Which hammer design is more effective for transferring kinetic energy?

[pwd]

Hi guys wonder if you could help me out with a little project I am working on building.. Basically its a device that fires a .22 blank and I am struggling with consistency of shot so I have two alternatives for the hammer action. First one A has the firing pin attached second one hits the firing pin which is rested against the blank cartridge ... can anyone tell me which is the more effective at transferring kinetic energy to the impact point . Both hammers if you like are exactly the same its just whether to make it hit the firing pin like B or to carry the firing pin to the blank like A . Hope that makes sense...to me they should be the same but there may be a reason why one works better than other .Thanks Paul

just to add the hammer is a quick solenoid acting like a shooting bolt , the overall travel is about 20mm

 

[Ranger Mike]

ever hear of a zip gun?

 

[pwd]

ever hear of a zip gun?

Yes thanks ever heard of a dummy launcher for Gundog training? If I want to train my dogs I need to know which gives the most transfer of energy to the impact area.

 

[berkeman]

Hi guys wonder if you could help me out with a little project I am working on building.. Basically its a device that fires a .22 blank and I am struggling with consistency of shot so I have two alternatives for the hammer action. First one A has the firing pin attached second one hits the firing pin which is rested against the blank cartridge ... can anyone tell me which is the more effective at transferring kinetic energy to the impact point . Both hammers if you like are exactly the same its just whether to make it hit the firing pin like B or to carry the firing pin to the blank like A . Hope that makes sense...to me they should be the same but there may be a reason why one works better than other .Thanks Paul

just to add the hammer is a quick solenoid acting like a shooting bolt , the overall travel is about 20mm

Either way should give about the same energy transfer. I think the choice depends on other issues, like the ease of making the hammer, and reliability over time. I would probably go with the pin option, and make the pin easy to replace.

 

[AlephZero]

You might have a problem here because if you hit the pin hard enough, it will tend to elastically buckle and then spring back straight when the hammer bounces off, instead of transmitting the load to the cartridge which is what you wanted it to do. (Of course if you hit it even harder, it will buckle plastically and be permanently bent).

The fix for that is to make the pin as short and as large diameter as possible. Making your large hammer with conical shaped end (say with a 45 degree cone angle) would be better than a long thin pin.

I know nothing specifically about firearms, so apologies if that idea is not practical for some reason that I don't know about.

 

[pwd]

You might have a problem here because if you hit the pin hard enough, it will tend to elastically buckle and then spring back straight when the hammer bounces off, instead of transmitting the load to the cartridge which is what you wanted it to do. (Of course if you hit it even harder, it will buckle plastically and be permanently bent).

The fix for that is to make the pin as short and as large diameter as possible. Making your large hammer with conical shaped end (say with a 45 degree cone angle) would be better than a long thin pin.

I know nothing specifically about firearms, so apologies if that idea is not practical for some reason that I don't know about.

You know what AlephZ...you might be onto something there with our proto type...the pin is very long and joined in the middle due to not wanting to cut an original to pieces just yet ...so it may be worth committing to a shorter firing pin length and thickening it...sort of a shorter dumpy affair...it sounds like the solenoid is giving it a good whack but there is something just not right at the mo..thanks for the input and may try the separate pin idea Berkman...if there is no difference then is easier to fix in two pieces .

 

[berkeman]

I'd model the pin on typical .22 rimfire firing pins. You can still have some length to it, as long as it's a good hard steel. The firing pins in my Marlin rifle and my Ruger semi-auto pistol are each a couple inches long.

Be sure to use a rectangular cross-section for the end that hits the rim of the cartridge. I think the ends of my firing pins are about 0.1" high by 0.05" wide. They srike the upper edge of the rim of the cartridge.

 

[AlephZero]

I'd model the pin on typical .22 rimfire firing pins. You can still have some length to it, as long as it's a good hard steel. The firing pins in my Marlin rifle and my Ruger semi-auto pistol are each a couple inches long.

Be sure to use a rectangular cross-section for the end that hits the rim of the cartridge. I think the ends of my firing pins are about 0.1" high by 0.05" wide. They srike the upper edge of the rim of the cartridge.

The buckling load for a 2 x 0.1 x 0.05 steel pin free at both ends should be about 75 pounds. If it is fixed to the hammer it would be less.

It is inversly proportional to length squared, so going up to 3 inches long would make a big difference (33 lb not 75)

For a circular pin the buckling load is proportional to diameter to the fourth power. For a rectangular section, it's proportional to the smallest dimension cubed x largest dimension. So size matters here!

 

[berkeman]

Yeah, the dimensions I gave were for the end that strikes the rimfire casing. The middle of the firing pin is generally taller. Like the 2nd image in this search:

http://www.google.com/images?hl=en&source=imghp&q=.22+firing+pin&gbv=2&aq=f&aqi=&aql=&oq=&gs_rfai=

The 3rd image shows what the casing looks like after it's been struck.

 

[pwd]

Interesting pic and comment about the firing pin being squared off , the original pin I have modified is flat round bar (like a needle but with a flat section at the tip )...the square end may well give more of a dent and stop the misfire problem...have just sourced from a guy another solenoide pusher with another 3 kilo of energy ..so now we are up to a striking force of 9kg...maybe we are getting there...I remember speaking to a guy a while back that invented a gundog dummy that fired a blank, he said lots of work went into the firing pin shape so again Berkman a valid point worth looking at...have to get this new lathe shipped in as soon as and get something specific cut save messing with the original Again thanks