Sandwich Crankshaft Bearings

Looking at the slot in the tender I decide to make sandwich crankshaft bearings for the Burrell. Sandwich refers to the layers of the bearings. Essentially a 12mm brass square that is 1.6mm thick in the centre with larger rectangular brass sheet either side.  

marking out crank bearings
There is something particularly calming about using a surface plate. This brings with it a resulting level of precision. Maybe it is mindfulness in the workshop.

Silver Soldering with Paste

silver solder paste

I decided to use the Cookson Gold Silver solder paste. A brass nut and bolt squeezes all of the parts together. It has a plain un-threaded section that spans the thickness of the sandwich.

The very small syringe of silver solder paste at first appears to be quite expensive, but I’m getting a lot of use out of this one tube.

silver soldering on hearth

I placed the pair of parts on my brazing hearth close together and in a corner. This allowed me to get the heat in quickly with a butane torch.

The brazing hearth is constructed from wood stove bricks that are easy to acquire and can be screwed together.

silver solder paste after heating with torch

As you heat the parts you will start to see a change in the silver solder past. Keep heating and you will see a flash of liquid silver. This is the indication you need that the paste has reached the correct temperature. Depending on the size of the part I continue to keep it at this temperature for another 30s to 1 minute. Just to ensure that all of the paste has reached the temperature at which the flux and solder works.

Bearing Blocks in Place

assembled crankshaft bearings
Assembled Sandwich Crankshaft Bearings
Burrell Traction Engine

Bearings in place, phosphor bronze bushes added. However, at this stage they had not been reamed as I need to fix and align them. Then I could ream them in place and both at once.

However, my main issue is the height of the crankshaft and the clearance of the crank with respect to the top of the firebox. This is an area that needs more thought around the design.

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