Rocket Tooling

[50caliber]

I'm going to make rocket tooling in my shop class and was wondering how long i should make the fuse hole. I'm going to make a copy of this

http://www.firefox-fx.com/images/dscn2019.jpg

but my tubes are 2 inches long and have a 6mm diameter with a 2mm wall.

[Mumbles]

2mm diameter would be good if you do indeed mean nozzle diameter and not fuse hole.

[50caliber]

oh sorry i ment how far should the fuse go into the rocket, like how long should the nozzle spindle be?

[Mephistos Minion]

That is what is known as the "core". For slower BP rockets (using 6:1:1 proppellant or similar) 7/10ths of the length of the grain is the norm.

 

Few terms:

 

Nozzel Diametre is the size of the hole that is in the clay plug.

Grain refers to the packed propellant in the tube.

Core length is how far the spindle goes into the grain.

Passfire hole is a small hole in the top clay plug, fire passes through this

[Pretty green flame]

6:1:1 is not a slow comp, it is infact used in end burner type rockets (it is very similar to the formula estes uses for their rockets) so it has to be quite fast.

 

6:3:1 is a slow propellant that works in core burners but won't lift an end burner.

[50caliber]

What is 6:1:1 and 6:3:1? if i was using basic black powder and the 2 inch long, 6mm diameter with a 2mm wall tube what would be a sensible core length? Is the passfire hole the hole the fuse goes in?

[rocket]

6:1:1 and 6:3:1 are mixes of BP in parts. A passfire hole is at the top of a rocket engine and enables you to add a header to a rocket, so when the rocket reaches the end of its burn a small amount of flame passes though the passfire hole igniting the header eg shell, salute.

[50caliber]

oh ok so you dont need the passfire hole

[rocket]

Yeah it’s the next step in rocket building. Once you got the hang of getting the rocket to fly straight then you should try headers. I’ve only tried one header but the damn rocket CATOed but it still went off.

[50caliber]

oh that sucks, but can someone tell me how far i should make the core length?

[rocket]

Well if you are copying the rocket tooling in the pic you posted then the spindle wont be very long. The tooling in the pic is for making end burners. So the spindle/core should be long enough to make the nozzle and go just into the grain say 5mm maybe more.

I’ve read that the nozzle material should be at lest the thickness of the ID of the tube so there’s a starting point.

 

 

 

 

Hey 100th post.

[50caliber]

oh ok, what are end burning rockets for? ive read some posts and i dont think i want them

[rocket]

Well there are two types of BP rockets cored and end burners. Core cored BP rockets burn a lot of BP in a sort amount of time thus releasing more gas which equals more thrust which then enables the rocket to lift large weights.

End burners have no core they burn from one end to another. They can’t lift as much weight as the cored rockets but the still can lift headers. They also have a longer burn time.

If you want to make rockets with headers buy all means make cored but if your just want to make a rocket that fly end burners are the way to go. You don’t need and spindles to make them but a spindle makes it easier and faster

[50caliber]

yea i think i want the end burners beacause the rockets are very small anyway so they dont need to lift headers. do you think if i made a 2cm spindle it would work well. the rocket would take off like a cored rocket then after the fuse has burnt through the 2cm core lenght it would start on the end burners?

[Pretty green flame]

Not really, you will get a very high pressure spike if you leave a core with end burner rockets, this will most likely CATO your rocket. You want aboslutely a minimal lenght of core, just enough for ignition of the rocket.

[50caliber]

oh so say something like 1cm including the clay plug

[Mumbles]

I don't know about even that much. I'd may 1-2mm into the BP would be ideal.

[50caliber]

oh so is it beter if the fuse just touches the black powder. i was positive that rockets with a long core lenght would travel faster not CATO

[Mumbles]

They do go faster, and thus require a slower fuel. The design you gave was for end burner tooling, so that is what we have been advising you on.

[50caliber]

i just put that picture as an example sorry i should have been more specific, i thought it would be a good idea to make the core lenght half the rockets lenght so it would act like a cored rocket at the start and when the fuse has finished it would act like a end burning rocket, is this the case?

[rocket]

To a extent it will, but you have to remember the grain will burn in the general shape of the core even if its only 1cm.

[50caliber]

im not quite sure what you mean sorry

[rocket]

Well the grain will burn from the core out right, it will also burn up so it will look lice a upside V burning up the grain so it wont turn into a end burner. A end burner would burn in a semi circle shape I would think

[50caliber]

oh ok i see, i think i might go with the cored rocket cause i will add headers to the rockets, so if i wanted to make a cored rocket how long should i make the core lenght? thanks

[moonshot]

I have made bottle rocket tooling for 2" long 6mm ID tubes. I use 10mm brass round stock to start and turn it down to 6mm. the base is 6mm diameter. The spindle length is 30mm long and 3mm dia. at the base tapering to 2mm dia. at the tip. I found that you have to do a lot of hand file work to finish these spindles. Also polish the spindle with very fine sand paper until it shines so it will release easily from the core when you twist it out. I have some pics of my tooling posted on the other rocket tooling threads. Good luck.