The great O ring discussion

[timo_gross]

"because they can".... even if it takes hours of labour and experimenting to get it right.
Cheers!
K2

I guess that brings us back to original post, that I interpreted "Just try if you can!" . So I am pushing my envelope further, but I try if the ring groves in the piston do the job for now. The piston rings are postponed, but not forgotten.

So do not feel discouraged or "doing it wrong" for now.

Cheers!

I recently saw some cast iron blanks lying in a pulley and gear shop. The blanks are maybe 2" diameter and 10" long. Would that be worth to try to make a cylinder or pistonrings out of this kind of material? I would guess they sell it for a reasonable price.

 

[Charles Lamont]

Unless you are running a locomotive or some serious load, then a few grooves acting as a labyrinth seal are usually adequate on most stationary models, that are idling rather than doing any serious work. The major advantage is the low friction of a labyrinth seal so the models run on a minimum of steam and the slow action looks more "real". Unless you have a high speed engine of course!

I have a Stuart Double-10 that I finished in the summer before going up to university (about 50 years ago). It has labyrinth grooves on the pistons, and glands packed with graphited yarn. The glands are good but there is a bit of a bit of blow-by, particularly on one piston. On the other hand, it will run on lung pressure - quite fast if you have plenty of puff, and it will move under the weight of its own parts.

 

[Steamchick]

Hi Charles: The old ones are the good uns! Graphited yarn olnly served a few centuries before "modern technology" replaced it with Viton seals... Took something REALLY good to replace it!
Timo - I am fascinated by this shop... "some cast iron blanks lying in a pulley and gear shop. " - But wouldn't pay more than scrap price for unknown cast iron. You need the correct "temper" and grain for rings and cylinders. Read around these threads - the Experts will tell you grades to buy. I rely on them. I have made stuff with wrong materials - only to berate myself later for being so stupid - when I had wasted my time making scrap.
K2

 

[timo_gross]

Haha that is true,
I am constantly fascinated.
I think to them it is raw material that they will not sell at scrap price. I will ask.
The problem is often to find the right source for something, I am getting better at it.

when I had wasted my time making scrap.
K2

I always though that is called hobby? Making swarf out of perfectly good materials, damaging expensive equipment in the process.
By chance I saw these signs on my morning bike ride on Sunday. It says piston rings on them .

Cheers Timo

 

[Steamchick]

The old adage... "A bad workman blames his tools" - well, it is often the wrong material selection that causes failures. - The "bad workman" just selected the wrong stuff for his parts - usually to save money, but more often because he didn't know what the right stuff was, or how critical it could be. E.G. the Victorian Tay Bridge disaster was caused by the wrong material for the fatigue stress at the base of the bridge piers. (It took 100 years of technological development to understand why the piers failed). So when you make such a mistake you are in "good company", just not the company you would really choose to be in!
Some of us (well rarely me...) know the "right stuff" for the job, and I have learned it is worth the extra cost of buying "the right stuff". So if material is "unknown" it is often better left alone than used to waste your money.
Regards,
K2

 

[Richard Hed]

The old adage... "A bad workman blames his tools" - well, it is often the wrong material selection that causes failures. - The "bad workman" just selected the wrong stuff for his parts - usually to save money, but more often because he didn't know what the right stuff was, or how critical it could be. E.G. the Victorian Tay Bridge disaster was caused by the wrong material for the fatigue stress at the base of the bridge piers. (It took 100 years of technological development to understand why the piers failed). So when you make such a mistake you are in "good company", just not the company you would really choose to be in!
Some of us (well rarely me...) know the "right stuff" for the job, and I have learned it is worth the extra cost of buying "the right stuff". So if material is "unknown" it is often better left alone than used to waste your money.
Regards,
K2

Pleez tell us who are ignorant of the Victorian Tay Bridge disaster. I know nothing of it. There are some parts, sometimes that are just parts. Virtually anything could be used. Knowing the difference, that is, which piece NEEDS aluminum or brass, or steel or cast iron and which piece doesn't matter if it's mild steel, or cast or something out of your metal pile. I use a LOT of material that I don't know what it is for just average parts. But there are many that I get a specialized metal.

 

[Steamchick]

https://en.wikipedia.org/wiki/Tay_Bridge_disasterThe pier bases were made from Cast Iron instead of wrought iron. Because they didn't know about materials and fatigue cracking failures.....

 

[Richard Hed]

Ah, very interesting. Does you know about the infamous "Tacoma Narrows Bridge" disaster? It was actually filmed during it's collapse. The man responsible for the insurance had stolen the insurance money. Very funni.

 

[awake]

All of them have a Brass cylinder with approx. 12 mm diameter and a rattlefitnesium piston.

Timo, good job obtaining the rattlefitnesium for your pistons - this is a good first material to use. The next step will be to see if you can source some semifitnalese for your next few rounds of model engine making. Ultimately, of course, you want to get hold of some unobtanium, or at the very least costarmandlegium, to make the very best models.

 

[awake]

Haha that is true,
I am constantly fascinated.
I think to them it is raw material that they will not sell at scrap price. I will ask.
The problem is often to find the right source for something, I am getting better at it.

I always though that is called hobby? Making swarf out of perfectly good materials, damaging expensive equipment in the process.
By chance I saw these signs on my morning bike ride on Sunday. It says piston rings on them . View attachment 125608

Cheers Timo

Timo, where is home for you? (I grew up in Southeast Asia - Philippines and Singapore - but the sign makes me think maybe East Asia?)

 

[Steamchick]

I knew a guy (ex. Blacksmith turned welder) who said the hardest welding rods to obtain were woodtrode (Often used in Teak and Lignite structures for strength), the most difficult to use for electric arc welding is nosparkium (used where the arc must be cool enough to avoid heat distortion), and when gas welding he hated welding with flammalobium! - Just too hot!
I haven't found a source of unobtainium yet - anyone found it? - it is supposed to be the best after Hen's teeth enamel? - That is supposed to be the best natural hard material for machining diamond. Also, in the natural world another incredible material is Unicorn Horn, for making musical instruments. One of the few natural materials of which we do not have a man-made substitute. Apparently when you hear a note played on a Unicorn horn you think the sound is Magic!
Oooh look! The flying-pig squadron is passing overhead!
K2