< Cylinder Drain Cocks 1 >
Typical Japanese steam locomotive has three drain cocks in each side. While
the outer two cocks are for cylinder drain, the inner one is for steam
chest drain. C53 has additional two drain cocks for the inside cylinder,
actually connected to both ends of the inside steam chest. So there are
four drain cocks in each side, totally eight. I decided to reproduce eight
functional drain cocks for my loco.
The picture shows drain cocks' section. The left one is of the outer drain cock, and the right one is of the inner one. There is a stainless steel ball in it and is push onto the seat by a coil spring. A push bar under the ball opens the ball valve. The top cap has a center hole for steam path from the cylinder. The inner drain cocks don't have path from the cylinder but have path from a copper tube connected with a ring between the cylinder block and the lock nut. Incidentally the cyan line shows cylinder block body and the gray line shows cylinder block cover. The copper tube is hidden between them.
I started with cutting screw holes at the bottom of the cylinder block. I also cut bolting faces around the holes by end mill. Note typical end mill has 'dish angle' at front and its bored face does not become dead flat but slightly tapered. So I cut the ring's bottom face also tapered.
Four cocks in each side are operated together with a slide bar. So they should have the same height. After turning the cock body in the lathe, screw them into the cylinder block and align their tops, then determine the slotting direction for the slide bar.
The photo shows the inner drain cock's parts. The design of coil spring, ball and seat is the same as the cylinder safety valve's. There are two cross holes in the cock body. The hole on the threaded part is drain inlet, while the hole on the hexagonal part is outlet. The former is a through hole while the latter is a blind hole. The ring and the copper tube are silver soldered. The ring have recess inside.
The photo shows the cylinder block turned upside down. The inner drain cocks are connected to desired positions of the cylinder block with 3 mm dia. copper tubes.
A tube from a drain cock comes from inside of the cylinder and connected to middle part of the steam chest. The connecting method is the same as the drain cocks.
The tube for both ends of the inside steam chest is connected with 'union joint' with a nipple screwed into the body in advance.
I will introduce operation parts of the drain cocks in the next time.