Palm Nailers

[cfellows]

Do any of you know how a Palm Nailer works? It runs on air, you put a nail inside the tube in the bottom, then when you press lightly against the wood, a piston inside moves up and down driving the nail into the wood. I've looked at parts diagrams on the web and there is a piston inside a cylinder which has rows of holes around the top and the bottom. A valve in the form of a sleeve slides up and down around the outside of the cylinder so that it can cover either the top or bottom row of holes but not both at once (I think). I can't figure out for the life of me how it works, but the design looks like it might be applied to a small, compressed air engine.

g

Chuck

 

[mklotz]

I can see it now - a compressed air pogo stick engine.

 

[Mawitö]

Hi, well i don't know how they work, but the hammers used for stone carving are just three pieces. Check out this video, i hope it helps

[ame]http://www.youtube.com/watch?v=Y3c-B10f4ug[/ame]

Thanks guys ;D

 

[cfellows]

I can see it now - a compressed air pogo stick engine.

Marv, that palm nailer does have a heck of a kick. There's no doubt in my mind that it would give CO2 engines a whole new lease on life.

Hi, well i don't know how they work, but the hammers used for stone carving are just three pieces. Check out this video, i hope it helps

Thanks guys ;D

Unfortunately the video moves kind of fast and it's hard to see where the ports are.

Curiosity got the better of me and I took the Bositch nailer part. It's an elegant little thing inside, but how it works still eludes me. I took measurements and made drawings, but I can't figure out for the life of me what makes it go. Here's a picture of my drawing:

The cylinder moves up and down in the housing between 1/16 and 1/8". The valve slides up and down on the cylinder by about the same amount. The piston moves up and down by 1/2" or so, but doesn't seem to travel that far in practice. I didn't show it in the drawing, but the air exhausts out of the housing from the space above the cylinder. There is an axial row of holes in the housing below the cylinder, but not much air comes out of there.

I'm amazed at how hard the piston hits. I used a T-handled hex key to test it. Just the slightest pressure against the ram and it fires, hard and sharp enough to hurt the palm of my hand. The piston will keep firing as long as you keep pressure against it. The harder you push, the faster it fires and the longer the stroke. When it stops running, the there is slight air leakage for about a second. Amazing little device. Gotta figure out how this thing works!

Chuck

 

[Rayanth]

Chuck,

I am not familiar with palm nailers in the slightest, but your description of its operation sounds very similar to the operation of a rivet gun. Perhaps you could look up how rivet guns work, to lead you in what might be the right direction?

Recoilless rivet guns have an interesting side effect that if you're not actively pressing them against something, they don't work very well - there's nothing to resist the initial burst of air, so they don't 'bounce back' which is what causes them to continue their cycle. Recoilless is probably a bit closer to your palm nailer than the older fashioned rivet guns, which I believe just use a cam to cause the vibration.

Worth a shot ;D

- Ryan

 

[milotrain]

Well let's start breaking down what we know it has to do.

1. There has to be a air volume change.
1a. A storage location for a volume of air that expands into another larger volume in order to provide the hit.

2. There has to be a recovery step.
- I was expecting to see a spring but maybe a smaller volume of air acts as the return spring, or maybe just the weight of the piston (I'm guess a smaller volume of air)

Fun thing to think about.

 

[Brian Rupnow]

Chuck---That is an impact cylinder like I posted about on your hit and miss air engine thread. The piston starts to move under a small air feed, untill suddenly all the air passages around the skirt are uncovered. Then a full pressure volume of air rushes in through all the orifices and slams the piston down like a bullet.---Brian

 

[Admiral_dk]

I'm only guessing, but looking at the picture :

Pressing the piston up, presses air out through the holes in the cylinder, witch in turn presses the valve down.
That uncovers the holes to the full air pressure from the outside. This forces the piston rapidly down, witch in turn press the air below the piston out through the holes in the bottom of the cylinder.
This presses the valve upwards and closes the air supply - press the piston back to top position and the process repeats it self.

 

[Mawitö]

Unfortunately the video moves kind of fast and it's hard to see where the ports are.

True, and the palm nailer have a feature that i think those hammers don't have, that presassure sensitivity you mention, the hammers i've seen ( my father is a stone carver but not the one in the video ) if you want more speed and force in the piston you have add more air preassure.

That tool has always fascinated me since the first time i saw it, please if you find out more you would make me very happy.

I try to google a patent of those hammers some time ago hoping to get more info on how they work, but i only came across an engraving tool that you already know.

http://www.homemodelenginemachinist.com/index.php?topic=1088.0

Thaks for all and happy machining

 

[cfellows]

Chuck---That is an impact cylinder like I posted about on your hit and miss air engine thread. The piston starts to move under a small air feed, untill suddenly all the air passages around the skirt are uncovered. Then a full pressure volume of air rushes in through all the orifices and slams the piston down like a bullet.---Brian

Brian, I had read your description, but unfortunately I couldn't grasp how it works. Brian, below is a picture of what I imagined your description to be. Is it close?

