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David Kerzel,     Pompano Beach, Florida

R-100, 1cylinder Radial CO2 type compressed air engine with a rotary valve  First posted 10/16/2004

For about 2 years I have been working on small compressed air engines.  It has been my goal to have the last engine in the series be a radial.  I have 2 other engines in progress now and there are 2 that were planned before the radial begins, but the radial is so fascinating I had to start.  I began by researching models in the gallery and plans from S.I.C. Magazine.  Then I started researching real engines on the internet.  What I learned was most of the models had tremendous amounts of detail missing or simplified away.

I wanted to start with a single cylinder and try to get a reasonable amount of detail for the scale.  Part sizes were reduced again ending up at 1/24 scale as a target.  Old techniques did not perform well.  Fixtures were essential for everything.  Most parts took several attempts.


I had hoped to finish the engine today.  Several people have asked about it so I am posting pictures as is.
All the major parts are done and fitted.  The piston moves and I can turn the shaft with my fingers. 
The head is a soldered assembly made out of 5 individual turnings.
The back and cylinder are held on with .08mm screws (.034 clearance holes for those of you who are into metric screws).
The crank shaft is pinned so it can be assembled in the crankcase with the connecting rod inserted thru the big hole.
I tried to polish the parts with Blue Magic but got deposit and a ugly film as can be seen on the head.
I took Dale Dietrich's advise and polished the cylinder with rouge and dental floss.
I have been calling this engine small, the bore is .125 and I think there are more parts lost on the floor than on the engine.

The fins on the cylinder are .012 hick with .008 gaps.  That is a little big for a true1:24 scale and a few fins are missing but the proportions of the cylinder and head are correct.  You can see I have a port in the valve box, it should be in the angled fins below but there is just not enough metal to connect a copper tube.

These photos that are so big make the parts look rough and crude.

3/12/2005  It has been a while since I made any progress.  In November I was polishing the corrosion off the head.  The buffer grabbed the part and tossed it across the shop.  I spent 3 days cleaning and moving everything but never found the head.  I have finally remade the parts, and gotten better at soldering them together.

When I started the engine I decided to simplify the design.  The real radial engine has the exhaust and intake pipes going into the finned angled valve guides.  I chose to move them to the valve boxes. As I reviewed the model and the original engine it just does not look right.  The finned valve guides will need to be longer.  The combination of the angled port holes and the fins are making these a challenge. 

I finished the finned guides and the main part of the head.  Next week I will start making the valve boxes and get it soldered together.


7/8/2005 I have started on the full radial this was a prototype for.  Click here to go to that project.



Copyright 2005,  Florida Association of Model Engineers and engine builder as noted above, All rights reserved.