< Brake Gear >
The original design doesn't include brake gear. Actually, active brake system is not effective in case of such a light weight locomotive. So I decided to make it as a parking brake which requires less relative components and is comparatively easy to make.
The picture shows hanger pins, which were made from a round steel bar and will be screwed into the main frames. The round side face was slightly cut to a flat, so that the pins can be fastened with a wrench.
The brake blocks are made from a fat brass sheet with a CAD paper pattern glued onto it. After opening pinholes, cut off one by one with a fret saw.
With a jig on the rotary table, outer 'V' shape, the tread face and shoulders were milled. Also the round tips of later items (hangers, fork-ends, arms) were milled in this stage.
Incidentally, my parts-making process is random, even though I explained them sequentially in the web site. Identical works of different items are done in one stage.
In the vertical slider, a deep slit was cut with a metal saw. The same jig was employed again.
The picture shows drawings of the jig. The black circles show 3mm and 4mm holes for detachable pins. The leftmost pin corresponds to the rotary table center. 4mm pins determine angle of the job. Each red line shows cutting line in each position.
The hangers were made from a flat steel bar. The brake blocks were fixed on the hangers with pins, nuts (for surface) and E-rings (for behind).
The brake beams were also made from a flat steel bar. The both ends were sawn out as the photo, turned to a pin shape and partially threaded in the four-jaw.
Three beams are glued one another, and milled to a diamond-shape.
The forked ends were made from brass square bar. Note some of them are integrated 2 in 1, as the brake rods will be aligned in a line.
The brake handle was assembled from stainless steel parts. The spindle was press-fitted to the head and secured with a small pin. The elbow was fixed in the head with Loctite.
In the cab, there is no space for brake handle column. So I mounted the handle directly on the cab floor. The handle bush is just a brass block on the running board.
The handle is screwed into a phosphor bronze nut which is sandwiched between two steel arms. Due to operation of the handle, the nut moves up and down and the pair of arms move. Note the arm has oval hole to catch boss of the nut (backside is the same). As the arms will be completely hidden behind the whistle, I didn't care for its look.
The photo shows a view from back of the chassis upside down. When the arms (left bottom in the photo) move, the first axle and the linked second axle rotate, then the other arms at each end of the second axle pull fork-ends of brake rods, then the brake goes. The first axle is hold in a pair of holes in the chassis, while the second is supported with a pair of brass brackets screwed onto a stretcher.
The brake rods were made of 3mm steel wire. Each end was threaded and screwed into the fork-end. End to end distance is adjusted by the screws and secured with lock nuts. Position of pins which secure the fork-ends on the brake beams was checked from job, so as to make all of brake blocks push the wheels at a time.
The third beam is just under the ashpan. So as to make the ashpan removable, the medium part of the third beam was sawn out. Note four rivets secure the fork-ends rigidly on the beams.
Actually, we hardly have chance to use parking brake in practice. It is rather for a model enthusiast to claim, "She has real brake system !"