Transitional Engine – Conrod

This Transitional Engine has a two-piece crank design with a slider. This is traditional steam engine design.

As this is meant to be an engine that has started life as a steam engine I thought it would be ok to make it from mild steel.

I calculated the distance between centres and then accurately marked these and drilled the mild steel blank.

This is a substantial piece of steel, but the intention is a lot will be removed by the time I finish.

The next stage was to braze the fixings to the big end before I slit the big end with a saw.

The small end phosphor bronze bearing is now in place along with the clamps for the big end.

After brazing and fitting the clamps for the big end the part does look rather a mess, but there is still a lot of work to do before I’m anywhere near finished.

I ended up bolting the conrod down to the milling table with fixings through the big and small ends. This allowed me to flip the conrod over easily and get a fast and accurate machinging operation on both sides.

The final part is shown in the main image and in the last image as mounted in the engine.

This is quite a substantial connecting rod even after I’d done quite a bit of machining to thin down the main section of the conrod.

I think I’m going to be designing a balance weight that will sit within the flywheel spokes to offset some of the big-end out of balance mass.

About Nigel 192 Articles
Have been making models since I was around 7 years old and using a lathe from the age of 11, a self taught engineer with a passion for making model engines.

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