Fire Piston

[Bernie]

Having read the Machete + Screwdriver Fire Piston thread (http://www.naturalbushcraft.co.uk/forum/showthread.php?1025-Machette-Screwdriver-Fire-Piston) and watched the videos, I was super impressed. While I sat there looking at the screen and my comments about giving it a go and I thought to myself... "Get off your lazy behind and go try it!"

So here's my result. Not tried it yet. I need to get something to wrap in the groove to act as the washer, and I need to find my charcloth before I can try it out. But given how good the fit is, I expect it to work. Makes a nice "pop" when I pull it out. :)

If you think it looks phallic, you should have seen it when the head had a ridge on it! :ashamed:
http://wrotyq.bay.livefilestore.com/y1pzGCWUiDeHYzODoHpZKmtLywCygHGoPZD2rE3LmrbgDRrrlE Z397dk_X_djUVwS-Bda5cS5R-HzVpV7a4wdPeHUejU7YPsNo_/IMAG0446.jpg?psid=1

The two components:
http://wrotyq.bay.livefilestore.com/y1pCZiK8L4u2YVaFEFHiopnGnBc1WMpzJhb8Wk_ZsP0hj38NuK 6eZSM0_MQvzhOOyOGfXRlBteqfdvZ492cAegZUqXeqCKhkv-k/IMAG0447.jpg?psid=1

The piston:
http://wrotyq.bay.livefilestore.com/y1pFN_4M_rO_jnG4NeS9FFzPHRxAB8-_IA2-pmhxYhOcJ2lqc_nNFlS9LAhLcrSQGbaeS06Qiek-klupOYDFTwxOXAYdcwRY0bU/IMAG0448.jpg?psid=1

The barrel:
http://wrotyq.bay.livefilestore.com/y1pWXSD-bbRdHn6xqWe3SA58yde1LZqcYReDDe0ISoBGSaqpIpDcFjV5JR wxhsEv9ikP42hFaEYQLOF2qOGYb4mMjF8lO_xfLY4/IMAG0449.jpg?psid=1

It's during the making of these things things that certain design criteria come out. Like the need for the top of the piston to meet the top of the barrel cleanly to avoid a jam or splitting the barrel.

Dinner soon so I must run, but will show my results as soon as I get my charcloth and try bang out a fire.

:campfire:

[comanighttrain]

you think it looks phallic, you should have seen it when the head had a ridge on it! :ashamed:

and try bang out a fire.


have you lubricated the barrel? :D

look forward to it, been interested in this concept after seeing les stroud do it

[Martin]

That's great work Bernie. As ever, I'm greatly impressed with your work. Your 'beaker' was getting rave reviews at Ten Tors last weekend. I don't think there was a person who saw the cup and never made a nice comment about it. :)

Martin

[Roadkillphil]

That's Bleddy 'ansome Bernie, can't wait to see the action pics :D

[fish]

super!

[Ben Casey]

Very good I

[Bernie]

Complete failure. I wrapped some twine and had a damned tight fit, but even with the plug filled with charcloth, my most aggressive strikes had no success. This is the first time I've ever tried this so I'm not sure if I'm doing something wrong. I'll bring it along next weekend to the meeting and see if anyone wants to have a go with it.

How about we agreed that the first person to get a glow can have it? Either that, or we could make it an offering to the fire gods :)

[Martin]

Bernie, can you feel 'compression' as you strike the piston? In other words, can you feel the piston bounce back as you strike it? If not, you aren't getting a tight enough seal.

Martin

[Bernie]

ROFLMAO!! Not tight enough! Good one. After the first strike I could barely pull it out.

There's no bounce though, just gets wedged in there. With some twisting and a lot of pulling I can get it out, but no glow. Ho hum.

Thank you for your kind words and encouragment. I'm glad to hear that beaker is getting out and about. :)

[Martin]

Well if you've got no 'bounce' then you don't have the compression. sounds like your piston or cylinder is tapered in some way.

