Sunday, February 27, 2011

Gusset Plates

The gusset plates strengthen the area where the sole-bars, headstocks and diagonal beams intersect, and protect the headstock from the movement of the buffer shaft.

As you can see the plates are bolted to the sole-bars and to the diagonals, they aren't connected at all to the headstocks. The buffer shaft passes through the headstock and through a square hole in the gusset plate and then bears onto the end of the transverse spring.

The photo shows one of the better preserved plates but all are seriously corroded and need to be replaced.

We wanted to make the new gusset plates as like the old ones as we could, and we wanted to have fun with the forge. So I marked up the steel bench with positions for a jig round which to bend the new plates.

John welded the parts of the jig to the table.

Meanwhile the rest of the willing volunteers made smoke with the forge.

This is where I run out of pictures. Possibly shame, possibly in the heat of the moment I didn't take more.

Beating even red-hot half-inch thick steel bar to right-angles round a jig is not so easy as I thought it would be. And it helps if the jig is strong enough, which it wasn't. The jig broke as we were doing our first one.

We discussed re-heating the bar and finishing it across the anvil but in the end Ollie decided to fabricate the plates, welding three pre-cut pieces into the desired shape. It's a pity, I'd have liked to make them using blacksmithing methods but it would have taken a little longer.

Looking back at the process it was too hurried. Doing work like this needs very careful and slow preparation and a lot of thought. We didn't do that but rather made a hurried jig in pretty much the wrong place (too near the adjacent wall) which meant moving the bench. If we'd thought about the forces we'd be applying when we hammered the steel round we'd have made the jig stronger and might have succeeded in bending the plates round. Another factor was waste. Not wanting to waste metal we cut the bars only two inches longer than they needed to be to allow for trimming when finished, but this meant that we didn't have enough leverage to bend them, though this is a moot point because we'd have had to hammer them round anyway.

I've gone back to the drawing board to prepare details of how to make the gusset plates. We'll make them in two stages. First we will weld the long side that bolts to the sole bar onto the section that runs along the back of the headstock. When the timber frame is assembled we will fit the plate section that runs along the diagonal to get the correct angle and finally we'll spot and drill the hole for the bolt through the diagonal.

It's all a learning process.


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