The following was received from Lee Hodgson describing ongoing development of the plans for the Hodgson 9 Cylinder Radial Engine:
I wanted to share with you the changes I have made to improve the
performance of the 9 cylinder radial.
Some of the small improvements are to the tooling, others have
improved the engine itself. I was determined to find and make the
changes necessary to make the engine start easier, have a better
throttle range and improve the fuel distribution.
After nearly 3 years of work I have the changes worked out.
I would like to share the improvements with you and your readers.
There have been three major changes to the engine design and plans.
- An improved cam with a constant acceleration cam profile.
- A hall effect transistorized ignition system.
- A full diameter impeller with a seal plate to separate the
intake space and oil pump area.
It was difficult to research cam data from production engines
as there doesn't seem to be a consensus on how long the intake and exhaust
duration should be. Only after repeated testing was a cam developed that
gave good starting and good power at high speed.
In addition, to the duration changes, the constant acceleration profile
is generated by moving the cutter to position in one degree increments.
The engine was originally designed with mechanical points.
They floated at high speed and there was internal arcing. The ignition
was changed to a system by
that operates with an
engine of an odd number of cylinders. This has proved to be a reliable
unit that operates over the entire speed range without the need for an
automatic advance / retard feature.
The Impeller and Seal Plate
By having the oil pump transfer lines extend radially outward from
the crankcase there is room behind the pumps for a seal plate between the
intake vacuum and the oil pump drive gear area.
The crankcase and intake pipes were extended by 0.788 to incorporate
a longer crankshaft driving an impeller, The impeller blades extend to the
inside diameter on the crankcase. The blades align directly with the intake
pipes and leave no place for oil and gas to pool at the bottom.