248 replies to this topic

[dr thrust]

The secret I find with larger BP motors is to use more granular charcoal for increasing fractions of to total charcoal content of the propellant as the size increases.

thank you, i had an inkling this was the case you just confirmed it, hmm,, need more screens

[shadowpyro]

Just thought, do any of you guys use delay comps at the top of the engine before the clayplug/passfire? Or just straight rocket comp, I seem to be having alot of issues with the payload firing prematureley (sp?)

I seem to remember most rocket articals on the net saying to just use meal...

Edited by shadowpyro, 11 August 2010 - 12:52 AM.

[Arthur Brown]

Lancaster and others give tables of content for rocket fuels and mention the need to change the comp with size.

[BrightStar]

Just thought, do any of you guys use delay comps at the top of the engine before the clayplug/passfire?

Yes, glitter delays seem to be popular (particularly Win 39), though charcoal star comps such as tiger tail or even coloured star comps can be used.

Karlfoxman describes an excellent glitter delay I've used myself here:

Topic 1686 - Rocket Lift Capacity

As a note to everyone, it's worth checking the 'Advanced Search' feature (the cog icon to the right of the search box). There's a huge amount of info in the forum that doesn't always show up by default.

[dr thrust]

no real issues using straight rocket comp as a delay, even up to 3lb, how much delay above your spindle?, end plug blowing out?
ive had success forming a 5-6mm passfire hole( in 1 lb motors) and pressing in comp making a small time delay fuse.
on nozzle-less bp motors, where no clay plug is needed, whistle makes a nice delay

Edited by chris m, 11 August 2010 - 10:04 PM.

[shadowpyro]

no real issues using straight rocket comp as a delay, even up to 3lb, how much delay above your spindle?, end plug blowing out?
ive had success forming a 5-6mm passfire hole( in 1 lb motors) and pressing in comp making a small time delay fuse.
on nozzle-less bp motors, where no clay plug is needed, whistle makes a nice delay

I havent actually had anything blow out yet, but just that the payload seems to activate too early, i also used a passfire hole (2mm) off centre in the clay plug. Also i havent been ramming the comp into the passfire, just using some loose meal. Now that i think about it, i actually though it would take too long! When you say you press the meal into the passfire hole, do you just mean sorta shoving the meal into it as tight as possible with a rod? or using specialised tools for it?

Haha i thought about trying nozzeleless sometime....just need to get hold of some willow wood from the forest....

Cheers

[dr thrust]

yep lightly pressed in with a rod, sometimes i add a couple percent of dark pyro ali for a nice hot fuse, if anything my headers take way to long to ignite .
maybe some ground testing/ filming( its really handy to look at the motor frame by frame) to assess what going on
maybe your pass-fire hole is going to deep into your delay, try another 6mm + on your delay, and by all means try out the tiger tail,and glitter comps

Edited by chris m, 12 August 2010 - 04:05 PM.

[starseeker]

Just thought, do any of you guys use delay comps at the top of the engine before the clayplug/passfire? Or just straight rocket comp, I seem to be having alot of issues with the payload firing prematureley (sp?)

I seem to remember most rocket articals on the net saying to just use meal...

I just press in the same fuel that i am using above the spindle,i then tend to build up my headers as a separate unit with there own fused delay.I tend to think that this makes things a bit more consistant.

[shadowpyro]

Sounds good guys!

Have taken a note of that and i'll have to do some tests when i get back from travels.

Cheers