In the fire piston I bought Ashley, there is a definite 'bounce' when you stike it. Admitedly, this is a metal piston and cylinder but should be the same principal. Check the tolerances of your kit mate, it will make a difference.

Martin

[Jack Russell]

Bernie, sorry tried to post earler on this but it got lost in cyber sapce somewhwere! Fear not son there's nothing wrong with your build. If you are using thread as your gasket/compression seal as opposed to rubber o-rings it needs to be fat moistened with something to prevent the thread from binding. Also, if your piston plunger was already "popping" on removal it's a tad too tight you run the risk of it binding as you describe, the plunger itself just needs to ride inside the piston chamber. Have you treated the ember cavity with anything to prevent leakage through the plunger face? Don't bin it - it will fire. Here in the sand dunes when it blows a hooley the fire piston is the weapon of choice. cheers jack.

[Bernie]

Good advice chaps - Looks like I need to work on the o-ring to get a better fit. I've put my first attempt online for a laugh. :D


http://www.youtube.com/watch?v=OGPbx4mVV2s

[Proventurer]

Nice bit of turning Bernie, I've cheked a couple of mine and I think martin has knocked it on the head, without a seal the shaft should be slightly loose in the cylinder, also you need +/- 2mm end clearance when the piston is fully compressed to form a combustion chamber, once the shaft size is correct, this end clearance will be critical to enable combustion.

[Ben Casey]

Great video just a shame it did not work keep on Im sure you will get there :)

[basicbushcraft]

great work mate

[fish]

makes you appreciate how good the abo chaps are making them with a machette!

[Jack Russell]

just watched your video Bernie. The compression ring seal you're using won't work - you need to wind a fine thread onto the plunger and use some sort of fat or lubricant to make it seal (the phillipino's swear by dog fat so the house pooch needs to hide quickly under the table).

I think you need to skim the plunger so it rides a little easier in the chamber before you "gasket" the seat - and take a short cut, even if you want to end up with a totally natural piston set it up with rubber o-rings first then choose a natural material to make your gasket after.

From the footage it looks like you've set your seal groove a little too far back - you may not get enough temperature at the fuel face in the chamber remaining. Looking at the video there's room to cut another seal groove closer to the piston face. Again have you done anything to seal the piston face?? Many wooden plungers leak air through the ember cavity - I use five layers of cyanoacrylate (superglue) as a quick prevention of this problem - once the piston is bedded and naturally charred this is no longer necessary.

Exactly as Martin described, the plunger should "bounce back" a little on every stroke but it does need to feel that you can bottom out when you give it a strike. You are looking to compress the available air to a space not more than the region of 1.0 mm to 1.2 mm of volume plus the size of your piston face cavity (your cavity looks pretty good).

Make sure that while you're testing you clean out the piston chamber of any charcloth debris after failed strikes as the debris will stop you achieving full compression and as an aside while testing strike it the other way up (thats knob down) your charcloth will have less tendency to spill into the chamber.

Final tip for now - even if you withdraw your rod (I just love fire piston lingo) and it looks like a fail to ignite, give it a kiss with your lips - you'll get a charcloth lipstick job but you'll feel if any heat has been generated.

Now I've seen the video, if you lose your temper with it stick it in the for sales and I'll happily buy it, make it work and sell it back to you for at least double. You're close matey...... so very close. Don't quit now - Jack

[Bernie]

Thanks for your encouraging words Jack. I've not given up on the idea yet, I'm just away from home at the moment. I think I might need to make another now that I have more detail on the dimensions and tolerances. On the next I'll make the fit a tad loser, the notch for the washer a little lower, and I'll pay more attention to the size of the chamber that remains when fully plunged. I've not given up on this one yet, but I've already learnt a few lessons.

Thank you all for the advice and encouragement.

