# Survival > Primitive Skills & Technology >  Fire Piston Optimal Size, Material and Seal

## bigbob

I have seen several videos about making fire pistons using plastic, wood turned or carved by hand, aluminum etc. The sizes vary a lot.
What is the optimum size for a primitive backpacker for a fire piston, what material, what seals?
Bigbob

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## WalkingTree

You'll probably get some better information from others than from me, but...whatever else, it needs to have an adequate compression ratio. Some sources say 18 to 1, and some say 25 to 1. However, many will say that they've never given the ratio a thought, and never had a problem getting a homemade piston to work. Though I suspect that this is just because it usually works out that different people typically design and build one of such dimensions that it accidentally has this ratio, because I don't think that it's that hard to accidentally get this ratio from a design that someone would conjure up.

Other than that, what is 'best' might be subjective. Might not really be a 'best'. There's a bit of flexibility with materials and design. You just need to imagine the piston being able to plunge fully and smoothly, yet not be loose and is a little tight - much of this being according to the o-ring seal (and a trace of lubrication) and needs to be straight. Cylinder and piston need to match well. Needs to seal, yet be amenable to being plunged quickly. Pretend that you'll always have some 'leakage', so it needs to plunge and reach ignition compression faster than the leakage would prevent this. On that note, for keeping the compression ratio in mind while designing, I figure that you'd want to design in a 'little extra' or a little higher ratio...this would make it 'forgiving' and let a slight lack of skill or experience still result in ignition. Would also compensate for seal leakage to some extent if a build wasn't perfect unknowingly.

Beyond that, I think that this is something which is on the one hand not too difficult to build effectively, while on the other hand is a matter of 'holding your tongue just right' while making and while using, versus there being a single perfect material or design.

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## crashdive123

I honestly don't know if there is an optimal size.  For backpacking - small and light.  I have only made one and used 1/2" copper pipe.

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## bigbob

Thanks, compression ratio is probably the answer, assuming well made such as on a lathe and good seal. Why this ratio?
Bob

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## Antonyraison

I also honestly do not know, I have seen one or two, never used one, never attempted to make one.

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## WalkingTree

> Thanks, compression ratio is probably the answer, assuming well made such as on a lathe and good seal. Why this ratio?
> Bob


https://en.wikipedia.org/wiki/Fire_piston

A side thought I just had: I've noticed that sometimes when a person pulls the piston back out, the tiny ember can pop off of the end, which either ruins that attempt or is just another thing momentarily that has to be dealt with. I'm thinking this is because, no matter what, you often wont have exactly the same air pressure in the cylinder as when you started...not still equal to the outside atmosphere but instead a tiny bit less (unless instead due to the ignition physics it's the other way around). And it kind of sucks it off as you pop it out. (Watch the dirty minds) So this is something to keep in mind either in designing the end of the piston or when operating it.

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## SurvivalGeek

I bought the item below (Fire Piston) from Amazon and never could get it to work correctly. Its was difficult trying to get the correct amount of pressure to create an ember. After a few hundred tries (and after destroying two rubber O-Rings - lubricated with vasoline petroleum jelly like the instructions requested - which are required to operate the fire piston) and I still had issues creating an ember using char cloth. It's not worth it my opinion. Carry a Bayite 1/2 inch by 6 inch ferro rod ($14 on Amazon) with you. That particular size ferro rod will give you thousands of strikes yielding bright sparks. Bayite makes several different ferro rods and are the best quality and price available in my opinion. 

The bad things about the fire piston is it requires a particular type of tinder to create an ember and requires rubber O-Rings to operate. If you don't have the O-Rings, the fire piston won't work.

If all else fails, try starting a fire using the primitive "Fire Saw" method. See the "King Of Random" demonstration on YouTube on how to use the "Fire Saw" to quickly make an ember using two pieces of wood. 

Sincerely, 
SurvivalGeek

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## BearCWY

If you really want to try and learn to use a Fire Piston I have found a great one to try, yes I do own one and use it. EBprimitives makes several versions, I own the Ultimate fire piston. I got the Plus version which gives you all the accessories and their patented tinder. I also bought Stone Tinder which is a clean and reliable tinder for fire pistons. Once I got the hang of this fire piston I can get ignition on the first try most of the time, if not by the second. You can find both of these products on eBay but as of writing this EBprimitives are out of stock but will be listing more by the end of September. I am not affiliated with either of these products and do not receive anything free from them. I bought them on eBay myself and just found a wonderful and reliable combination.

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## WalkingTree

> If you really want to try and learn to use a Fire Piston I have found a great one to try, yes I do own one and use it. EBprimitives makes several versions, I own the Ultimate fire piston. I got the Plus version which gives you all the accessories and their patented tinder. I also bought Stone Tinder which is a clean and reliable tinder for fire pistons. Once I got the hang of this fire piston I can get ignition on the first try most of the time, if not by the second. You can find both of these products on eBay but as of writing this EBprimitives are out of stock but will be listing more by the end of September. I am not affiliated with either of these products and do not receive anything free from them. I bought them on eBay myself and just found a wonderful and reliable combination.


Agreeing with what many in here would say...that one should just keep some bic lighters with them...something like this is just for 'playing'; Whenever any of us want to understand something like a fire piston, it's only so that we might be able to make one when out in the bush or in a real situation wherein we don't have something better - and even a bow drill might be better. That means being able to make and use one from resources found in said bush. So anything precision manufactured that also wants some patented accessories like the charcloth makes one ask why go to all that trouble versus getting some bic lighters.

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## Michael aka Mac

I totally agree that one should carry a Bic lighter with them, not some dollar store lighter, a Bic. I usually carry a Bic lighter and a mini Bic as a backup (on top of numerous other fire starting gadgets). But I have had too many times when Murphy's Law was interfering. On islands or deserts I have had my Bic's fail from the sand. It is amazing how a single sand particle can due so much havoc. Other times they got soaked and had to let it dry out before I could get it to light.

I don't consider the fire piston a toy. It is fire by science. Problem is most of these manufactures don't know the science ('pv=nrt'-ideal gas law) and do not build it to the proper specifications, they don't work, like the knock-off versions from china that you are seeing on Amazon & places like Walmart.

It reminds me when the microwave 1st came out, and so many were reluctant to use them. Ironically microwaves were created due to an observation.  Some guy i think left his candy bar near communication and radar equipment and came back and found that it had melted.  Think he tried frying an egg after that,  next thing you know they build a microwave, size of a small car if I remember correctly, anyway I digress.

My point is sometimes you forgot your Bic lighter, or it runs out of fuel, it breaks, or your friend never gave it back lol, and now you're in a survival situation where you need to make fire.  I rather be the guy that learns how to create fire by every technique available using whatever is on hand, even if I only use the technique once in my life in a survival situation, it would be worth knowing.

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