Chuck

 

[cfellows]

I'm only guessing, but looking at the picture :

Pressing the piston up, presses air out through the holes in the cylinder, witch in turn presses the valve down.
That uncovers the holes to the full air pressure from the outside. This forces the piston rapidly down, witch in turn press the air below the piston out through the holes in the bottom of the cylinder.
This presses the valve upwards and closes the air supply - press the piston back to top position and the process repeats it self.

Your description of how the piston fires sound plausible. Not so sure about the return mechanism. I do know that when the piston fires, the cylinder pops upward to the limit of its travel, then returns rapidly to the bottom as the piston resets.

Chuck

 

[Rayanth]

Chuck,

Does the palm nailer keep firing after returning to the top of its stroke, or is it one shot only?

If it keeps firing, then the mechanism is probably almost identical to a pneumatic rivet gun, as I suggested earlier

 

[cfellows]

Chuck,

Does the palm nailer keep firing after returning to the top of its stroke, or is it one shot only?

If it keeps firing, then the mechanism is probably almost identical to a pneumatic rivet gun, as I suggested earlier

It only keeps firing as long as you keep pressure against the ram. If you keep pressing down, it will fire repeatedly.

Chuck

 

[Rayanth]

Sounds like the exact same mechanics behind the rivet guns then. I will see about getting some more info on their inner workings, should be more readily available. (Only difference is we require trigger and pressure for the recoilless, just trigger for old style...but if you take pressure off of a recoilless, even while pulling trigger, it should stop firing.)

- Ryan

 

[Brian Rupnow]

Yes Chuck, that is the general idea. The Hi-presure air can rush in thru the hole unpugged by the rod end, or it can rush in thru a bunch of holes drilled around the side of the cylinder that get uncovered by the piston skirt.

 

[cfellows]

True, and the palm nailer have a feature that i think those hammers don't have, that presassure sensitivity you mention, the hammers i've seen ( my father is a stone carver but not the one in the video ) if you want more speed and force in the piston you have add more air preassure.

That tool has always fascinated me since the first time i saw it, please if you find out more you would make me very happy.

I try to google a patent of those hammers some time ago hoping to get more info on how they work, but i only came across an engraving tool that you already know.

http://www.homemodelenginemachinist.com/index.php?topic=1088.0

Thaks for all and happy machining

Here's a book, available for downloading free from Google, that explains chipping hammers, stone carving hammers, etc.

http://books.google.com/books?id=W3MPAAAAYAAJ&pg=PA447&dq=pneumatic+tools&hl=en&ei=kGL7TdOoIoqztweOjPG8Dg&sa=X&oi=book_result&ct=result&resnum=1&ved=0CEcQ6AEwADgK#v=onepage&q=pneumatic%20tools&f=false

Chuck

 

[Brian Rupnow]

Chuck--If you are thinking of using that type of cylinder for a hit and miss engine I can do up a quick model/drawing of what I think would work. You only need that massive hit of power on the extend stroke. The return stroke could be pneumatically powered, or could be flywheel powered. I had another look at the cut away drawing you posted, and at a quick glance it seems that the outer sliding ring slides down and enables an impact stroke on the return stroke as well. You wouldn't want that on a hit and miss engine, as the return would be so incredibly quick that the crank throw wouldn't have time to make it over dead center. The secret of impact cylinders is not just that you have a high pressure air supply---You have to have a pressurized "VOLUME" of air waiting to flood the cylinder, otherwise you're limited to how large the air hose is which is supplying the high pressure air. --Brian

View attachment IMPACT CYL ASSEMBLY.PDF

 

[Brian Rupnow]

To give you some idea of the impact forces this can generate, have a look at the picture. That is 1/8" diameter s.s. stranded cable you are looking at. The "swage" on the end of one of those peices was performed in one "hit" of a 1.25" diameter x 1.5" stroke impact cylinder I designed, using 80 psi air pressure. The cable was held in a collet-vice, and the impact piston rod stalled out against the end of the cable NOT against the inside end of the rod end cylinder cap. Each hit sounded like a thunder clap when the high pressure "dump" holes were all uncovered at once!!! The swaged end of these cables were then placed in a die and molten zink was forced into the die cavity to solidify and make the end for an automobile emergency brake cable. All e-brake cables had to undergo a "pull-test". the cable would brake before that end pulled off!!!----Brian

 

[cfellows]

Thanks, Brian, that's looks good. Clearly it would have to be scaled down some so I didn't blow the bottom out of the engine! :big:

Chuck

 

[Mawitö]

:O Brian this came to mind to understand how dangerous can it be.

now i have more clear the hi-preassure low-preassure concept involved in this. I have a question though, this means that in the palm nailer is moving the piston and the outer ring to make the returning stroke??

Chuck thaks for the book.

Thanks for all guys