Klemm project
Headset review
Vintage fantasy…
Jim Copeman reports on the progress of British Klemm, G-ACXE, a fascinating vintage machine
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ince the previous report in early 2020 much has happened to progress the restoration of our 1934 British Klemm L25C, despite the interruptions of Covid. In fact, I think I wrote the original article as a way to fill time during the early days of the pandemic… So, what has been done? Well, you may recall from the previous article that we needed a new combustion air inlet duct and an exhaust system for the Pobjoy engine. The inlet duct was designed from various photo evidence of BA Swallows, manufactured, painted and fitted.
Exhaust ring
The exhaust system for this delightful little radial, as you might expect, is pretty involved, but luckily this was one of the few major items we had a pattern for, a rather holey, rusty and very thin example for sure, but it was an original. Some months before, we’d had the two half round headers prefabricated by a local welder and bends with 42 | LIGHT AVIATION | December 2021
Above The Klemm nears completion and is seen here less cowling after its first engine runs.
tails made at Pipecraft. The time had come to see if we could join the bits together. Being a seven-cylinder engine, three cylinders per side discharge into the two separate ring headers, with the seventh ducted as an extra into the left header. This means that the headers have asymmetrical internal pressures, so they are coupled to either side of the inlet casting to allow the pressures to equalise. This was handy in the 1920/1930s as the heat from this flow is absorbed into the casting and thus the inlet charge. Pre-WWII, fuel was very different from today and needed help to vaporise, and this heating of the charge helped combustion. The total exhaust system has come together very well to produce a neat exhaust ring, in keeping with the period and as near to the original as possible, but with the addition of modern springs to hold the joints together to make it reliable in flight. The exhaust system was completed by my partner in the aircraft, Tony Palmer, including the finer details such as the loops for the retention springs, while I was away in Wales helping on my daughter’s farm during lambing.
