First Device Finished – Gerb

[Eagle66]

I’ve finished my first device, a Gerb. I made the Gerb described in Perigrin’s book Introductory Practical Pyrotechnics. The compound was 72/20/8 (450g/90g/60g) Powder using Tree of Heaven CC, ball milled 2-1/2 hrs, then moistened & granulated through a 16 mesh screen, then dried for a couple of days. My end plug/nozzle clay was plain kitty litter (that's Bentonite, right?) milled to -70 dust. I used a ¾” bore rocket tube 5.25” long. I assembled it according to his directions. My ramming tools were made from hardwood dowel. The end /nozzle plugs were rammed by 8 blows from a 3-1/2# lead mallet;

 

(http://www.amateurpyro.com/forums/topic/10037-lead-mallet/ )

 

Except, the mallet had lead heads on both ends. The powder was rammed in 6 measures each with 5 blows from the same mallet. The nozzle was drilled out to 3/8”, fused with Visco and a pinch of 4fg in the cavity with the fuse end. Here’s a picture of the finished piece.

 

 

And the shoot.

 

 

Well. Here I thought I was making a Gerb, not a salute.

 

I was able to find a few pieces of the tube all from the top half.

 

Help please.

[rogeryermaw]

I'm sure others will disagree, but when I make a fountain, I have trouble ramming granulated powder. Same for rockets. I just use mill dust and they work fine. I have no idea how fast ToH black powder is but I doubt that is the problem. If your ramming doesn't fully consolidate the granules into a solid grain, it'll pop every time.

[Bobosan]

Wood rammer partly at fault, especially using granulated fuel. Water or alcohol granulation?

 

Cover the face of the wood rammer with a couple layers of aluminum tape and/or try the gerb using your 72/20/8 mill dust

[Maserface]

Commercial powder doesnt consolidate well for me (the few times I tried) but it certianly did. I absolutely prefer water or alcohol granulated fuel for rockets/gerbs- fluffy fuels are too messy in my opinion.

[dagabu]

I’ve finished my first device, a Gerb. I made the Gerb described in Perigrin’s book Introductory Practical Pyrotechnics. The compound was 72/20/8 (450g/90g/60g) Powder using Tree of Heaven CC, ball milled 2-1/2 hrs, then moistened & granulated through a 16 mesh screen, then dried for a couple of days. My end plug/nozzle clay was plain kitty litter (that's Bentonite, right?) milled to -70 dust. I used a ¾” bore rocket tube 5.25” long. I assembled it according to his directions. My ramming tools were made from hardwood dowel. The end /nozzle plugs were rammed by 8 blows from a 3-1/2# lead mallet;

 

(http://www.amateurpyro.com/forums/topic/10037-lead-mallet/ )

 

Except, the mallet had lead heads on both ends. The powder was rammed in 6 measures each with 5 blows from the same mallet. The nozzle was drilled out to 3/8”, fused with Visco and a pinch of 4fg in the cavity with the fuse end. Here’s a picture of the finished piece.

 

Gerb First Piece.jpg

 

And the shoot.

 

First Device Gerb.wmv

 

Well. Here I thought I was making a Gerb, not a salute.

 

I was able to find a few pieces of the tube all from the top half.

 

Help please.

 

Shoot me a PM, I have something for you to make this easier/better.

[rogeryermaw]

Commercial powder doesnt consolidate well for me (the few times I tried) but it certianly did. I absolutely prefer water or alcohol granulated fuel for rockets/gerbs- fluffy fuels are too messy in my opinion.

messy is right! an o-ring on the rammer to seal dust from flying out of the tube helps but it's still a "black booger" job.

[Bobosan]

Outside, with the wind at your side....or, there is the respirator.

[kpknd]

DO NOT ram granulated powder, it will always have voids in it some where that will lead to firecrackers. Just use the milled powder. There is no need to complicate things, Try it!

Edited September 30, 2014 by kpknd

[Maserface]

DO NOT ram granulated powder, it will always have voids in it some where that will lead to firecrackers. Just use the milled powder. There is no need to complicate things, Try it!

 

 

I have no idea where you got the idea that granulated powder is un rammable, but its about the most far off thing I have heard all day! Ramming granulated powder works great!! It reduces the dust to almost zero and it makes measuring easier- I have never had a cato due to my fuel being granulated.

[dagabu]

DO NOT ram granulated powder, it will always have voids in it some where that will lead to firecrackers. Just use the milled powder. There is no need to complicate things, Try it!

