< Inner Crosshead >
The drawings show section of inner crosshead and inner slide bar. The slide bar has T-slot faced down. The T-shape crosshead travels along the slot. The slide bar's T-slot is formed with flat bars and rectangle bars.
I started with the crosshead. The side plates are laser-cut. The bush part for piston rod is exactly the same as the outer crossheads. The top plate and inner block is made from steel flat bar. All of parts are assembled with small brass screws before silver soldering.
Silver soldered crosshead. After that the brass screws are filed off.
Inner crosshead and inner piston rod are not so easy to assemble between the frames. So I utilized screwed type connection with a lock nut instead of the tapered connection with a cotter. The screwed hole in the crosshead bush is centered on the basis of the top plate.
In order to oil the crosshead, I opened lubrication hole in the top plate. It has a shallow recess and two small holes toward the both sides of the main rod end. The slide bar also has a hole that leads oil to the crosshead.
The sliding plates are made from phosphor bronze sheet. They cover top and bottom of the crosshead top plate. The large one is for the top and has a hole for lubrication.
The slide bar parts and assembled slide bar. T-slot width is fitted to the crosshead width and fixed by screws.
The outer parts of T-slot have deep chamfer. It is cut by a chamfer cutter.
Piston, slide bar and crosshead were assembled for testing. Actually they have to be mounted to the body one by one.
Back end of the slide bar is fixed under a stretcher between the frames. So I have to drill a hole on the stretcher. But the stretcher can't be removed without removal of the front coupling wheels, because some of the screws fixing the stretcher are behind tires of the wheels. At first I removed the wheels as the photo shows. It was a hard work because the chassis weight is already close to 100 kg.
Mount the stretcher between the frames again. Fix the slide bar front end to the cylinder block. Then copy the hole of the stretcher to the slide bar.
I checked smoothness of crosshead sliding without O-ring and main rod. After that, O-ring is inserted and the crosshead is connected to the main rod. The gudgeon pin is exactly the same as outer crossheads. But I didn't make a castle nut but utilized a simple commercial nut.
All of three main rods are connected to each cylinder. Then rolling test is done on straight and curved track.
