Ron Wanttaja wrote:
snip
I think the lesson would be to strive for maximum redundancy. There
*should* be two completely independent ignition systems.
snip
I'm cautious about auto-engine conversions, but I wholly support those who
want to experiment with them. I like your attitude about wanting more
details to help improve your own work. Please continue to plug yourself
into information sources to build the safest engine possible.

The project I'm working on (1924 Epps Light Monoplane replica) motivated
me to learn about modern motorcycle engines. The original engine in the
original plane was an Indian Chief motorcycle engine. From photos it
looked like he initially had it set up as a direct drive, then
subsequently built a chain drive PSRU.

At some point before the plane was sold, it was converted to a Lawrance
A-3 engine. I've heard two stories about why he changed the engine.
One is that he wanted more power (28 hp for the Lawrance vs. 17 hp for
the Indian). The other story is that he got tired of the chain breaking.

In trying to decide what engine to put on the replica, I did a lot of
research on modern motorcycle engines. I found that there are modern
V-Twin engines (Honda VT1100 and Kawasaki 1500) that already have two
spark plugs per cylinder. They do not have redundant ignition systems,
but they lend themselves to building your own.

You pointed out that the PSRU is a single point of failure. One
attraction with many modern motorcycle engines is that most have a well
engineered gear reduction system in place. The down side of it is that
there are usually 4 or 5 reduction ratios more than you need, and there
is a substantial weight penalty associated with the integral transmission.

One interesting motor I found is the Honda series of V-4 engines.
Though they have only one plug per cylinder, they have dual spark boxes.
Some riders I know have lost half their ignition system and had a hard
time telling something was wrong; they just seemed to be down a bit on
power, even though they were running on only two cylinders out of four.

The biggest down side to the use of a modern motorcycle engine in a
plane is that so few people have done it; you are truly experimenting,
which entails obvious risks.

--
David Hill
david at hillREMOVETHISfamily.org
Sautee-Nacoochee, GA, USA

filters, they're not just for coffee anymore
The following needn't bother to reply, you are filtered:
Juan E Jimenez, Barnyard BOb, Larry Smith, John Nada