Opposed-Piston Engine Project - The Steam Version

[Steam Captain]

Hello,

Thank you for being interested. The construction is in its heat. I will definitely load up fotos sooner or later. But to let you know about its progress, I am sawing out all the pieces for the engine. Right now, I don't have any power-tool-means of doing it. So, I saw one piece every time I go to the workshop. Otherwise I'd get a tennis arm.

Since there won't be any cylinder head, I had to think about a solution, which allows me to more or less easily remove the crankshaft-rod-piston assembly. I will show fotos later, but it is simple. Immagine a short lenght of square tube as the crankcase with the ends of the crankshaft looking out of the open ends. These ends get closed by thick blocks, that will be welded to the square tube. The blocks get previouslyturned out to receive the ball bearings and rubber washers to prevent oil leakage. I need one of these crankcases for each end of the cylinder. And each of them is divided along the axis of the crankshafts to make it possible to insert the crankshaft. It is not an optimal solution to have ball bearings in a split bearing block, but I'll see how it gonna work.

Now, I just need to cut 4 of 8 blocks of steel (2 bolted together are one ball bearing block and the bolts double as holding the outer halfth of the crankcase (effectively the oil pan) onto the inner halfth), 2 of the 4 U-profile steels, that are going to be the 2 square tubic segments housing the crankcase.

But I need to finish the lathe to turn out these bearing blocks, 2 of the U-profiles to receive the cylinder and bore out the cylinder. I just got a suitable motor and the PWM unit got mailed to me. I am bustling with ideas

I hope this life sign from my side is satisfactory for now.

[TahoeSteam]

I'm really interested in how this will work. I would love to see some more pictures. Are you going to pressure lubricate, and of so, are you going to use a scavenger pump to clear the crankcase?

[Steam Captain]

I will definitely show many pictures here. I promise you that Now, I tested the PWM module with the washing machine motor for my lathe and everything is working as hoped. So, I can get busy, soon. Actually, I pondered about the lubrication issue a lot. The bottom crankcase won't be any problem with the crank webs splashing the oil around like in lawnmowers, classical motorcycles and such. BUUUUUHT the upper crankcase is another story. The piston would be beneath the crankshaft and the oil would collect inside the piston.

I think when the pistons are moving, the oil won't have a chance to collect and gets thrown around and atomized. Only the time when the engine won't run would be something to have a look into, because if too much oil collects inside the piston, it will seep out through the piston pin hole, because it doesn't have a proper seal of any kind. So, the idea I was having is to use an oil pump for the upper crankcase and reduce the amount of circulating oil to not swamp the upper piston. This connected with a way to have the oil flow back down into the oil pan of the bottom crankcase.

I wonder how Junkers solved this. But maybe this is another thing, that needs compromising for a steam engine variant. I mean an IC engine would handle lubricating oil seeping into the displacement space much better, because it simply gets burned. Choosing the proper oil would reduce the soot issue there. I am not sure how my steam engine will behave about it though. But I guess it'll just show.

Thus, despite the lubricating oil only being inside the crankcases, I do calculate quite some oil reaching the steam exhaust manifolds. That's why I intend to use non-emulgating oil like most of you and I will experiment with oil separation. Either those vortex separators used everywhere in the industry (I am sorry - they have a proper name and it lies on the tip of my tongue, but I think you will know what I mean.) or using filtering material of different materials either in front of the condenser or behind, inside the hotwell.

[Maltelec]

This (if it shows ok) is one I have designed.

[Mike Rometer]

Random thought, having watched the motion on that. Will the steam not have to expand at twice the usual rate? Would that not cause a much more rapid temperature drop and therefore greater condensation in the cylinder? 'Tis only a late night thought, and I could be totally up a gum tree. Off to bed!

[TriangleTom]

This (if it shows ok) is one I have designed.

That's a really clever and fascinating design. How do you anticipate dealing with condensation in the crankcase?

[fredrosse]

"Will the steam not have to expand at twice the usual rate"

ANS: Not really, the piston(s) displacement, whatever it is, will still fully occur over 180 degrees of crank rotation, no different from a conventional engine running if at the same RPM as the one illustrated here.

[fredrosse]

"How do you anticipate dealing with condensation in the crankcase?"

One of my closed crankcase single acting trunk steam engine used a chain saw lower end, fully enclosed. Where the reed valve was originally located I put a plate with two ball check valves, one into the crankcase, one out of the crankcase. The engine would produce a foam type emulsion of condensate (from steam leaking past the piston rings and crosshead rings) and lubricating oil. I used an oil tank to continuously feed oil into the crankcase, sucked in when the crosshead was on the upstroke, and discharged out of the crankcase on the downstroke. Needle valves metered the oil so it would use about one quart in two or three hours. The vented oil/water discharge went into the firebox and was consumed.

On the continuous run Domestic Heat-Power Module engine (same type of trunk engine, but a unflow), a conventional splash lubricated crankcase was used. A steam coil kept the insulated crankcase oil above 220F, so any water that got into the crankcase oil was immediately boiled away/evaporated and vented to atmosphere. That engine would run 6 months 24/7 with no oil needed.

[Mike Rometer]

"Will the steam not have to expand at twice the usual rate"

ANS: Not really, the piston(s) displacement, whatever it is, will still fully occur over 180 degrees of crank rotation, no different from a conventional engine running if at the same RPM as the one illustrated here.

The difference is that the "cylinder head" (other piston) is moving away from the "piston" at the same rate, therefore doubling the expansion in the cylinder.

[Mike Rometer]

"Will the steam not have to expand at twice the usual rate"

ANS: Not really, the piston(s) displacement, whatever it is, will still fully occur over 180 degrees of crank rotation, no different from a conventional engine running if at the same RPM as the one illustrated here.

The difference is that the "cylinder head" (other piston) is moving away from the "piston" at the same rate, therefore doubling the expansion in the cylinder.