Schmidt Water Pressure Engine
South Carolina, USA - Manufacture date: 2008
Bore = 13/16", Stroke 1", Flywheel diameter = 4 1/2"
Style: Double Acting, Modified Oscillator

Dimensions: 7 1/2" length x 4 1/2" width x 6 1/2" height
(includes base)

Video Available:

The Schmidt Water Pressure Engine

recent email arrived, offering an unusual engine for sale. I'd never seen one like it and with the price the seller was asking, it wasn't likely I'd be seeing his anytime soon. It did, however, tweak my curiosity and I did a few searches for "Water Pressure Engines". As luck would have it, I stumbled onto a rough wood cut engraving of the same engine style and after a bit of eyestrain, I began to think it just might be possible to build one.

Thus began the project I'll share with you on this page. There were no drawings and the photo of the offered engine, along with the very rough engraving were all I had to work from. I hope you'll forgive me if a bit of artistic license was taken to make it uniquely my own engine creation.

The available history for the Schmidt Water pressure engine is somewhat scant, but I've managed to piece together some of it.  The design is a unique take on the use of an oscillating valve system, due to the radial configuration which lets the horizontal cylinder rock back and forth in a semi-circular saddle.

The original engine was built in the mid 1800's  by a Mr. Schmidt, of Switzerland and was designed to run on water, steam or air. The engine was used to pump potable water to remote villages in the Swiss Alps. It was fed water under pressure to run the engine and the exhausting water was fed into the outgoing water lines with enough pressure to make the long trip up the mountain side. In essence, the engine serves functions as both, the motor and pump.

The unusual copper dome is there to absorb the shock of  water hammer. Since water doesn't compress, any sudden change in incoming pressure could literally destroy the engine. The air in the column was there to compress and cushion the system and prevent damage.

View of the Water Hammer Column

The Unique Valve Configuration

3D Rendering for Proof of Concept

The project began with a close study of the available photo and the engraving. Once I had a feel for what was going on with the design, it was then modeled out in 3d to prove my thoughts were indeed right. Only then did I begin the process of cutting metal. Each individual piece was carefully marked out to match the  calculations  I was able to make while modeling the engine.  The components were then carefully machined from raw metal bar stock, one at a time, using only manual machining techniques. No CNC was used in building the engine and the only parts not hand made  were the bolts and dowel pins used to put the engine together.

The Cylinder Parts Begin to Take Shape

Cutting the Valve Saddle Blocks

 The Crankshaft, Early Base Block 
During Center Line Elevation Check

Crank Installed, Cylinder Location  Established,  Supports and Base Bored for Contouring

I would be remiss if I didn't come clean about now. Looking back over the photos it's easy to see where they could give the mistaken impression that everything was accomplished without any problems. That impression would be wrong...(grin). An errant end mill, due to a vise, that I forgot to tighten, required making a second cylinder and a small miscalculation had me redoing the valve blocks, due to an improper radius where they mated to the cylinder. The large radius of those interrupted boring cuts to the base had me sweating bullets before I was done.

The project was an exercise in mental gymnastics. I was often cornered by some procedure that required a bit of thought before things would work. While working without drawings let's you make changes on the fly, those same changes often beget more challenges and changes. Luckily, I enjoy the challenges and although some of my solutions might not be found in any machinist's manual, they worked for me and I still have all my fingers and toes.

With the centerline established, it was easy to relatively easy to locate the holes for the crank shaft, the side arm ends and the cylinder pivots. The side arms stabilize the cylinder, provide it with a pivot point while allowing tension to be adjusted on the valve blocks in order to control how they seal and for speed control. Tthe more tension applied, the slower the engine can be made to run. They also allow the cylinder to be swung out of the way for maintenance and lubrication.

Interestingly, the real world engine apparently used water as the lubricant of choice and a certain level of leakage was accepted during operation.

First Side Arm Fitting

Cutting Side Arms on Rounding Table

Finished Arms, Base Porting, Rear Tension Bar

Studs, Ports and Packing Gland Finish the Cylinder

The Tiny Rear Tension Handwheel

Making the side arms was accomplished using a slightly modified home made tool that Marv Klotz shared with the members of the HMEM hobby machinist forum. It allowed the arm ends to be manually rounded and contoured, as well as making the inner and outer tapering cuts dead easy to do. Completing the cylinder was a landmark in the build, as it marked the point were the engine ceased to be a pile of small parts and began to become assemblies.

The small handwheel was also manually cut using my handy dandy home made indexing table. While I worried about working at this small size but it all went smoothly and without event. When I shared this wheel with the guys at HMEM, I was a little amazed to hear 30 year machinists exclaiming that they'd never be able to work that small. One of them finally explained that most job shops work with large items taking huge cuts, espcially when compared with my small equipment. I had to admit working on large stuff would intimidate me in the same way. Who knew?....LOL.  Either way.... it definitely added a nice touch to the engine.

Close Up of Small Details
as the Engine Nears Completion

As things progressed, the addition of small details like pillow block bearings, working wick oilers and decorative end caps for the dowel pins began to add interest as well as functionallity to the little engine. The stuffing box or packing gland was fitted and graphite string installed to seal the rod passage (thanks Tim) and provide lubrication to the piston rod. Small locking bolts were added to the side arms to hold them in their proper positions and caps were made to finish off the small 3/16 diameter oilers.

Progress slowed quite a bit as these small but important items were made and fitted. Luckily, the satisfaction levels made it worth all of the seeming lack of progress.

At this point, the engine was tested on air and found to be in need of running in. The crank shaft end was chucked in my small drill press and carefully powered, with lots of lubrication. After about 30 minutes, the engine turned relatively free and only required 15 pounds of air to run at a rather fast clip.

Things only got better from there. Soon the engine would run at a nice comfortable speed on as little as 5 PSI, even with the tension set fairly heavy on the valve blocks. The engine now turns over by hand with an almost totally undetectable level of friction

Water Pressure Engine After Running In

The engine obviously looks a little naked without a flywheel. After all the time I'd studied it, a single flywheel just wasn't going to finish the engine. I decided to make a pair of them and as luck would have it, a friend in the UK provided me with a copy of Philip Duclos' instructions for manually making curved spoke versions. It didn't seem like such a huge step after the tiny handwheel so I took up the challenge and decided to give it a try.

The instructions were perfect and well thought out, so I soon had a matching set of S spoked flywheels ready to fit up to the engine. What is that you say?.... uh... yeah... the instructions were for curves. Uh...yeah... I did say "S" spokes.

Okay... one last confession....LOL. While making the curved spokes, my indexing table slipped (my fault for climb cutting) and the end mill came to a stop in the middle of the previous spoke.  One of those AWWW *&@$# moments for sure. Luck was on my side. The mistake turned out to be the exact way to make classic S style spokes.

Fitted with Rough Cut "S" Spoked Flywheels

The Finished Engine with Soft Flywheel Contours and Rounding....all  Hand Filed

This project is my second engine and took from April until September to complete.. While the first engine project turned out ok, this one came much closer to my self expectations and boosted my confidence.  I now have little fear that I can accomplish just about anything that I can imagine.  I'm pleased with the results and I hope you too approve of how things turned out. Thanks for sharing in the fun.


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