Bristol radial engines......cowling colour

Most technical artists render the leading edge of wartime Bristol
radial engine cowlings a copper-bronze colour.

Several wartime colour photographs (of the Vickers Wellington etc)
show this same effect.

The 'Halifax' restoration/reproduction at the Yorkshire Air Museum has
it's Hercules engine cowlings painted a reddish-brown colour.

This seems to be characteristic of most Bristol radial engine
installations of the period.

Being involved in the restoration of a 1945 vintage 'Hercules' engined
aircraft I am greatly interested to know how this effect came about.

It is NOT RUST because the original cowlings are made of Aluminium.

Was it due to a special formulation/colour of the original protective
paint? If so can anyone refer me to the specification?

Or was it as a result of heat on standard night black camouflage paint.
The cowling is separated by an air gap from the Townsend exhaust
collector ring, but substantial heat would build up particularly during
idling/taxying. All the same the colour seems so uniform on photographs
that I doubt that a heat effect would create it.

Even if a heat effect is the case.....I assume that YAM have painted
theirs because their restored engines cannot be run to create a natural
effect.

Any directions gratefully acknowledged.

RC

Sorry.

I think I mispoke in coupling the Townsend Ring and exhaust collector
in one phrase. I believe that the cowling itself serves the same
purpose as the Townsend Ring i.e. to provide a minimum resistance to
airflow around the cylinder heads.

Hello RC,

most of the Bristol engines had the exhaust collector ring to the front of
the engine (e.g. Pegasus, Mercury, Hercules). The reddish-brown coloured
ring is the exhaust collector and it is actually not painted. The heat of
the exhaust gases would not allow paint to stay long on the collector ring.
So it is the natural colour of the metall. In many photos you can see that
the exhaust pipe is runing from the collector ring.
Another Bristol feature is, that unlike most inline engine manufacturers
Bristol delivered not only the engine but the whole powerplant. That means
that the engine nacelle with the collector ring and the distinguish cowling
gills was a Bristol design. This was only slightly varied during the war.

Hans


"Rod" schrieb im Newsbeitrag
ups.com...
Most technical artists render the leading edge of wartime Bristol
radial engine cowlings a copper-bronze colour.

Several wartime colour photographs (of the Vickers Wellington etc)
show this same effect.

The 'Halifax' restoration/reproduction at the Yorkshire Air Museum has
it's Hercules engine cowlings painted a reddish-brown colour.

This seems to be characteristic of most Bristol radial engine
installations of the period.

Being involved in the restoration of a 1945 vintage 'Hercules' engined
aircraft I am greatly interested to know how this effect came about.

It is NOT RUST because the original cowlings are made of Aluminium.

Was it due to a special formulation/colour of the original protective
paint? If so can anyone refer me to the specification?

Or was it as a result of heat on standard night black camouflage paint.
The cowling is separated by an air gap from the Townsend exhaust
collector ring, but substantial heat would build up particularly during
idling/taxying. All the same the colour seems so uniform on photographs
that I doubt that a heat effect would create it.

Even if a heat effect is the case.....I assume that YAM have painted
theirs because their restored engines cannot be run to create a natural
effect.

Any directions gratefully acknowledged.

RC