Firepiston technique.........or lack of.........

[stoviecraig]

Evening guys,

Wondered if you could help - I got a firepiston from Bushcrafttools.com and having mixed success with getting it to work. Does anyone have any tips/hints?

I've tried greasing the o-ring and also adjusting the 'spread' of the washer to vary the tightness of the seal as well as hitting it as hard as possible but am only getting about a 20% success rate. FYI - using charcloth to light.

Not sure exactly where I'm going wrong but all advice greatfully received.

Cheers

 

[BOD]

Only a bit of grease is needed.

Is your charcloth sufficiently charred? black and almost brittle as opposed to dark browny-black?

Are you sure your charcloth is 100 cotton and not a mix? Char a tampon if in doubt.

The piston needs to be depressed swiftly. If you are not doing it fast enough, and lack power like I do, turn the piston around and slam the head against the floor onto a rubber mat or book.

My experience has been mainly with native-made fire pistons. If you have one I'd say you have not wet the gasket with enough water (but that's another story)

 

[Stringmaker]

The only tip I picked up wasn't about bashing the piston down hard, but firmly and then removing it super fast.

In other words the key seemed to be to remove the piston immediately after the stroke, don't hesitate for even a second.

 

[BOD]

Swift compression stroke then swift upstroke to remove it from the cylinder.

 

[bushcraftmyway]

are you getting enough sealing (does the shaft bounce back when pressed down, does it make a "plop" sound when you pull it out)?

is the charred cloth dry (plus what bod said)?

if yes, you should get a much higher rate of success...

 

[ged]

As has been said, if you let the piston rest at the bottom of the cylinder for any length of time all the oxygen will be used up and the ember will die.

I like to make sure that the air in the cylinder is fresh. I press the piston down gently until it sits at the bottom of the cylinder with no force (i.e. all the air has escaped) and then quickly pull out the piston (which will make a 'plop' sound). My theory is that most of the stale air is pulled out with the piston and fresh air has a chance to get back in.

 

[Shark Tinderbox]

When you press home the piston and pull it out, even if there is no ember, do you smell or see any smoke?

 

[stoviecraig]

Hi Guys,

Thanks for all your feedback, much appreciated. I've had a tinker with the piston tonight, trying out some of your advice and am having a bit more success. As always, one answer leads to another question.........

1) When seating the piston how far in should you place it?

2) re. the fit of the piston, how 'tight' should it be? I get a 'plop' when its pulled out and it also 'bounces' when inserted - how much resistance should you get?

3) Leading on from the second question, how much of the sealing ring should protrude from the piston body? Seem to get better results when about 0.5mm is exposed all round.

4) How much grease do you really need to use - a smear or a 'dollop' all round.

Mark - I've smelt some smoke and also seen smoke in the body of the piston holder after an attempt - does this mean theres too much grease in the piston body?

Last but not least - what grease do you guys use? Petroleum jelly isn't recommended but the small pot supplied sure looks like it is!

Thanks for your help and if you're still online enjoy whats left of your day!

Craig

 

[wedgie]

hi is the gasket an oring or string?
the best lube for an oring is rubber grease as this does not rot the oring like petroleum jelly does.

i have spent many hours trying different greases for the orings and the string gaskets.
if its an oring what i found was that if you smear enough grease just around the oring its self you will find that you will not manage to get the piston to bottom out unless the oring is on its way out. it will practically bounce its self out with air pressure as the seal is so good.

all that being said you do need to keep the bore clean as any deb-bury in the cylinder will stop it from working and remember grit and grease will make a grinding paste that will if not removed score the cylinder and the piston seal so you will have to replace the seal more often if it hasn't scored and ruined the bore.
i found that just a little fleck of charcloth on the edge of the oring was often enough to stop it working if every thing is clean it should work at least every second or third hit at the outside
remember it does take a fair bit of getting used to, to learn a new technique and each one is slightly different in application their is quite a bit of difference between the oring technique and the string technique when you first try the two types side by side

 

[Shark Tinderbox]

Hi Guys,

Thanks for all your feedback, much appreciated. I've had a tinker with the piston tonight, trying out some of your advice and am having a bit more success. As always, one answer leads to another question.........

1) When seating the piston how far in should you place it?

2) re. the fit of the piston, how 'tight' should it be? I get a 'plop' when its pulled out and it also 'bounces' when inserted - how much resistance should you get?

3) Leading on from the second question, how much of the sealing ring should protrude from the piston body? Seem to get better results when about 0.5mm is exposed all round.

4) How much grease do you really need to use - a smear or a 'dollop' all round.

Mark - I've smelt some smoke and also seen smoke in the body of the piston holder after an attempt - does this mean theres too much grease in the piston body?

Last but not least - what grease do you guys use? Petroleum jelly isn't recommended but the small pot supplied sure looks like it is!

Thanks for your help and if you're still online enjoy whats left of your day!

Craig

Where there is smoke there is fire! If the piston is working it will ignite the tinder and create smoke, however it may not always create an ember. If you can smell smoke it aint your technique that’s the issue, it may be to do with your fuel air mix (in principle this is a simple Diesel engine. “Suck, Squeeze, Bang, Pop!” but without the Suck).

Suggestions:

1. After each attempt turn the piston upside down, so that the smoke can fall out, or, without spittle, simply blow out the exhaust gasses. This should allow fresh clean air into the ignition chamber.
2. Your fuel may be packed to tight. When packing the piston end make sure that the Char is just tight enough to allow it hold. Alternatively leave a little tab of Char sticking out above the end of the piston.
3. The end of the Chamber is now so clogged up with lub it is choking up the whole process. Clean out the end of the chamber with a cotton bud, if it’ll reach, or use a bamboo kebab stick with some cotton wool secured to one end.
4. Cold and damp will affect the pistons performance, just like starting a cold engine. Warm it up next to your body first.
5. Your Char sucks! (No offence given), try seeing if the char works well by another means; as someone else has mentioned it may be a cotton/manmade fibre mix. Try some Kapok, Amadou, Chaga or Punk wood instead of the Char; beside char is dirty and abrasive, which will wear out your piston faster.
6. You need to pull out the piston as soon as it has been pressed home …if not sooner!. Absolutely no delay. Upon compression (The Squeeze) the air is super-heated which ignites the tinder. This creates the Bang. The Pop is when you withdraw the piston, but now there is no more air to sustain the ember. So the ember will only live if it gets some air to allow the residual heat from the Bang to rekindle to it. You are also creating a vacuum, which in this case causes the Pop; when a gas is rapidly expanded it rapidly cools down, which will suck the heat out of any ember that may have formed.

I wrote a small article for The Bushcraft Magazine Autumn 2011 here is the link to the magazines back issues … the article might help.

http://bushcraft-magazine.co.uk/backissues.php

 

[stoviecraig]

Hi guys,
Thanks for all the great feedback,much appreciated!! I've tried out your tips and I'm glad to report a much improved success rate.
Have a great weekend and I hope I can repay the favour sometime.

Cheers,
Craig