WIX Archives
Re: Engine component wear
Posted by bdk on Wed Feb 25, 2004 10:11:00 PM
In reply top Engine component wear posted by AndyG on Wed Feb 25, 2004 03:20:14 PM
I can tell you first hand about my Stearman engine. While not a fire breathing fighter engine, it would be comparable to most smaller (low performance) radials up to an R-1340 I would think.
I had a bearing start to disintigrate, which caused high vibration at certain RPM's. This caused a regoin of small fatigue cracks along the radius of the crankshaft master rod journal. It was cheaper to buy an entire core engine than to buy just a crank, so that's what I did. I took a risk that the crank in the core engine would be serviceable- which it was.
The metal from the disintegrating bearing also damaged the oil pump, so I used the one from the core engine in the rebuild.
The cylinders were just out of limits for standard bore, so I contemplated new .010 oversize pistons and having the cylinders ground oversize. I found out it was far cheaper to buy 7 new-old-stock (NOS) cylinders and reuse my old pistons. It seems that those exact same cylinder assemblies were used in early model Stuart tanks and LVT's.
The ball bearings used one the crankshaft were available as new manufactured parts. They are a standard commercial bearing size and were relatively inexpensive. Piston rings and gaskets were available relatively inexpensively surplus. Link rods were so cheap surplus that I bought a set NOS. My master rod bearing was OK from the core engine, so I reused it. That one is a babbit bearing rather than a ball or roller bearing.
I assembled the engine myself, following the manual and using dry ice and an electric oven as suggested by the manual to fit the interference fit ball bearings onto the crankshaft, and then to fit that assembly into the bearing retainer which bolts to the case.
The Continental W670 (220 HP) is a very simple engine as far as radials go, so it may not compare directly with a big radial, but there are similarities.
Most aircooled engines will require an occasional cylinder replacement during their life. Typically this is due to leakage by the rings or the valves. You then have to replace the rings, lap or grind the valves or seats, or overhaul the entire cylinder if the easy fix can't be done.
If the engine is maintained and operated properly, things like pistons can last a long time. Cylinders can be chromed back to standard bore diameter, valve guides, valves, and valve seats can be replaced.
Cylinders and pistons are in short supply on some engines. Cams on radials tend to last since they have roller followers (unlike Merlin fingers). Bearings can be reworked/replated and bushings can be made, and crankshafts can often be chromed back to size if they are scored or severely worn.
: I would be interested to find out a brief history of typic
: al engine component wear patterns for current water cooled
: V and radial historic aeroengines. (not for reno type ope
: rations!!)
:
: Consider for say a restoration in the past ten years.
:
: eg. When a radial or a watercooled V goes for a post origi
: nal first restoration major overhaul, what are the typical
: consumables? Under normal annual display/personal operati
: onal useage, would a set of pistons go again? If so would
: the same rings go again too? Re-bore or new sleeves? camsh
: afts? bearings? Cams? valves? Reduction gears?
:
: Just a flavour of what is typical would be great.
:
: Thanks
: