Black Powder Eprouvette

[Peret]

I'm of a mind to make a proper black powder tester, because I don't have any faith in open-channel burn rate tests. BP burns differently under confinement and if I'm going to entrust my carefully made shell to home made lift, I want to know how it will perform in the mortar. I'm quite surprised that no such thing is available from any of the usual tooling dealers. There is this, from Dixie Gun Works (no, it's not an antique), but $175 will buy a lot of Goex that doesn't need testing.

 

http://www.dixiegunworks.com/images/PH0541.jpg

 

The old books, eg Cutbush, discuss various ways of proofing, such as the English method of firing 2 ounces of powder in an 8 inch mortar with a 64 pound ball - it's supposed to go 180 feet. I judge that to be impractical in my neighborhood, same as Billski's copper and PVC mortar. If it's likely to leave my property when fired, it's impractical.

 

Here's another method - "..2 drachms, when put into the eprouvette, must raise a weight of 24 pounds to the height of three and a half inches". 3.5 inches is a practical distance. Assuming that's the Apothecaries drachma, two of them is 1/4 ounce or 7 grams. That sounds ball-park accurate, but I can't visualize what the apparatus would look like.

 

Cutbush:

Dr. Hutton is of opinion that the best eprouvette is a small cannon, the bore of which is about one inch in diameter, and which is to be charged with two ounces of powder, and with powder only, as a ball is not necessary; and the strength of the powder is accurately shown, by the arc of the gun's recoil.

Dr Hutton's apparatus was a brass cannon 30 inches long suspended on a steel rod that was free to swing in an arc, with associated silver scales, brass pointers and other Victoriana ("which any blacksmith will make for sixpence"). That's too rich for me - the cost of the brass blank would pay for an awful lot of Goex. And two ounces of powder, according to the English test above, is massive overkill that might propel my whole apparatus into the next property. I may have a go at making one of these with a small bore pipe, brass or steel, and loads in the few-grams range.Has anyone else ever tried?

[hillbillyreefer]

Why not use your BB cannon, with some sort of scale attached to it. Measure the recoil. BBs are uniform, use goex or another brand in known quantities for a baseline and go from there.

 

A pen attached to the cannon held against a piece of paper would give you insight into your powder. Your not going to establish SAAMI specs with it but should work for interests sake.

Just brain storming.

 

 

Not sure why but I thought I was replying to a dagabu thread. Sometimes beer is not your friend.

 

There is the Oehler ballistics lab. A bit on the expensive side but you can mount it on anything and test to your hearts content.

Edited April 10, 2011 by hillbillyreefer

[dagabu]

There are a whole crap-load of ways to test BP, shoot baseballs, PVC pipe (the one in favor at this time), golfballs or even a swing arm eprouvett. The one benefit that the swing arm eprouvette has over the others is that NO shot has to be fired, just a wad can be used.

 

You can make one using 2x4s and a short section of schedule 80 gas pipe and fittings. *SAFETY ALERT* Putting any amount of black powder into a steel casing can end up badly, duh! When the loaded eprouvette fires, the section of tube attached to an arm will swing up in an arc and a video can capture the furthest travel it makes with a known load. The best this is that this is fully scalable.

 

A 12" high eprouvette can be made and a .25" ID tube can be used.

 

I use an arm with a 20# lead weight on my 4' trebuchet with a short barreled gun to test BP, 93gr of SWISS 4FA (5g) moves the arm 17" while the hottest stuff I have ever made moved it 22" and broke the attaching bolt for the arm. I shoot only to repeat the 17", nothing more.

[dan999ification]

grain size,density, the shells fit in the mortar and mortar length also play a part in the performance of bp

making a tester is very appealing to me however impractical since i dont need large batches of consistent bp laying around and to a certain degree different applications require differrent standards most of my bp is made job specific.

can i suggest any testing be done with a cardboard mortar in case of overloading.

imho fast bp for lifting small shells/ break. slower bp for bigger shells/prime all i need is for it to combust as much as bp will anyway

if you find a way to test small amounts accuratley be sure to post how you got on i wouldnt mind knowing if my bp is as good as it can be[for lift anyway]

 

2 ounces for a test seems a bit extreme to me aswell

dan

[dagabu]

can i suggest any testing be done with a cardboard mortar in case of overloading.

dan

 

Overloading BP on top of a ball shell is not an issue with the shells that I shoot and that we shoot professionally, you could add an extra pound under a 5" ball shell and the only issues would be a larger flame from the mortar, louder pop and the shell would end up 100-200' to high.

 

Mum can tell us about cylinders but an overcharge under a ball shell is no real issue. We have been forced to double load some shells that had damp lift bags with great success.

[dan999ification]

sorry, i meant instead of the sch 80 pipe incase of failiure or even better a real mortar that can take bigger loads, though i doubt the pipe would fail with just a wad and sensible amounts for the test

safety first

 

i shot a few cake inserts with too much lift they do look pewny all the way up there

Edited April 10, 2011 by dan999ification