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Dario Brisighella      Oak Creek, WI    3/22/2009


The basic design of this engine comes from Mr. Jan Ridders from Holland, who designs and builds some very unique small engines.. He was kind enough to send me his drawings. The drawings were as one might expect, done with Metric dimensions. Rather than begin construction and do the conversions one at a time, I chose to redraw the entire engine and convert the dimensions and redesign some of the components.

As you might also suspect that once converted, there were all sorts of strange dimensions or at least many that were quite odd. When the drawings were finished I opted to enlarge the engine to wind up with a .750” bore, rather than 18MM (.07086”), which is just over an increase of a bit over five-percent.

I also simplified the engine mountings to simple aluminum plates. The plans called for

pillars to support the cylinder and the crank-shaft assembly. Other changes included an aluminum cylinder with a cast iron liner verses a full cast iron cylinder or stainless steel one. I used whatever materials I had in the drawers which include a steel flywheel verses one of brass and some over-sized bearings.

The unique thing about Jan’s design is what he aptly calls “an internal valve”. No cam is involved in controlling the intake cycle. The power piston controls the cycle, that is it

moves the “internal-valve” (like another small piston at the top-end of the cylinder). As the piston moves to TDC, it contacts the internal valve to open the intake port. A small protrusion on the top of the piston moves the internal valve to close. The basic adjustments are very simple indeed. A set screw on the valve adjuster push-rod needs only be adjusted to contact the piston skirt as it is in the BDC position. This moves the internal-valve to close the intake port. The valve rod then returns the valve to the closed position as the piston skirt contacts the valve rod as it approaches BDC. The design is simplicity in itself.

Both the power piston and the internal valve were made of fine grain cast iron. Like most all Atmospheric type engines friction is a “killer” and care is required in polishing the bore, the piston and the internal valve. I found that lapping the sleeve with 1000 grain lapping compound wasn’t quite smooth enough and finally finished the pistons and the liner with a very fine grade of rubbing compound until I has mirror like surfaces.

Controlling the flame for the engine is quite critical. The wick for the alcohol must be a bit taller than the intake port and actually in contact with the cylinder, just a bit forward of the intake as well, to prevent room air from being drawn into the engine. Denatured alcohol is use for the flame source.

I am rebuilding the engine now and this time I am using C-40 cast iron for the cylinder (as I hate to machine stainless steel), and Graphite for the piston and internal valve. The nice part of graphite is that it is more or less self-lubricating. I learned two things with this engine. First, the heat traveled to the far end of the cylinder rather quickly and that hampered it’s operation and rust developed rather quickly causing the engine to seize-up after a minute or two due to condensation build-up. The new materials should improver the engine immensely. Guess we learn by our mistakes. The engine must be cleaned internally after most long runs or it will gum-up. A bit of WD-40 does a nice job.

Mr. Ridders sent me his drawings over the inner-net without charge. I in turn sent him my drawings with the English measurements and he advised me that I could share these drawings to anyone interested in building the engine. I have the drawings in the PDF type files and am willing to make them available to any FAME member that may be interested. The material changes I mentioned are incorporated in the drawings and sources are also noted. Keep in mind “friction” in this type of engine is a “killer”..

Copyright 2009,  Florida Association of Model Engineers and engine builder as noted above, All rights reserved.