The Myrsky engine NACA-ring and lower cowling completion
Keskiviikko 7.2.2024 - Tuesday Club member
The engine’s NACA-ring of the VL Myrsky II (MY-14) under restoration was completed when the tightening collars, made at the Tuesday Club for the four machine gun flash tube openings at the upper part of the NACA-ring, were fitted. With the tightening collars the flash tubes made of steel will be locked to the four openings intended for them in the NACA-ring. Of the four openings the two midmost will have 70 mm flash tubes and the lateral ones will have 45 mm flash tubes. The midmost flash tubes will be fastened at their rear end to brackets on the ring of the engine cradle. The machine gun barrel will thrust itself into the rear end of the lateral flash tube, holding it in place.
The excessively long flash tubes are still “sticking out” of the NACA-ring flash tube openings. They will be cut shorter, so that the flash tube ends will only protrude to some extent out of the flash tube openings.
The difference in sizes of the flash tubes is due among other things to the fact that there’s no room at the side of the engine under the upper cowling for thick flash tubes. There are shields as well made of steel plate above these narrow flash tubes. They protect the upper cowling, which is nearly touching the flash tube, from overheating when the machine gun is firing. But all the same, both sizes of the flash tubes serve the four 12,7 mm LKk/42 machine guns.
Building of the lower cowling is almost completed at the Tuesday Club. The last tasks have been the guides, which will be fastened on the cowling’s inside surface stiffening strip, the guiding pegs to the front end of the cowling, and the tightening latches, with which the lower cowling will be locked to the upper cowling. Let it be pointed out, that the MY-14 engine upper cowling will be built in the Finnish Air Force Museum.
The guides, as well as the guiding pegs, and the tightening latches were made at the Tuesday Club. Owing to the guides and the guiding pegs, the lower cowling is easy to fit into place. Three slot-formed guides were riveted on the cowling’s inner surface rearmost stiffening strip. With the aid of these slot-formed guides the cowling “snaps” in place to the fastening ring of the rear part of the engine.
Photo by Jorma Laakkonen.
The three guide pegs of the cowling’s front edge were riveted on the inner surface of the cowling’s front edge. The guide pegs of the front edge push into the holes drilled in the NACA-ring hem, thus fastening the cowling from its front edge on the NACA-ring. An insulation strip made of fabric was glued to the hem of the NACA-ring to separate the two metal surfaces from each other.
The upper and lower cowlings are locked to each other with four tightening latches. These four complicated tightening latches were built at the Tuesday Club, according to Myrsky blueprints. With adjustable tightening latches the upper and lower cowling can be locked to each other to suitable tightness. The parts of the latches with springs will be fastened to the upper edge of the lower cowling and the parts with levers to the upper cowling. The parts of the latches with springs are tentatively in place, waiting to be riveted.
After the guides and guiding pegs had been fastened on the cowling, the cowling’s fastening to the NACA-ring was tested. The testing was done while the cowling was still fastened on the last where it was built. It was noted that the guiding pegs fitted expectedly to the holes drilled in the hem of the NACA-ring. Thus the NACA-ring was fastened in place on the Pratt & Whitney R-1830 Twin Wasp engine, after which the lower cowling was fastened from its upper edge to the NACA-ring and from its lower half to the fastening ring of the rear part of the engine. The engine is beginning to resemble that of the Myrsky fighter.
Photos by Lassi Karivalo except if otherwise mentioned.
Translation by Matti Liuskallio.