Engine break-in???

[Tri-Pacer]

I have a friend who is in the process of finishing one of the Rutan design
pushers. He wants to break in the engine on the ground, on the aircraft,
before first flight.

I don't see how he can accomplish this without a test club and shrouding to
direct the airflow over the engine.
In fact I'd be leery of much ground running at all with the cowling off.

Anyone have any ideas?

I've broken in engines on a proven airplane, but nothing like this.

Thanks for any input.

Cheers:

Paul
N1431A
KPLU

[Orval Fairbairn]

In article >,
"Tri-Pacer" > wrote:

> I have a friend who is in the process of finishing one of the Rutan design
> pushers. He wants to break in the engine on the ground, on the aircraft,
> before first flight.
>
> I don't see how he can accomplish this without a test club and shrouding to
> direct the airflow over the engine.
> In fact I'd be leery of much ground running at all with the cowling off.
>
> Anyone have any ideas?
>
> I've broken in engines on a proven airplane, but nothing like this.
>
> Thanks for any input.
>

Paul,

You are right! The main objective of breakin is to seat the rings, which
is a lapping process and requires high pressure (high manifold pressure)
to force the rings against the cylinder walls.

This is why most manufacturers recommend mineral oil for breakin -- its
lubricating properties are not as good as the compounded stuff.

Chrome cylinders are especially critical, as they tend to build up a
glaze early and take longer to seat the rings.

An ideal method is to instrument each cylinder for temperature and note
when you get a large drop in operating temperature. When all cylinders
show this drop, the rings are seated and you can switch to "good" oil.