The building of a Stuart S50 Engine

The Boxhead

30th October 2017

Having a watched an interesting video on YouTube I decided to follow the example of Keith Appleton and use my Linisher to prepare the base of the Boxhead.

There is only a few thou to remove as the casting is of good quality.

I then placed the part on my glass surface plate which had been made by my Father in Law Don Bruce sadly now departed, and the base proved to the flat as expected and as required.

31st October 2017

The marking out of the Boxhead did not prove to be easy so I reverted to a tried and tested way of machining up a spacer the correct length 1 1/2" and a second one with 21/64" added. I had to convert the dimensions to Metric as my lathe is Metric !
With the Boxhead proved to be without rock on the bottom I placed a sheet of paper on the mill and then clamped the Boxhead down firmly enough to hold but not too tight to risk breaking the bolt down location at each end.

The mill was set to height and milling carried out where the cylinder will rest.

The milling for the base of the cylinder completed
Then the mill was re-set to the greater height and the slide bars milled.

The milling for the guide rails completed
There are several holes which need to be drill in the box head, three to mount the cylinder which are clearance holes for 7BA and four holes to be tapped 7BA to mount the slide bars.
I make up drilling templates to act as guide for the holes and there by making the parts fit well.
For the slide bar the templates are the slide bars themselves and the photo show an optical punch, with the optical part in the holder which is then removed when lined up and the metal punch inserted and a gentel tap to make the mark ready for drilling.

A separate piece of metal for the location for the cylinder will be used.

The photo shows the guide for drilling place  and securely clamped to the miller/driller and the tapping size drill to 7BA ready to drill.

The spacers were made up.

Here the guides are assembled with their spacers to the boxhead.

25th September 2018

I have drilled the holes in the base in slightly the wrong place so using a Slot Drill I carefully extennded the holes towards the centre so that some adjustment is possible after locating and tapping the fixing holes in the cylinder.

The base was drilled a little under 1/4” to take the main shaft and then a 1/4” reamer  put through which provides a good running fit to the main shaft
Through the top of the bearing for the main shaft oil ways were drill 1.2mm
2 October 2018

Today I was able to drill and tap the three fixing holes on the underside of the cylinder and bolted the part down and the cross head still slid in the guide bars.
You can see in the photo that I have installed one of the bolts holding one side down and there is also a second bolt hidden in the photo.

The drill is set up ready to drill the 7BA tapping hole.

The phtot shows the engine cylinder bolted to the base.

The next part to be made is the connecting rod which I have already reduced one end to 3/16" and then engineering blue applied so that it could be marked out to the dimensions as shown on the plans so the centres of the holes were 2 inches and 1316 centres

9th October 2018

The boxhead was masked up and spray printer with a primer in readiness of the main colour being painted on.

The base has been painted Stuart Black as supplied by Stuart Models.