steel cylinder?

[steamboatjack]

The simplest system I have seen is a small poppet valve which allows the any pressure above that of the steam inlet pipework to flow back into it. I hope your car man is right concerning the stainless liners! that's a step farther than I would take, I believe cast iron is the material for cylinders and always will be but I would be happy to be proved wrong.
Regards
Jack

[russkey]

...I believe cast iron is the material for cylinders and always will be...

This is actually something that has puzzled me for some time. Why *do* people still use cast iron? Why not lighter, stronger materials? Is it some sort of heat transfer concern?

Al

[87gn@tahoe]

Why have a liner at all? Why not nikasil (or the newer version of coating method) coat the block or weldament? Then use low-tension automotive piston rings with better sealing characteristics and less drag...

[Rainer]

...I believe cast iron is the material for cylinders and always will be...

This is actually something that has puzzled me for some time. Why *do* people still use cast iron? Why not lighter, stronger materials? Is it some sort of heat transfer concern?

Al

Hy Al,

cast Iron was and is used because of the graphite in the material itself. So you have a natural lubrication. Additional it is cheap and easy to pour in every shape you like.

For stainless you have to find the correct piston rings to overcome the poor friction figures of stainless. Try to have a good ride on the new stainless shutes on the playgound of your kids - the old rusty steel shutes 40 years ago where much better in this )

What kind of lighter and stronger materials do you have in mind?

[barts]

Why have a liner at all? Why not nikasil (or the newer version of coating method) coat the block or weldament? Then use low-tension automotive piston rings with better sealing characteristics and less drag...

For commercially produced engines, this might be interesting... but cast iron is really the material of choice for low volume production, and it finishes really nicely in the home shop as well. In addition, it forms a nice glaze over time that works well in steam engines, which are quite difficult to lay up dry.

- Bart

[DetroiTug]

Cast Iron is also porous like a powder bronze bearing, which will store oil and emit it on the mating surfaces as the temperature rises and thins it.

Ray Hasbrouck undoubtedly tried the no sleeve route, but his larger weldment engine design called for one. My guess without it, the engine would need continual lubrication.

We took the Tug up the Detroit River past Tuesday and when the swift oiler ran out, the engine started squeaking. Had to refill underway. That is with saturated/ non-superheated steam.

-Ron

[russkey]

What kind of lighter and stronger materials do you have in mind?

Perhaps not lighter and stronger, but easier to work with. I've always thought that cast iron was rather hard to machine due to some sort of crumbly nature. But perhaps that is just some silly thing I've picked up. Do the castings that are made require post-machining? Can castings really be made accurately enough to avoid it? Personally I was thinking something like a tough aluminium alloy, or perhaps stainless (granted, not an easy thing to work with either).

[Aheadslow]

Using the correct methods you would be surprised at the accuracy that can be achieved with Iron castings. There are four basic types of cast iron:: they are

( White Cast Iron)

Characterized by the prevalence of carbides, impacting

. high compressive strength
. hardness
. good resistance to wear

(Gray Cast Iron)

Characterized with graphite in the microstructure, giving

. good machinability
.good resistance to wear and galling

(Ductile Cast Iron)

Gray iron with small amounts of magnesium and cesium which nodulates the graphite, resulting

.high strength
. high ductility

(Malleable Cast Iron)

White cast iron heat-treated to improve

. higher ductility


At the turn of the century Gray Cast Iron was popular in engine block castings as was Ductile cast iron ,, I've personally found antique engines that have been setting in barns for 80 years , and with a little cleaning started them up and had them run good as new. In a hundred years or so, we will see if the newer ,stronger ,lighter materials can stand up to that same test of time.
I believe that if you want to use stainless ,it would need to be a very specific type. Because the conditions inside a steam engine are very different from an IC engine. We have 300 years field testing on the use of cast iron in steam engines along with the advances that came with all that time. I'm sure that someone on this forum could explain it better, but I've been building engines for 35 years and I stay away from stainless because I have had too many bad experiences with it.

[fredrosse]

The uniflow engine on my domestic heat-power module had a vent valve on the cylinder, and it would just blow (and waste steam) when starting up. I would think this vent steam could be used to work your ejector and bring up initial vacuum, then be manually shutoff as the normal vacuum pump was up and running. Then this cylinder vent would protect the cylinder from water during startup, as well as facilitating initial vacuum formation at the same time.

When that heat-power module engine was running with exhaust to atmosphere, it sounded just like a four stroke gasoline engine with an open exhaust pipe, unlike any steam engine I had ever heard. Of course, when exhausting to the condenser, the only sound was the valve tappet clearances, as it had mechanical lifters, basically an ordinary IC engine OHV setup working an ordinary IC engine poppet valve in reverse flow (steam supply tends to force the valve shut) for steam admission.

The cylinder was an iron casting, with 18 uniflow exhaust ports 3/8 drilled. The exhaust plenum is a steel weldment, brazed to the iron cylinder. Top and bottom cylinder flanges are also steel, brazed to the iron cylinder.

[barts]

I'm sure that someone on this forum could explain it better, but I've been building engines for 35 years and I stay away from stainless because I have had too many bad experiences with it.

In my experience:

Good things about stainless:

* high temperature resistance
* many alloys resist corrosion well in the presence of air
* reduced heat transfer coefficients compared to steel or cast iron

Bad things:

* tends to pit and have corrosion issues in non-welded joints in
the absence of air, particularly w/ chlorides present.
* tends to gall unless rubbing materials very carefully matched
* if using acids, can form toxic chromium & nickel compounds
* many grades difficult to machine; grinding can be necessary for
fine finishes.

Example applications where it works well:

* superheater tubing
* valve & piston rods if there's little/no metal-metal contact w/ glands
* small fasteners that tend to corrode; install stainless ones w/ never-seize.
* hot wells, piping/tubing, boiler jackets, firebox wrappers, etc.

Examples where it works poorly:

* chain plates on sailboats - crevice corrosion occurs underneath in salt water
* fired pressure vessels w/ distinct water levels (fully immersed pumped flow as in
monotube or Lamont boilers seems to work ok).
* surfaces that rub under pressure - bearings, cross heads, slide valve surfaces, etc.

- Bart