Which cast iron to choose for cylinder ,piston and rings .

Hi ,

I will be starting on a hit and miss engine later this year , i picked up the castings from that auction site we all know but the materials for the cylinder liner and piston were not included .

The drawings only state cast iron for both so i need to purchase some cast iron bar to make these but ...

I can get 4E grade in the right diameter for the liner and have some 2P grade here that will do the piston and rings .

So what i want to know is :

Will the 4E grade be ok for the Cylinder?

Will the 2P grade be ok as piston/rings running in the 4 E grade cylinder ?

I am led to believe that 4E is slightly softer and a little less wear resistent tha 2P and its structure is a little different ( pearlite v semi pearlite etc )

Up until now my engines have been Aluminium piston in what ever chunk of cast iron i could scrounge for a cylinder and i used thae same suff for rings .

Ian..

I'm not sure of your code numbers down under but grade 250 (17) is what is mostly used here often refered to as meehanite.

Both your refs seem to point to a grey cast iron similar to Gr17 so should be OK

What is the engine?

I am also looking at some cast iron for the cylinder of a IC engine, it has the number 63260 on it, got it 6 or 8 years ago and I can't remember the grade of iron it is. It should be ok, I'v made a piston for another motor from the same stuff.

Ian S C

Thenks Jason and Ian .

The 2P and 4E seems to be something the manufacturers have conjured up as i can't find anything about what it means and there is the 3D for ductile .

They are both covered under AS & BS as the same classification but they do differ in composition , the 2P has some different elements that make it more wear resistant, they both seem to sit mid scale for pressure rating @ 250 mpa.

I suppose for a low speed model engine that will not do a lot of work the softer 4E will do .

Funny thing about meehanite , from what i can gather it is more about the manufacturing process than actual composition as Wikipedia have as a patented manufacturing process for fine grain grey cast iron .

The engine is a 62 cc Rosebery

Ian.

I work on full size vintage ic engines and grey cast iron was used almost exclusively for cylinders, pistons and rings. The best material I have found for making new piston rings is unvented car brake discs. I made 5.5 inch rings for a 100 year old petrol engine which has just completed 1000 trouble free miles.

I too have used brake disc cast iron for piston rings, I did use the rim of a V pulley to make a ring fot a vintage Continental industrial engine.

Ian S C

Great minds think alike Ian ! Cars yield a lot of quality metal such as drive shafts and shock absorber shaft and tubing as well as aluminium for melting.

Terry C

If you can get them, truck drive shafts are good for large diameter tube. Old shock absorbers are another good source of materials. For pistons in my hot air engines I use old window weights, one of those has done over 2000hrs in a steel/iron water pipe cylinder, no measurable wear, 1 3/4" bore.

Ian S C

I'm not surprised. All the sash weights I get my hands on are bright silver inside and suitable for making tools for cutting HSS. I think they are pure Mithril

Neil

I know Neil, I got one that finished off a carbide tool, I was a bit worried about it when I dropped the weight, it broke in 3 pieces. the other weights were ok. when looking for weights, try and get them as fat as possible, I had some a bit over 2" diameter, lovely stuff to work with as cast iron goes, the ones I have now are only 1.5" dia, and a bit patchy. I have not been to the demolition yards since the earth quakes 5yrs ago, there should be plenty of weights unless they all got sent off as scrap, you might get them back from China as a lathe.

Ian S C