The Schroeder 09 for Ignition or Diesel

Created: Nov 8, 2009
Series first published in Engine Collectors' Journal
starting wirh Issue 49, Jan/Feb 1974.

Name Schroeder 09 Designer Roger J Schroeder
Bore 0.500" Stroke 0.500"
Type Spark or Compression Ignition Capacity 0.098 cuin
Production run Shop-built Country of Origin USA
Photo by Ron C, Les Stone Year of introduction 1974


The Schroeder 09 was the first "full" engine design to appear by (wait for it), Roger J Schroeder. It appeared in The Engine Collectors' Journal at the beginning of 1974 and was Roger's second construction series for ECJ. Prior to this, he had described a little horizontally opposed twin based on Cox 020 cylinders and it was the positive response to this engine which decided him that an audience existed ready and eager for the Words and Music (as LBSC might say) for simple IC engines for home construction.

The first part of the new series had been preceeded by a lead-up over several issues in Roger's regular "Engin-uity" column where he discussed aspects of design he thought were important in an engine that could be built from scratch by anyone of modest mechanical ability, with limited shop facilities. Bravely, he built the prototype virtually in step with the publication dates and it must have been a relief to him that the finished product ran to expectations without any changes to prevoiusly published plan parts.

Design-wise, the '09 contains a few things that Roger later changed his mind about, but that is part of the learning, evaluating, and revising cycle. Let's look at the basics first. The engine is fully machined from bar-stock and apart from the points, no commercial items are used. It is a square (equal bore and stroke) bulkhead mounted two-stroke with a front rotary valve induction (FRV) and fluted Cox-style transfer passages that can be built for either spark or compression ignition. In the latter case, the timer assembly is omitted and a taller cylinder and contra-piston added. The bulkhead mount doubles as a fuel tank.

Now for the less usual features. The crankshaft is supported in twin ball-races. This requires high precision from the builder and Roger states a tolerance of plus/minus 0.0 in this regard. Fine if you've some sound machining experience, but a bit of a challenge otherwise. The piston is a thin cast iron shell, recessed near the bottom for a steel circlip that retains a wrist-pin carrier. Roger had a sound reasons for this, namely to prevent the wrist pin from floating into transfer or exhaust ports and jamming with disastrous results. Then there's the way the prop driver is retained via a screw-in pin that engages both sides of the driver through a hole in the crankshaft, and all the fine threads that a builder needs to cut. The two-piece piston is not awful, though a failure around the circlip groove is a distinct possibility, as we later experienced with the M&M. The weakening hole in the shaft however is a bad idea and simpler, stronger, equally effective solutions are available such as the split taper collet we all later came to favour. Taken all in all, the '09 is a sound and interesting design, but one that requires some experience on the part of the builder, or determination coupled with no reluctance to scrap parts and try again, and again...

About the time the last part in the series appeared in Issue 54, Roger added basement sand casting to his list of skills. This allowed him to adapt the design to one based around a cast crankcase with a distinctive square shaped head which he named the Windsong.

Well over a quarter century after the engine first appeared, Roger mailed me all of his original tracing sheets and instructions saying that I might like to make them available through the Model Engine News web site. This I was most pleased to do, though I'm sorry Roger passed away before seeing them re-released. So follow this link to the Schroeder 09 Construction Series where you'll find Roger's own building notes. I considered doing a CAD job on the drawings, but decided that as they are in no way "broke", so such effort would just be a waste of time and effort. If you build one, be sure to send us photos.

Construction Index

Download Planset (PDF 3.5MB, 8 Sheets)

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