Ubehage Posted June 2, 2015 Posted June 2, 2015 I just got myself a new rawhide hammer, to use with my pyro.But I am a bit concerned, beause I think the hammer is too hard. I have this crazy idea that a "soft" hammer is preferrable, because it won't transfer as much instant-energy when it hits.Am I totally wrong about this?
nater Posted June 2, 2015 Posted June 2, 2015 Yes, you are wrong about that. You want the energy tansferred to the propellant composition so it is appropriately compacted. Anything lost in the face of the rammer or lost to the surface the tooling is resting on is wasted. Ramming is only safe on BP compositions, but still obtains less pressure than most of us use when pressing. The propellant grain needs to be solid to prevent a CATO. Rawhide mallets are great because they are so hard, heavy, will not spark and will not damage your tooling. Rubber mallets are too soft and will bounce while metal hammers can spark and damage your rammers. 1
GMetcalf Posted June 2, 2015 Posted June 2, 2015 A nice solid hammer is preferable! In fact I used to use a metal hammer for most of my ramming (only using wooden rammers, so no spark producing contacts were ever made) because it's the hardest and heaviest hammering tool I could find! Ramming is only safe on BP compositions, but still obtains less pressure than most of us use when pressing. The propellant grain needs to be solid to prevent a CATO. It's the rapid change in pressure that becomes a worry during ramming, not the overall pressure which, as you quite rightly pointed out, is much less than would be used when pressing with a hydraulic press. However a press produces the pressure slowly so when the molecules of the powder move past each other it happens slowly and this makes it safer. Ramming causes the molecules to move past each other very fast as well as producing a shock wave of vibration which travels through the solid parts of the composition being rammed. The rapid movement means ramming compositions with metal powders can be dangerous (if they're spark producing metals) and anything but Black Powder (which is pretty insensitive to shock since none of its components can be mechanically made to decompose) could in theory be ignited with enough shock force which for certain compositions may well be reached through ramming. 1
screentoppers Posted July 20, 2015 Posted July 20, 2015 http://www.ptreeusa.com/carving_products.htm best rammer youll ever find scroll down 2225 1
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