The Steamboating Forum

Hi All,

I have been tearing into my new boat (San Joaquin) for overhaul. The engine is a 1905 Davis and Son "A" frame compound with piston valves set on the starboard side of the engine. The rings on the HP piston valve are all broken. There are four of them and they were replaced by the previous owner. Looks like I'm into making new ones. Any suggestions for the type of material to use (they appear cast iron) and where to get it?
They are fairly large in height than a normal cylinder ring.


Thanks,

Alex

Stuart Turner, the famous maker of quality British model steam engines sells piston rings up to 2-1/2 inch bore, with many smaller sizes also.

Stepped rings (where the gap in the rings forms a step so no leakage past the gap) are better, and several manufacturers of industrial hydraulic cylinders use the stepped iron rings. Sizes range from 2 inch diameter on up to several inches. Most hydraulic cylinders use elastomeric piston and rod seals, but some industrial heavy duty hydraulic cylinders (for service to 300F) use the stepped iron rings. My sidewheeler uses stepped rings from a Parker Industrial Duty hydraulic cylinder, 3-1/4 inch diameter. Fifth season underway with no problems.

For a piston valve, the rings must cross over steam ports, similar to ordinary 2-stroke engines, so the rings catching on the ports should not be a problem, provided a sharp edge is honed very slightly.

I have made bronze piston valve rings for a small engine, piston valve 3/4 inch diameter, running in a steel sleeve with steam ports. Making a stepped ring is not too difficult, let us know if you intend to make them, there are a few machining tricks required.

One source of iron for making a ring is an ordinary cast iron screwed pipe coupling. Chuck up a pipe nipple in the lathe with the coupling screwed on tight, then machine the free end of the coupling to make the ring. Finding enough iron, of the right diameter may require using the high pressure rated fittings, as they have seriously thick walls compared to the standard stuff. Be sure to use malleable iron fittings, not forged steel fittings.

Alex/asal0312,

A picture is worth a thousand words...

Can you upload a picture of the rings or the HP cylinder? Or put them up somewhere online.

I uploaded this "mystery" piston with "fairly large in height" rings.

I wouldn't recommend anything personally without some pictures at least of the HP cylinder/broke rings.

-CB

Here is another source for piston rings:

Auto Diezel Piston Ring Company
3145 Superior Ave East
Cleveland, OH 44114

Telephone: (216) 781-5200

-Ron

Here are some pictures. The piston itself needs work also, it is worn where the rings seat.

As long as the wear to the grooves isn't too severe, they could be re-cut, and rings made to suit. Making rings is very easy, requiring only quite basic lathe turning skills. There are several videos on-line showing how. Heck, I did it for that single I renovated last year.

For a cost and availability comparison tey "STARBOLT ENGINE SUPPLIES". I have purchased rings from them and the are OK.