 

Bigger Hammer? I only ram rockets with granular powder, powders are way too messy!

[MrB]

I don't ram much rockets, when i do, i tend to use mill powder, or even justs green mix. Granulated stuff, with little, or no binder should have no problems what so ever when ramming, while harder stuff, using binders, and / or solvents could pose an issue. I used corned stuff when pressing, but it's not quite the same thing. The forces involved in pressing is a lot higher then when hand ramming.

 

B!

Edited September 30, 2014 by MrB

[Eagle66]

In answer to your questions;

 

 

I'm sure others will disagree, but when I make a fountain, I have trouble ramming granulated powder. Same for rockets. I just use mill dust and they work fine. I have no idea how fast ToH black powder is but I doubt that is the problem. If your ramming doesn't fully consolidate the granules into a solid grain, it'll pop every time.

ToH powder is just a bit slower than willow, all other things being equal. A thought just occurred to me about consolidation. Maybe I'm trying to ram too much at a time? I put in 2 teaspoons then rammed. That resulted in almost 1" compacted per charge. Maybe more like 1/2 a teaspoon?

 

 

Wood rammer partly at fault, especially using granulated fuel. Water or alcohol granulation?

 

Cover the face of the wood rammer with a couple layers of aluminum tape and/or try the gerb using your 72/20/8 mill dust

I use a 50/50 water/alcohol mix. I'm not understanding your point about the wooden rammer. Please elaborate.

 

 

I don't ram much rockets, when i do, i tend to use mill powder, or even justs green mix. Granulated stuff, with little, or no binder should have no problems what so ever when ramming, while harder stuff, using binders, and / or solvents could pose an issue.

 

B!

 

Using green mix sounds interesting, and a lot simpler. Especially if I want to try a new mix, and don't want to run a full 600g batch in my mill.

 

I didn't use any binders

Edited October 1, 2014 by Eagle66

[rogeryermaw]

i watched the ned gorski rocket tutorial (available on skylighter) and i believe he only rams a rounded 1/4 teaspoon at a time. personally, my increments usually compact to between 1/4 and 1/2 inch.

 

the wood rammer bob is questioning, i suspect, is due to wood being light, porous and soft. it won't provide the solid compaction of a metal rammer but i know wood dowels work fine will mill powder as that is the was i made my first fountains.

 

using green mix vs milled powder gives me pause. i know both will work but a comp screened will perform differently than the same comp milled

[MrB]

using green mix vs milled powder gives me pause. i know both will work but a comp screened will perform differently than the same comp milled

It does indeed. For perfect performance, you should use milled stuff. But if consistent behavior, and ease of production is factors, then you should be more then good to go with just well mixed green mix.This is, of course, assuming that your chem's are sufficiently fine to start with.

B!

[dagabu]

It has been postulated many times by those with much greater intellects than I that increments should never exceed 1/2" ID. I like 1/4 to 1/3 ID but have done full 1 ID increments in the field to test rockets and they do just fine if I haul on the hammer!

[Bobosan]

The face end of the wood dowel where it contacts the BP in the tube usually has a cross grain consisting of hard and soft wood areas. Impacts on granulated BP could cause indentations in the softer wood area and reduce the effectiveness of hammer blows. A couple layers of aluminum tape covering the face end of rammer would alleviate some of that wood deformation. Properly prepared wood dowels are very acceptable rammer tools for small devices, they just don't last as long as aluminum. Oak is the preferred dowel material.

[Blackthumb]

...been using the same oak rammers for almost five years...

[Sparx88]

The face end of the wood dowel where it contacts the BP in the tube usually has a cross grain consisting of hard and soft wood areas. Impacts on granulated BP could cause indentations in the softer wood area and reduce the effectiveness of hammer blows. A couple layers of aluminum tape covering the face end of rammer would alleviate some of that wood deformation. Properly prepared wood dowels are very acceptable rammer tools for small devices, they just don't last as long as aluminum. Oak is the preferred dowel material.

 

All true. Having this happen to me with the face end, I came up with a solution that I always use now.

 

Seriously consider this. Buy a quart of Olympic Interior Clear Gloss Polyurethane (oil based). Drill a small hole in the hammer end and tie a peice of string through it. Like making candles. Sand the face end of the dowel until smooth. Tape off that end so only the end is showing, then dip into the polyurethane, dry hanging verticle, and do this 3 times. Letting it dry fully between coats. Once done just clean the edge with some fine grit if it's rough and thats it. It will last you a looong time.