[Jack Russell]

If you're happy that the cylinder body is true and smooth bored, stick with the one you've made so far Bernie, skim a bit off the piston rod with fine emery (I shove mine in a battery drill chuck and spin 'em up but might be problematic if you've already permanently fixed the striker knob) - there's enough room to cut a new o-ring groove below your first attempt and make your seal with thread (I use fishing rod whipping silk, the stuff they put rod rings on with set in the groove with a smidge of epoxy then greased up with vaseline or a silicone base) - I've been asked to knock up some first generation pistons for a couple of local chaps - have to see if I can post a "how to" with piccies. I tend to use brass tube chambers and silver steel plungers now for quicker builds then put them into pretty cane or turned wooden bodies but the principals are the same on this type. Get this one sorted then think about making a second generation piston with a release vacuum valve so the piston rod stays captive when not in use. Fire by compression is absolutely "de rigeur" in my sand and salt air very windy environment, you can stick a tinder bundle under your armpit, strike a piston and quickly transfer the ember without the makings of your campfire wandering off into the sand dunes at a high rate of knots.

[Bernie]

Thanks Jack, I will have a go at shaving the shaft. For what it's worth, the striker knob and the shaft are one piece of wood. No time now - loads of work still to do. Been a long week and tonight I must pack and prep for Ivans bushmeet.

"release vacuum valve" :o Wassat?

[Jack Russell]

"release vacuum valve" :o Wassat?[/QUOTE]

Right then let's see. The piston you have made is what is now termed "first generation" - the piston rod compresses air at the bottom of the chamber and bounces back a little after the stroke. When not in use the rod can come out of the chamber (unless you design in a retainer clip of some sort). "second generation" pistons have an air release screw at the bottom of the chamber which can be opened allowing the piston rod to travel all the way to the bottom of the cylinder then closed to make the cylinder airtight again. When this is done you create a vacuum which will hold the piston rod inside the chamber (if you pull on it, it gets sucked back to the bottom). Now, because I live and play in a sand/salt environment the advantage is that a lubricated piston rod doesn't get contaminated as it's captive in the chamber. Check out the wilderness solutions ones on Amazon (seriously posh so don't mention them to Martin cos they're shiny and VERY expensive) or look them up on fleabay (a guy called walleringbear stocks them and there's a linky for a demo video on youtube in his sales blurb). I still do first generation pistons for all the surf bums and dune hobo's cos they are quick builds but a second generation adds a nice challenge to the project if you've mastered the basics.

[jbrown14]

I'm watching this thread with interest. It's a nice job you did there.

What kind of wood is it? There are some lovely colors in it!

[Metal mug]

If I made a fire piston out of wood it'd probably catch fire. :D

[Bernie]

I'm watching this thread with interest. It's a nice job you did there.

What kind of wood is it? There are some lovely colors in it!

Thank you very much jbrown. The wood is Yew. I have a fair bit of it so it seemed suitable. It's fine grained and finishes very smooth if cut well. It has very pale sapwood and heart wood ranging from amber to deep red, even purple at times. Yew will carry the iron from nails up through the tree which both colours the wood and helps make tools blunt very quickly. Over time (a long time), exposure to UV light will turn Yew a deep brown, and the beauty of it's youth is lost. It's a good lesson for turners to not rely on the beauty of the wood, but to make form and shape that will appeal to the hands and eyes even when the visual appeal has faded.

Yew is poisonous to eat, even the bark. I've heard (I have no proof) that the reason they're often found here in England in church graveyards, is to keep cattle out. I've also heard stories of fallen Yew trees pulling up bones from those graveyards when their roots were drawn out of the soil by strong winds and softened earth. Some people develop an intolerance for the dust which can lead to rashes and breathing problems.

But it is a very pretty wood; there's no doubt of that. :)

[Edwin]

Would a wooden "pirate" pop gun work? I will try when I can find one we used to have knocking about. Plenty of compression.

[Ashley Cawley]

Beautiful Fire Piston Bernie, I somehow missed this thread first time round, looks great did you ever get it working?

I would say Martin was right about the bouncing-back will be a good indicator of a proper seal for the chamber and compression working.

If it helps here's the video of mine in action, hopefully you'll see a bit of bouncing-back. I intend to use mine more this year :)



http://www.youtube.com/watch?v=RZyzbe2l0T4