Vintage Oil Coolers
All Bases Covered
When it comes to oil coolers for vintage aircraft, Pacific Oil Cooler Service, Inc. has all the bases covered; A substantial on-hand inventory of yellow-tagged Vintage oil coolers to fit most any WWII era aircraft – and the experience, the unique know-how – and the qualifications -required to expertly Overhaul and Repair these highly complex pieces of hardware.
FYI: They’re Just… Different
Compared to modern aircraft engine oil coolers (ie; those manufactured prior to the late 1950’s) Vintage-type aircraft oil coolers appear to be completely different creatures. And in fact they are different – in almost every respect.
The most obvious differences are the shape and size; Modern Aircraft oil coolers tend to be either square or rectangular in shape, while Vintage units – almost without exception – are either round or oval and use air flow tubes, instead of fins. Vintage oil coolers are also many times larger – and heavier – than their modern-day counterparts; larger due to the enormous size of the engine used – and heavy because they were constructed mostly of non-lightweight metals (copper, brass, and sometimes steel). This gives Vintage aircraft oil coolers the feel of a locomotive part, instead of an airplane part.
The P-51 oil cooler pictured above isn’t a very large unit, as far as Vintage oil coolers go (roughly 24″ wide, by about 9″ tall, and 10″ in depth) – and weighs-in at nearly 70 pounds (without any oil in it). It wasn’t until around 1950 that tube-type oil coolers began being manufactured out of aluminum.
Tip – how to tell an aluminum oil cooler from a brass and copper oil cooler, just by looking at it: Aluminum oil coolers have round air tubes. Brass oil coolers have hex-shaped air tubes.
Now & Then: Stacked Vs. Tubed
By and large, the majority of today’s aircraft engine oil coolers utilize what’s known as a “stacked plate” construction method of the core matrix; First, a row of very thin-gauged, wavy aluminum “air fins” is laid down with a sheet of .020″-thick aluminum on top (called a Conductor Plate). Then comes a Turbulator Plate, which is another piece of sheet aluminum – but this one has tiny, staggered corrugations stamped into each side. Another Conductor Plate is stacked onto the assembly, forming the first oil row (or “oil pass”).
This stacking order begins again with another layer of air fins, etc., and continues over and over until the prescribed number of oil rows are present. Finally the stacked assembly of loose pieces get clamped tight together, then oven brazed into a single, highly thermally conductive unit.
It is important to note that the engine oil flow is contained between the Conductor Plates – which also have sandwiched between them the Turbulator Plate. The engine oil has no place to go except for the very small spaces created by the staggered corrugations stamped into the Turbulator Plate. This is why it requires highly specialized flushing equipment, as developed and used by Pacific Oil Cooler Service, Inc., to remove 100% of the foreign matter from your aircraft’s oil cooler.
For example, imagine taking an average paperclip and bending it straight. The diameter of this paperclip wire is too large to fit into any of the oil flow passageways inside a stacked plate oil cooler. Plus, these passageways have very short straight sections, 1/8″ long, at most. Foreign materials like varnish, carbon, coked oil, dirt, gasket maker, or metal debris from your engine – once caught inside the oil cooler, will not come out using the “soak and shake” solvent-tank method. Just think of your engine’s oil cooler as a secondary oil filtration device – with no effective in-situ cleaning method.
The payback is small size, light weight, and high efficiency. Today’s stacked-plate type oil cooler is the mother of all heat rejecting devices (ie; it is highly efficient). The tight oil flow spaces described above – as provided by the Turbulator Plate’s staggered corrugations, allow lots of contact area between the oil cooler’s innards and the hot engine oil that’s being shoved on through.
The Bloop Tubes
The photo at left shows the honeycomb-like appearance of Vintage, “tubed” oil cooler construction. The tubes used in this oil cooler are made of copper – and are about the same diameter – and have roughly the same wall thickness, as an ordinary drinking straw. Ambient air flow is transmitted through the oil cooler via this bundled collection of very thin gauged metal tubing.
There are several variations in Vintage oil cooler construction methods, but basically (as shown in this example), the drinking-straw sized air tubes are encased in a brass housing – as many tubes as will fit – with solder holding it all together.
The tubes actually start out perfectly round, the ends are flared into a hexagon shape in order to provide a virtually gapless fit with each adjoining tube. This, along with a series of small outward facing dimples along each tube’s center section, provide space for oil to travel between them. As with stacked plate type oil coolers, the space through which hot engine oil must travel while visiting the cooler is quite cramped; there’s less than a business card thickness gap between each air tube inside a typical tubed oil cooler. This is by design, of course, in order to create as much hot-oil-to-cooler contact as possible.
And, as you are probably thinking by now, the care and feeding (ie; the Overhaul, Repair and Re-Certification) of these huge – yet precision made, pieces of aircraft hardware-past, require exceptionally specialized equipment – and highly talented labor. Exactly like what you will find within the world’s largest and most experienced outfit of its kind; Pacific Oil Cooler Service, Inc