[english] selfmade firepiston

[Waldhoschi]

After talking about the pros and cons of a Firepiston, i´d like to know whats the point of create a piston on my own.

I am going to organize some aluminium-alloy bushs and staves that fit accurate together. I want to try to make something that works. Does anybody have the oportunity to shape such sleeves?

Are there reasons to create it of wood, or is there a way to do it in metal? In my opinion metal has got the advantage of not swelling in cause of getting wet. In addition the sleeves could be thinner. On the other hand its specific heat is superior...

Bassically the form of the prototype is simple. One hollow sleeve and a suitable piston with concave tip. I used to have two exactly shaped brass sleeves flying around in my room. No Idea wehre they´ve gone...

I think of a screwable firepiston thats hollow space could be used as depository for emergency material.

Maybe ill do a little layout after some hours of learning mathematics...


Grüße Joe.

[Jeff Wagner]

Hi Joe,

I can help you in making a wood piston, however I have not made one from metal. In order to be true to the original form and materials used in ancient times I have only worked with wood and buffalo horn. The coco bolo wood contains a natural oil and is not so much affected by moisture. In fact I can soak a wooden piston in a sealed Nalgene bottle full of water and this causes no problem. Certainly metal is more durable than wood. Surface oxidation of the metal might present performance problems over a long time. The surface of the bore needs to remain smooth for best perfromance. The modern style fire pistons I have seen made from metal or plastic use rubber O rings to make the seal on the piston shaft. There are usually some aluminum pistons of this type an American Ebay. If you do this, I would suggest using two or three O rings because as the piston moves forward, the pressure increases and there is a tendency for the compressed air to slip past a single O ring. I call this "Blow-by". When this happens the piston looses compression and will not light.

Ich wünsche Ihnen Erfolg

[Waldhoschi]

Thanks Jeff.

@All:
Answers please in english. This is an english-marked topic.
[edit]Right - also have a look at http://forum.outdoorseiten.net/viewtopic.php?t=12431[/edit]

[Jeff Wagner]

You are welcome Joe and thanks for the English thread.

[Waldhoschi]

Maybe there is a way to use a alloy of aluminium and titanium etc. Materials like cold released Aluminium (T4 or T6) are resistent to corrusion and bending. I think a dry lubricant like grafit in carboniced steel of the head of the pistan would have som advantages. I guess it would be fun to engineer a high-tech piston. Indebendent of its usability

[Indi]

How would it be with piston rings like from an autoengine?

[Jeff Wagner]

Maybe there is a way to use a alloy of aluminium and titanium etc. Materials like cold released Aluminium (T4 or T6) are resistent to corrusion and bending. I think a dry lubricant like grafit in carboniced steel of the head of the pistan would have som advantages. I guess it would be fun to engineer a high-tech piston. Indebendent of its usability

I have thought about such a high tech piston for military application and to appeal to persons who have more modern interests. Titanium, aluminum or stainless steel al should be possible although SS would be heavy. Carbon / graphite is an interesting idea. I think it would be advantage if we could design one that did not require lubrication at all. This would make for less maintenance and improved reliability in remote locations. Perhaps teflon for the bearing surface....

[Waldhoschi]

Erm. I guess its pretty difficult to create such a spring ring with small diameter. Maybe with a little rubber O-ring. Or even with wound cord thats lubricated with spit or oil.

Grü Joe

[Indi]

If the Firepiston is so good, why then verbesserungen? (sorry.. verbesserungen?)

[Jeff Wagner]

How would it be with piston rings like from an autoengine?

That might work in a metal cylinder casing. The fire piston is essentially a small version of a Rudolf Diesel engine. One concern that comes to mind is that in an engine, the piston is never removed from the casing. The rings can be made to fit tight. In a fire piston, the piston is removed and re-inserted. If it had rings it might be difficult to put it back inside the cylinder. Perhaps if the rings were made of a plastic...

Good ideas, both of you.

[Indi]

or teflon

[Jeff Wagner]

Erm. I guess its pretty difficult to create such a spring ring with small diameter. Maybe with a little rubber O-ring. Or even with wound cord thats lubricated with spit or oil.

Grü Joe

Ja, I have used spit on a string gasket when the grease had become depleted. It worked good enough to get ignition.

[Jeff Wagner]

If the Firepiston is so good, why then verbesserungen? (sorry.. verbesserungen?)

It seems to be our nature - to look for ways to make something better..

[Indi]

ok, that´s right

[Jeff Wagner]

Bis spater. My tea is now finished and I must go back to the work shop for a while.

[Chalk2]

hm, reading all that...

try to come along with a diffrent solution, why dont leave the piston in the chasing, and make the lower part screwable, kinda like silencers for weapons work.

Chalk2

[Waldhoschi]

Hi, the Word indi´s looking for is "improovements".
Iam just trying a new desing.
...hope its finished later ;)

[Waldhoschi]

Well now, i designed something. There are two different posibilitys for heads. The first is a Head of carbonized Steel (c>6%) the second one has got gaps for two different o-Rings. The heads are about half an milimeter thinner than the piston to minimize the friction.
The Heads have got half centimeter long gaps to include the thinder.
I suppose the thing could work. Erm, forgot: To the sleeve and the piston are Threads aplied to close the thing tightly.

[Jeff Wagner]

Ja, Danke. I looked up verbesserungen on Babelfish..

Some really good ideas there. The O ring concept will work. I have done this in a wood piston and there is no reason it would not also work in metal.

Threads at the mouth of the bore is interesting, however there is something you would not know without seeing a fire piston. When the piston is inserted into the cylinder the trapped air prevents the piston from coming close enough to the cylinder for the threads to be engaged. This why you will unusally see my pistons not completely closed. I have developed a spacer / adapter ring that fits between the head and the body to overcome this.

[Waldhoschi]

So there should be a little screw or knob-ventil at the end of the Zylinder to release the traped and compressed air.

Should go to bed.... g´night