71 replies to this topic

[Mortartube]

The clay seems to vary depending on the location of the factory. Most of the Chinese goods about 15 years ago had bright red clay, the colour of terracotta flower pots when new and no other bits mixed in.

[AdmiralDonSnider]

Alright guys, here are two rammed chinese plug taken from commercial cakes, this stuff literally looks like it was dug up from the backyard and rammed into the tubes as is





It reminds me of crushed clay flowerpots (the orange stuff) bit I have no clue as to what the white stuff may be. It's not bentonite i'll tell you that. And what's amazing is that this stuff adheres to the paper wall REALLY well (glue? Sodium silicate solution?) you can't remove tha paper from the clay plug.

And this type of "clay" is VERY VERY hard, I tried to scratch it with my finger nail, no go. And even with a hardened steel tip I had to put it under considerable pressure to scratch it. Amazing stuff.

DonSnider, have you tried asking your chinese contact for any info on the clay they use? He seems cooperative.

I have to apologize for the delay, I didn´t realize the new posts for quite a while.

The material shown here is the same I frequently found in cake items. It seems to consist mainly of coarse particles made from baked clay or similar. The word "grog" may be used to describe what that is. Maybe the pure bentonite approach isn´t the deal. However, I have no idea if a ceramics supply will source this kind of stuff, or if it´s just waste/fragments. What if one smashed a brick and used the resulting granules?

[spanner]

What if one smashed a brick and used the resulting granules?

That'd get you the grog part...

[Bonny]

I'm not sure about all pottery shops, but my local one sells grog in fine and coarse...maybe medium too.

[AdmiralDonSnider]

Probably a bit off topic now:

When making a bombette, does the style/thickness/quality (I mean: clay plugs, epoxy, hot melt, just a thick disk glued in) of the end plugs make any significant difference in the appearence when we use flash brakes? I get the impression that flash will expand in a speed that renders any discussion about wall thickness and end plugs unnecessary...

I´m asking this because I reviewed a video by Tony Petro entitled "Multi-break small shells for rockets". Although this guy doesn´t make bombettes in the video, he shows how to make 1" I.D. cylinder "shell" cases for his rockets - essentially the same as a bombette, but propelled by a rocket engine.

The construction method he uses deviates from the ones discussed here so far:
Petro uses:

a.) 2 turns of #70 kraft to make the case (much thinner wall than we focussed on)
b.) epoxy to plug the bottom of the case (no clay)
c.) one or two turns of newspaper rolled on a 3/8 inch rod, glued in centered to contain the volume loaded flash break, formula KNO3 50 parts, S 30 parts, dark Al 20 parts (should produce more gases than the ordinary 70/30)
d.) a 1/16" chipboard disk, held in place with elmers to close up the top (nothing more, no clay either)
(e.) no spiking)

The things brake nicely although being constructed in such a simple manner...

[AdmiralDonSnider]

When making a bombette, does the style/thickness/quality (I mean: clay plugs, epoxy, hot melt, just a thick disk glued in) of the end plugs make any significant difference in the appearence when we use flash brakes? I get the impression that flash will expand in a speed that renders any discussion about wall thickness and end plugs unnecessary...

Does anybody know if that is a right assumption?

[cooperman435]

I woild agree that the casing for a flash break simply needs to survive the lift and does little to assist in the break its self

[Arte valdo]

Hi, I wanna show you my technique how I do bombettes, hope you like it.

Edited by Arte valdo, 13 September 2011 - 05:54 PM.

[ukpyro.com]

I have to apologize for the delay, I didn´t realize the new posts for quite a while.
The material shown here is the same I frequently found in cake items. It seems to consist mainly of coarse particles made from baked clay or similar. The word "grog" may be used to describe what that is. Maybe the pure bentonite approach isn´t the deal. However, I have no idea if a ceramics supply will source this kind of stuff, or if it´s just waste/fragments. What if one smashed a brick and used the resulting granules?

Excuse me dragging up an old thread.

Yes it is grog, it's cheap and you can get it in different meshes and made from different clays. The coarse stuff is crushed and graded firebrick. You can get white very hard stuff called Molochite, very expensive, but no better for your application. http://potclays.co.u...roducts_109.asp

[Arthur Brown]

My bag of "sharp sand" from B&Q recently was really crushed and graded demolition muck-away. It contained obvious signs of blue brick and crushed concrete. I think my bag was £1 because it was damaged but list is about £2.99 for 20 kilos or so, and most of us have a builders' merchant nearby

[AdmiralDonSnider]

In the meantime I found a very cheap "grog" supply - my local tennis court.