Visco fuse machine questions

[OblivionFall]

hi there, I'm building a Visco Fuse machine and I have a couple of questions.

 

1. What compositions are best for slow burning/Visco fuse? I was thinking of using Black Powder. Do I have to granulate the BP?

 

2. How do you determine/choose the size of the fuse (diameter e.g. 2.2mm, 3mm,) coming out of the machine?

 

3. How do you determine/choose the rate at which the fuse burns?

 

Thanks

[Mumbles]

1. Yes, for flow purposes, the BP is normally granulated. It's pretty fine though, probably -30 or -50 mesh. The composition is typically pretty close to standard BP. Some have extra sulfur. Some have extra nitrate to help consume the string and stuff. Trust me, the formula is going to be the least of your concerns.

 

2. Personal preference or supplies available most likely.

 

3. The formula, and again, personal preference.

 

If you ever find commercial fuse powder information, it will usually have a number associated with it. It will be fuse powder 117 or something like that. The number is seconds per meter.

[Ubehage]

For question #3, I would say that particle-size of your BP will also be a factor.

A very small factor, indeed, but still one that should not be completely overlooked.

 

The finer the particles, the slower it will burn. If even for milliseconds, I feel it's worth the time and work to make sure the mix is absolutely uniform, and made for the fuse you wish to have.

[FlaMtnBkr]

BP is the most common. You can change the ratios to speed it or slow it just like you would with rockets.

 

You want a very fine granulate because it flows out of the funnel and into the fuse easier. If you use fine powder it doesn't flow good and will make a hole in the center and then stop flowing. Even if using a knocker or tracer threads through the funnel it won't be reliable and consistent.

 

The size of the fuse will be determined by the size of the hole going through the die where the threads get wrapped. You will have to experiment with the rate of thread production versus how fast the threads get wrapped on. Not enough wraps and powder will fall out before the second wrap. Too many and there will be excess thread that will leave a ash behind and have to be changed often. If you come up with a good ratio of pull speed to wrap RPM let us know.

 

You might want to try soaking the thread into a saturated KNO3 solution and then let it dry. Also, you probably don't want to pull the fuse and control the pull rate by loading onto a drum. As you collect fuse the diameter will increase along with the pull rate. Just some thoughts.