Thread: It got a leg out of bed!!!!!!

Originally Posted by Bigbjorn

John, it looks to me like it was copied around aero engine practice of WW1 & 1920's.

Yes, exactly. Have you seen the versions of the Liberty engine with electrodeposited copper water jackets? I don't know which manufacturer came up with that idea - they made the water passage out of wax on the outside of each cylinder, painted it with graphite, electrodeposited a thick layer of copper over the whole lot, cut holes as necessary, and brazed on fittings. Unfortuanately, copper, subjected to vibration, work hardens, and this seems to have been so successful that it convinced the USN at least to never again touch a liquid cooled engine for an aircraft.

Other manufacturers used fabricated steel water jackets welded on, and, I suspect, cast alloy ones like this engine - probably all of them like this had the alloy sealed with O-rings or gaskets, probably not very successfully. Note that the engine shown almost certainly did not have detachable cylinder heads - the valves would have been in separate screw-in plugs.

Originally Posted by JDNSW

Yes, exactly. Have you seen the versions of the Liberty engine with electrodeposited copper water jackets? I don't know which manufacturer came up with that idea - they made the water passage out of wax on the outside of each cylinder, painted it with graphite, electrodeposited a thick layer of copper over the whole lot, cut holes as necessary, and brazed on fittings. Unfortuanately, copper, subjected to vibration, work hardens, and this seems to have been so successful that it convinced the USN at least to never again touch a liquid cooled engine for an aircraft.

Other manufacturers used fabricated steel water jackets welded on, and, I suspect, cast alloy ones like this engine - probably all of them like this had the alloy sealed with O-rings or gaskets, probably not very successfully. Note that the engine shown almost certainly did not have detachable cylinder heads - the valves would have been in separate screw-in plugs.

I didn't know about that one. It probably seemed like a good idea at the time. The USN decision to go with radial engines was confirmed by experience in WW2. Liquid cooled engines don't run for long with the complex cooling system shot full of holes. Radial engines were found able to absorb quite a bit of battle damage and still fly home. Instances recorded of radials getting back to the carrier with a cylinder completely shot off. Emphasis was placed on getting the pilots back on board. US industry was building aircraft faster than carrier pilots could be trained. This brought about advances like self sealing fuel tanks and armour plate to protect the pilot.

Yes, radial engines can absorb battle damage a lot better than liquid cooled engines. But as with any factor there are compromises. Compared with liquid cooled engines, radials have a much larger frontal area, and it took the industry nearly thirty years from about 1915 to be able to reliably cool aircooled engines, especially high power ones - and someone, I think it might have been Continental, actually built a liquid cooled "corncob" radial in the mid 1940s, presumably to get over the problems of cooling the back three rows.

To quote wikipedia on one of the large aircooled engines in the B-29 "Although the Wright R-3350 Duplex-Cyclone radial engines later became a trustworthy workhorse in large piston-engined aircraft, early models were beset with dangerous reliability problems."

Originally Posted by JDNSW

To quote wikipedia on one of the large aircooled engines in the B-29 "Although the Wright R-3350 Duplex-Cyclone radial engines later became a trustworthy workhorse in large piston-engined aircraft, early models were beset with dangerous reliability problems."

The early ones had a propensity to catch fire. To fly at high speed and maximum ceiling with full fuel and bomb loads required the B29's to be run virtually flat out. Oil leaks and proximity of red hot turbochargers to magnesium castings were a problem.

Another "it seemed like a good idea at the time" - in the early 1900s there was built a new J-class yacht, I think in Florida (obviously for someone with more money than sense). With no expense spared, it was framed in monel, plated with pure aluminium, and fastened with copper rivets. It lasted a couple of months in salt water. The designer obviously was ignorant of elementary electrochemistry. (Admittedly a slightly esoteric field at the time, but galvanising had been in use for fifty years, so it was hardly an unknown subject.)