]

The charcoal might have just opacified the composition, resulting in an increased speed.

[PIL]

Opacifier,usually lampblack, is used to protect the grain inside from heat radiation so that the grain will burn layer by layer.

When charcoal is added, its porous nature result in a propellant grain full of air pockets.Potassium nitrate recrystalizes into charcoal's pores and makes sulfurless BP.I guess these are the main factor of a quicker burn.

Edited September 11, 2015 by PIL

[Mumbles]

How does potassium nitrate crystallize into anything if it's never dissolved or molten?

[MadMat]

PIL might have a point as I add a small amount of water as I'm heating my Rcandy mix. I then boil the water off. It saves having to grind my KNO3 and sugar.

[AAF]

madmat IIRR the dry ram guys were adding 15% or so to there mix, ie 100g kno3/su mix to 15g baking soda. might be a good place to start

[MadMat]

Thanks for the info!

[deer]

What I'd do:

* Dial down the comp to say 50:50 (don't go too low or burning gets unreliable),

* Reduce delay diameter, more rcandy = more heat, faster burn (stay above 10mm, otherwise it gets erratic),

* Use Paraffin bound powder mix (needs solid plug above it with quite small opening due to weaker structure).

 

E.g. mix with:

10 parts powdered KNO3,

6 parts powdered Sugar,

2 parts Paraffin and

1 part Baking soda

This produced one of the slowest mixes I was able to do with rcandy that doesn't go out. Plus, it and can be cast well under 100C.

 

P.S. When inhibiting mixes you might want to embed some pure 65/35 or BP at very end of delay, because it might not produce enough flame, pressure and hot gas to ignite e.g. plain visco or whatever ejection / burst thing you have that's not in direct contact with delay mass.

Edited October 10, 2015 by deer

[mabuse00]

I believe you do not need to slow down Candy fuel to create a delay. Rather the opposite.

 

 

The burn rate of typical sugar-type propellants is so slow - especially when the cored part has burned out and the pressure drops - that it's actually hard to produce a delay that burns through in time without beeing to slim.

 

You'll need certain thickness to cope with the pressure.

Also the timing will be very unprecise compared to fast burning delays like normal BP or whistlemix.

 

You can try out Pirotex2005's contruction, he seems to use a pressed BP insert above of the KNSB fuel.

 

 

What kind of rocket are you planning to create? What shall be lifted with it?