Tuesday, May 27, 2014

Halting work on the airframe in order to concentrate on engine parts. I really need to make more progress on the engine for several reasons...chiefly due to the likelihood of rust creeping in. The cylinder walls are in good shape, so I'd like to finish them first so I can apply oil to the bore to prevent rust there. (It would not be good to apply oil now because the blast media—glass bead— would adhere to the oil...what a mess.) The inside of the cylinder heads (the domes) needed to be bead-blasted which necessitated making an extension to my bead-blast nozzle so the blast media would only impinge on the carbon build-up in the heads and not blast the cylinder walls.
This worked fine, now it's time to paint.

The plan is to paint the cylinder sleeves black and leave the heads natural aluminum, with maybe a touch up of silver here and there. Once all of this is done, we can hone the cylinder walls and apply a nice coat of STP or other thick oil as the rust preventative. Then the valves and springs will be installed along with the rocker arms.

The cylinder painting went very well except that the color I thought was black was actually a metallic black. Not a big deal, but wanted gloss black to look more period-correct. This one is okay. It is a 650°F auto engine paint laid on in three coats with no primer. Glad to have that done. Jan helped with masking, so that saved me enough time that all seven cylinders were done in one afternoon. There are little counter-bored areas around the cylinder base stud holes that had to be masked off, because I didn't want paint under the washers. It so happens that the diameter of the washers is equal to the diameter of a paper hole reinforcement sticker, so we used those to mask off those areas.

The engine case is next: bead blasting followed by paint (grey) and installation of the new main bearings. I haven't bought them yet...very expensive. But the main reason for the rush is to have enough engine completed to mount on the airframe so I can start fabricating the sheet metal nose which will fair into the prop spinner. This will require having the engine (at least the case) installed so I can run the metal around the cylinders. I've seen other Travel Airs made that way and they really look good (photo).

The cylinders stick out of the nose cone leaving the case to stay toasty warm under a shroud of sheet metal. I've heard that fully open engines, like on the Stearman, stay a bit too cool except in hot weather. I'll ventilate the compartment with louvres which I'll have to figure out how to fabricate. Any ideas? If anyone reads this and knows, let me know, please. Aside from making dies from solid steel, I'm not sure how it would be done. Maybe fiberglass...