13 replies to this topic

[dr thrust]

ive been messing about with long core tooling for 1lb whistle and a few have gone off with a chuff chuff chuff noise, and quite under-powered to , whats exactly happening in the motor to cause it to chuff? micro explosions in the core? anybody!

Edited by dr thrust, 24 December 2013 - 05:57 PM.

[wjames]

cracks forming in the grain perhaps....or a blow by ?

[Mortartube]

How well mixed was your composition. It may be uneven burning. Chuffers are an actual desired effect in some instances.

http://uk.youtube.co...h?v=EVWg3et15cE

[rr22]

Could it have been un-evaporated solvent?
I think this is used (by some) for the effect Mortartube posted.
When I saw yours go off, I thought the effect was intentional!

[spanner]

Could it have been un-evaporated solvent?

There may be other things that could cause whistle rockets to "chuff", but solvent left in the comp will definitely do it. Even in relatively small amounts.

[dr thrust]

ahh!! i see said the blind man, thats got to be it then, it must of been the cold muggy weather effecting drying .
so whats happening in the red magnalium rocket in the vid, to cause chuffing?

Edited by chris m, 05 November 2008 - 07:08 PM.

[spanner]

Actually, the amount of chuff in the above video is minimal compared to some I've heard. But, yes, it could be caused by solvent.

According to Dave Stoddard http://www.skylighte...red_rockets.asp
"I have since discovered that the VM&P Naphtha is responsible for the chuffing effect, and allowing the naphtha to evaporate completely from the mix results in no chuff whatsoever."

But LadyKate http://www.creagan.n...iumrockets.html
says, "While Dave's instructions state that the composition must be slightly damp to chuff, I've found that it will chuff even if dried thoroughly..." "It is important to use the same size magnalium each time. Different sizes affect both power and chuffing with smaller size magnalium making a faster rocket and little chuffing. Naphtha does increase the chuffing..."

I have seen for myself that using larger rather than smaller mesh magnalium will "enhance" the chuff.

Edited by spanner, 05 November 2008 - 09:13 PM.

[dr thrust]

interesting stuff, just out of interest what could be added to whistle, to make it chuff( apart from to much solvent which isn't ideal) maybe oil?

[portfire]

I think one way is to have whistle-BP in layers.I.E whistle, BP, whistle, BP etc You get the idea

[Bailey]

Chris m, have you seen the creagan fireworks site. Not directly connected but the magnalium rocket section might interest you.



Sorry just read previous post.

Edited by Bailey, 12 November 2008 - 07:40 PM.

[dr thrust]

I think one way is to have whistle-BP in layers.I.E whistle, BP, whistle, BP etc You get the idea

yeah the stepped bp/whistle/bp whistle motors are cool, and there on my "to do"list ive got a vid here of one of my motors(ignore the first rocket), vid i want to be able to make these repeatable ,so there not dependent on how how much solvent is left in the comp( it may dry out and the effect is lost). if something could be added to the whistle that effected the burn and induced chuffing , but didn't evaporate therefore it could be repeatable?, its a nice effect

Edited by chris m, 13 November 2008 - 05:23 PM.

[Creepin_pyro]

Thought I'd dig out this post from Passfire on the chuffing subject - nice vid:

From: Dan Thames
Date: 8/18/2007
Subject: Video of Carley Blackman Chuffer
Jed Carter was mentoring a young woman, Carley Blackman. Their powder was too fast and while experimenting with mineral oil to slow the fuel, chuffing developed with 4% added oil. 6% oil gave this result (video). Carley placed 4th and 6th with chuffing and non-chuffing pairs of 6 pound rockets in the Best Large Rocket Motor class. It is great to see women competing.

http://www.pyrobin.c...6lb-chuffer.wmv

[wjames]

that i a great video......i might stick that on my youtube collection.......

[dr thrust]

ive made bp rockets with, oil and Vaseline, to granulate the propellant, and mineral oil gives a cleaner burn, but vaseline seems to bind the propellant grain better, so ill try a batch of whistle comp with an excess of Vaseline, and a batch with a mixture of oil and Vaseline, should be quite interesting
the rockets themselves , cant carry much of a payload, i think they would be more suited as a flight of "honorary" rockets