Part 12 by Jason Ballamy

Fabricating frames and bearing blocks

Next on the agenda are the "A" frame supports that the beam tie bars fix to. I started out by marking the shape onto an odd bit of 1.5mm plate, clamped it to a second piece, rough sawed the two out and then filed to the final shape.

Next a couple of strips of the same material were cut off, I find the easiest way to cut thin sheet is to place it between two scraps of MDF as this stops it flapping about and jamming the saw blade.
These were then just bent by hand and tweaked until they followed the shape of the "A". I also machined up a bit of 3/8x 5/16 with a slot in the top to form the feet.
Some slightly thinner material was cut and bent to form the inner flanges and then the lot silver soldered together along with a flat piece of plate for the cross tie. After that I soft soldered in a piece of copper to complete the flanges as it was getting hard to hold any more pieces together for silver soldering.
Finally some brass disks were soft soldered on to form the bosses where the rods and tie bar fix.
The flanges and bosses were then all milled back to the correct widths, the outside one is narrower than the feet and the inner ones narrower still. Fillets added with Miliput, primed and a few simple turned parts from steel and another part can be crossed off the list.
The vertical movement of the valve rods is transferred from the horizontal movement of the eccentrics by cross shafts which run in bearing blocks. These are of a far simpler design than the ones for the crank and ladder frame shown earlier and were just milled and drilled from steel.
These were then cut with a slitting saw and some bronze split bearings added.
And here they are with the rods in place and one of the levers, there are several other levers which are basic milling work with the rotary table so I won't detail them here.
What I will show is the way I fabricate links rather than the more common method of turning from flat stock and then rounding off the ends. Start by cross drilling some over-length rod that will become the eyes of the links to fit the bit in the middle. A few punch marks on the rod hold things in the right place while they are soldered
Once cleaned up one of the eyes can be held in the lathe and carefully faced back to length and bored, followed by the other

As the eyes are getting a bit short now its best to transfer to the mill and flycut the two eyes to length.

And the finished pair of links
And here are all the bits together.